Citation
The impact of wet season and dry season prescribed fires on Miami Rock Ridge Pineland, South Florida

Material Information

Title:
The impact of wet season and dry season prescribed fires on Miami Rock Ridge Pineland, South Florida
Added title page title:
Miami Rock Ridge Pineland, South Florida
Creator:
Snyder, James R. ( Dissertant )
Ewel, John J. ( Thesis advisor )
Bowes, George E. ( Reviewer )
Judd, Walter S. ( Reviewer )
Popenoe, Hugh L. ( Reviewer )
Place of Publication:
Gainesville, Fla.
Publisher:
University of Florida
Publication Date:
Copyright Date:
1984
Language:
English
Physical Description:
viii, 154 leaves : ill. ; 28 cm.

Subjects

Subjects / Keywords:
Burning ( jstor )
Dry seasons ( jstor )
Fires ( jstor )
Forests ( jstor )
Hardwoods ( jstor )
National parks ( jstor )
Nutrients ( jstor )
Pine barrens ( jstor )
Understory ( jstor )
Vegetation ( jstor )
Botany thesis Ph. D
Dissertations, Academic -- Botany -- UF
Forest fires -- Environmental aspects -- Florida ( lcsh )
Pine -- Ecology -- Florida ( lcsh )
Prescribed burning -- Florida ( lcsh )
Miami metropolitan area ( local )
Genre:
bibliography ( marcgt )
non-fiction ( marcgt )
Spatial Coverage:
United States -- Florida -- Dale County

Notes

Abstract:
In the subtropical pine forests on oolitic limestone in Dale County, Florida, Pinus elliottii var. dense grows over a species-rich understory (> 128 sop.) of shrubby hardwoods (mostly tropical evergreen species), palms, and herbs, including several endemic taxa. Fires prevent rapid conversion to hardwood forest. To compare the response of these pinelands to burning during the lightning fire season (hot, wet, summer months) and the management fire season {cooler, drier, winter months), paired burns were conducted at two sites in Everglades National Park, one burned 3.5 yr previously and the other 6 yr, Above ground understory biomass and nutrients were measured immediately before and after, and it 2, 7, and 12 mo after the four burns. The barns top killed all the understory vegetation. The fires volatilizes 1-1.5 kg/a 2 of organic matter and 5.7-9 g/m 2 of N. Meteorological inputs and symbiotic and non-symbiotic fixation should easily replace N lost in the burns. Losses of P, K, Ca, and Mg were not detectable except for * in one of the burns. The rapL3 unierstory recovery was almost entirely vegetative regrowth of the top killed plants. Pine seedlings were abundant after the wet season burns, however. Herbs and palms recovered dry mass more rapidly than hardwoods an'' reached pre-burn levels within 1 yr. Hardwoods recovered only 18-395 of their pre-burn biomass. Total understory vegetation recovery was 27-63% of initial amounts, but leaves recovered 58-93% yet primary productivity the first year after burning was 144-200 g/m2 . Recovery of nutrients was more rapid than biomass because of higher nutrient concentrations in regrowth tissues. Some herb and pals nutrient standing crops reached pre-burn levels within 2 mo. After the burns litter mass and nutrients often showed an initial decrease before recovery began. At 1 yr litter mass was 42-625 of the pre-burn amount. Annual pine needlefall averaged 259 and 320 g/m 2 at the two sites. The amount of hardwood recovery was not determined by season of burning; higher fire temperatures (wet season burn in one case, dry season burn in the other) resulted in less recovery.
Thesis:
Thesis (Ph. D.)--University of Florida, 1984.
Bibliography:
Bibliography: leaves 110-122.
General Note:
Typescript.
General Note:
Vita.
Statement of Responsibility:
by James R. Snyder.

Record Information

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University of Florida
Holding Location:
University of Florida
Rights Management:
Copyright [name of dissertation author]. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Resource Identifier:
030487822 ( alephbibnum )
11898805 ( oclc )
ACN6476 ( notis )

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THE Im1?Ar 3?F Ar SEASON AND D2Y SEASON ?BEPSt-"RFn PT'
ON irAMI ROCK PTDGE PTNELAND, SOUTH LOIT'A







BY


JAMFS R. SIUYDiF


A DISSPRTArION PNESESTFD TO THE S3ADUATF SCHOOL
OF THE UIV?.RSTTY OF FLORIDA TN
?4?TIAL PULPILLNEN'T OF T? ?OnfTREMPFmTS
P?)3 rE DEGREE OF DOCTOR OP P!ILOSOP'Y



UNIVI7SITY 3?F LORIDA


1984















ACKNDWLEDGEDENTS


Tha major portion of this work was supported directly by

the South Florida Research Center, Everglades %ltional Park,

and I owe s3ezial thanks to Dalq Taylor, formerly fire

ecologist, ai Gary Hendrix, research director. Numerous

individuals it th= Pesearch Center aided in the filll wor:;

in particular Rebecca Rutlelge, Virginia Louv, Arthony

Canrio, Laeis Sharman, ani Donna Blake spont many hours

under trying conditions. Alan Heraion, besides helning with

fill work, identified plants and shared his knowledae of

local plant :ommanities. Pill Robertson, Jr., hloe1 snrac

my interest in tasse unusual pinlands. The ?or? r=snur7?

manaqgemnt staff (lead by fire bosses Phil Foeon, Leon '~nz,

ini Ron Sutton) 3arriel out the prescribed burns. ?aul rrt!

of the AgrLcultural Research and Education Center,

Homestead, generously permitted the use of his facilities

for tissue grinding.

In gainesville my committee chairman, Jack Ewel, provided

logistical sioport, advice, and guidance. Committee nembbrs

Seorge Bowes, Walter Judd, and Tugh Popenoe made useful

comments and suggestions throughout the study. Jack Pu'z

provided a tiorogh review of the manuscriot and sqsested

numerous impcovenents. Mary McLeod, Craig Peed, and Linda









Lee of the Forest Soils Lab were of great technical

assistance with the chemical analyses. George u1ller

drafted most of the figures. Xen Portier aevised on

statistical nattscs. computing was done with the facilities

of the Northeast Regional Data Center.

In recognition of less tangible contributions, I thank n7

father, Robert Sayder, for instilling in ae an aopre-iation

of the great out-of-doors and my wife, Jean Snyder, for

continuing encoucagement and support.
















TABLF OF CONTENTS





ACK O L G TS . . . . . . . . . ii

ABSTS ACT . .. . . . . . vi


CHAPTER

I. NTRODU TCrT . . . . . 1

Dbjpctivos . . . . . . . .. . .
he ecosystem . . . . . . 3
Cli e . . . . . . . . 3
a-ol3gy and Soils . . . . . . . 7
Vegetation . . . . . . . 11
'ire Ecology . . . . 17
?rPasnt Extent an- Conlition . . . .
7verVlades National ark . . . . 2

II. 'T.O S . . . . . . . . . . 27

7xporimnatal Design and Site Selection . 27
The Burns . . . . . 29
Abajeqrannd Mass Sampling .. . . . . 31
eagetatian and Litter . . . , . 31
?3stburn Ash . . . . . . . . 34
Litterfall . . . . .. . . . 35
Soil Sampling . . . . . . . .. 36
issue and Soil Analysis . . . ... . 37

ITT. RESULTS . . . . . . . . . . . 39

Tnitial ageattion Structure . . . . .. 39
Burn Descriptions . . . ... . .. . 4
Pica Effects an Unlerstory Mass aan Nutrients .r2
faitial Distribution of Mass an! Nutrients 52
ksh Collection methods . . . . .
?ost3urn Distribution of Mass ard Nutrients 57
Postfica Recovery of Mass and Nutrients . 58
vegetation .9.. .. ... .... . B
Littr. ...... .......... .. .70
Impact of Fires on Pines . . ..... .. 75
Soi . . . . . . . . . . .. . 79









IV. DTSC SS N . . . . . . . . . 32

Fice-caused Losses of Nutrients . . ... 2
?3stfice Recoverv . . . . . . 0
TfE~at 3f Season aE Burning on Hardwool recovery 93
Regrovti Vegetation as a Nutrient Sin .- . 101
Sumnary and Conclusions . .. . . 10

LITE RAT ED . . . . . . . . . 11


APPENDIX

A. VASCULIS PLANT TAXA PRESENT IN STUDY PLCTS . 124

B, STANDI13 ;ROPS OF DRO MASS AND NUTrTTS . . 130

1ETB PAPHICAL SETCrH . . . . . . . . .















Abstract of Dissertation Presonte~ to the (raduite School
of the Universitv of 7lorida in Partial F lfillmeon' f the
Requir3en2ts for the Degree of Doctor of Philosophy



THP IIPACr DF WET SASSDN AND DRY SEASON ?PFSCrT'D) "TiP
3N rEA1I aOCK RIDGE PINELAND, SOUTH PLOISDA


qV


James R. Snvyer


August 1984


Chairman: Join J. Ewel
Major Department: Botany



In the subtropical pine forests on oclitic li.mstone in

Dade Countv, "lorida, "inu3 elliottii var. 3easa qrows over

a species-cizh unaarstory (> 128 sop.) 3f shrabbh hardwoods

(mostly tropi-cl evergreen species palms, and herbs,

including several endemic taxa. Fires prevent rapid

conversion to hardwood forest. To compare the response of

these pinelais to burning during the lightning Cire season

(hot, wet, summer months) and the management fire season

(cooler, drier, winter months), aired burns were condnc't?

at two sites in Rverglades national Park, one bi=rnd 3., vr

previously and the other 5 yr. Aboveground inderstory








biomass and attriants were measured immediately before and

after, and it 2, 7, and 12 mo after the four burns.

The burns topkilled all the understory vegetation. Thp

fires volatiLizel 1-1.5 kg/m2 of organic matter and 5.7-".

g/m2 of N. Meteorological inputs and symbiotic and

nonsymbioti Efixation should easily replace N lost in the

burns. Losses of P, K, :a, and Ig were not letectable

except for K in one of the burns.

The rapil un]irstcry recovery was almost entirely

vegetative rgrowth of the topkille9 plants. 'ine seenlin4

were abundant after the wet season burns, however. fera;

and palms recovered dry mass more rapidly than hardwoods an,

reached prebucn levels within 1 yr. Hardwoods recovered

only, 18-39% of their preburn biomass. Total understory

vegetation re3ovecy was 27-63: of initial amounts, but

leaves rpecovceI 58-931. Net primary prodlctivitv t'- first

year after burning was 144-200 g/m2.

Recovery if nutrients was more rapid than bioass because

of higher nutrient consentcations in regrowth tissues. Some

herb and pall nutrient standing crops reached preburn levels

within 2 mo.

After the burns litter mass and nutrients often showed an

initial decrse before recovery began, kt 1 vr litter iass

was 42-62" of the prebnrn amount. Annual pinon no1=lef-ll

averaged 260 and 320 g/m2 at the two sites,










The iaouat ff hacrwood recaverv was not determined by

season of burning; higher fire temperatures (wet season b'rn

in one case, 3ry season burn in the other) resulted in less

recovery.


























































viii


1














CRAPTER I
INtODUCTION


The importance of fire as an environmental factor

influencing ecosystem structure and function is widelv

appreciated today (Ahlgren and Ahlgran 1960, KozlowsIi and

Ahlgran 1974, Moanev et al. 1981, Rundel 1981, Wright ana

Bailey 1982). Fire is often thought of as a succ-ssion-

initiating listurbance (White 1979). However, in

communities that iave evolved under a regime of frequert

fires, it is tie exclusion of fire that may result in

3raiatic--if not su3ian--changes. Much of sonth?-stern

U.S., particularly the coastal plain, is covere wvith

vagatation that requires periodic burning (Chris~'nsn

1981). lany southern pine forests, for example, levelon

into hardwool forests in the absence of burning warren n

19u3).

The regrowth vegetation in some frequently burned '

ecosystems comes Erom seeds present in the soil or release!

from killed plants. gore commonly, however, individuals

survive and sprout back from belowgrouni parts. In

chaparral it is common for species to show mixed s'-1ling

and sproutinJ recovery mechanisms (Keeley and Koeley 1991).








Fire is very prominent in South Florida ecosystems, both

in terms of area burned and as a leterminant of vegetation

pattern (,obertson 1953, Wa3e et al. 1980). Of particular

interest in this study are the subtropical pinelands founi

on the Milni Rock Riige in southeastern vlorida. These Dine

forests differ Erom other southeastern coastal plain oina

forests in two ways: they include a large number of

tropical species in the understory and they grow directly on

a limestone substrate nearly devoil of soil.

Prescrib.l fire is used throughout the southern nine

region for site preparation, fuel reduction, and range

improvement. It has also become a tool in natural area

management in places such as Everglades National ?ark. Tn

most southeastern pine forest types (with one maior

exception) fire loes not kill the canopy trees as it locs in

many conifernos forests (Heinselman 1973). This, along wilt

its common use for other purposes, may be why the us0 of

intentionally set fires was so readily accepted as

management techniLue in natural areas.

Prescribed burns in the southeast are traditionally

carried out lurina the cooler months because fires durirg

this time are less likely to damage overstory trees and

because the casprouting vegetation provides forage vhich is

otherwise limited at this time. Before the influence of

humans, however, fires were primarily ignited bv lightning,

which occurs during warmer months.








Objectives

i wished to examine some ecosystem-level responses on

Miami Rock Ridge pinelands to fires during the natural

lightning-cuaisd fire season and the traditional nanagament

fire season. T was particularly interested in the

following:

(1) The amount of mineralization and loss of organic

matter and natrients due to fires.

(2) The pattern of recovery of understory mass and

nutrients during the first year after burning.

(3) The degcre of recovery of the unnarstorv 1 yr af'er

burning, viti :mplasis on the recovery of hardwoods.

(4) Rasad on the above items, to draw some conclusions

about the potential role of fire in nutrient cycling and the

use of pres=ribeS fire in the management of a natural area.



The ecosystemm

Climate

The cliiate of South Florida has two salient features:

(1) moderate, almost frost-free winter t=aperatures and f2)

a marked seasonality in rainfall (?ig. 1). These

characteristics result in a hot period of high rainfall

(May-Oct.) and a cooler period of much lower precipitation

(Nov.-April These are known as the wet and Irv seasons,

respectively, in keeping with tropical terminology.











30




;25

w


20

a-

w
15- -









it






.555 F;~ :. .... ..... ,.. .
J F M A M J J A S O N D


Figure 1. Mean monthly precipitation (bars) and
temperature (dots) at Royal Palm Ranger Station,
Everglades National Park (after Rose et al. 1981). Mean
annual rainfall is 146.3 cm.








Mean montily temperatures range from about 18.0oC in

December an3 January to about 27.50C in July and August.

Prosts occur in the homestead area about once every two

years on the average (Brallev 1975). These frosts can

damage winter vegetable crops and production of avocados and

mangos for the ensuing year. Many of th3 native plant

species are also susceptible to Erost damage (Craigheal

1971), soaecially plants in open areas. freezingg

temperatures were recorded during both 1981 and 1982, bit

the study areas were little affected. Only a few of t'h

minor species dropped leaves and none hal stems kili"d.

Total annual rainfall averages 146 cm in the southern

portion of tia Miami Rock Ridge, with almost 90: (117 ca)

coming during the six wet season months (Fig. 1). 7ater

levels vary seasonally with a maximum in Senotaber and a

minimum in Aoril, During the wet season clous" bnil, un iL

the afternoon and result in brief thundershowers; the

lightning that accompanies these storms is a potential

ignition source for wildfires. Although most summer

rainfall is :onve:tional, tropical cyclones can bring large

amounts of rain. In August 1981 Long Pine Key in Everglades

National Pinr received more than 40 cm of rain in thrs dItys

from tropical storm Dennis.

The soutaeastern coastal area of 'lorida can exact a

tropical cyclone once every 5 yr and a hurricane-fnrce storm

once everv 7-9 yr (Gentry 1974). The damage to vegetation








in South Fladria by hurricane Donna in 1960 was substantial,

especially in th~ mangroves on the southwest coast

(Craighead and gilbert 1962). The pinelands of Wveralades

National Park suffrsed little damage in spite of

experiencing wind speeds greater than 160 km/hr. Th? hiah

water levels Orought on by heavy precipitation can affect

the pineland vegetation more strongly than the high vinds.

although South Florida is north of the Tropic of Cancer

(Long Pine Key is about 250 23' N latitude it is commonly

referred to as "tropical Florida," especially hv those

concerned with fl3ristics (e.g., Tomlinson 19i0, Lona and

Lakela 1971). In fact, a world-wiie climatic classification

scheme based on that of Koeppen (Ccitchfield 197u) considers

the southern tip of Florida to have an Aw, or tropical

savanna, linate of the vet-and-dry tropics. It is included

as a tropical climate only because the mean monthly

temperature of the coolest month is greater than 180C. T"-

common occurrence of frost at sea level would perhaps ma~k

subtropical a better designation for the climate. The

classification system of Holdridge (1947), which is based on

temperature ian precipitation, places southern Florida in

the Subtropical Ioist Forest life zone.








Geolo yand Soils

South Florida is extremely flat: a function of its

marine depositional history, low elevation, and relativelv

short periol of emergence. The broad, shallow Pverqlades

basin which ertenis south from Lake Okeechobee is bounded on

the east by the slightly higher Atlantic coastal ridge. Thp

southern end of this ridge in Dade County is an outcropping

of oolitic limestone known as the !iami Rock Ridge (Davis

1943). This region, previously dominated by pine forests,

extends from the vicinity of ?iami southwestward to

Homestead ani westward into Everilades National Park (Vin.

2). The mai[mum elevation of the ridge is about 7 m in

Coconut Grove (Hoffmeister et al. 1967) and it drops to less

than 2 m in everglades National Park, where it disappears

under the surrounding wetlands,

The iiami Limestone (rqoffmaister at al. 1967) which m'ake

up the Miami Rock ?idje is the surface rock of virtulallv all

of Dade County. It represents Pleistocene marine deposition

of calcium carbonate during the Sangamon stage (Cooke 19ac).

The upper oolitic faces which forms the rock ridge is

composed of Doids, pellets, and some skeletal sand. To th=

north along the coastal ridge the limestone is blanketed by

a layer of Pamlico sand, and at lower elevations to the west

and south it may be covered with late Pleistocene or "eccen

marls and pets. Several transverse depressions nassina

through the ridge represent valleys in tha rock that have








been partially filled by deposition of marl and/or organic

matter (igs,. 2 and 4).

The formation of the Miami Rock Bidge is described hv

Hoffmaister :t al., (1967). They compare it to processes

occurring tolay on the northwest section of the greatt Bahama

Bank, where loose mounds of ooids are forming and shifting

in the shallow water on the eastern edge of the Straits of

Florida. The tilal channels that cut through the broal

ridge of unconsolidated oolitic sediment are thought to be

analogous to thos that form the transverse valleys in 1h,

Miami Sock Ridge.

The oolite rock is soft and friable until indurated hv

exposure to the atmosphere. Dissolution of the rock has

left the surface honevcoibed with numerous holes and

fissures, anl armed with sharp, jagged projections. In i's

most treachercus form it is known as pinnacle rock. Th'

diameter of solution holes can range from centimeters to

meters as can the depth, although 0.5 m diameter and 1 m

depth might be common dimensions for the larger holes. The

character of the rock surface varies from place to olace,

with differences in the degree of solution and the amount of

loose rock fragments on the surface.

In the pineland areas of the Miami Rock Pilqe the scanty

soil is founi in solution holes, depressions, and cracks in

the rock. The soils are members of the Rockdale series,

which is classified as a Lithic Ruptic-Alfic -utrochrcpt,






10

clayey, mizel, hyperthermic (Soil Survey Staff 1975), 'he

surface soils range from dark grayish brown to brown fine

sands or fin* sandy loams. The subsurface layers (where

present) are light gray to yollowish-red fine sand and brown

to reddish-bcown sandy or clay loams (Soil Conservation

Service 1958). In the northern portions of the ridge in the

Miaai area, the soils tend to be very sandy due to

deposition oF sands during the Pamlico stage. To the south

there are often reddish-brown residual soils; the

predominance of these soils in the area !ist north of

Homestead is responsible for the appellation "3llands" qivan

to the area. In most areas there is little soil ezposed on

the surface ind plant roots run through cracks and channels

in the rock that are filled with a mixture of organic matter

and weathering products of the limestone. causee the roc'

ridge is the highest part of 'he landscape and is formc of

porous limestone the soils are generally well-drained,

However, high water tables can reach the ground surface in

the lower lying areas during the wet season. The soils are

neutral or slightly alkaline in reaction and are deficient

in N, P, and K for agricultural crops. The fact that the

exploitable soil volume is so small also contributes -n

making this i very oligotrophic ecosystem.

The nearly frost-free dry season makes southern vllrila

in important production area for winter vegetables. Current

farming practices require extensive site preparation before






11

production. After bulldozing off the native vegetation the

surface 15 cm of rock is scarified with heavy eguinment

(rock plowes), resulting in a "soil" composed of a mixtur-

of rock fragnants, pulverized limestone, and a saill iaount

of original soil. This treatment increases the rooting

volume and raises the pa t3 8 or higher. Crops (such as

tomatoes, squash, and pole beans) req'iire heavy

fertilization and irrigation. Experience in Everglades

National Parr suggests that once the substrate has bee-

altered in tais way the native vegetation does not normally

reestablish.



7eVetation

The vngetition of the Miami Rock Ridge is essantiallv a

mosaic of three basic vegetation types: pineland, hamoc',

ani prairie. Te pinelands form the dominant matrix on -he

higher grounI, with small islands of tropical hardwood

forest known as hammocks scattered within this matrix. Tn

the shallow transverse depressions that run through the

ridge are herbaceous prairies, or glades, similar to the

vegetation bordering the ridge. Long (1974) estimates that

the vegetation of South Florida is about 5,000 yr old.

2nsnral dessciptions of the natural vegetation of southern

Florida, including the rock ridge, have been provided by

several authors: Harshberger (1914), Harper (1927), Davis

(1943), Craijhead (1971), and Rade et al. (1990).








hammocks ice patches of closed forest of essentially

evergreen, bcoadleafed trees. They are found in the higher

areas of the ridge; where they are seldom flooded, if ever.

The soil is a thick layer of organic matter that has

accumulated on the surface of the limestone. Tmoortant

canopy species include Nectandra coriacea, Coccoloba

diversifolia, 212E c S IEiriniana, Lysiloma latisi5ionm,

12Metpiu toiferau, Ficus aurea, gBumlia salicifolia, and

Bursera simacuba (Phillips 1940, Alexander 1967, Craighea!

1974, Olmste3 et al. 1980a). Of these only Q, virinia.ns is

not a typically tropical species. The unierstory consists

of saplings of the canopy species, a number of small tree

species, and a a few shrubs. Relatively few herbs are

present on the ground, but epiphytic bromeliads an! -rchis

are quite common.

The seasonally flooded prairies that border the lovwr

fringes of tie pinaland are Dominated bv grasses and sedes

(e.g. juhlenberjia filip2s and Clalium jnamaicens:) but

include numaeous forbs (Pocter 1967, Olmsted et al. 1983).

Here the water table is above the ground surface for 2-'1

3m/yr and the limestone is topped with a thin layer of marl

(Olasted at al. 1980b).

The pinelinds, which oc-upy most of the iami pock Ridge,

are monospecLfic stands of Pinus elliottii var. tn4a, the

South Plorida slash pine, with a diverse understory of

palms, hardwoods, and herbs. The South Florida varietv o.






13

slash pine differs from the commercially important northern

variety (var. alliottii) in several respects (Little and

Dorman 1954a,b). lost conspicuous is the grass-like

seedling stige reminiscent of Pinus palustris (lonqleaf

pine) in which the seedling grows for several years without

stem slongatLon. wavever, Squillace (1965) showed more or

less continuous variation across the range of slash pine for

12 traits, i2cluiing seedling height and stem diameter. "'ho

range of Souti Florida slash pine extends from the Lower

Florida Keys to about Polk County in the center of

peninsular Florila and Levy and Volusia Counties alonq the

Gulf and Atlantic coasts, respectively (Langdon 19A3).

Sandy flatwools are a more widespread habitat for South

Florida slash pine than the limestone of the "iami lock

Ridge.

In contrast to the monotony of the pine overstory, +h-

understory is relatively species-rich. The shrub layer is

composed of 15-25 hardwood species per 0.16 ha (Loope et al,

1979), most of which are tree species maintained as shrubs

by repeated fires; the palas Sabal palmetto, Serenoa reens,

and Coccothrinax ar entata; and a cycad, Zamia numila.

Hardwoods commonly found as shrubs in the pinelands and as

trees in himmocks include letonium toxifarum, Sum-lia

salicifolia, srXEsine flori3ana, Guettarla scabra, anC

Ardisia escallonioides. Most hammock tree snpcies are founI

at least occasionally growing in pineland. Some smaller









shrubs (e.g. Dolonaea viscosa, Lantana de rEEssa, and t.

involucrata) are found in the open oinelanas but not in the

shade of hammocks.

Most of the hardwoods are West Indian in distribution and

are found only in extreme southern Florida or along the

coast to northern Florida. Only a few of the more important

species are founl as far north as Gainesville, 'lorida:

Rhus conalli a, zrEica cerifera, llex cass.in, Persea

borbonia, ini Q!erzus virriniana. Notably absent from th-

rock rid3j pinalinds are llsx lab hp (gallberrv) and members

of the Ericaceae, s3 important in most southeastern

pinelands. Apparently the high soil OH excludes these

species. Tie biogeography of pineland shrubs in South

Florida, including the Miami Rock Ridge, has been detailed

by Robertson in Olmsted et al. (1993).

The herb Layec is dominated by grasses but also contains

seiges, forbs, and three common ferns. The number of herh

species per 0.16 ha varies from 50 to 75 (Loope et al.

1979), The relative importance of hardwoods, palms, an1

herbs varies depending on local elevation and fire history.

In the lower, vwtter pinelands the understory tends to have

fewer hardwoods and has an herb layer that shares many

species with the prairies. ?reaaently burned sits have

better developed herbaceous layers than infrequently burned

sites.








Loope et il. (1979) list 196 plant taxa for the rock

ridge pinelaais, an3 67 of these are restrict!I to pineland

habitats. Tha number of South Florida endemics found in

pinalands (32, 17 of which are found exclusively in

pineland) is by far the highest for any South Florida

vegetation type (Avery and Loope 1980a). All the endemics

are herbs ex~:pt for the shrubs ForestiEra speqceata var.

2inatorum an Laitana L dl erssa (Table 1). South 'lorida

slash pine, although found north of Lake Ckeechobee, is

endemic to peninsular Florida and the Florida Keys.

The pinalians most similar to those of the Miami Pock

Pidge ire those of Pig Pine Key and several other Lover Fnvs

where the Miami Limestone also outcrops. These pinelands

differ mainly in the presence of several tropical hardwoods

characteristic of the Florida Keys or nearby coastal areas

and the oroninence of tree-size~ palms of Coccothrinav

arqgntata and Thrinax morrisii (Alexander and Dickson 1972).

The pinelanis of the Bahama and Caicos Islands are also vsry

similar to those of the rock ridge except that tha pine is

P. caribaea var. bahamensis (March 19U9, Luckhoff 1964,

Lamb 1973). The substrata is weathered coralline limestone

very much lit the oolitic rock of South Florida. many of

the understocy species are the same as those found in rock

ridge pinelinas (Coker 1935, Correll and Correll 198?),

although Robertson (1962) noted the conspicuous absence o"

Sersnoa renens. Even though it grows in an ecological






16


Table 1. Vascular plant taxa endemic to South Florida and
found in Miami Rock Ridge (MRR) pinelands,
including those of Everglades National Park
(after Avery and Loope 1980a).


Exclusively Present in
Taxon in MRR Everglades
Pinelands National Park

Amorpha crenulata *
Argythamnia blodgettii *
Aster concolor var. simulatus *
Brickellia mosieri *
Chamaesyce conferta *
C. deltoidea var. adhaerens *
C. deltoidea var. deltoidea *
C. garberi *
C. pinetorum *
C. porteriana var. porteriana *
Croton arenicola
C. glandulosa var. simpsonii *
Dyschoriste oblongifolia
var. angusta *
Evolvulus sericeus var. averyi *
Forestiera segregata *
var. pinetorum
Galactia pinetorum *
G. prostrata *
Hyptis alata var. stenophylla *
Jacquemontl curtisii *
Lantana depressa *
Linum arenicola
L. carter var. carter
L. carter var. smallii
Melanthera parvifolia *
Phyllanthus pentaphyllus
var. floridanus
Poinsettia pinetorum *
Polygala smallii *
Schizachyrium rhizomatum *
Stillingia sylvatica ssp. tenuis *
Tephrosia angustissima *
Tragia saxicola *
Tripsicum floridanum *








setting virtually identical to that of the roci ridge, .

caribaea vic. bahamensis do0s not have the grass-like

seedling stage that characterizes South ilorida slash pine.

It should be noted that for many years P. gll.l-tiii o

southeastern U.S. was considered the same species as P.

caribaea of the West Tndies and Central America P(Little ard

Dorman 1954a,b)



Fire Fcology

The rock cidge pineland, like most southern pine forests

(!arran 1943), is a fire-maintained vegetation type that

develops into hardwood forest in the absence of turning.

Robertson (1953) estimated that within 15-25 vr of the

cessation of burning, open pine forest would become sensee

hardwood focSst (hanaock) under a stand of relic pines; this

happened in a small area of pine forest in 7ver la=s

National Pack that was protected from fires by the

construction of a road (see photographs in Wade et al. 10)0,

p,93), Alaian~ic (1967) documented the rapid succ-ssion o'

pineland to hammock elsewhere in the rock ridge. The

succession to closed hardwood forest results in the

elimination of sose shrub species and the rich herbaceous

flora characteristic of pinelands (Loope and Dunevitz 1991).7

This is probably due to the reduction in light ceachinq the

ground but it may also ba due in part to the thick

accumulation of organi' matter that is normally removed by








fires. Loops and Danevitz (1981) found fewer species in a

frequently barnel piaeland than in a pineland unburned For

35 yr.

Fires in pinelands are surface fires that move along the

ground consuming litter and understory vegetation. Thp

density of the pine canopy is such that crown fires are

unknown, although the trees can be killed by convectional

heat under severe burning conditions. Prairies burn readily

when sufficient fuels are present but hammocks under normal

circumstan-cs do not. Pineland fires usually burn lin to th"

edge of hammaiks ani go out; however, during extreme

droughts the fire nay smolder through the hammock, consuiin'

the organic soil and killing the trees, Craighead (197U)

suggests that once soil moisture content in hammocks drons

to 351 they ire susceptible to soil fires.

All the species present in thq oinelanis are adapted '

fires. ~lture slash pines are very resistant to fire

because of a thick, insulating bark and the relatively heavy

buds surrounaed by long needles (Hare 1965b, Bvram 19U8).

Both varieties of slash pine are able to recover from 100'

crown scorz= in some cases (Wade 1983, personal

observation). Besides being fire-resistant as an adult, the

South Florida slash pine has a fire-resistant seedling stag

much like lonaleaf pine (Littl- and Dorman lq54a,b). An

accidental fire in a plantation of both var. densa and var,

elliottii seeilings killed a smaller proportion of th? South








Florida variety (Ketcham and Bethune 1963). Seedling

establishmint is also favored by fires occurring soon before

seed fall (Klukas 1973).

The hardwoods in the understory all have the ability to

sprout back after being topkilled. Some, such as Dhus

g oEllia, are prolific root-sprouters, but most sen! up new

shoots from the rootstock at the base of the stem.

generally, few shrubs are tilled completely by single fires.

Robertson (1953) recorded mortality of 0-10" in nine specie-

after a fire. Depending on the funl accumulation and

burning conditions, some fires may have no annarent Cfcact

on larger hardwoods. All the herbs arn perennials that

sprout back auizkly and seem to flower more profusely in

recently burad areas than in unburned areas. Some of t'is

apparent increase in reproductive activity may be lue to

improved visibility or more synchronous flowering, hut thcr

is no question that flowering of many species of grasses is

stimulated by burning (Robertson 1962).

The fire history of the rock ridge pinelands is difficult

to reconstruct with any degree of detail. The use of fire-

scarred trees is limited because of the small number of

suitable traes and the ambiguity involved in ring counts in

South Florida slash pine (Tomlinson and Craighead 1972, Arno

and Sneck 1977, Taylor 1980). The only methodology

available is to deduce from present-day fire patterns and

species attributes what might have occurred in the past.








Lightning fires are a common occurrence today and are

likely to have been so ever since the most recent emergence

of South Plorila from the sea. The lightning is pronuce-

during freqaunt convectional storms during the wet season.

The average annual number of lightning strikes reaching the

ground in the rock ridge region is 4-10 per km2 (Taylor

1980). The =ommon sight of single dead pine trees with

longitudinal fissures running down their bark is testimony

to the high incidence of lightning strikes. In Fverqlad-s

National Part lightning-caused fires accounted for 2P' o'

all fires ini 181 of the park area burned during the peri1-

1948-1979 (Taylor 1981). Almost all these fires occurr?!

within the wet season months of "ay to October (?ig. 3).

During this study (on Aug. 2, 1990) a small lightning fire

burned about 3 ha of pineland near one of the sites.

Egler (1952) assumed a low frequency of lightning fires

in southern Florida and felt that before the arrival o'

people the uplands were covered by broad-leafed forest.

Robertson (1953,1954), whose viewpoint seems to be

substantiate by more recent estimates of the incidence of

lightning--aused fires, felt that the vegetation pattern was

much as seen today. He also argued that the presence of

pineland an!aeics implies a long period of existence of this

vegetation type. Both agree, however, in suggesting that

the arrival of Anerindians about 2000 yr ago (Tebeau 19A3)

brought about a marked increase in fire frequency an' that









60-



40-



20-



0-


M J J A S O N D


J F M A M J J A S O N D


Figure 3. Monthly distribution of lightning-caused
fires in Everglades National Park and prescribed fires
conducted in Long Pine Key pinelands within the park (after
Taylor 1981).


J F M A








most of thesa fires probably occurred early in the dry

season. The arrival of European settlers on the scene

probably r3sulti in an even higher fire frequency

(Robertson 1953,1954). Besides the obvious effect as an

ignition souc-c (or fire suppression agent), modern man has

other more subtle effects on the fire pattern. The lowering

of water levels by drainage starting in the 1920's has

increased tha time that many vegetation types are burnable

and therefore should increase fire frequency. Lowered water

tables also increase the incidence of severe droughts,

resulting in more fires ia organic soils. On th- other

hand, roais, canals, ani other cultural features form

firebreaks that impede the natural spread of fires.



Present xtent and Condition

The Iiami Rock Rilge pinslands originally covered th!

rock ridge from Iiami to near Mahoqany Hammock in rverglae0

National Park. Davis (1943, see ?ig. 2) estimated the

original area cvaered by pine forests to be about 72,900 ba,

although he stated that this was certainly an overestimate.

The area of the Rockdale soil series can be considered an

independent estimate of the original extent of the rock

ridge pinelands. This has been given as 66,700 ha (Soil

Conservation Service 1958) or 62,800 ha (Leightvy t al.

1965).








Today the rock ridge pinelands are almost restricted to

the confines of Everglades National Park. A 1975 survey of

pinalands ani hammocks in Dade County found only 2984 ha or

pinelands outside the national park (Shaw 197r). By 1079

the area had dwindled to 2429 ha (Metro-Dade 1979). Yost of

the pinelands have been destroyed for agriculture or urban

development, Oaly a few areas of pine forest outside of

Everglades iatioaal Park are likely to be preserve! for th"

foreseeable future. The Dade County Parks and Recreation

Department manages three properties with considerable arzas

of pinelani: Larry and Penny Thompson Park (100 ha), ",av

Wells Pineland Preserve (100 ha), and the recently acquired

Tamiami Pineland Preserve (25 ha) which has sandy soil

overlying the limestone (2. Washington, Pade Co. Parks and

Oec. Dept., pers. comm.). There are many other smaller

parcels of rock ridge pinelands in the southern part of the

ridge, but almost without exception they are heavily invaded

by Schinus terebinthifolius, a weedy exotic tree, and are

not properly maintained by prescribed burning (Loope and

Dunevitz 1981).

Although the pineland fire management unit of Everglares

National Park is about 8000 ha (Everglades National Park

1979), plinimetry of a vegetation map of Long Pine Kev

(Olmsted et al. 1983) and topographic sheets of adjoining

areas show tiat only about ~650 ha are in fact pinelands (T.

:aprio, S. Fla. Research Center, pers, comm.). vven within






2aL

the park about 500 ha were lost to agriculture before the

land was purchased by the federal government (?art of th"

area known as the Hole-in-the-Donnt).

Today, therafare, less than 10t of the original rockland

pine forest is extant and under some form of management,

There is a very strong possibility that many of the plant

taxa endemic to the liami Eock Ridge pinelands will be lost

inasmuch as only 8 of 17 are presently found in 7verglades

National Park (Table 1).



Eversladesl national Park

The Dinelinds west of Taylor Slouch in "veralales

National Part, known as Long Pine Key (?ig. 2), are thF only

major area of rock ridge pinelands remaining today. There.

is also a suall amount of pinelann east of Taylor Slough

near the main oark entrance. The Loni Pine Key Din.elann

are dissactel by at least six major transverse prairies adi

contain more than 100 tropical hammocks. The pineland

vegetation is described by Robertson (1953), Loope mt al.

(1979), and 31msted et al. (1993).

Evergliles National Park was dedicated in December 19U7,

about the time that the logging of the pine forest begun in

the mid-1933's was finished. The pine stands fond today

are almost entirely second growth, representing the progeny

of Zcll trees. The initial park fire management police for

the pinelands (and the rest of the park as well) was active








fire suppression, in keeping with National Park Service

policy. This initially resulted in qood regeneration of

pine but probably also allowed establishment of larne

numbers of iardwoods and an increase in size of those

already present.

k park service study of fire in the park carried out yv

Robertson (1953) concluded that fire was needed to maintain

pinalands ani prevent succession to hammock. This led, in

1958, to Everglades National Park becoming the first park

service unit to use prescribed fire. Roads wer= construct-e

to divide most of Long Pine Key into ten management blocks,

Details of fire management are described by Klukas (1971),

Bancroft (1976,1979), and raylor (1981) and in the currentt

fire management plan (Everglades National Par'- 1979). After

the initial buris of the management blocks in the lat-

1950's it was often 10 yr before the next burn; since about

1970 the burning rotation has been shortened to about Fverv

5 yr (Taylor 1981). Until 1980 the prescribed burning of

oinalani was :arried out almost exclusively in the cooler

dry season months (Fig. 3). Since then many burns have be'n

carried out luring the lightning fire season.

Prescribe burning is used by the park service to reduce

fuel loads to "natural" levels and as a substitute for

"natural" fire where oresent-day conditions do not permit

the normal pattern of burning (Everglades National Park

1979). A liEficulty in carrying out this type of management






26

is that ther2 is no explicit sttaement of what constitutes

the natural stat,. Fires caused by indigenous people might

be considered as natural as lightning-caused fires.

It is quite possible that the hardwood understory in the

pinelands af !verglades National Park is today more

conspicuous than it was a hundred years ago. Logging and

the subsequent period of fire suppression may have changed

the balance between herbaceous and woody species. The

prescribed burning program has not significantly reduce the

amount of hiriwools from levels present when the program

began (Taylor and Herndon 1981).















CHAPTER TT
NFTnODS



RFperimental Design and Site Selection

Paired plots were set up at two sites

representative of the rock ridge pinelands of Long Pine Kev,

7verglades National Park. One randomly selected member of

each pair wa3 burned during th wet season of 1990 an~ the

other during the dry season of 1980-81. The burns ver-

intended to be is similar as possible except for air

temperature ind fuel moisture conditions, which vary

seasonally. Aboveqround understory biomass anr litter were

simple before burning, immediately postburn, anl at 2, 7,

and 12 mn after burning. The aboveground biomass ind

nutrient stocks of the regrowth vegetation were taken to be

measures of ecosystem recovery.

The sites wers chosen to exemplify both the higher, more

frequently barnel pinelands in the eastern end of Long Pine

Key, and the lower, less frequently burned pinelands to the

west. The choize was restricted to areas that had been

unburned fir a long enough period that sufficient fuels for

complete burns were present. Pineland managsennt blocks T

(site 1) anl E (site 2) were chosen as appropriate sites

(Fig. 4).















a),-

4-O)


0
0w 0

a
0 0 0

-0 *
0 4-1
P4 Z



I-I (o



<4 0
4 m0






> 0)rd
I S. *


o4

j r. 0 M-
-r Co



SEl =M 0-





z Ow to)
OOt








mm OO







o n

41O
0
4 '04
4 a0
-rl 0 01































00
-- .4a
01-I















3 4-'






29

Site 1 contains some of the highest ground in Longq ine

Key and hal been burned more frequently than any other

management block (burns in 8/57, 3/63, 2/63, 12/99, 3/71,

and 11/77). The shrub layer at this site was generally

below 1.5 i, with few hardwood stems greater than 2 cm

basal diameter, and there was a well-developed herb laver.

Site 2 was the least frequently burned management block

(burned 1/59, 4/69, and 1/75) and is in an area where th?

water table occasionally reaches the ground surface. The

hardwoods at this site were larger, often 2-3 a tall, ani

basal diameters of 3 cm were common. Solution holes are

common in site 2 and there was a less well-develooed herb

layer than it site 1. The pine canopy at site 1 was made

up of larger, more widely spaced trees than those at site 2.

The criteria for plot locations were that they ba arhas

of at least 3.5 ha with relatively homog0neons overstorie-

and understocihs. The plots (Fiq. L) were located near

roads (but > 5 m away) for ease of access and to simplifv

the development of firebreaks.





The Burns

The burns were conducted at last 3 a after a rain when

conditions met the criteria of the park fire management

plan, including wind direction and air quality standards.

Prescriptions were kept broad to insure that the burns coul







31

be done close to the intended date. Fires were set on the

leeward siles of the plots because backing fires arp more

easily controlled and are less likely to cause crown scorch

in overstory pines than head or flanking fires. All burns

were conducted nier midday by the park resource management

staff.

Preburn faals ind the material remaining after the 'urns

were collected as part of the biomass and litter sampling.

Wine-fuel-m3istrwe samples (material < 7 mm diameter in 0.25

m2 quadrats) were collected during the burns and dried at

7003. Relative Eire temperatures were measure with plates

placed at ground level, 0.5 m, and 1 m on 12 poles at pos--

burn sampling locations. The plates were made by spotting

temearature-sensitive paints (Tempilaq, Tempil Div., "ig

Three Ind.) on steel plates (75 X 130 X 2.5 mm, 250 7).

The paints had maltinq points of 52, 70, 93, 1'1, 121, 1 ,

149, 177, 203, 232, 263, 298, 302, 316, 343, 371, 3o1 427,

and 45 oC according to the manufacturer's soncifications

(but see 9obbs et al. 1984). The large mass of the Dlates

tends to depcess the maximum temperature registered by the

melting paints so that they more closely reflect

temperatures experienced by the heavier vegetation rather

than maximum flame temperatures. The resource management

staff measuraS ambient air temperature, relative humi'it7,

wind direction and speed, and rate of spread. "irelin-

intensity was calculated by assuming a heat yield of 14,000







31

kJ/kg of fuel (Wide 1983) and using the following equation

(Brown an? Divis 1973, Wade 1983):


I = Hwr


where I is fire intensity in kW/m, H is heat yield in kJ/kq,

w is mass of fuel consumed in kg/mn, and r is rate of spread

of fire front in m/s.



Atbs2erounl Mass Samoling

Vegetation anl Litter

Abovegrouid understory vegetation and litter were

!sstructively sample! for rry mass. The sampling was don=

in 60 X 80 m plots (0.u8 ha) subdivide! into 12 20 7 20 a

subplots. Within each subplot, potential sampling

quadrats were arranged in a grid pattern. At sito 1 there

were 16 2 X 2 m guadrats and at site 2, nine 3 Y 3 n

quadrats available per subplot. 4t each sampling period two

randomly chosen quadrats per subplot were sampled at site 1

and one quicrat per subplot at site 2. Therefore,

approximately equal areas were sampled in both sites, but

larger qualrits in site 2 plots were used to reduce between-

guadrat variance. Buffer strips 3 m wide between quadrats

permitted movement through the plots without disturbing

sampling sites.

l11 plants ware clipped at ground level exceDt palms

which were clipped at the base of the petioles. In LonT






3?

Pine Key Sibil aLimett, anid occothrinax arqentata usually

have little stem projecting ab-ve ground, and although the

horizontal, creeping rhizome of Serenoa reo-ns is often -on

top of the rack substrate, it is generally unaffected hb

fire and is Eunctionally much like a belowgronnd structure.

Shrubs and palms were collected from the entire quadrat.

eHrbs and litter were harvested only from 1 7 1 m quadrats

nested in tha nW corner of the larger shrub quadrats. Tn

the site 2 plots, herbs and litter were sampled from an

iiditional 1 X 1 a 7uadrat in the S7 corner of the shrub

gaadrat beginning with the 2-mo postburn sampling. Pinp

seedlings were counted in the herb and litter quadrats.

Litter was defined as any dead plant material

iientifiable as to origin, essentially the L and 7 forest

floor layers of the older forest soils literature F(ritchett

1979). generally there is little humus material (U lav-r)

present in Long Pine Key pinelands because of frequent

fires, but in site 2 especially there were occasional

pockets of well-3ecomposed plant matter. A prominent part

of the litter after a fire in these pinelands is the

standing deal hardwood stems: these were sampled from the

entire shrub aualrat. Dead palm fronds were included with

forest floor litter in the 1 X 1 m quadrats as were any pipe

needles draped in the understory vegetation.

The harvested material was sorted into various

compartments, iried at 700C to constant mass, and weighed to






33

0.1 g. Shribs were sorted by species; leaves (plus rarely

occurring reocodnc:tiv parts) were separated front stems For

the preburn, postburn, and 12-mo sampling periods. PatioleT

ware not separated from blades of palm leaves. Herbs were

treated as a single compartment although record was keot of

all species observed in each plot. Litter was separated

into pine aia non-pine components. In the prbnurn sampling

only subsaomles of litter were separated and the

proportions were applied to total dry mass. At later

sampling periods pine litter was further subdivided into

needles and other pine and the non-pine litter was

categorized as herb litter, forest floor shrub litter, inl

standing dead.

Por nutrient analysis, vegetation and litter from three

adjacent subplots were bulked by tvoe and a large subsamle

kept. In general the categories were the same as those

reacrded for mass, except that only two or three of the most

important shrub species in a given set of subplots were kept

separate and the rest were combined.

The diameters at 1.5 m (dbh) and height of all pine trees

in each plot were recorded along with the number of standing

dead trees (snags) and stumps. Regression equations from

the literature were used to estimate biomass of the

overstory.








Postburn Ash

Accounting for the mass and nutrient content of the ash

following the fires posed a special methodological problem.

The ash was :ollaetel by two methods. The first consist-e

of placing four Petri dish bottoms (9 cm dia., 21 mm dlpth)

under the litter before the burn at 12 nostburn samnlina

locations (oae in each subplot). Immediately after the

fire, covers were put on the dishes and they were taken

back to the lib. The contents of the four dishes from each

location wera caobined to form a single sample. The

aivantag2 of this method is that the samples can he

collected as soon as the fire front passes; a sudden rain

does not prluale sampling. The disadvantages are the

relatively small area sampled and the difficulty in nlacina

the dishes uader all the fuel, especially in an area wit- a

substrate as rough as Miami oolite.

The se;Bon method was to oick up the ash with a small

vacuum (Car-Yac, Black and Decker) powered by a 12 V

battery. At the same 12 postburn sampling locations a I.?

m2 area was vacuumed and the material was transferred to

plastic bigs. This method cannot be used once the ash is

wetted. It is very effective at picking up all the ash, but

there is potential for contamination with soil. 'oth tvpes

of ash samples were analyzed individually for nutrient

content, although N was measured only in the vac-um samples.








Litterfall

The contribution of the pine overstorv to 1indrstor7

littermass and nutrients was measured by collecting

litterfall for the 12 mo post-fire period. Dine needles,

bark, and male cones were collected in litter trays

(galvanized greenhouse flats, 0.187 a2, with drainage holes)

placed two per subplot in each of the treatments. Trays

were also put out in an unburned area of site 2 to see if

burning increased needlefall. The trays were emptied at 2-5

wk intervals inl material from three adjacent subplots was

pooled to give four samples per plot. The litter was ovpn

dried (700:), sorted into needles and other fine pine

material, aid weighed to 3.1 g. All other material was

discarded. The input of larger material which is

inadequately sampled by litter trays (branches and s'ee

cones) was measured separately at both sites. All newly

fallen (un=hicrri) material was picked up from a strip ?.5 r

wide outside the dry season burn plot borders twice during

the year after burning. Collecting was done in 20 m

lengths, resulting in 14 50 m2 sampling areas. Brarcher

were separated iato 1-cm diameter classes before oven drvin7

and weighing. I assumed that branch and sepd cone

litterfall was tie same at both plots in a given site.

Needlefall was bulked by plot for a drv season perio.

(Dec.-Jan.) for nutrient analysis because these samples were

least subject to leaching losses while in the litter trays.






36

The total annual fine litterfall (mostly bark) was bulked by

plot for analysis. The nutrient content of branches and

seed cones was measured on material that fell during a 77 ,1

period lurinj the dry season at the site 2 dry-season plot.

materials from the (three or four) sampling areas on each

side of the plot were combined and subsampled to givP four

samples of each type. The nutrient concentrations of the

2-3 cm branch class were applied to the small amount of

material larger than 3 cm diameter.



Soilsamalinc

Two types of soil samples were collected to characterize

the surface soil (0-7.5 cm) and to detect changes in soil

properties prassat 12 mo after burning. The first type was

samples take from the preburn biomass quadrats in all tho

plots and from the 12-mo quadrats in two of the plots. "en

scoops were taken with a trowel in each subplot and then

bulked to form 12 samples per plot. The sampling spots wero

soaked as evenly as possible in each guadrat, but

considerable searching in cracks and crevices was often

required before a scoopful of soil was found.

At site 1 areas of refdish-brown mineral soil were

encountered La the preburn soil sampling: these araas were

readily apparent after the burns. The extent of these

pockets of "Redlind" soil in the site 1 plots was estina+ed

by line-intercept along the 20 m borders of all subolots






37

(n=31 in easi plot). Because the preburn soil samples wero

heterogeneous with respect to the type of soil sampled, a

second sampling restricted to the Redland soil was done.

oomoosite samples of 10 scoops of mineral soil froa

throughout each of the subplots in the site 1 Iry season

plot were taten 12 m3 after the burn. In the adjacent area

which harnel 5 yr previously composite samples were

collected in a similar manner along 10 m segments of a 120 m

transect. 411 the soils were dried (700C) and sieve~ (2 mn

screen) before analysis.



Tissue and Soil Analvsis

Subsamples (0.5-1 L) of the bulked vegetation and little

material for chemical analysis were ground in a largP Wilev

mill, thoroughly mixed, and store- in polvathvleno bottles.

The ground samples were retried at 700C before wigqhinq.

Nations (Ca, "g, and K) and P were measured on 1.i0 g

samples placed in 50 ml Pyrex beakers and ashed at 5000C for

at least 3 hr. The resiane was dissolved and then brought

to dryness first with 5N HC1 and then concentrated !Cl

before filtering (Whatman No. 42) and bringing to 50 ml

final volume with 0.1 R C1, Calcium and ng concentrations

were determined by atomic absorption, K by flame emission,

and P by automated colorimetry (Mitchell and Sh',? 1979).

Nitrogen was analyzed by a micro-Kjeldahl procedure usia7

0.500 g of litter and stem tissues and 0.250 g of all other






31

materials. lamonium was determined by automated colorimetry

(Anonymous 1977), The cation and P content of the postbhrn

ash was determined by similar methods except that the

residue aftec fishing was dissolved in larger (107-20X)

volumes of acid because of much higher nutrient

concentrations. Following Kjeldahl digestion of the ash,

ammonium was measured by distillation and titration.

As a chaek on analytical procedures, replicates of a

single leaf tissue sample were run with each set of dry-

ashed s3mples. The ropliration was good, with co-ffici n's

of variation of 4.0 3.57, 3.0O, and 2.u' for K, Ca, "7,

and ?, respectively. recovery of K, Ca, and P from four

samples of Nitional Bureau of Standards pine needle tissue

averaged 81X, 1181, and 98% of the values listed for these

elements. There is no published value for 'g. The 7.,.S.

pine needle tissue was run with each set of Kj1ldahl

analyses and always was within 35 of the nominal value,

Soil pH was measured in a slurry of 25 ml of soil an! 50

ml of water eguiLibrated for 30 min. Organic matter was

measured by the Walkley-Blick vet oxidation method on 1.0 q

samples, Citions and P were extracted by the double-acid

(0.05N HC1 3.025N 12504) method and analyzed as for plantt

tissues. Details of methods are found in Mitchell ana Phua

(1979).















CHAPTFP Tir
RESULTS



initial _Veetation Structure

Pins elliottii var. densa was the sole canopy tree

species in all the plots. Both sites had apparently been

logged not long before the establishment of the oark;

numerous stumps still remaining have resisted iore than 11

yr of exposuca and several fires. The density of pinp traes

at site 1 was about half that at site 2, but the mean hasal

area per tree was about twice as large, so total basal area

at the two sites was similar (Table 2). The trees at si'- 1

were also tiller than those at site 2. "any o' the larger

pines at site 2 had misshapen crowns and probably represent

cull trees.

There weca very few pine saplings (< 5 cm dbh) at site 2

and none at site 1 (Figs. 5-7). There were also very few

pines <1.5 m tall that had grown out of the "grass" stage at

either site. Before the burns site 1 had 1.2-1.5 seedlings

(no stem Plongation) per m2 and site 2 had 0.1-0.3 fTahbl

10).

k total of 12q taxa wers observed in the plots during the

course of the study (Table 3, Appendix A). This is a slight

underestimate of the number of species present because some















'a'C
40







SE m CN co in
4- a a co o
0 -4O H

ml

0 0 i-
4Ja 1- vm
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0 Z D m C\ m cN
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IN M -

>
oC 0 in I N 0
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4-z il E!a H m r ;
0-4 a '- IN IN -i -I
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Li-S -
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a-H
r II(1
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LL 1
LU

5-

O

s 10-








0 5 10 15 20 25


20-
SITE I
DRY SEASON
OI 5 BURN
LUF
O
I-
-0 -15 20 25
I t.
0

LLJ 5
O -




0 5 10 15 20 25
DIAMETER CLASS (cm)

Figure 5. Size-class distribution
the site 1 plots.


30 35


of pine trees in










65



60 -



55



50-



45 SITE 2
WET SEASON
BUPFr

40- 11



I 35


30
LL


L 25


z20
0 -



15


10 1
5 -








0 5 10 15 20 25 30
DIAMETER CLASS(cm)

Figure 6. Size-class distribution of pine trees in
the site 2 wet season burn plot. Unshaded bars represent
trees dead at 1 yr postburn.
























SITE 2
DRY SEASON
BuRN


0 5 10 15 20 25
DIAMETER CLASS(cm)


Figure 7. Size-class distribution of
the site 2 dry season burn plot. Unshaded
trees dead 1 yr postburn.


pine trees in
bars represent


55[



50-



45-


40-



35-


30-



25-


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/-

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I0-


















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nct
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ru


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r-I m r- -p in (N
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HIfl 0(N 0
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ED U 4-0 4- 41 4-
a) 0 -I 3 > r r a









uncommon spazies were probably missed and because a few

herbs were identified only to genus. Within the herbs the

Asteraceae, Poaceae, Euphorbiaceae, and Fa'acea- were

particularly well represented. ?ive shrub species arT

members of the Babiaceae, which contributes an additional

four herb species. Other important shrub families

reflecting tie tropical origins of the flora include the

Arecaceae (piims, 3 spp.), Anacardiaceae (4 sop., including

one exotic), Sapotaceae (3 spp.), and Myrtaceae (3 sup.).

The overall soecits richness dii not vary much hetve-n

sites: however the site 1 plots had higher herb speci-s

richness and the site 2 plots had higher hardwood species

richness. This pattern may be due to characteristics of

the substrate and the close association of the site ? olnts

with hardwood haamocks that aan serve as seed source's: it

could also be due in Dart to more frequent burning o' site

1. Some herbs in site 2 are restricted to the w=tter

microhabitats in solution holes (e.g. Cladiun jamaicpnse

and Thelzpteris kunthii) and some grasses and sedoes at sit"

1 seem to be found only in the patches of ?edland soil (e.g.

hznchoshEorE a E bulais and Desmodium lineatsm). The

hardwood species found in site 2 and not in site 1 are

mostly species characteristic of lower, wetter areas (e.g.

chersobalanus icaco and Ilex cassino) or species found in

nearby hammocks (e.g. Ccccoloba liversifolia and Ivsiloma

latisiliqia).






U6

The pine overstory clearly dominates the vegetation in

terms of bionass (Table 4). The understory vegetation, in

which the hardwoods are the dominant component, made up 6f

or less of tie total aboveground biomass. The understory

vegetation is much more important in terms of nutrient

content because so much of the overstory biomass is wood,

which has low nutrient concentrations.

Although herb species richness was due largely to forh

species, grlminoais in general contributed more to hbrb

biomass. Prominent grasses include Schigachvria rhioemat'li

(a South F.icida endemic) and An rop2aon cabanisii. Tho

major exception to this was occasional patches dominated by

the fern PtEriLm aguiliaum at site 1. The relative

dominance of the understory shrub species as expressed by

percent biomiss is shown in Figure 8. Puettaria scg-hr wpa

the lominint species at both sites, but less so a+ sit= '

where there were more species. At site 1 Dodonaaa viscose

was the second most important species, a position held by

Evrica cerifers at site 2. At site I the top two species

account for about 55X of the shrub biomass, and at site 2

only 41g. The palms Sabal nalmetto and Sgrenoa renens are

among the top ten species at both sites, but S. reoens is

more important at site 1 and S. palmetto at site 2.

occzothriqnax ar ntata is rare at site 2 an' is nuch less

important than the other two pals at site 1. The biomass

relations of the palms are a reflection of their densities
















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m+I+
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0 o.5
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0.1 WET


0.05
DRY



WET
0.0 I I I I I I
I 5 10 15 20 25 30 35

SPECIES SEQUENCE

Figure 8. Dominance-diversity curves for preburn
shrubs in the study plots. Circles = hardwoods, squares =
palms, and triangles = Zamia floridana. Site 1 plots are
represented by closed symbols and site 2 plots by open
symbols.








at the two sites (Table 5). Zania Epuila had the eighth

highest preburn biomass at site 1 but was rare it site 2.



Burn Descriotions

The wet season burns were carried out under conditions of

relatively iigh ambient temperatures and humidities,

although the nfel moisture of the site 1 wet season plot was

as low as the dry season plot (Table 6). The site 2 vet

season fuel was such moister than the dry season fuel.

All four burns resulted in 100? topkill of the unacrstory

vegetation, wita minimal canopy scorch. About 707 of ''=

fuel was consumer in the burns except for the site 2 wet

season burn in which high moisture content reduced

consumption to about 50%. The ash resulting from the burns

formed a thin, discontinuous layer on the cock surface un'il

the first posthucn rain washed it away.

The rate 3f spread of the fire front was less than 1.5

cm/s arcapt for brief head fires during wind shifts in the

site 1 dry season burn. The intensity of the burns was

within the optimum range far prescribed fires (73-260 kW/m,

Wade 1983) recept for those brief periods in the site 1 ric

season burn that resulted in the scorching of about 10 of

the crowns.

The averij3 fire temperatures recisteres by the

temnerature-sensitive paints varied significantly aeong t'=

burns (Table 6). The site 2 dry season burn, where the







50





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greatest amount of fuel burned, had the highest

temperatures; however, the ground-level temperature was not

significantly different from the site 1 wet season burn.

The ground-level temperature of the site 1 dry season olct

was lower thin the w-t season plot, probably because of

lower ambient temperatures and the more rapid movement of

the fire over th? plot. Temperatures decreased with height

above the grannd, although this pattern was least pronounced

it the site 1 dry season burn.



Fire -ffects on gUn.erstory ass and Nutrients

Initial )istcibution of Mass and Nutrients

The relative Jistribution of the preburn fuel mass amonq

live understory vegetation, understory litter, and pine

litter was similar in all four plots (Figs. 9 and 10). ?Pi.

litter account-3 for 50-70L of the mass and liv2 vpegtation

for 251 or less. The distribution of N and Ca was similar to

mass, but Mg, P, an3 especially K wero relatively high in

the live vegetation. In fact, 75-80 of the K in the fu1e

was containal in the live vegetation. Potassium is easily

leached and gaickly lost from dead tissues. Within the live

vegetation hardwood shrubs were responsible for > 507 of the

mass and nutrients, more so at site 2 which had not b'rne~

for a longer time.

























































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Ash Collectian methods

There were no significant differences between postburn

ash colleztipn methods for mass, nutrient concentrations, or

nutrient staiiing croos in the site 1 burns with a single

exception: liighr 3g concentration by the Petri dish methfo

from the dry season burn (Table 7). There was, however, a

consistent pattern of higher mean nutrient concentrations in

the ash collected by the patri dish method. A light rain

falling near the end of the site 2 wet season burn proclud=d

the collection of ash by the vacuum metho feor that hurn.

In the sita 2 dry season burn the estimates of ash mass ani

all nutrient standing crops were significantly higher for

the vacuum 2eth3]. The tendency for higher nutrient

concentrations in the petri dish ash was also found here,

with only Mg significantly higher. Apparently at site 2

substantial aaounts of unburned humus and/or mineral soil

were pickz1 ap by the vacuum. This would account for bo+h

the higher mass and the tendency toward lower nutrient

concentrations. Because of the larger surface area sampled

by the vacuui method, it produced smaller coofficients of

variation for mass and nutrient concentrations in 14 of 15

cases.

The dry mass and nutrient cationss and P) values froi the

patri dish acthoi were used to estimate postburn starling

crops because they were available for all the burns anJ

because vacaui samples gave over-estimates at site ?.

















4-1







4*-)
**>o N *T i^ co
r4 14
fC N- 0 o 9C 9 0 0 0 00 N CN N -
C N C ( N *
0 O 0 0 0 0 0 O x a a t s 1
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C .. m ,o
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02I N N) N N N (N (N D a O




NJ No 0^ '' -' N N
+91 S N 19 0 .9 0 N .9 N .9

020 9 '0 &
02 i 0 I .9 I I CM ++ N +l (N U, +
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N O l +i N +i l9 I M [- l n m o 9 9 + (


O 0 N U,0

















wu w
(9 NN N U U N ON C .
E N U N U IF 9~ 9 NI




'C) ., 42 o 2 2 *I



0 u +9 +9 + +9 +i +0 +9 U, m (N

I+iO N NP N^ No N- (N N- +9 o 0 +9
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9+ (N .90 (N
(N Nl 0 U . -o- c
aC >uIC +9 +9 +9 N N N -
(990. Ul U,' NO N NO M (NO.9
02 Q C ) I r CT co ul r~

C0 U'' C U' '
-j02 .9 C) C +9+9) C 0 -5) E e C


+9 +f1 Cr '4 14 C CCC + .9 +9. 39 C C
. -i ,? U' C^ E' C^ N*- U' C" U ^
rl ., I- I 3 D -
a vll X: E. +I U J U +1 *











024 w '9 '9
04 in r a u
fa n3 o











00 C U
C (99 +4 J >. +9 .99

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~ 3 n 01 3 CJ 3 kj

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.fl +9 (N (N +

02 .4 E .









Nitrogen in ash was estimated from the mass an? nutrient

con7entratioa data collected by the vacuum netheo. Since

these data iare not available for the site 2 v t season

burn, the meB n J concentra ion for thm site 2 3rv s-ason

burn was applied to the wet season oetri dish estimates of

ash mass. Tie estimate of N in the postbcrn ash at tbh sito

2 dry season burn is undoubtedly an over-estimate and

thicefors qi4?s a conservative estimate of the loss of for

that burn.



Postburn istribhution of !ass anj Nutrients

lost of tie litter (except for the heavier pine branches

and cones) was consumed in all tho burns (iqs,. 9 and 101;

in the site 2 wet season burn considerable amounts of th?

oartiallv lo3ompos lovwr layers of litter in '~oressions

wrea also left. Yost of the preburn vegetation di- nomt qrn

ercept in the s[ta 1 wet season burn where sliqhtlv morn

than half wvs consumed. Herbs were almost completely

consumed in the burns (exIcpt for petioles of teridiun),

but shrub stams ian most leaf material remained. The shrub

stems that remained upright became the standing dead

compartment of the nostburn litter. The blad-s of paln

fronds were often at least partially consumer but the

patiolbs did not burn. rhe 78-95 g/mn of postirrn ash

accounted foc 9-2;- of the mass remaining after the brrs.







5P,

The losses of nutrients from the litter and vegetation

were roughly proportional to the losses in mass (pies. 9 anP

10). one-haLf or more of the standing crops of the non-

volatile elements other thin K were found in the ash after

the burns. A large proportion of the K remained in thi

dead, but unconsumed, vegetation (mostly shrubs). The

nostburn distribution of N was similar to the nosthurn

distribution of mass.

The overall losses of organic natter from the ecosystem

ranged from bout 1-1.5 kg/m2 (Table 8). The losses of 7

ranged from 5,7-9.5 /ma2. There were no sijnificane

differences between preburn and postburn standing crons of

the non-volitLle elements except for a loss of K in the sit?

1 wet season burn. This represents one of 16 tests (at 0.0~

level) for nonvolatile nutrients and may bh a falss

rejection (i,e, a tvoe I error). There is li'tl- re:-so '

exoect detectable losses of K in relatively cool fir-s sIuch

as these,



Postfire Pecoverv of ahss and Nutrients

VYqetation

Although abovaground plant parts were killed hv the

burns, I observed almost no plant mortality. r'e of *he

most striking feitur-s of th= postburn period was the rail

reappearance of green tissues, especially herbs anl nalis.

Within days aftar the burns fresh blades of grass apnear"-












>1

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from the ground and palm fronds pushed out from the stem

oices. f arwoon recovery began somewhat later.

Essentially all the recovery during the first year was

ieu to snrouting from belowground parts. Among the

hardwoods only Dodonaea viscosa and Rhus sooallina hai any

seedling regeneration, but this contributed an insignificant

amount to tta total recovery. The seedlings probably came

from seeds present in the soil or litter before the iurnm;

both genera are known to have fire-stimulated germination

(Ploy 1966, larks 1979). 7o data on reproductive activi'v

were taken, 3ut luring the year following brr.in7 I o'bserv

flowering of every herbaceous species Dresent in t'he plots.

Within a aoith after the site 1 wet season burn inellia

caroliniensis was flowering and by 2 mo 15 aliitional

snesies were in flower. productivee activity of palms was

not noti.Ze-bly different in bu n unbrn ai na? ar as. Mo t

hardwoods dil not flower during the first year after %rning

except for t1e weakly woody Lantana devrossa, 1orinda rovoc,

and Zcoton line ris. Occasional individuals of Psidium

lon2!ai2S 3lrsonima lucida, Iodonaea viscosa, anI Ficus

zitrifolia also flowered within the first year.

Harbs reached their preburn biomass levels within 7 mo

following dry season burns and hy 1 yr after wtt season

burns, even though the 2 mo recovery was grea +r after wV

season burns (Fig. 11, .ppendix B). In all four of the

plots palm biomass by 7 mo was statistically







61

indistinguisiable from preburn amounts. Hardwoods recovered

more slowly than herbs and did not approach their preburn

levels by thE eni of the first year. Recoverv a' 1 yr

ranged from 19-39' of the orebturn biomass, Certain hardwood

species sprouted sooner than others (D. viscosa and 2.

c2Eallina wece two of the earliest). Hardwood biomass

increased at each of the sampling periods following wqe

season burns, but showed no increase from 7-12 mo after th

dry season barns (Fig. 11). The overall pattern of r;coverv

indicates that koril to August is a more favorable qrowi-r

p~riol than the rest of the year.

Before the fires, stems accounted for most of the

hardwood biomass, whereas 1 yr after burning leaves

accounted for equal or greater amounts than stpas (Appendti-

3). ar.wn33 Leaf biomass recovered to 32-68- of t.h

prehurn biomass but stems reached only 12-2' oi' *he

original amounts. The preburn stems, of course, represent~?

the wood increments of 3.5-6.5 yr of growth.

The relatively rapid recovery of leaf biomass combinoI

with complete recovery of herb and palm biomass means that

the functional capacity for photosynthesis recovers faster

than tha structural characteristic of biomass. If ons

assumes that the sum of herb, palm, and har-wood leaf

biomass is a measure of ph3tosynthetic capacity, then t"- 1

yr recovery of the vegetation for wet and dry season burns

is 82 and 93t at site 1 and 74 and 58' at site 2. The









corresponding recovery of total vegetation biomass

(including hardwood stems) is 55, 63, 41, and 27?.

The above7rouad net primary production of the unerstorv

for the first veir after burning can be estima-ed ty adding

the litter produced during the year to the standing crop op

biomass at the and of the year. There was no palm leaf

litter an! little hardwood leaf litter produced during the

first year, iad this litter was not measured seoaratelv from

the hardwood litter resulting from the burns. There were

substantial amounts of herb litter produced hv I "r

(11.7-39.5 I/a2, Appendix B). Fstinates of not production

are 156 and 166 1*m-2+vr-I for wet and dry season turn plots

at site 1 ani 20) and 144 g*m-2*yr-l for wet and dry season

burn plots at site 2. In addition to the few hardwood

leaves shEt1 y 1 vr and the loss of mass by herb litter

through leaching and decomposition, herbivor' is also not

accounteS fcr vb this estimate. Grasshopnprs anq

lepidoptcran larvae were the most conspicuous invertebrate

herbivores; the caterpillars of the echo north (Sqirarri-

echo) grazea the young leaves of Zamia Eamila vary heavily.

I also witnessed four white-tailed deer feeding on the voung

regrowth of 3a0 3o the plots.

Because tie herb and palm biomass 1 yr after burning wr-'

not significantly different from their preburn values, th=re

is little evidence that the season of burning had an effect

on their recovery. Variability in the data nake it









impossible to detect small differences that miaht have a

cumulative effect after several burns.

Rardwoods, on the other hand, showed arkd differences

in recovery among the four plots. The absolute recovery of

hardwood bianass was greater at site 2, but that site had a

nmuh higher initial hardwood biomass. At site 1 the

hardwood recovery was significantly lower following *he wat

season burn (29 ;/ma or 20) than the dry season burn (f?

g/m2 or 39f). At site 2 the trend was reversed, with

greater recovery after the wet season birn (137 7/m2 or I"1)

thin the dry season burn (78 g/m2 or 18!) Th? most~ li'=lv

explanation for this apparent inconsistency is that fire

temperatures had a greater effect on recovery than season of

bnrn.

The recoverv of nutrients in the undzrstorv veetation

followed a pattern very similar to that of biom~ss ficn.

12-16, Appealix 5). The maia difference was the somewhat'

faster rate of recovery because of elevated nutrient

concentrations in the young regrowth tissues. The recovery

of Ca, however, was delayed somewhat relative to biomass

because the 2 io tissue concentrations of palms and

hardwoods were lower than the preburn concentrations. Herbs

in particular often reached preburn levels of nutrient

standing cross earlier than biomass. For exarple, ?

standing cron in herbs was not significantly diff-rent fro?

the preburn amount for both dry season burns at only 2 mo












OTHER
SHRUBS


WET SEASON
BURN


GUETTARDA
SCABRA


200


E
S150



2 100
0
m


50



0







200



S I 150
E


U)


o
0
0

0


WET SEASON
BURN


0 2


12 0 2
MONTHS POSTBURN


Figure 11. Postburn recovery of understory biomass.
Bar on left shows preburn values.


S456

















cU 1.4
E
0 1.2

WZ 1.0
(0
0 0.8
I-

Z 0.6

0.4

0.2

0




2.0

1.8

1.6

S1.4
E
o 1.2



0 0.8
h-
Z 0.6

0.4

0.2,


3.3 7
-S3


SITE 2

DRY SEASON
BURN


12 0 2
MONTHS POSTBURN


8 12
8 12


Figure 12. Postburn recovery of nitrogen in understory
vegetation. Bar on left shows preburn values.


0 2 7 12 0 2 7


3.02






























0 2 7


0.164


0 2


SITE I

EASON DRY SEASON
WN BURN
















12 0 2 7 12

SITE 2
J 0.167
SON 7 DRY SEASON
BURN
















12 0 2 8 12
MONTHS POSTBURN


Figure 13. Postburn recovery of phosphorus in under-
story vegetation. Bar on left shows preburn values.











SITE I


Cu
E 1.2-
-^

1.0-


S0.8-
N .-


O 0.6-
a-
0.4-

0.2-

0-




1.6-

1.4-


S1.2-
E
o, 1.0-
-

2 0.8-
U,
0.6-
--
O
0.4-


0.2-


WET SEASON
BURN


DRY SEASON
BURN


I I
12 0 2
MONTHS POSTBURN


8 12


Figure 14. Postburn recovery of potassium in under-
story vegetation. Bar on left shows preburn values.


SITE 2


[1 - - -


0 2












WET SEASON
BURN


SITE I

DRY SEASON
BURN


2

7.01


7 12
SITE 2


DRY SEASON
BURN


12 0 2
POSTBURN


8 12


Figure 15. Postburn recovery of calcium in understory
vegetation. Bar on left shows preburn values.


OTHER
SHRUBS







GUETTARDA
SCABRA


0 2 7
MONTHS











OTHER WET SEASON
0.35Z SHRUBS BURN


SITE I


0.30

E 0.25
GUETTARDA
0.20 SCABRA

( 0.15
w
Z PALMS
< 0.10 HERBS

0.0 5

0
0 2 712 0 2 7 12

0.788 SITE 2
0.40 WET SEASON 1 0.737 DRY SEASON
BURNBURN


0.30
E




0.2 5







0o
0 2 7 12 0 2 8 12

MONTHS POSTBURN

Figure 16. Postburn recovery of magnesium in under-
story vegetation. Bar on left shows preburn values.






70

postburn; thi standing crap of K in herbs in the site 1 wet

season plot also reached the preburn level by 2 mo. Tn one

case (Ca, site 1 wet season burn) the standing cror was

significantly higher 1 yr aftar burning than before th-

fire. For palms, both N and P standing crops were not

significantly different from preburn at 2 mo for the sit- ?

wet season burn. All other palm nutrient standing crons,

like palm biomass, dil not rcach initial amounts until 7 mo

postburn.

The pattecn of recovery of nutrient stanlini crops in

hardwoods was the same as for biomass except thit K at 'lh

site 1 dry season plot at 7 mo and the site 2 wet season

plot at 12 no were not different from the prpburn amounts.

The percent recovery of all nutrients in hardwoods at 1 vr

was greater than th? corresponding biomass recovery tecausn

of hiTh nutrient concentrations. The Dercent recovzer7 o

the total -veg;attion nutrient standing crops was greater

than the reco7vry of biomass for the same reason. Th- t

standing crops in the two dry season plots at 1 vr ware not

significantly different from the preburn standing crops,



Litter

The standing :rop of litter sass (and nutrients) iurin-

the 1 yr postbura period is a function of the amounts

present immediately after the burns, inputs, and losses

through learning and decomposition. Even though nearly all






71

of the preborn understory litter was consumed in the burns

(Figs. 9 ind 10, Appendix B), the understorv vSgatation that

was killed bat not consumed by the fire replace, it. In th?

dry season plot in site 2 there was actually more after th=

burn than before, The understory litter compartment

received no inputs for several months until herbacouss

material h-gan to die. By tho 12 mo sampling nerioi some of

the hardwoods had also shed some leaves. At 1 yr some ')

the oldest palm fronds were becoming senescent, buit were not

dead and therefore not 7et part of the unnerstory li'tor.

There was some decrease in understory litter nass diiin

the first two months after burning in all plots (Annen-li

3) From 2-7 mD after burning the dry season brn lots

showed continued loss of mass (because these were wet season

months), while the wet season plots did not (h=cduse it was

dry). "rom 7-12 mo there was an incrpas3 in Pass excent at

the site 2 Iry season plot where decomposition out'acpe

meager litter production by shrubs and herbs. At si*e 1

much of the input to understory litter is attributable to

herbs.

kt the ead of the first year the standing crops of

understory litter mass were not different from anmonts

present immediately after the burns, except for the si'e ?

dry season plot. however, the standing crops w-r0 h-low

their preburn levels except a the site 2 wet season plot

where there eas a large amount o" unconsumed v=gotation ani

rapid recovery of litter-producing hardwoods.






72

The standing crops of nutrients in the nnd-rstorv litter

shovel various patterns during the postburn year. Larqe

fecreasss often occurred luring the first posthurn rainy

period, 0-2 no following wet season burns and 2-7 ml after

dry season barns. Potassium in particular showed leachinq

losses of >80-90t of the amount in the postburn litter. Fr

most of the nutrients there was some net increase d rini the

7-12 mo periLd. Phosphorus, however, showed initial losses

and no significant change during the last S no period.

"itrogen and Ca showed the least net loss during th- voer

and were not different from the amounts present immediat=lv

after the burns (except for the site 2 dry season plot which :

lost mass throughout the period).

In contrast to the understory litter compartment, which

had no innuts during the firs several months 1cter birninr,

the pin. litter rcecived continual inputs. ?n.c nertle?

fall throughout the year, but at highest rates during th?

wet season (Pig. 17). Short term peaks in neertlfall ar?

caused by high winds. The annual needlefall was about 320

g/mn for site 1 and 260 g/m2 for sit- 2 (Table 9).

Seedlefall constitutes 75-80 of total pins litterfall.

Pine branches, mostly <3 cm diameter, contribute about a

tenth of tha litterfall mass, and seed cones and

miscellaneous materials make up about the same fraction.

Some vear-to-year variation in litterfall is to he Ypex'ect-

needlefall during the study period was about vveraqg a-









SITE I
WET SEASON
BURN
I .0

0.5
, L


I I I


DRY SEASON
BURN



rrTh


UNBURNED


AS J I F M IM I J I J I I I I S I I J I
A S O N D'J FM A M J J A S 0 N D'J FM


1981


1982


Figure 17. Pine needlefall in the study plots and an
unburned area of site 2. Closed triangles show time of burn
and open triangles the 1 yr anniversary of the burn. Absence
of bars means that no sampling was done.


I I I I I I I I 'a I I I I


1.5
1.5 -j


? 0.5


- 1.5

S 1.0

w 0.5"-
_J :


z -
LJ :
E 0.5:

0-


1.5-

1.0-

0.5-

0


1980
















r-H m -lm rl r0 nl rm
A in Z3 mn r' -I CV IT





.T d C r OtoOD -1 C a) 0 -4 m
iLHC- yH(N (NH I.-1 N m LA 0
H- -1 -4 -4 r-4 r-q I H -4 H -4


ra



U)
40
(0









Uo
II
(C







m 0
0)




0>

*H O




UU
r4




o
0 0


4H-




+1 a
u
0



'-M0
rn m



U) 0

4J,4 -I










woe
0 '


aa









E A
5 -


--4 0
0^,0


(U4)











a)


r-4N N o- 0


SO r 7 Ho! NH

O( NH mr(Ln mm (NmN
O r, D 00 o 0


vnW o (NL .N M mmm oor No
a m i m N c m c


SCN N c mm
- W r r- -i
0 r oN- N
rH -4H H H-


oUoa
* i
i L
H U1
+1 +1
n n



m 4


* il r-
N *
(N l (VN
+1 +1 +1 +1
0 00 0 qr

a; 1 r


CN Lo all C) Ln Ch m fi ^> msCN M
[r- (r'- in) OO O()a%-4 m oL r-
N 0 0 0 m 0
r-4 -o o


* 00

m 0
+1+1


o
T (N o
(N m


WDm 0
* ooo o
H ..

+1 +1 +1 +1
oC) ) o-

r-(N a
(N m


0 O


*+ +
N

+1+1




(N m


C $ C r r.
0 0 0 0
Un E Hi a) H U) ) U) 0

r-H *- H *O U (n 4-H H *O- -I U L 4) 4-)
0'0a u 0 a'o r C0 c o ()a 0c0 u 00
0 ) U) E-p 0 ) U) M Z E O Q) UJ O- ww 0 z E-4 (a CE-a
U) w)-4 ( i H 0 U) ) *. a) -. p o o)-1
m (Z Z0U M UZ XE-1 mZxqU a)za



) 0 0
0 o T3 3


S(N (N (N

) a) a) ) a


u 0E m
LA LA LALA


o a


CN 1D
o- o-


0
I-4






S,














4-)
0Q -












0



H
-4>







75

other locations in Long Pine Key (A. Herndon, unpublished

data). The number of seed cones was probably higher than

average, at least for site 1, because there was a better

than average seed crop in the autumn of 1939. The

deposition of nutrients through pine litterfall ranged from

about 2 g/m2 of Ca and 1 g/mr of N to 0.03-0.05 q/m2 of ?

(Table 9). Ine notable aspect of the nutrient inrnts is tF'

high concentration of K and the low concentration of Ca in

pin czones relative to other litter tvpes.

Pine liter mikes up the maior portion of the f'il mags.

The material remaining after a Fir? is mostly heavier pieces

such as branches and cones, unless the fuel is moist (;,4.

site 2 wet season burn). Pine litter mass showed a more or

less continuous increase ercent for the 9-2 mo oerio,

following tih wet season burns where moist con1;tios anI

the nutrizent release in the ash may have 3timula*

lecomposition. By 1 yr all plots were still- far below

preburn levels: site 1 about 50* and site 2 33-40' -o

preburn.

The nutrient standing crops in pine litter showed' a

pattern very similar to mass with some decrease 0-2 mo

following wet season burns and increases otherwise. The

percent recovery at 1 vr was similar to mass for all

nutrients except N, which only reached about 337 at site 1

3nd 20% at site 2.









The recovery of total litter mass followed a pattern

dominated by the pine litter except for the ldcline between

7 and 12 no it t1s site 2 dry season burn plot causs by! a

drop in understory litter. At one year litter mass was

42-62% of its praburn level. Phosphorus and Ca recovered in

proportion t3 dry mass. Nitrogen was much lower 1han dry

mass (26-37A) because C:N ratios decrease with

decomposition. Potassium recovery was high relative to

mass, esenaiilly at site 2, because of the high proportion

of relatively unweathered litter materials.



TPMact of wires on Pines

There is some indication of a slight increase in the rate

of needlafall immediately following the burns (Oiq. 17),

even though there was little scorching of neseles. The

stress of hijh taeperatnres may lead to senescence of nrePl0

fascicles earlier than normal.

In both site 1 plots there was no mortality of pip? trees

during the year after burning (Fiq. 5). In contrast, a'

site 2, where the trees were smaller, some trees died (vigs.

6 and 7). In the wet season plot at site 2 six trees were

dead 1 yr ifter the burn and in the dry season plot 98 +*res

were dead, including virtually all trees < 7 cm dbh., one

of these treas showed substantial scorching ind n 1al npe"r

to be healthy for the first few months after the fires.

There was evidence of bark beetle activity in all the 9e







77

trees, but there is no way of knowing whether the insects

were responsible for the deaths of the trees or whether they

only attack] trees that were already dying. T' is cl-ar,

however, that high temperatures around the stcms of Sout'h

Florida slash pine trees can lead to their deaths. Three

years after the dry season burn at site 2 most of the pines

had cracks erudinj resin in the bark of the basal 1-? m of

the trunk.

Under the burning conditions of the eTperimental burns

all Dine seedlings were killed by the fires (Table 105). ms

season of burning has a pronounced effect on +-h

establishment of new seedlings. Seedfall is from S-teimber

into Novembrc; therefore burns that occur in the wet season

before seeffall create excellent conditions for see?

gernination inl seedling establishment. Burns that occrr in

the dry season (after seedfall) destroy the caorrc* ve-r's

seed crop ani by the n-xt period of seedfall conditions ar=

less favorable for seedling establishment. The 198n se53

crop in Long Pine Key was relatively good and the wet season

birn plots hid much higher seedling densities 1 yr later

than dii plots burned in the dry season (Table 10).





























r-


o
+1
I
m

o r-i


(o



a i i




+ I







a) 11







"-
S' )















.4040
Ul


S0)

EU



x0 4
tU 1C! -0
D 0 -H

--4
d d
M M










0.)
0 w 0)
04









4'- 04
a o


*a 3













4- 4



-O4U
00
a

















0.
0 0
1a
0r ,~





t0-~
E- i


4) >4 4-) >4
Ct M (
g Q S Q


o 0 0


C00




0)



-4
.4-
mn









Soil

Soil analyses show some striking differences in th-

properties Eo the substrate between the two sites (Tabl?

11). Th'se differences are largely due to +he oresence of

pockets of tie reddish-brown "Redlani" soil at site 1. The

wet season CLot had 8.21 (S.E.=1.62) of the surface covered

by mineral sails and the Iry season plot B.uT S.7.=1.42).

A very few packets of the Pedland soil were present in the

site 2 dry season plot and none were seen in the site 2 we1

season olot,

The organic matter content of the soils was much h.'br

at site 2 (iaout 46-) than site 1 (about 183), although bot-

sites are relatively high for upland soils. The higher

organic content nay account for the slightly lower nrnhurn

op at site 2. ?reburn extractable K an( M'I to not show ich

difference between sites, although K ray he so3ew'- hi T'-r

at site 2. Phosphorus is much higher at site 2 than sit? 1,

suggesting a relationship with organic matter.

Burn eff-;ts on soil properties remaining 1 yr postbnrn

include an increase in pR. This was most pronounce! in *he

site 2 samples ani in the paired Redland soil samples taken

in site 1, were initial p" was lower. Soil organic master

was unaffected by burning. There is an indication that

extractable P was reduced 1 yr after burning. The amounts

extractable by weak acid in the Pedland soil samples were

below detection limits both in burned and unburned soil.








80


mw
9 in in o .
,H-i 0
m I in --4 r- -4 L)
4- +1 +I +I +1 +1 +1 +1 +1
O 0 H m 0 -i
,- D -0 I 0 0)
Q L Hl H H N C4N H
0
a+1i
NC C' 00 C 0N 0 rH to O
4 a m m r-
4-) en m to 0 N 0
.> n) Q .34 (N H HA H H 3cH
0 M +1 +1 + +1 +1 +1 4 +1
O m r- r' N o m m
,.C ) 5- .. ..
t C H LA O A O O to L A
3HO -0 en L m a n N en
O" L

,'- 00 L.r) o 'o r-.
S-i I I I n a in n
0 0 ..


*H (N N rH
o En .0

a) a) a


w CN r, m0 H
40 W- U
Qo-,-i Wr 44 o - m U O o "
"-I +i +i +i +i +i +i +1 +1 +i
HI'n CJ4 ( N ND O in o N -t
0 )O .
,- .,- H ) H 0 en en en o 0 r-,
H ) .4,+ + +5 +3 +O + L + +a

M U
r--I co co 0 1 O O ) O-
O -3't O o4 o ( ,o 3d L '.0 on o ,
O .
n D -I + +i +i +i +i + +i + +i
C M) 00




Om
H 43 4 N ON N A N ON O




5C)3d H
-1 ) 4(
(a ON In N ON Loo LA
mo p r* :: 0





U 1 4
H41 |l4J m' C C C





rn : cc
WU)UH 0 C 4g ) C >1U C) C) >cU) eH >1[n
(a0 m o4 p4 H 04 04 oioR w Hp4

U) 1
4-1IC) t4)


E5-4 0 0 C
3 ec4 4c Ct>
U'o 00 4-i >j >1 4.1 >1 >1 .3 >,
CG4J-m1 H C) 1 1 C) C- 14 C 3.







H C) ]








Extractable Ig May be somewhat higher after burning, at

least at sit? 1. Burning increased extractable K in both

types of soil simples at site 1 but the increase was

statistically significant only for the Rodland soil. At

sits 2 th=re was a .dcrease in K after hurning. This may

result from aore rapid uptake by the vegetation at site 2.















CHAPTER 17I
DISCUSSTON



Pire-caused Losses of Nutrients

One of the most obvious effects of fire is the removal of

organic matter. Nutrients are also lost by volatilization

or articulate emissions. Numerous studies have at+emnote

to ai-sure tiass losses in several kinds of ecosystems. 'n

prescribed b.ining situations it is possible to sasnl"

standing croos before and after the fire, as was done in

this study. Wit1 wildfires the approach has usually been to

compare starling crops in the burned area vi-h nearby

unburned analoqs (e.g. 3rier 19751. Spatial hferogenoi'

of fuels inl the collecti~q of nostburn ash co3se Frble's

for field studies (Prison 1980). "or example, in a lic

prescribed birn in southeastern coastal plain oine forest,

Binstock (1979) and Nguyen (19781 measured higher Tean

values of mass and nutrients after the burn than before. In

a study of fire in heather ecosystems in nqglan! Svans and

Allon (1971) gave up on field measurements and performoi

artificial barns in the laboratory. This reoresents th~

other common approach to measuring losses during fires.

Simulated burning has been done both as open ignition or in

a muffle furnace. The additional accuracy in measuring'









losses, however, is at the expense of the realism of the

burning conditions.

Table 12 presents the average mass halanc? for th foie

burns in this study along with data crom several other

southeastern pinelands and a few other ecosystems. Th-

table does not include examples of slash burning (e.g.

Harwood and Jackson 1975, Evel Pt al. 1991). Comparisons

must be tBmnerei with a degree of caution because

methodologies anI conventions differ somewhat amoag thb

studies. Ti sone cases the fuel rPnrZsents only the fore: t

floor (litt=r) and in others litter 'rd veq-mttion. T '

studies h7 3ough (1991), Kadama and Van Lear (1o ?inh'=r

et al. (1932), Debano and Conrad (1978), and grier (1971

involved field simpling of ash, Debano and Conra vacu e--'

the litter and ash in their stuiv of chaonrral. 'o'lu-

picked uo the ash "by hand" and stated that som? ash was not

collected. The study by rough (1981) '1als with the

situation most similar to the "iami Fock Pidqg oinelanos.

The overstory was mixed stands of slash and lonqleif oines

with relatiTvly Iense understories dominated by Sersnoa

rsgons (saw nalomtto) and lex glabral (gallherryv.

The fuel consumption in the Long Pinea ey burns was

within the ringe of the other pineland burns [Table 121,

The lower consuaptiDn (both absolute and percanta e) i ;

three of tae other southeastern oineland burns is idue o

hiqh moisture content of the lower layers of the for-qt




































OC NNNNNNN N


41
m r
O 0
I-I -4
0 41






4>

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86

floor (Sweenav and Biswell 19F1). Wildfires under oxtrerm

conditions 3in oF course Lead to very large losses (Grior

1975) rasslani fuels (Lloyd 1971, ChristPns-n 1977) also

have high percentage consumption rats.

The losses of 5 seem, for all oractical purposes, to bn

proportional to losses of total mass. Hough (1901)

developed i cegression equation to describe the loss of in

prescribed barns:


N (k~ /ha) = -10.55 + 0.0071 ()


where X is the loss of mass in kg/ha. The ePan I

concentration in the fuel of these stands is aboit 0.7='

(Hough 1992). La a field study not included in Table 12,

Klemmedson at al. (1963) found losses of 30T of mass and 11'

of N after prnscribed burning of ponderosa pine litter. T-

a lab stidy Kni;ht (1966) burned conifer fores- floor

samples in a muffle furnace and found losses of 1Q0 nd 2"?

for mass in! N, respectively, at 300oC and 53 and 61' It

6000C. Tn Lab studies on southeastern oine litter in whiSh

feel samples were simply ignited, Denell and Ralston (197n)

recorded losses of 71% of the mass and 58q of N whi Le',;is

(1975) founi losses of 39 and 56% for mass and N,

respectively. Tr these relatively cool burns most of the '

was lost as linitrogan gas.

Pires may also result in losses o' the so-called ish

elements (Cliyton 1976, Table 12). Rowever, undar nost








circumstances it is not possible to show statistically

significant Losses by preburn and postburn sampling (e.q,

this study and Pichter et al. 1982). The magnitude of these

losses as ocrsentei in much of the literature is lik lv Io

be overestimated. In field studies it is difficult to

sample the ash. When small plots ire burned, and psecia!l?

if samples oF fuel are burned in laboratory settings, thcre

is no opportunity for the particulate matter to settle b-ck

down on the sampled area. Significant amounts of nutrients

in articulate matter are carried away from small ",urns

(Smith and PBwes 1974, Wvans and All-n 1971). Tn nore

extensive burns much of the particulate fraction of smoko

will rttura lirzetlv to the ground. Some of the narticuilate

emissions are deoosited on the canopy ani are returned to

the forest floor by the first rain after the bolrn. Ther is

also a tendency to consider any loss reported in the

literature as rail while gains after burning are iqgored

(e.g. Boerner 1982). For example, the increase of 25! in

the amount of Mg reported by Debans and Conral (1978, Table

12) makes the loss of 16t of K seem of questionable

significance.

The ash element most likely to be lost by volatilization

is K, which is volatilized at temperatures above? 500oc. In

what ar3 pr:Sably the two hottest fires listed in Tabl! 1?

(chaparral and the Entiat wildfire) the percietaae of K 0lot

was higher than that of any other ash element. This wae

also true of the lab simulations on heather.








The ash lepositel on the soil surface is subject to

erosion losses om sloped terrain, but not in Soutnh Florila.

Much of the mineral contest of the ash is easily leach-d

into the soil by rainfall (Allen 196i, Lewis 197U,

:hristensen 1977). Recently burned ecosystems may

experience losses to groundwater, however thsse losses s=em

to be very small for coastal plain pinelenls (Boerner an-

Forman 1982, Rizhter et al. 1982). In Long Pine Key th=

high soil organize matter content should giva the soil a hiTh

catioa xcha~7e a paaity and P should be qui'klv immobhli.-~

by the abuindint :a. The rapid recovery o' +t1 vegetation

also acts as a sink for the nutrients released by th" fi-r

(see below).

Althon)h the losses of nutrients (other than N) in the

borns in this study were not statistically significant it is

certain that som? losses did occur. "ow=v-r, evsn if 'n

assumes a loss of 10' of the standing crop oa the ash

elements, tiase losses could be replaced by precipitation

inputs over the period of a burning rotation, 3.'-6 7r.

Annual deposition of N, P, K, Ca, and Eg in bulk

precipitation in northcentral Florida is about 1-1.4, 0.1,

0,3-0.6, 1-1.5, and 0.2 g/ma respectively ('pndry and

Brezonik 199), Riekerk et al. 1979). Depending ipon the

estimate of input by precipitation, this may or may not

replace the substantial loss of V because losses ranqed from

1.4-2.2 g*ma-*yr-i when averaged over the time since= th-

previous fire,








It is to be expected that nutrient losses should more or

less cqual irnuts in ecosystems that have a long history on

frequent burning. In fact, fire may be a mechanism by which

nutrient-poor ecosystems prevent the accumulation of

nutrient capital.

Several agents of biological N-fiiation could aid in

recovery of N lost through burning. Although several

herhaceous laiumns are common (e.g. Cassia spp., Crotalaria

umrill) they are not likelv to fix significant amoilnts

(Pundal 1981). Lvsiloma latisil:l!_ is a legaiino_,s tre-,

but it is not zomaoa enough in pinelands to aid mich

nitrogen. Zimi E 1umila has a blue-green algal endophvt?

that fixes (Lindblad 1984). Eyrica cprifera, an

actinomycete-nodulated shrab, has substantial biomass in

much of Lonj Pine Key (inclulinq site 2) and may fir

appreciable i~ounits of 4. Tn a northern 1lorila slash -);in=

plantation Permar and Fisher (1993) estimated that "

cerifera witi a crown cover of 8" fixed 1.1 a nT*c-2*yr-1.

Nonsymbiotic N fixation by soil microorganisms in forest

ecosystems his often proved to be a rather minor source o' '

relative to arszipitation inputs (rjepkema 1979), Jorgens'n

and Wells (1971) found indications of increase soil

iaetylene relation activity in burned loblollv pine lots

compared to inburned controls. A later stufy by Jor"ensen

(1975) -ii lot support this finding and found 4-fixation

rates of < 0.1 g*m-z*yr-i. Vance at al. (1983) found even








lo er rites (0.01 g*m-2*yr-i) and no effect of long-ter-

prescribed burning in oak-hickory forest. In a orairi?

site, DuBois and Kapustka (1983) measured 0.8 qm-2*vr-1 f

nonsymbioti= T-fixation, about half of which was du- t3

cyanobacterii. Blue-green algae are not found in acid

coastal plaia soils (Jurgensen and Davey 1968) but theyv r?

coamon in ciccumneatral soils (;ranhall and Henriksson l119)

and abound 3i the oolitic limestone of the "iani Rock idgi-.

I ran an acetylene reduction assay on a few samples of rok

front the stuly area and fo:nd measurable rates afteT hr

If incubation. Crude =alculations indicated rates on t+e

order of 0.1 g*m-2*yr-1. It would seem that fixation bv

various taxi plus precipitation inputs over a burning

rotation could easily account for th- losses of N r-corr~l

for the experimental fires.



Pistfire aecoverv

In the !imi Rock Ridge pinelands virtually all recovrv

of understorv species is by vegetativP means rather than hv

seedling reproduction. This is fairly common in ecosystem~

that exnpric= z high fire frequnncies. Abrahanson (193aa)

found very little change in species composition after fire'

in several pLn?-1ominated plant coamunities in southcuntral

"lorida. Bo2rne' (1981) also note relatively little chaenr

in speci-s c=apo3ition in burned areas of the vew Jorse-

Pine 9arrens,






91

This is La contrast to situations, often whsre fires are

of lower frequency but higher intensity, in whi-h there i a

distinctive )ostburn flora. The large number of herbaceoii

annuals that appear after chaparral fires is a Iramatic

example (Christensen and Iuller 1975). The degree to which

species changes result from burning depends in part on the

severity of the fire. In jack pine communities, fires

during the Iry summer months consume the upnse organic

layers of tie soil, whereas fires during the moister snrimn

do not. Sia3e species with shallow regenerativ- organs ~a

eliminated by ground fires, numerous postfire disturbanr.c

species like Fpilobinm (firewesd) become established after

summer fires (Ohmann and Grigal 1981).

Even though recovery in the rock ridq3 pin-lands is

vegetative, there are differences among the different growth

forms in the rat3 of recovery. Herbs and palms renrow v=rv

quickly, reaching their preburn dry masses within 1 yr. Tho

monocots (jcaminaid herbs and palms) and ferns havy

protected maristems that are seldom damaaed by Fires.

grasses are sell known for their rapid regrowth after top

removal (Iiltan and Lewis 1962, Daubenmire 1968). The

recovery of licots (whose buds are usually killed) rcuirrs

the activation of previously inactive maristems or the

production 3f aiventitious buds, whether thny bp on

rhizomes, roats, or the base of stems; woody dicots take

longer than iarbaieous dicots to show regrowth. eowver, a







92

study by Hounh (1965) in =eorgia found that Serenoa repnen

only reached 55- of its preburn mass 1 yr after burning

whereas 11 x labra, a hardwood, returned to 70q of its

preburn leveL. This is somewhat anomalous because the

preburn vegetation had bean unburned for 15 vr and there

should have been considerable stem biomass. S. reoons was

found to have greater cover 1 yr after a burn 'thn heforp

the born in i study by Abrahamson (198qb). This agrees more

closely with my findings in the rock ridge Dinelands.

Iv 1 yr IEtae the experimental burns, 130-190 7/m? of

regrowth vegetation appeared in the burned plots. This is a

fairly large amount in relation to some other postf-irn

recoveries. One year after a prescribed burn in the nw

Jersey Pine Sirrens the regrowth of herbs, shrubs, and oak

sprouts was 113 1/a1 (Boeraer 1991). In jack pin- stands

baraed by wilifires-in Mianesota the vegetation recovery

ranged from 21-131 g/a2 after one complete growing season

(Ohmann and 3rigal 1981).

The raeovrcy of photosynthetic capacity is ev=n more

rapid than the recovery of biomass because hardwoods orolnce

leaves more rapillv than support tissues. In the four burns

in Long Pine Key the recovery of ohotosynthetic tiss' s (sum

of herbs, palms, and hardwood leaves) was 59-937 of th2

prohurn amount at the end of 1 yr. Th, first ve:r recovery

of hardwood leaves alone ranged from 32-68" of the initial

quantities. The rapid recovery of photosynthetic surface is




Full Text

PAGE 1

THE IMPACT 3? tfET SEASON AND DRY SEASON' PRESCRIBED P T H' OH *EAMI 30CK PTDGS PTNELAND, SOUTH FLO c I">A BY JASF3 R, SNYDER A DISSFHTMION P5ESESTPD TO THE 3PADHATE SCHOOL OP THE rj"JIVE?. STTY 0? FLORIDA IN PARTIAL PTILPTLL^ENT OP ""HP PEQHIRPMPITS P)R THE DEGREE OF DOCTOR 0? PHILOSOPHY USI7E3STTY DP FLORIDA 1984

PAGE 2

ACKNOWLEDGEMENTS The magor portion of this work was supported directly bv the South Florida Research Center, Everglades National Parle, and r owe special thanks to Dale Taylor, formerlv fire ecologist, aad 3ary aendrix, research director. Nuaerous individuals it the Research Center aided in the field vrork; in particular Rebecca Rutledge, Virginia Louw, Anthony Ca^cio, Lewis Sharman, ani Donna Blake sp°nt many hoars under trying conditions. Man Hernion, besides helping with field work, identified plants and shared his knowledae o F local plant communities. Bill Robertson, Jr., helne' 1 spark my interest in tnese unasuil pinelands. The park resource aanageaent staff (lead by fire bosses Phil Koeno, Leon *
PAGE 3

Lee of t!i2 Forest Soils Lab wera of great technical assistance with the chemical analyses. George ^tiller drafted most of the figures. Xen Portier advised on statistical natters. Zomputing was done with the facilities of the Northeast Regional Data Center, In recognition of less tangible contributions, I thank ay father, Robact Snyder, for instilling in ae an aoorociation of the great oat-of-doors and my wife, Jean Snyder, for continuing encouragement and support.

PAGE 4

TABLE OF CONTESTS PASE ACKNOWLEDGMENTS &BSTB1CT , . , , CHAPTER I , INTR0D0Cri3N 1 0bi2Ctiyes.. 3 Tha Ecosvstem » . , . ............ . 3 rliaate ..... 3 5?ology and Soils >.>..>>......, 7 7egetation 11 *ire Ecology .,,>,,,.,, 17 Present Extent and Condition ........ ?2 Evarjlades National ^ar^ .......... 2« IT. METHODS •«««• ••••....•••».•. ?7 "xpsriaBatal Design and Sits Selection . .... 27 The Burns ........ »,..,,» . , , . 29 Aboyegraund "?ass Sampling 31 Vegetation and Litter ............ 3 1 Postburn Ash ..... ...31 Littarfall ..,....,...,.,...,, 35 SoiL Saapling 36 Tissue and Soil Analysis ............ 37 ITT. RESULTS 39 Initial Vegetation Structure 39 Bura Descriptions ..,.,...,,,,,,, 5° Pic? Effects on Understory »ass and Nutrients . ^2 Initial Distribution of ffass and Nutrients , ^2 \sh Collection Methods ........... r 5 Postaurn Distribution of Mass and Nutrients . 57 Postfire Recovery of Mass and Nutrients .... r >8 Vegetation ................. C! 3 Litter 70 Tapict of Fires on Pines ......... ...76 SoiL 79

PAGE 5

IV, DTSCOS5I3S 32 Pica-caused Losses of Nutrients ..».*..» 82 ?33tfire Recoverv ..,.,.. . . 90 Sffsst 3f Season of Burning on Hardwood Recovery q 3 Sagcovti Vegetation as a Nutrient Sip* .... 101 Suinary and Conclusions ..... ...... 101 LITERATES CITED 110 APPENDIX A. VASCfTUR PLANT TAXA PRESENT IN STDDY PLCTS 3, STANDI*3 CROPS OP DRY MUSS AND NUTRIENTS EIOSRAPHTCAL SKETCH 12^ no

PAGE 6

abstract of Dissertation Presentel to the Graduate School of the rinivarsitv of Florida in Partial Fulfillment of the Reguiraa^ats for the Degree of Doctor of Philosophy THE IMPACT DP SET SEASON AND DRY SEASON PPFSCRIHEO FIFES dm urAai 2ocf: ridge pinelasd, sohth Florida By James 3. Snyder August 1984 Chairman: Join J. Ewel Major Departsant: Botany In the suatropical pine forests on oolitic limestone in Dale County, "lorida, 2.inus elliottii var» 3 ansa qnvs ovsr a species-ci-h ualarstory (> 128 sop.) of shrabbv hardwoods (mostly tropical evergreen species), palms, and herbs, incluling sareraL endemic taxa. Fires prevent ranid conversion to hardwood forest. To compare the response of these pinelaals to burning during the lightning c ire season (hot, wet, saamar months) anl tha management fire season {cooler, Iriar, winter months), tiaired burns were conducted at two sites in Everglades National Park, one burned 3r ; *r previously and the other 6 yr, Aboveground understory

PAGE 7

biomass and nutrients were measured immediately before and iftsr, and it 2, 7, and 12 mo after the four burns. The barns topkille-3 all the understory veaatation. The fires volatiLizei 1-1.5 kg/a 2 of organic matter and 5.7-9. "> g/m 2 of N. Meteorological inputs and symbiotic and nonsymbiotic fixation should easily replace N lost in the burns, Losses of P, K, 3a, and 3g were not 3etactabl
PAGE 8

The amount of hardwood rscovsrv was not determined by season of burning; higher fire temperatures (wet season burn in one case, 3ry season burn in the other) resulted in less recovery.

PAGE 9

CHAPTE8 I INTHODOCTIOS The importance of fire as an environmental factor influencing soosystem structure and function is videlv appreciated today {Ahlgren and Ahlgren 1960, Kozlowski and Ahlgren 197!», Mooney et al. 1981, Rundel 1981, Wright an^ Bailey 1<*32), ?ire is often thought of as a successioninitiating iisturbance (White 1979). However, in communities that aave evolved under a regime of frequent fires, it is the exclusion of fire that may result in draaatic--if not sudden — changes. luch of southeastern 0. S. , particularly the coastal plain, is covered with v^gstation that requires periodic burning (Christensen 1981). ^anp southern pine forests, for example, levelon into hardwooi forests in the absence of burning (barren 19U3) . The regrowth vegetation in some frequently burned ecosystems comes from seeds Dresent in the soil or released from billed plants, ?lore commonly, however, individuals survive and sprout back from belowground parts. Tn chaparral it is common for species to show mixed seedling and sprouting recovery mechanisms (Keeley and Keeley 193 1).

PAGE 10

Pica is v = ry proainant in South Florida ecosystem?;, both in terms of irea burned and as a determinant of vegetation pattern (Sobartson 1953, Wa3e et al. 1980). Of particular interest in fiis study are tha subtropical pin^lands -found on the Miami Rock. Ridge in southeastern Florida. These Dine forests differ from other southeastern coastal plain nine forests in two ways: they include a large number of tropical species in the understory and thev grow directlv on a limestone substrate nearly devoid of soil. Prescribe! fire is used throughout the southern nir.3 region for site preparation, fuel reduction, and range improvement. It has also become a tool in natural area management in places such as Everglades National Park. In most southeastern pine forest tyDes (with one maior exception) fire loes not kill the canopy trees as it floes in many coniferous forests (Heinselman 1973). This, along with its comaon use for other purposes, may be why the use o c intentionally set fires was so readily accepted as a management technique in natural areas. Prescribe! burns in the southeast are traditionally carried out luring the cooler months because fires durlrg this time ace less likely to damage oversfory trees and because the cespcoutiug vegetation pcovides forage which is otherwise United at this time. Before the influence of humans, however, fires were primarily ignited bv lightning, which occurs during warmer months.

PAGE 11

Objectives I wished to sxamiae some ecosystem-level rssoans^s o^ Miami 8oc!r 3idg? pinelands to fires during the natural lightning-caased fire season and the traditional manag o iuent fire season. I was particularly interested in the following: (1) Ike amount of mineralization and loss of organic matter and natrients due to fires, (2) The pattern of recovary of understory mass and nutrients daring the first year after burning, (3) The degree of recovery of the nnlerstory 1 yr af-^ar burning, witi emphasis on the recovary of hardwoods. (4) Basad on the above items, to draw some conclusions about the potential role of fire in nutrient cycling and the use of prasoribel fire in the nanagemsnt of a natural area. Ill£_;i£25Y.5tam Climate The cliaata of South Florida has two salient features: (1) moderate, almost frost-free winter teiperatures and '2) a marked seasonality in rainfall (Fig. 1) . These characteristics result in a hot period of high rainfall (Hay-Oct.) an-3 a cooler period of much lower precipitation (Nov, -April) , These are known as the wet and drv seasons, respectively, in keeping with tropical terminology.

PAGE 12

30 r Figure 1. Mean monthly precipitation (bars) and temperature (dots) at Royal Palm Ranger Station, Everglades National Park (after Rose et al. 1981) . Mean annual rainfall is 146.3 cm.

PAGE 13

Ham aontiLy temperatures range from about 18.5°C in December and January to about 27.5&C in July and August, Frosts occur in the homestead area about once every two years on tha average (Bradley 1975). Thase frosts can daaage winter vegetable crops and production of avocados and mangos for the ansuing year. flanv of the native plant species are also susceptible to frost damage (Craicrhea 3 1971), aspaciaLly plants in open areas. Freezing temperatures were recorded daring both 1981 and 1982, but the studv areas ware littla affected, Dnlv a few o c the minor species dropped leaves and none had stems billed, Total aanaal rainfall averages 1Uf> cm in the southern portion of tie Miami Rock Ridge, with almost 80* (117 era) coming during the six wet season months (Fig. 1) . ^ater levels varv seasonally with a maximum in September and a minimum in April, During the wet season clouds build up in the aftarnoon and result in brief thundershowars; the lightning that accompanies these storms is a potential ignition source for wildfires. Although most summer raiafall is convactional, tropical cyclones can brini large amounts of rain. In August 1981 Long Pine Key in Everglades National Pare racaived more than '40 cm of rain in three days from tropical storm Dennis. The soutieastarn coastal area of Florida can expect a tropical cyclone once every 5 yr and a hurr ican°-f orce storm once evarv 7-3 yr (Gantry 1971), The daaage to vegetation

PAGE 14

E in South Plarila by hurricane Donna in 1960 was substantial, especially In the mangroves on the southwest coast (Craighead and Gilbert 1962). The pinelands of ^veralades National Pack suffered little damage in spite of experiencing wini speeds greater than 160 !cm/hr. ^he high water levels Drought on by heavy precipitation can affect the pineland vegetation more strongly than the high winds, Although South Florida is north of the Tropic of Cancer (Long Pine Kay is about 25 3 23' N latitude) it is commonly referred to as "tropical Florida," especiallv by those concerned with floristics (e.g., Tomlinson 1980, Lena and Lakela 1971). In fact, a world-wiie climatic classification scheme base! on that of Koeppen (Critchfield 197U) considers the southern tip of Florida to have an Aw, or tropical savanna, cliaate of the wet-and-drv tropics. Tt is included as a tropical climate only because the ciean monthly temperature of the coolest month is greater than 18°C, The common occurrence of frost, at sea level would perhaps ma^e subtropical a better designation for the climate. The classification system of Roldridge (19*17) , which is based on temperature ml precipitation, places southern Florida in the Subtropical loist Forest life zone.

PAGE 15

G9olo22_and._3.oil3 South Florida is extremely flat: a function of Its marine depositional history, low elevation, and relatively short period of emergence. The broad, shallow Fverglad°s basin which artanis south from Lake Okeechobee is bounded on the east by the slightly higher Atlantic coastal ridge. The southern end of this ridge in Dade County is an outcropping of oolitic limestone known as the F!iami Sock Ridge (Davis 1943). This region, previously dominated by pine forests, extends fron th.3 vicinitv of ?*iami southwpstward to Homestead aai westward into Everglades National Park f^irr, 2), Tha maicLmum elevation of the ridge is about t i in Coconut Grove (Roffmeister et al. 1967) and it drops to less than 2 a ia Everglades National Park, where it disappears under the surrounding wetlands, The '*iami Limastone (4of f meister et al. 1967) which makes up the "liaai Ro~k Pidga is the surface rock of virtually all of Dade County. It represents Pleistocene marine deposition of calcium carbonate during the Sangamon stage (Cooke 1945), The upper oolitic facies which forms the rock ridge is composed of ooids, pellets, and some skeletal sand. To the north along the coastal ridge the limestone is blanketed by a layer of Pamlioo sand, and at lower elevations to the west and south it may be covered with late Pleistocene or 'scon* marls and peats, Savaral transverse depressions oassincr through the ridge represent valleys in tha rock that have

PAGE 17

bean partially filled by deposition of marl and/or organic tatter (Figs.. 2 and '4). The formation of the Biaai Pock Pidge is described hv Hoffmeister =t al, (1967), Thev compare it to processes occurring today oq the northwest section of the Sreat Bahama Bank, where loose mounds of ooids are forming and shifting in the shallow water on the eastern edge of the Straits of Florida. The tidal channels that cut through the broad ridge of unconsolidated oolitic sediment are thought to be analogous to thoss that form the transverse vall^vs 5n the *iami Pock Ridge. The oolits ro?k is soft and friable until indurated hv exposure to the atmosphere. Dissolution of the rock has left the surface honeycombed with numerous holes and fissures, and armed with sharp, jagged projections. Tn its most treacherous form it is known as pinnacle rock, ^h^ diameter of solution holes can range from centimeters to meters as caa the depth, although 0.5 m diameter ani 1 m depth might be common dimensions for the larger holes. The character of the rock surface varies from place to olace, with differences in the degree of solution and the amount of loose rock fragments on the surface. In the pinelaad areas of the *iami Sock Pidge the scanty soil is found in solution holes, depressions, and cracks in the rock. The soils are members of the Rockdale series, which is classified as a Lithic PuDtic-Alfic ^utrochrept ,

PAGE 18

10 clayey, mixed, hyperthermic (Soil Survey Staff 1975) , "'he surface soils range from 3ark grayish brown to brown fine sands or fin* sandy loams. The subsurface layers (where present) are light gray to yellowish-rei fine sand and brown to reddish-brown sanly or clay loams (Soil Conservation Service 1958) . In the northern portions of the ridge in the Hiaai area, the soils tend to be very sandv due to deposition of sands during the Pamlico stage. To the south there are often red3ish-brown residual soils; the predominance of these soils in the area lust north of Homestead is responsible for the apellation "Pedlands" given to the area. In most areas there is little soil exposed on the surface and plant roots run through cracks and channels in the rook that are fillei with a mixture of organic matter and weathering products of the limestone. because the rock ridge is the highest part of •'-he landscape and is for^.c^ of porous limestone the soils are generally well-dra inei, However, high water tables can reach the ground surface in the lower lying areas during the wet season, The soils are neutral or slightly alkaline in reaction and are deficient in N, P, ani K for agricultural crops. The fact that the exploitable soil volume is so small also contributes to making this a very oligotrophic ecosystem, The nearly frost-free dry season makes southern ^lori^a an important production area for winter vegetables. Current farming practices reguire extensive site preDaration before

PAGE 19

1 1 production, After bulldozing off the native vegetation the surface 15 cm of rock is scarified with heavy equipment (rock plows!) , resulting in a "soil" composed of a mixture of rock fragaants, pulverized limestone, and a s»all amount of original soilThis treatment increases the rooting volume and raises the oH to 8 or higher. Crops (such as tomatoes, squash, and pole beans) require heavy fertilizatioa and irrigation, Experience in Everglades National Pare suggests that once the substrate has beer altered in tiis way tha native vegetation does not normally reestablish. I§iI£tation The vegetation of the *iaai Rock Ridge is essentiellv a aosaic of these basic vegetation types: pineland, hammock, and prairie. The pinelands form the dominant matrix on *-he higher grounl , with small islands of tropical hardwood forest known as hammocks scattered within this matrix. Tn the shallow transverse depressions that run through the ridge are herbaceous prairies, or glades, similar to the vegetation bordering the ridge. Long (1974) estimates that the vegetation of South Florida is about 5,000 yr old, Ssneral descriptions of the natural vegetation of southern Florida, including the rock ridge, have been provided by several authors: Harshberger (1914), Raroer (1927), Davis (1943), Craighead (1971), and Wade et al. (1980),

PAGE 20

12 ^ammocics ire patches of closed forest of essentially evergreen, broadleafed trees. They are fonnd in the higher areas of the ridg? where they are seldom flooded, if ever. The soil is a thick layer of organic matter that has accumulate! an the surface of the limestone. Important canopy species include Nectandra coriacea, Coccoloba iklSE§if2liE» 2'22E222 ll£li3iili§r Ll§i.i232 lati si li g nam , Nstopiura toxLferua, Ficus aurea, Suaelia salicifolia, and iHE§§£§ 5.15L2E22S. (Phillips 1 9ar> r Alexander 1967, Craighead 1975, Olmstel et al. 1980a). Of these only £• virainian^ is not a typicaLly tropical species. The unierstory consists of saplings of the canopy species, a number of small tree species, and a a few shrubs. Relatively few herbs are present on the ground, but epiphytic bromeliads and orchids are guite coaaon. The seasonall7 flooded prairies that border the lower fringes of tie pineland are dominated bv grasses anc! sedges (e.g. !l2lii!122E2i2. £kliE22 an ^ ii.ili.3.1 iiE3.i220.52) tu *" include numerous forbs (Porter 1957, Olaste! et al. 193.3). Here the water table is above the ground surface for 2-a mo/yr and the limestone is topped with a thin layer of marl (Olasted et al. 1980b) . The pinelinds, which occupy most of the liami "ock f?idge, are monospecific stands of Pinus elligttii var. ^ensa, the Sauth Florila slash pine, with a diverse understory of palms, harlwaods, and herbs. The South Florida varietv o e

PAGE 21

13 slash pina diffars from the commercially important northern variety (var, =.lliottii) in several respects (Little and Dorian 1934a, b). lost conspicuous is the grass-like seedling stage reminiscent of 213.3.5 2§l3§tEi5 (lonaleaf pina) in which the seedling grows for several years without stem elongation. However, Squillace (1965) showed more or less continuous variation across the range of slash pins for 12 traits, including seedling height and stem diameter. The range of Souti Florida slash pine extends from the Lower Florida Kays to about Polk County in the center of peninsular Florila and Levy and Volusia Counties along the Gulf and Atlantic coasts, respectively (Langdon 1963). Sandy flatwoods are a more widespread habitat for South Florida slash pine than the limestone of the *iami Pock Ridge. In contrast to the monotony of the pine overstory, the understory is relatively species-rich. The sh^ub layer is composed of 15-25 hardwood species per 0,16 ha (Loope et al, 1979), most of which are tree soecias maintained as shrubs by repeated firas; the palms Sabal Palmetto, Serenoa reoeris, and Coccothrinax argjsntata; and a cycad, £aaia pu^ila. hardwoods commonly found as shrubs in the Dinelands and as trees in haaaoc.ts include ^etoDiua toxi^erura, 5un°lia SiLlSif 2ii§» il2E§i5.2 Ii2Ei35.Hi' 5-2§£tarda §2§l2£§» an(, illi§i§ §S2§kk2Q.i.2ii§§' Kost hammock tr=e species are found at least occasionally growing in pineland. Some smaller

PAGE 22

14 shrubs (e.g. 22l2M^i Zlscosa, LiH-L^m dapjressa, and L. involucrata) ic3 found in the open oinelands bat not in the shade of hammocks. Most of tha hardwoods are West Indian in distribution and are found onlv in extreme southern Florida or alonrj the coast to northern Florida. Onlv a few of the sore important species are Found as far north as Gainesville, Florida: Rhus cooalliai, 5Z£i2a cerifera. Ilex casslne. Per sea borbonia, and 2u§.rcus virginiana. Notably absent from the rock ridga pinelands are Ilex llabra (gallberrv) and members of the Sricaceaa, so important in most southeastern pinelands. Apparently the high soil dH excludes these species. Tie biogeography of pineland shrubs in South Florida, including the Miami Sock Sidge, has been detailed by Robertson in Olmstsd et al. (1993), The herb Layer is dominated bv grasses but also contain* sadges, forbs, and three common ferns. The number of h 3 rh species per 0.16 ha varies from 50 to 75 (Loope et al. 1979). Ths relitiv-3 importance of hardwoods, palms, and herbs varies depsnding on local elevation and fire history, In the lowar, watter pineLands the understory tends to have fewer hardwoods and has an herb layer that shares manv species with the prairies. Freoaantly burned sites have better devaloped herbaceous layers than infrequently burned sitss.

PAGE 23

15 Loope et al. (1979) list 186 plant taxa for the rock ridge pinela;iis r an! 67 of these are restricts to pineland habitats. The number of South Florida endemics found in pinelands (32, 17 of which are found excluslvelv in pineland) is by far the highest for anv South Florida vegetation type (*very and Loope 1980a). All the endemics are herbs except for the shrubs ^orestiera s^regata var. Dinetorura and L§.iti3.i deprassa (Table 1). South Florida slash pina, although found north of Lake Okeechobee, is endemic to oaainsular Florida and the Florida Keys, The pinelands most similar to those of the Miami Rock Pidge are those of Pig Pine Key and several other Lover Keys where the fliami Limestone also outcrops. These pinelands differ mainl? in the presence of several tropical hardwoods characteristic of tha Plorida Keys or nearby coastal areas and the proalneace :>f tree-sized palms of C*occot hrina^ arqentata and T-hrinax i2£El§ii (Alexander and Dickson 197?). The pinelanl3 of the Bahama and Caicos Islands are also verv similar to those of the rock ridge exceot that the pine is £• ciEikaea vir. bahameflsis (*arch 19^9, Luckhoff 196'4, Lamb 1973). Tha substrate is weathered coralline limestone vary much lice the oolitic rock of South Florida. *any of the understory species are the same as those found in rockridge pinelands (Coker 1935, Correll and Correll 1982), although Pobectson (1962) noted the conspicuous absence o? S§.Einoa rep_ans. Evan though it grows in an ecological

PAGE 24

16 Table 1. Vascular plant taxa endemic to South Florida and found in Miami Rock Ridge (MRR) pinelands, including those of Everglades National Park (after Avery and Loope 1980a) . Exclusively Present in Taxon in MRR Everglades Pinelands National Park Amorpha crenulata * Argythamnia blodgettii * Aster concolbr var. simulatus * Brickellia mosieri * Chamaesyce conferta * C. deltoidea var. adhaerens * C. deltoidea var. deltoidea * C. garberi * C. pmetorum * * C. porteriana var. porteriana * * Croton arenicola C. glandulosa var. simpsonii * Dyschoriste oblongifolia var. angusta * Evolvulus sericeus var. averyi * Forestiera segregata * * var. pinetorum Galactia pinetorum * * G. prostrata * Hyptis alata var. stenophylla * * Jacguemontia curtisii * Lantana depressa * * Linum arenicola L. carteri var. carteri L. carteri var. smallii * Melanthera parvifolia * Phyllanthus pentaphyllus var. f loridanus * Poinsettia pinetorum * * Polygala smallii * Schizachyrium rhizomatum * Stillingia sylvatica ssp. tenuis * Tephrosia angustissima * Tragia saxicola Tripsicum f loridanum

PAGE 25

17 setting virtually identical to that of the rock ridge, P. caribaea vac. ^.§.kiIS5.§.l2 loss not have the grassli^e seedling stage that characterizes South Florida slash pine, It should ba noted that for many years P. §.LLi2iiLLi °* southeastern n.S. was considered the same sp°cies as P. caribaea of the Hast Indies and Cantral America (Little and Borman 195tta,b) Fire Ecology The rock ridgs pineland, like lost southern pice forests (barren 19131 , is a fire-maintained vegetation type that develops into hardwood forest in the absence of turning. Bobertson (1953) estimated that aithin 15-25 vr of the cessation of burning, open pine forest would become dense hardwood forest (hammock) under a stand of relic pines; this happened in a small area of pine forest in Fverglades National Park that was protected from fires by the construction of a road (see photographs in Wade et al. 1 oo .0, p*93). Alaxaniar (1967) documented the rapid succession o* pineland to hammock elsewhere in the rock ridge. The succession to closed hardwood forest results in the elimination of soae shrub species and the rich herbaceous flora characteristic of pinelands (Loope and Panevit?: 19-91) ,| This is probably due to the reduction in light reaching the ground but it may also ba due in part to the thick. accumulation of organic matter that is normally removed by

PAGE 26

18 fires. Loopa and Danevitz (1981) found fawer species in a frequently barne3 pineland than in a pineland unburned for 35 yr, Fires in pinelands are surface fires that move along the ground consuaing litter and understory vegetation, The density of the pine canopy is such that crown fires are unknown, although the trees can be killed by convectional heat under severe burning conditions. Prairies burn readily when sufficiaat fuels are present but hammocks under normal circumstances do not. Pineland fires usually burn 'in to the edga of hammocks aui go oat; however, durina extreme droughts the fira nay smolder through the hammock, consuming the organic soil and killing the trees. Craighead (1971) suggests that once soil moisture content in hamaocks droos to 35% they ire susceptibla to soil fires, All the species present in the pinelanis are adapted to firss, Mature slash pinas are verv resistent to fire because of a thick, insulating bark and the relatively heavy buds surrounded by long needles (Hare 1965b, Bvram 19Q8). Roth varietias of slash pine are able to recover from 100? crown scorcl in some cases (Wade 1983, personal observation). Besides being fire-resistant as an adult, the South Florida slash pine has a firs-resistant seedling stage much lika lonjleaf pine (Little and Dorman 1954a r fa), An accidental fire in a plantation of both var. densa and var, elliottii seailings killed a smaller proportion of the South

PAGE 27

19 Florida variety (Ketcham and Bethune 1963) , Seedling establishmant is also favored by fires occurring soon before seed fall (Klukas 1973). The hardwoods in the understory all have the ability to sprout back after being topkilled. Some, such as fhus C2EiiiiQ.§.' ace Prolific root-sprouters, but most sen-? up new shoots from the rootstoct at the base of the stem. Generally, f?w shrubs are tilled completely by single fires, Robertson (1953) recorded mortality of 0-10* in nine species after a firs. Depending on the fu=>l accumulation and burning coalitions, some fires may have no apparent ef-ec 4 : on larger hardwoods. All the herbs are perennials that sprout back guickly and seem to flower more profusely in recently buried areas than in unburned areas, Some of this apparent increase in reproductive activity may be due to improved risibility or mora synchronous flowering, but th^re is no question that flowering of many species of grasses is stimulated by burning (Robertson 1962) . The fire history of the rock ridge pinelands is difficult to reconstruct with any degree of detail. The use of firescarred trees is limited because of the small number of suitable tr=?s and the ambiguity involved in ring counts in South Florida slash pine (Tomlinson and Craighead 1972, Arno and Sneck 1977, Taylor 1980). The only methodology available is to deduce from present-day fire oatterns and species attributes what might have occurred in the past.

PAGE 28

20 Lightning fires are a :ouaoB occurrence today and are likely to have been so ever since the most recent emergence of South PlorLia from the sea. The lightning is produced during freqiant convections 1 storms during the wet season. The average annual number of lightning strides reaching the ground in the rock ridge region is 4-10 per km 2 (Taylor 1980) . The comaon sight of single dead oine trees with longitudinal fissures running down their bark is testimony to the high Incidence of lightning strikes, Tn Fverglades National Park lightning-caused fires accounted for 23^ of all fires anl 18* of the park area burned during the period 1948-1979 (Taylor 193 1). Almost all these fires occurred within the wet season months of Say to October (Fig. 3). During this study (on &ug. 2, 1980) a small lightning fire burned about 3 ha of pineland near one of the sites. Sgler (1952) assumed a low frequency of lightning fires in southern Florida and felt that before the arrival o^ people the uplands were covered by broad-leafed forest. Robertson (1953,1954) , whose viewpoint seems to be substantiate! by more recent estimates of the incidence of lightning-caused fires, felt that the vegetation uattern was much as seen today. fie also argued that the presence of pineland enemies implies a long period of existence of this vegetation type. Both agree, however, in suggesting that the arrival of \aerindians about 2000 yr ago (Tebeau 1963) brought about a aarkad increase in fire frequency and that

PAGE 29

21 CO

PAGE 30

22 most of these ficss probably occurred early in the drv season. The arrival of European settlers on the scene probably resulted in an even higher fire frequency (Robertson 19 53,1954). Besides the obvious effect as an ignition source (or fire suppression agent) , modern man has other lore subtle effects on the fire pattern. The lowering of water levels by drainage starting in the 1920's has increased the time that many vegetation types are burnable and therefore should increase fire frequency. Lowered water tables also increase the incidence of severe droughts, resulting in more fires in organic soils. ^n the other hani, roa3s, canals, anl other cultural features form firebreaks that impede the natural spread of fires. 2ES.§iHi_^I*5.3.t_i3.i_C-2n^iti2n The ""iami Rock Ricjge pinelands originally covered the rock ridge from Siami to near Mahogany Hammock in Everglades National Par<. Davis (1943, see Pig. 2) estimated the original area covered by pine forests to be about 72,900 ha, although ha stated that this was certainly an overestimate. The area of the Rockdale soil series can be considered an independent estimate of the original extent of the rock ridge pinelands. This has been given as 66,700 ha (Soil Conservation Service 1958) or 62,800 ha (Leighty et al. 1965) .

PAGE 31

23 Today ti? rock ridge pinelands are almost restricted to the -onfines of Everglades National Park. ft 1975 survey of pinelands anl hammocks in Dade County found only 298^4 ha o c pinelands outside the national park (Shaw 197 c ;). 3y 1°79 the area had dwindled to 2'429 ha (."!etro-Dade 1979) , *ost of the pinelands have been destroyed for agriculture or urban development. Oaly a few areas of pine forest outside of Everglades Actional Park are likely to be preserved for the forseeable fitura, The Dade County Parks and Recreation Department manages three properties with considerable areas of pineland: Larry and Psnny Thompson Park (109 ha) , "a?y Wells Pinelaad Preserve (100 ha), and the recently acquired Tamiami Pineland Preserve (25 ha) which has sandy soil overlying the limestona (f!» Washington, Dade Co. Parks and Pec. Dept. , pers. com.). There are many other smaller parcels of ro~k ridge pinelands in the southern part of the ridge, but aLmost without exception they are heavily invaded by Echinus 1 a r ej^n thj.f ol ius , 3 weedy exotic tree, and ac? not properly maintained by prescribed burning (Loope and Dunevitz 1981) . Mthough the pineland fire management unit of Everglades National Park is about 8000 ha (Everglades National Park 1979), planimetry of a vegetation map of Long Pine Kev (Olmsted et al. 1983) and topographic sheets of adjoining areas show tiat only about 4650 ha are in fact pinelands (T. Caprio, S. FLa. Research Center, pers, comm,). ?ven within

PAGE 32

2 a the park about 500 ha were lost to agriculture before the land was purchased by the federal government (part of the area known 53 the Hole-in-the-Donnt) . Today, fchacefDr3, Less than 10? of the original rockland pine forest is extant and under some form of management, There is a vary strong possibility that many of the plant taxa endemic to the 3iami Rock Pidge pinelands will be lost inasmuch as only 8 of 17 are presently found in Everglades National Park (Table 1) . Everglades National Park The pinalands west of Taylor Slouah in ^veralaies National Part, known as Long Pine Key (Fig. 2), are the only major area of rock ridge pinelands remaining today. There is also a snail amount of pinelani east of Tavlor Slough near the main park entrance. The Long Pine Key pinelanls are dissectel by at laast six major transverse prairies and contain more than 100 tropical hammocks. The pineland vegetation is described by Pobertson (1953), Loope et al, (1979), and Dlrasted et al. (1933). Svarglaies National Park was dedicated in December 19^7, about the tine that the logging of the pine forest begun in the mid-1930' s was finished. The pine stands found today are almost entirely second growth, representing the progeny of cull treas. The initial park fire management police for the pinelands (and the rest of the park as well) was active

PAGE 33

25 firs suppression, in keeping with National Park Service policy. This initially resulted in good regeneration of pine but prDbably also allowed establishment of Isrge numbers of lardwoods and an increase in size of those already present. k park service study of fire in the park carried out bv Robertson (1953) concluded that fire was needed to maintain pinelands ani prevent succession to hammock. This led, in 1958, to Everglades National Park becoming the first park servioe unit to use prescribed fire. Roads were constructed to divide most of Long Pine Key into ten management blocks. Details of fire management are described bv Slukas (1971) , Bancroft (1975,1979), and Taylor (1<*81) and in the current fire management plan (Everglades National Par<<1979) . After the initial buns of the management blocks in the late 1959»s it was often 10 yr before the next burn; since about 1970 the burning rotation has been shortened to about everv 5 yr (Taylor 1981). Ontil 1980 the prescribed burning of pinelani was carried out almost exclusively in the cooler dry season months (Fig. 3). Since then many burns have bean carried out luring the lightning fire season. Prescribed burning is used by the park service to reduce fuel loads to "natural" levels and as a substitute for "natural" fire where present-day conditions do not oermit the normal pattern of burning (Everglades National Park 1979). A aifficulty in carrying oat this tvpe of management

PAGE 34

25 is that taera is no explicit statement of what constitutes the natural 3tat2, Pices caused by indigenous people might be considered as natural as lightning-caused fires. It is qnita passible that the hardwood understory in the pinelands of ^vsrglades Rational Park is today more conspicuous than it was a hundred years ago. Logging and the subseguetit period of fire suppression may have changed the balance between herbaceous and woody species. The prescribed burning program has not significantly reduced the aaount of aardwoois from levels present when the orograsi began (Taylor and Herndon 1981).

PAGE 35

CHAPTKR TT SFTITODS Experimental Design and Site Selection Paired plots were set up at two sites representative of the rock ridge pinelands of Long D ine Kev, Everglades National Parle. One randomly selected member of each pair was burned during the wet season of 1^90 and the other during the dry season of 1980-81, The burns wer^ intended to be as similar as possible except for air temperature ind fuel moisture conditions, which varv seasonally. I\boveground anderstory biomass and litter were sampled before burning, immediately postburn, and at 2, 7 , and 12 mo after burning, The aboveground biomass and nutrient stories of the regrowth vegetation were taken to be measures of acosystera recovery. The sites were chosen to exemplify both the higher, more freguently barnel pinelands in the eastern end of Long Pine Key, and the lower, less frequently burned pinelands to the west, The choice was restricted to areas that had been unburned for a long enough neriod that sufficient fuels for complete burns were present. Pineland manaoement blocks I (site 1) an! E (site 2) were chosen as appropriate sites (Fig. H) . 27

PAGE 36

28 I I DI Z

PAGE 37

2« Site 1 contains some of the highest ground in Long Pine Key and hal been burned lore frequently than any other management block (burns in 8/57, 3/61, 2/63, 1?/ G 9, 3/7U, and 11/77), Tha shrub layer at this sita was generally below 1.5 i, with few hardwood stems greater than 2 cm basal diametar, and there was a well-developed herb laver. Site 2 was the least frequently burned management block (burned 1/59, '4/69, and 1/75) and is in an area where the water tabla occasionally reaches the ground surface. The hardwoods at this site were larger, often 2-3 m tall, and basal diamatars of 3 ca were common. Solution holes are common in site 2 and there was a less well-developed herb layar than at site 1, The pine canopy at site 1 was made up of larger, more widely spaced trees than those at site ?, Tha criteria for plot locations were that they be areas of at least 0.5 ha with relatively homogeneous overstories andunderstocies, The plots (Fig. U) were located near roads (but > 5 m away) for ease of access and to siaolifv the development of firebreaks. The_Burns The burns wero conducted at least 3 3 after a rain when conditions sat the criteria of the park fire manag°ment plan, including wind direction and air quality standards. Prescriptions were kept broad to insure that the burns could

PAGE 38

30 be done close to the intended date. Fires wera set on the leeward siies of the plots because backing fires ar^ more easily controlled an! are less likely to cause crovn scorch in overstory pines than heal or flanking fires. All burns were conduct?! near aidday by the park resource management staff. Preburn fuels and the material remaining after the bnrrs were collected as part of the biomass and litter sampling, "ine-f uel-moisture samples (material < 7 mm diameter in 0.25 m 2 guadrats) were collected during the burns and riried at 70°r. Relative fire temperatures were mpasurei with plates placed at ground level, 0. 5 m, ani 1 m on 12 poles at pos v burn saaplinj locations. The plates were made by spotting temperature-sensitive paints (Tempilag, Tempil Div», D ig Three Ind.) on steel plates (75 X 130 X 2.5 am, 25" 1 g) . The naints hid melting points of q 2 , 70, 93, 101, 121, 13% 149, 177, 204, 212, 263, 298, 302, 315, 393, 371, 3<»% U2% and U5U°C accorling to the manufacturers sDecif ications (but see flobbs et al. 199U) . The large mass of the olates tends to depress the maximum temperature registered by the melting paints so that they more closely reflect temperatures experienced by the heavier vegetation rather than maximum flane temperatures. The resoarce management staff measured aabient air temperature, relative humidity, wind direction and speed, and rate of spread. ^'irelin intensity was calculated by assuming a heat vield of m,000

PAGE 39

31 kJ/fcg of fuel (Wade 1983) and using the following eguation (Brown and Oavis 1973, Wade 1983) : I = Flwr where I is firs intensity in kW/m, H is heat yield in kJ/kq, w is raass of fuel consumed in kg/m 2 , and r is rate of spread of fire front in m/s. Z§2§iiii22_3:Si_L.iH§£ *bovagrouid understory vegetation and litter were destructively sampled for dry mass. The sampling was done in 60 X 80 plots (0.U8 ha) subdivided into 12 20 7 20 a subplots. Within each subplot, potential sampling quadrats were arranged in a grid pattern. *t site 1 there were 16 2 X 2 D gu ad rats and at site 2, nine 3 v. 1 m quadrats availabla per subplot, !Vt each sampling period two randomly chosen quadrats per subplot were sampled at sit? 1 and one quairat per subplot at site 2. Therefor?, approximately equal areas were sampled in both sites, but larger quadrats in site 2 plots were used to reduce betweenquadrat variance. Buffer strips 3 m wide between quadrats peraittad moyement through the plots without disturbing sampling sites. Ml plants ware clipped at ground level escer>t realms which were clipped at the base of the petioles. In Lonq

PAGE 40

32 Pine Kay Sabil Eilmetto and ~?_cc°thEiQa.x arqentata usually have little stem projecting abr>v° ground, and although the horizontal, creeping rhizome of Serenoa reo^ns is often on top of the rock substrate, it is generally unaffected by fire and is functionally much like a belowground structure. Shrubs and palms were collected from the entire quadrat. Herbs and litter were harvested only from 1 7 1 ra quadrats nested in the !7W corner of the larger shrub quadrats. Tn the site 2 plots, herbs and litter were sampled from an additional 1X1 a guadrat in the SE corner of the shrub guadrat beginning with the 2-mo postburn sampling. Pine seedlings wars counted in the herb and litter gnadrats. Litter was defined as any dead plant material identifiable as to origin, essentially the L anr? ? forest floor layers of the older forest soils literature (Pritchett 1979), len^rallv there is little humus material (H laver) present ia Long Pine Key pinelar.ds because of frequent fires, but in site 2 especially there were occasional pockets of wall-decomposed plant matter. A prominent part of the littar after a fire in these pinelands is the standing dead hardwood stems; these were sampled from the entire shrub guairat, Dead palm fronds were included with forest floor litter in the 1 X 1 m quadrats as were any pine needles draped in the understory vegetation, The harvested material was sorted into various compartments, dried at 70°C to constant mass, and weighed to

PAGE 41

33 0.1 g. Shribs were sorted by specias; leaves (olus rarely occurring reproductive parts) were separated from stems f or the preburn, postburn, and 12-ato sampling periods, Petioles were not sapiratad from blades of palm leaves. Herbs were treated as a single compartment although record was kept of all species observed in each plot. Litter was separated into pine anl non-pine components. Tn the preburn sampling only subsamoies of litter were separated and the proportions wara applied to total dry aass. At later samoling periods pine litter was further subdivided into needles ani othar pine and the non-pine litter was categorized as herb litter, forest floor shrub litter, and standing dead. For nutrient analysis, vegetation and litter from three adjacent subplots wer° bulged by tvpe and a large subsample kept. In ganeral the categories were the same as those recorded for aass, except that only two or three of the most important shrub species in a given set of subplots were kept separate and the rest were combined. The diameters at 1.5 a (dbh) and height of all pine trees in aach plot were recorded along with the number of standing dead trees (snags) and stumps. Regression eguations froa the literatara were used to estimate biomass of the overstory.

PAGE 42

34 £ostburn_Ash Accounting for the mass and nutriant content of the ash following the fires posed a special methodological problem. The ash was soLlscted by two methods. The first consisted of placing four Petri dish bottoms (9 cm dia. , 20 mm depth) undar the litter before the burn at 12 oostburn sampling Locations (oie in each subplot). Immediately af*er the fire, covers were put on the dishes and they were taken back to the lab. The contents of the four dishes ^rora each location wer = combined to form a single samols. The advantage of this method is that the samples can be collected as soon as the fire front passes; a sudden rain does not pr^oluie sampling. The disadvantages are the relatively siall area sampled and the difficulty in placing the Wishes un3er aLl the fuel, esoecially in an ?srea with a substrate as rough as Miami oolite. The seooni method was to pick up the ash with a small vacuum (Car-7ac, Black and Decker) powered by a 12 v battery. \t tha same 12 postburn sampling locations a D.2 2 area was vacuumed and the material was transferred to plastic bags. This method cannot be used once the ash is wetted. It is very effective at picking up all the ash, but there is potential for contamination with soil. Both tvpes of ash samples were analyzed individually for nutrient content, although N was measured only in the vacuum samples,

PAGE 43

3^ Litterfall The contribution of the pins overstorv to understory littermass and nutrients was measured by collecting litterfall foe the 12 mo post-fire period, °ine needles, baric, and male cones were collected in litter trays (galvanized greenhouse flats, 0,187 a 2 , with drainage holes) placed two psr subplot in each of the treatments. Trays wars also put out in an unburned area of site 2 to s?° if burning increased needlefall. The trays were emptied at 2-5 wk intervals and taterial from three adjacent subplots wis pooled to gi72 four samples per plot. The litter was oven dried (70°3) , sorted into needles and other fine pine material, aid weighed to 3, 1 g. All other material was discarded. The input of larger material which is inadequately sampled by litter trays (branches and seed cones) was neastired separately at both sites. Ml newly fallen (nncharred) material was picked up from a strip 2.5 ns wide outside the dry season burn plot borders twice during the year after burning. Collecting was done in 20 m lengths, resulting in 14 50 n 2 sampling areas. Branches were separated into 1-cm diameter classes before oven drving and weighing, E assumed that branch and se=d cone litterfall was tie same at both plots in a given site. Needlefall was bulked by plot for a drv season period. (Dec. -Jan.) for nutrient analysis because these samples were least subject to leaching losses while in the litter travs,

PAGE 44

36 The total annual fine litterfall (mostly bark) was bulked byplot for analysis, The nutrient content of branches and seed cones was measured on material that fell during a ^ 7 '1 period durinj the dry season at the site 2 dry-season plot. Materials from tie (three or four) sampling areas on each side of tha plot were combined and subsampled to give four samples of each type. The nutrient concentrations of the 2-3 cm branch class were applied to the small amount of material larger than 3 cm diameter. Soil_Sa ailing Two typas of soil samples were collected to characterize the surface soil (0-7.5 cm) and to detect chan7es in soil properties present 12 mo after burning. The first tvpe was samples taken from the preburn bioraass quadrats in all th Q plots and from the 12-mo quadrats in two of the plotsm en scoops wers taken with a trowel in each subplot and then bulked to form 12 samples per plot. The sampling snots were spaced as avunly as possible in each quadrat, but considerable searching in cracks and crevices was often required before a scoopful of soil was found, At site 1 areas of reddish-brown mineral soil were sncounterel In the preburn soil sampling: these areas were readily apparent after the burns. The extent of these pockets of "S^dland" soil in the site 1 plots was estimated by lineintercept along the 20 m borders of all subplots

PAGE 45

37 (n=31 in ea7i plot) > Because the preburn soil samples wer= heterogeneous with respect to the type of soil sampled, 3 second sampling restricted to the Hedland soil was doneComposite simples of 10 scoops of mineral soil from throughout each of the subplots in the site 1 !ry season plot were tacan 12 mo after the burn. In the adjacent area which hurnel 5 yr previously composite samples were collected in a similar manner along 10 m segments of a 120 m transect. \11 the soils were dried (70°C) and sieve! (2 mm screen) before analysis. li§sjie_aji!_SoilJlna lysis Subsamples (0.5-1 L) of the bulXed vegetation and litter material for chemical analysis were grouni in a larg^ Wiley mill, thoroughly mixsd, aad store! in polvethvlen^ bottles. The ground saiples were redriad at 70°C before weighing. Cations (Ca, Hg, and K) and P were measured on 1,000 g samples place! in 50 ml Pyrex beakers and ashed at 500°C for at least 3 hr. The residue was dissolved and then brought to dryness first with 5N HCl and then concentrated HCl before filtering (Whatman So. H2) and bringinj to 50 ml final volume with 0.1N HC1. Calcium and *q concentrations were determined by atoaic absorption, K by flame emission, and ? by automated colorimetry (ffitchell and Shue 1979). Nitrogen was analyzed by a micro-K jeldahl procedure usim 0,500 g of litter and stem tissues and 0.250 g of all other

PAGE 46

3? materials. \amonium was determined by automated colorimetry (Anonymous 1977). The cation and P content of the postburn ash was determined by similar methods except that the residue after ashing was dissolved in larger (10X-20X) volumes of acid because of much higher nutrient concentrations. Following Kjeldahl digestion of the ash, ammonium was ueasured by distillation and titration. As a cnesk on analytical procedures, replicates of a single leaf tissue sample were run with each set of dryashed samples. The replication was good, with coefficients Df variation of S.O?, 3.5% 3.0"., and 2.U"* for K, Ca, !»q, and ?, respectively. Recovery of K, Ca, and ? froa four samples of National Bureau of Standards pine needle tissue averaged 5 1?;, 1185, and 98% of the values listed for these elements. There is no published value for v g. The r.R.S, pine nesdl? tissue was run with each set of Kjeldahl analyses and always was within 3% of the nominal value. Soil pH was measured in a slurry of 25 ml of soil and ^0 ml of water equilibrated far 30 min. Organic matter was measured by the Walkley-Black wet oxidation method on 1.0 g samples. rations and P ware extracted by the double-acid (0.05N HC1 D.025N T2SOU) method and analyzed as for plant tissues. Details of methods are found in Hitchell ar.^ ?hu(1979) .

PAGE 47

CRaPT™ TIT RESULTS LaitL!ll_I§3°tation_St.ructure EiH2§ §!i!:2££Li var. dsnsa was the sole canopy tree species in all the plots, Both sites had apparently been logged not long before the establishment of the park; nuaarous stuaps still remaining hav = resisted Tore than '40 vr of exposura and several fires. The density of pinp trees at site 1 was about half that at site 2, but the mear. basal area per trea was about twice as large, so total basal area at the two sltas was similar (Table 2). The trees at si*-e 1 w = ra also taller than those at sita 2. !lany o c the larger pines at sita 2 had misshapen crowns and probably represent cull trees. There wera very few pina saplings (< 5 eta dbh) at site 2 and none at site 1 (Figs. 5-7) . There ware also verv few pines <1,5 a tall that had grown out of the "grass" stage at either site. Before the burns site 1 had 1.2-1.5 seedlings (no stem elongation) per a* and site 2 ha* 0.1-0.? (Table 10). \ total of 129 taxa wera observed in the plots during the course of the study (Table 3, Appendix A). This is a slight underestimate of the number of soecies present because some 39

PAGE 48

4 co P O H a • CO >i-P T3 O 3 -H P O, co XJ rd to x: CN 00 rH CD O .C p U 3 MH o o m x: CD U X (0 P CD P C rd -H >i CD M CD O P P CO U -P CD CO > CD O <-\ rH CD (0 a p H am o CD X\ c P rd CD <+H g O CO -H O •H P -P XI CO rji •H -H P. CD i (0 04 U U en rd ox 3 • p o CO C en -^ C CO •H T3 CO X T) (0 CD "••» C CD CD • fO H3 ^ O P PC CO «— >i-P ax o tP~. c-h g rd CD — u x rH CO rd X co ^ T) XI (0 g CDH u CD iH CD C rd rd M rd CO CD P CD rd P. **» £ XI iOcn g iH iH rd CO rd rd X! P CO CD \ O (0 P1 p >1 P CD P a s a

PAGE 49

41 30 25 UJ UJ a: UJ 20 I 5 I SITE WET SEASON BURN I I l l •L -l-TTT. iT i i / ' i i iT M , V . , |'M > n 20 25 30 35 w ..^. ......... -.-.-.--. 10 15 20 25 30 DIAMETER CLASS (cm) 35 Figure 5. Size-class distribution of nine trees in the site 1 plots.

PAGE 50

42 SITE 2 WET SEASON BURN 10 15 20 25 DIAMETER CLASS(cm) 30 Figure 6. Size-class distribution of pine trees in the site 2 wet season burn plot. Unshaded bars represent trees dead at 1 yr postburn.

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43 SITE 2 DRY SEASON BURN 15 20 25 DIAMETER CLASS(cm) Figure 7. Size-class distribution of pine trees in the site 2 dry season burn plot. Unshaded bars represent trees dead 1 yr postburn.

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44

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uncommon species were probably missed and because a few herbs were i3entifiei only to genus. Within the herbs the Asteraceae, Poaceae, Euphorbiaceae, an! Fabaceae were particularly well represented, Eive shrub species ar° members of tie Babiaceae, which contributes an additional four herb species, Other important shrub families reflecting tie tropical origins of the flora include the Arecaceae (piims, 3 spp,), Anacardiaceae (H sop., including one exotic), Sapotaceae (3 spp.), and Myrtaceae (3 spp.), The overall species richness dii not varv ouch hetween sites; however the site 1 plots had higher berb sp=ci~s richness and the site 2 plots had higher hardwood species richness, This pattern may be due to characteristics of the substrate and the close association of the site ? plo*:s with hardwool hanocks that can serve as seer! sources; it could also be lue in part to more freguent burning of site 1, Some herbs in site 2 are restricted to the wetter microhabitats in solution holes (e.g. Cla.li22 i§.maicfnse and Thely_p_teris iLIUlthii.) <*nd some grasses and selaes at site 1 seem to be found only in the patches of Pedlanl soil {e.g. £hvnchos£ora gl2k^Ii£i§ aQ & !22§9l2ii2.1 lineatum) . The hardwood species found in site 2 and not in site 1 are mostly species characteristic of lower, wetter ar^as (e,a, £!l£Z2222k§2!i2 12222 an llx.1 cassine) or species found in nearby hammocks (e.g. Q.£222l2k a ii?5£§i'2li3. aa '3 IJSiiSS.* i.2.i.I§ili2'13:)

PAGE 54

The pine overstory clearly dominates the vegetation in t=ris of biosass (Table 4), The understory vegetation, in which the hardwoods are the dominant component, made up 5? or less of tia total abovaground biomass. The understory vegetation is much more iiportant in tens of nutrient content because so much of the overstory biomass is wood, which has low nutrient concentrations. Although herb species richness was due largely to forb species, gnainoids in general contributed more to herb biomass. Prominsnt grasses include Schi-rachyri j_m Ehi?o:sat;i:n (a South Florida endemic) and Andropggon cabanisii, Th a major exception to this was occasional patches dominated by the f=rn ?t3ridLum aqnilinum at site 1, The relative dominance of the understory shrub species as expressed by percent biomass is shown in Figure 8. Saettarda scabra was the dominant speoies at both sites, but less so at sit a 3 where there were more species. At site 1 ^2!l2Q.^S§; Zi&cosa was the second most important species, a position held by 5lEi.2i x§EifrEi at sits 2. At site 1 tha top two soecies account for ibout 55^ of tha shrub biomass, and at site 2 only U1«. Tha palms Sabal o^ISi^-to aQli Serenoa E222B§ are among the top ten species at both sites, but S, reoens is more important at site 1 and S. B§.l§§Jr£2 at site 2. ~2222thrinaic argantata is rare at site 2 and is much less important thin the other two palms at site 1. The biomass relations of the oalms are a reflection of thair densities

PAGE 55

47 p (0 -o c (0 p + 1 c ro ID e c

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48 C/) (J) < O CD UJ > < UJ cr 0.05 SPECIES SEQUENCE Figure 8. Dominance-diversity curves for preburn shrubs in the study plots. Circles = hardwoods, squares = palms, and triangles = Zami a flor idana. Site 1 plots are represented by closed symbols and site 2 plots by open symbols.

PAGE 57

'i a at the two sites (Table 5). Zand a p.umila had the eighth highest preburn bioraass at site 1 but was rare at site 2, 3. l 2£3._5.2§S.£iHtL2°5 The wet season burns were carried oat under conditions of relatively tiigh ambient temperatures and humidities, although the fuel moisture of the site 1 wet season plot vas as low as the dry season plot (Table 6) . The site 2 wet season fuel was «uch moister than the dry season fuel. Ml four burns resulted in 100* topkill of ^he nnde rstory vegetation, trita minimal canopy scorch. About 70 t of the fuel was consume! in the burns except for the site 2 wet season burn in which hijh moisture content reduced consumption to about 50%, The ash resulting from the burns forced a thin, discontinuous layer on the roc 1 : surface ut>.*-i1 the first postbura rain washed it awav. The rate of spread of the fire front was less than 1.5 cm/s exoapt Cor brief head fires during wind shifts in the site 1 dry season burn. The intensity of the burns was within the optimum range for prescribed fires (73-260 XW/ra, Bade 1983) except for those brief periods in the site 1 dry season burn that resulted in the scorching of about 10? of the crowns. The 379C1J3 fire temperatures reaistered by the temnerature-sensitive paints varied significantly among the burns (Table 6). The site 2 dry season burn, where the

PAGE 58

50 X! • K) 03 CO P 0) 3 -P p m jc tn £ 03 3 03 . -H > 03 i-H 03 (U m am oj OEoh rH (0 -H a 03 ex a) (0 H >i 3 T> P 3 3 -P XI 03 -P 03 B C 03 03 +J > 03 3 i 3 H -P P (0 H 3 > 03 X> C 0) 03 03 p .3 £1 q a+j p C P o o 03 H (0 a, 0) 03 3 p >i 3 P X! Q C P o 03 iH us a, 03 03 C p -P 3 03 XI s C P o o 03 ,H i 3 P XI a c P o o 03 H flj ft 03 03 C P P 3 03 XI 5 03 0) H o a) a. CO (0 P (0 P 3 0) Ol P
PAGE 59

51 2 o Xi tn g a J3 3 am >i 0) tn QJ +J HDO, a, u -h CM • i +> e >i en en Oj .q -p -h >i 'O 0) ou a; g ai -a p a) s m 3 n a o O) m w e m CD (0 a) -p o m Ji a) g: m-i > •p in .u 3 tn in r-i •— • C rH

PAGE 60

52 greatest amount of fuel burned, ha3 the highest temperatures; however, the ground-level temperature was not significantly different from the site 1 wet season burn. The ground-l^vel temperature of the site 1 dry season plot was lower thin ths w a t season plot, probably because of lower ambient teaperatures and the more rapid movement of the fire over th? plot. Temperatures decreased with height above the gr>nnd, although this pattern was least pronounced it the site 1 dry season burn. £!i£S_?f£§2i§_2!i_Il I'd? I§i2E2_^ §§§_§!! 3_ Nutrients Initial_Distc ibution_of_^ass_and_Nutrients The relative distribution of the preburn fuel mass among live understory vegetation, understory litter, and pine litter was similar in all four plots (Figs, 9 and 10), Pi^o litter accounted for 50-70' of the mass and live vegetation for 25^ or less. The distribution of 8 and Ca was similar to mass, but Sg, P, an3 especially K were relatively high in the live vegetation. In fact, 75-80!? of the K in the fuel was containei in the live vegetation. Potassium is easilv leached and gaickly lost from dead tissues. Within the live vegetation airdwool shrubs were responsible for > 507 of the mass and nutrients, more so at site 2 which had not burned for a longer time.

PAGE 61

53

PAGE 62

54

PAGE 63

55 *§b_Col le^t ion _1et hods There war; n3 significant differences between postburn ash collection methods for sass, nutrient concentrations, or nutrient staining croos in the site 1 barns with a single exception: lighar Hg concentration by the Petri dish method from the •iry season burn (Table 7). There was, however, a consistent pattern of higher mean nutrient concentrations in the ash collected by the petri dish method. A light rain falling near the end of the site 2 wet season burn precluded the collection of ash by the vacuum metho3 for that burn. In the site 2 dry season barn the estimates of ash iass ani all nutrient standing crops were significantly higher for the vacuum lethol. The tendency for higher nutrient concentrations in the petri dish ash was also found here, wita only Hg significantly higher, Apnarentlv at site 2 substantial aaounts of unburned humus and/or mineral soil were pickei id br the vacuum. This would account for both the higher aass and the tendency toward lower nutrient concentratiois. Because of the larger surface area sampled by the vacuui method, it produced smaller coefficients of variation for aass and nutrient concentrations in 14 of 15 cases. The dry aass and nutrient (cations and P) values f ro , a the petri dish mathoi were used to estimate postburn stardim crops because they ware available for all the burns and b°cause vacuum samples gave over-estimates at site ?,

PAGE 64

56 +J

PAGE 65

Nitrogen in ash was estimated from the mss an? nutrient concentration data collected by the vacuum method. Sine? these data nr? not available for the site 2 wet season burn, the asin S concentration for the site 2 dry season burn was applied to the wet saason netri dish pstiftutes pf ash mass, Tie estimate of N in the postbnru ash at the site 2 dry season barn is undoubtedly an over-estimate and therefore gi/9s a conservative estimate of the loss of " for that burn. ggstbura .Pisfcribatiqa_of _Hass ^ni Nutr ie nts 'lost of tie litter (excapt for the heavier pine branches and con?s) wis consumed in all th a burns (?igs, 9 and 10) ; in the site 2 wet season burn considerable amounts of the partiallv darorappsed lower layers of litter in deoressions were also left. v .osf of the preburn vegetation Sid not burn except in th? sita 1 wet season barn where slightlv jior n than half was consumed. Herbs were almost completely consumed in the burns (except for petioles of ^teriiiga) , but shrub stams and most l=af material remained. The shrub status that remained upright became the standing dead compartment of tie postburn litter. The blades of pais fronds were often at least partially consume 1 , but the petioles did not burn. The 78-95 g/m 2 of postburn ash accounted for 9-25* of the mass regaining after the burns.

PAGE 66

5<1 The losses of nutrients from the litter and vegetation were roughl? proportional to the losses in 5iass (^iqs. 9 an 1 10), One-half or sore of the standing crops of the nonvolatile elenents other than K were found in the ash after the burns, ft large proportion of the K remained in the dead, but unconsumed, vegetation (mostly shrubs). The postburn distribution of N was similar to the postburn distribution of aass. The overall losses of organic natter from the ecosystem ranged from about 1-1.5 kg/a* {Table 8). The losses n^ m ranged froa 5,7-9.5 j/m 7 . There were no significant differences between preburn and postburn standing crons o^ the non-volatile eleaents except for a loss of K in the site 1 wet season burn. This represents one of 16 tests (at 0,05 level) for nonvolatile nutrients and may be a false rejection (i,e, a type I error). There is little reason f o exoect detectable losses of K in relatively cool fires such as these, ?ostf ir e_?ecovery_of _Hass_and_^utrients Vegetation Although aboveground plant narts were killed bv the burns, I observe! alaost no plant mortality. one of the aost striking features of th = postburn period was the rapid reappearance of green tissues, especially herbs and nalis. Within davs after the burns fresh blades of grass appeared

PAGE 67

59 >i p o i x P co cn to -H -H P P S-l (D (0 (U T3 +J P G W CO CD • >. •G~.Q P p o c C P 5 •HMO 0) £ to CO C P ~ CD 03 ** -H T3 P C II -P rd 3 P C C CO T3 h-i P G CO (0 C i£ P P -^-H T3 C7> r0 — ' tt m 0£ en in CO (0 o a O T3 o n c O 10 II oi * a. G M~ •H 0) T3 P CO C P 0) cd -H co -P .-H CO CO o H >i c O P •rH G P (d (0 u P -H CD M-l & &>-H a) c -O > Cn c -h (0 u> CO c c P T3 a) u p c Ph-H CO CO e p >i o u Q

PAGE 68

*9 from the groand and palm fronts poshed out from the stem adces, Sariwooi! recovery bagan somewhat later. Essentially aLl the recover? daring the first year was lue to sprouting from belowground parts. Asong the hardwoods only Dodonaea viscosa and Rhus cooallina ^ a ^ ar 7 seedling regeneration, but this contributed an insignificant amount to tha total recovery. The seedlings nrobablv ca^oe froa seeds present in the soil or litter before the burns; both genera are known to hav? fire-stimulated germination (Floyi 1966, larks 1979) . 5o data on reproductive activity were taken, out iuriag the year following burning 1 observed flowering of every herbaceous species Dresent in the plots, Within a aoith after the site 1 wet season burn ^uellia S.II2ii.D.iiS.§L2 W3?; flowering and by 2 ao 1S additional soecies w 3 r? in flower. Seproductive activity of palms was not noticeably different in burned and unburnel areas, Most hardwoods dii not flower during the first year after burning except for tie w=a!cly woody Lantana depr°§sa, ^.orinda royoc, and ~coton kLDLiiE.i.§' Occasional individuals of ?§idiuri k2Hli2°§» ^yrsonima lucida, ^odonaea yiscosa, and Ficus citrifolia also flowered within the first year. Serbs reached their preburn bioaass levels within 7 ro following 3ry season burns and by 1 yr aft=r wet season burns, even though the 2 mo recovery was greater after wet season burns (Fig, 11, »ppen3ix B) . In all four of the plots pala bioaass by 7 ao was statistically

PAGE 69

61 iniistinguist able from preburn amoants. Hardwoods recovered more slowly than herbs and did not approach their preburn levels by the eni of the first year. Reooverv a1 : 1 yr ranged from 18-39"? of the preburn biomass. Certain hardwood species sproated sooner than others (D. viscosa and R. 22Eii.iiS.§ "2^e two of the earliest) , Hardwood bionass increased at each of the sampling periods following we^ season burns, bat showed no increase from 7-12 mo after the dry season barns (Fig. 11). The overall pattern of recover? indicates that s.oril to August is a more favorable growim period than the rest of the year, Before tha fires, stems accounted for most of the hardwood bi^mass, whereas 1 yr after burning leaves accounted for equal or greater amounts than stems (Appendix 3), RariwiDi Leaf bismass recovered to 32-68'^ of thr preburn biomass but stems reached only 12-24* o c the original amounts. The preburn stems, of course, represented the wood increments of 3.5-6,5 yr of growth. The relatively rapid recovery of leaf biomass combined with complete recovery of herb and palm biomass means that the functional capacity for photosynthesis recovers faster than the structural characteristic of biomass. If one assumes that the sum of herb, palm, and hardwood lea F biomass is a measure of phatosynthetic capacity, then the 1 yr recovery Df the vegetation for wet and dry season burns is 82 and 92% at site 1 and I'-i and 58* at site 7. The

PAGE 70

corresponding recovery of total vegetation biosass (including hardwood stems) is 55, 63, 41, and 2795. The abovegrouid net priaary production of the anderstory for tha first year after burning can b° estisat.ed by add .in j the litter produced during the year to the standing crop o^ bioaass at tha end of the year. There was no palm leaf litter and littla hardwood leaf litter produced during the first year, and this litter was not measured separately from the hardwood litter resulting from the burns. ""here wer substantial aaoants of herb litter produced bv 1
PAGE 71

63 impossible to detect small differences that miaht have a cumulative effect after several burns. Hardwoods, on the other hand, showed marked differences in recovery iaong the four plots. The absolute recovery o p hardwood biDaass was greatar at site 2, but that site had a much higher initial hardwood biomass. At site 1 the hardwood recDvery was significantly lower following the wet season burn (29 g/m 2 or 20*,) than the dry season burn f^O g/m 2 or 39f). At site 2 the trend was reversed, with greater r^corerv after the wet season burn ( 1 37 g/m 2 or 3 r ~) than the dry season burn (78 g/m 2 or 18*) . The mo^'r lively explanation for this apparent inconsistency is that fire temperatures had a greater effect on recovery than season of burn. The recovsrv of nutrients in v he und^rstorv vegetation followed a pattern very similar to that of biomass (?igs. 12-16, Anpealix 5). The main difference was the somewhat faster rate of recovery because of elevated nutrient concentratioas in the young regrowth tissues. The recovery of Ca, however, was delayed somewhat relative to biomass because the 2 ao tissue concentrations of palms an A hardwoods were lower than the preburn concentrations. Herbs in particular often reached preburn levels of nutrient standing croos earlier than biomass. For example, ? standing crop in herbs was not significant lv different fro? the preburn aaount for both dry season burns at only 2 mo

PAGE 72

64 250-1 SITE 2 7 12 2 MONTHS POSTBURN Figure 11. Postburn recovery of understory biomass. Bar on left shows preburn values.

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65 SITE I 7 12 2 MONTHS POSTBURN Figure 12. Postburn recovery of nitrogen in understory vegetation. Bar on left shows preburn values.

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66 SITE 0.12-1 OTHER WET SEASON i SHRUBS DRY SEASON BURN SITE 2 7 12 2 MONTHS POSTBURN Figure 13. Postburn recovery of phosphorus in understory vegetation. Bar on left shows preburn values.

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67 .8.6 1.4 SITE I WET SEASON I OTHER BURN |l SHRUBS DRY SEASON BURN SITE 2 WET SEASON BURN DRY SEASON BURN MONTHS POSTBURN Figure 14. Postburn recovery of potassium in understory vegetation. Bar on left shows preburn values.

PAGE 76

68 3.0 n SITE I DRY SEASON BURN 7 12 2 8 12 MONTHS POSTBURN Figure 15. Postburn recovery of calcium in understory vegetation. Bar on left shows preburn values.

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69 0.4 0-1 SITE 12 2 MONTHS POSTBURN Figure 16. Postburn recovery of magnesium in understory vegetation. Bar on left shows preburn values.

PAGE 78

7"> postburn; the standing crop of K in herbs in the site 1 wet season plot ilso reached the prebarn level by 2 mo, Tn on a case ("a, sit? 1 wet season burn) the standing cror> was significantly higher 1 yr after burning than before the fire. For palms, both N and P standing crops were not significantly different froa preburn at 2 mo for the site ? wet season burn. All other palm nutrient standing cro^s, like palm bioaass, did not reach initial amounts until 7 mo postburn. The pattern or recovers of nutrient standing crops in hardwoods was the same as for biomass except that '< at *-he site 1 dry season plot at 7 mo and the site 2 wet season plot at 12 so were not different froa the preburn amounts. The percent recovery of all nutrients in hardwoods at 1 vr wis greater than the corrasoonding biomasa recovery because of high nutrient concentrations. The percent recover? e r the total -vegetition nutrient standing crops was greater than the recovery of biomass for the same reason. The " standing croos ia the two dry season plots at 1 vr w^re not significantly different from the prebarn standing crops, Litter The standing rrop of litter mass (and nutrients) luring the 1 yr postburn period is a function of the amounts present iraaeiiately after the burns, inputs, and losses through leaciing and decomposition. Even though nearly all

PAGE 79

71 of the prebarn anierstory litter was consumed in the barns (Figs. 9 ia^ 10, Appendix 3), the understorv v-getation that was fcilled bat not consumed by the fire replaced, it. In the dry season pLot in site 2 there was actuallv more after the burn than before. The understorv litter compartment receive3 no inputs for several months until herbaceous material began to die, Bv the 12 ao sampling oerioo" some of the hardwoods hal also shed some leaves. At 1 yr some o F the old?st palm fronds were becoming senescent, but were not dead and therefore not yet Dart of the understory litter. There was some decrease in understorv litter mass during the first t*o months after burning in all plots (Anpendix 9). From 2-7 mo after burning the dry season burn plots showed continued loss of mass (because these were wet season months), whiLe the wet season plots did not (because it was Iry) . 7 coi 7-12 ao there was an increase in mass except at the site 2 3rv season plot where decomposition outpace! meager litter proluctioa hv shrubs and herbs. At si*-e 1 much of the input to unierstory litter is attributable to herbs. *t the ead of the first year the standing crops of understory litter mass were not different from amounts present immeliately after the burns, except for the si 4 -? 2 dry season pLot. However, the standing crops w?r° below their prebura levels except at the site 2 wet season clot where there ns a large amount o f unconsumed vegetation and rapid recovery of litter-producing hardwoods.

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72 Th9 standing srops of nutrients in the nnrterstory litter showed various patterns during the postburn vcar. Larqe 3acreis53 oftan occurred during the first postburn rainy periol, 0-2 no c ollowing wet season burns and 7-1 no after dry season barns. Potassium in particular shovei leaching losses of >8Q-90X of the amount in the postburn litter. ?or most of the autrients thera was some net increase ^urinT the 7-12 mo period. Phosphorus, however, showei initial losses and no significant change during the last 5 no neriod, "itrogen ani 3a showed the least net loss during the vear and wers not liffersnt from 'he amounts present immediately after the bacns (except for the site 2 3ry season plot which lost mass throughout the period). In contrast to the understory litter compartment, which had no inputs iuring the firs 4 several months a c ter burning, tha pinlitter received continual inputs. Pine needles fall throughout the year, but at highest rates during the wet ssjsoa (Pig. 17). Short term peaks in needlefall are caused by high winis. The annual needlefall was about 320 g/m* for sits 1 and 260 g/m 2 for site 2 (Table 9). Seedlefall constitutes 75-SO 1 * of total pine litterfall, Pine branches, aostlv <3 cm diameter, contribute about a tenth of tha litterfall mass, and seed cones an-i miscellaneous materials make up about the same fraction. Soas vear-to-year variation in litterfall is to be expected; neeilefall daring the study perioi was about average a 4 -

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73 "P""' ! "••r i V T — i — i — i — i — i — i — i — i — ' — ' — i — T ASON D'JFMAMJ J ASOND'JFM 1980 981 982 Figure 17. Pine needlefall in the study plots and an unburned area of site 2. Closed triangles show time of burn and open triangles the 1 yr anniversary of the burn. Absence of bars means that no sampling was done.

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74 13

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7S other locations in Long Pine Key {K, Herndon, unpublished data). The number of seed cones wis probably higher than average, at least for site 1, because there was a better than average seed crop in the autumn of 1980. The deposition of nutrients through pine litterfall ranged from about 2 g/a2 of :a and 1 g/m 2 of M to 0.03-0.05 g/m 2 of ? (Table 9). ine notable aspect of the nutrient inputs is t v ? high concentration of X and the low concentration of Ca in pin? :or.?s relative to other litter tvpes. ?iae lifter mik.es up the maior portion of the fuel mass, The material remaining after a *ire is mostly heavier p\?c^~ such as branches and cones, unless the fuel is moist (e, g, site 2 wet season burn). Pine litter mass showed a raore or less continuous increase except for the 0-2 ao period following tie wet season burns where moist conlftions an* the nutrients released in the ash way have stimulate-! decomposition. By 1 yr all plots were stillfar below preburn levels: site 1 about 50* and site 2 33-U0* o^ preburn. The nutrient standing crops in pine. litter showed a pattern very similar to mass with some decrease 0-2 mo following wet season burns and increases otherwise. The percent re-ovary at 1 vr was similar to mass for all nutrients except. N f which only reached about 33at site 1 and 20* at site 2.

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76 The recovery of total litter mass followed a pattern dominated by the pine litter except for the decline between 7 and 12 ao it the site 2 dry season barn plot caused by a drop in understory litter. At one year litter pass wes 42-62? of its prabura level, Phosphorus and Ca recovered in proportion t? dry mass. Nitrogen was mach lower than dry mass (26-37*) because C : N ratios decrease with iecompositioa. ?otassiua recovery was high relative to miss, especially at site 2, because of the high proportion of relatively unweathere3 litter materials. Tmj>act_of _?_irej^on_Pines There is some indication of a slight increase in the rate of needlefall imiadia^ely following the burns fig. 17) , even though thara was little scorching of needles. The stress of high temperatures may lead to senescence of needle fascicles eacliec than normal. In both sita 1 plots there was no mortality of pipe trees during the yaar after burning (Fig. 5). In contns f , i 1 site 2, where the trees were smaller, some trees died (Figs. 6 and 7). In tie wet season plot at site 2 six trees were dead 1 yr after the burn and in the dry season plot 9? trees were dead, including virtually all tr^es < 7 cm dbh, 'Tone of these trees showed substantial scorching and all appeared to be healtiy for the first few months after the fires. There was evidence of bark beetle activity in all the dead

PAGE 85

77 trees, bat there is no way of knowing whether the insects were responsible for the deaths of the trees or whether they only attacked trees that were already dying. T*: is clear, however, that high temperatures around the stems of South Florida slash pine trees can lead to their deaths. Three years after the dry season burn at site 2 most of the pines had cracks ecuding resin in the bark of the basal 1-° n o^ the trunk. Under the burning conditions of the experimental burns all pine seedlings were killed by the fires (Table 10), Th*> season of burning has a pronounced effect on the establishment of new seedlings. Seedfall is from September into November; therefore burns that occur in the wet season before seedfall create excellent conditions for seed germination and seedling establishment. Burns that occur in the dry season (after seedfall) destroy the current year's seed crop and by the next Deriod of seedfall conditions are less favorable for seedling establishment. ^he 1980 seod crop in Long Pin? Key was relatively good and the wet season barn plots had much higher seedling densities 1 yr later than did plots burned in the dry season (Table 10).

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78 CO T3 -P U ft C (0 (T5 3 tr CN CD rt II s "5T C cn cn * c o CN T3 CD T3 X! cn iJ3 CD T3 CD CO 3 U -P CX CD cn C CD •H CD X SXJZ -P P M-l S-l o c o -H IH •h p a cn O CD c p. o CD P X Q CD CD -P C O P H 3 CM CQ P Q >i P a

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79 Soil analyses show some striking differences in fh Q properties of tha substrate between the two sites (Table 11). Thf»se differences are Largely due to *he oresence of pocltets of tie reddish-brown "Redland" soil at site 1, The wet season pLst had 8.2* (S,E,=1.62) of the surface covered by mineral soils and the dry season plot 3 . H 7 fS. U. =1. '42) . A very few packets of the Pedland soil were present in the site 2 dry season plot and none were seen in the site 2 wet season olot, The organic natter content of u he soils was much higher at site 2 (aaout 46?) than site 1 (about 13f.) , although both sites are reLati/ely high for upland soils. The higher organic content nay account for the slight lv low^r orehurn pT at site 2., Pr^burn extractable K an^ r lg do not show much difference between sites, althou7h K tray he soaewhat higher at site 2. Phosphorus is such higher at site 2 than si +c 1 , suggestin? a relationship with organic matter, Purn eff 3 ,ts on soil properties remaining 1 vr postbnrn include an iacrease in pH. This was most Dronounced in *he site 2 samples and in the paired RedlanS soil samples taken in site 1, wiere initial p w was lower, Soil organic matter was unaffected bjr burning. There is an indication that extractable ? was reduced 1 yr after burning. The amounts extractable bv weak acid in the Pedland soil samples were below detection limits both in burned and unturned soil.

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80 o CD +i . -P en II C 4-> 10 & 3 CD ^ O e JZ~ CD &i C 3 rH O O -H Sh O >i -C en X! rH C 6 r« S O M O in CD -C m 3 en CD 4-> T3 u c CD rO cn 0) u c CD S-l rH T3 CD O CD M-l o a; O o w M-l co 4-1 — . en CD en t) >i CD r4 4-> (0 U C og (C •H O en en 4H CD O Sh +J en en >h o O • U u CD en E ^ 4J rej (C o h w>a ^ 3 C -P en T3 to (D c -P u ed (0 en o U V4 •H CD C4J-> rcj 4-> <#> Cr> (C -~ m e o 44 C O-H rH CD 04 e e rl fC Eh en +1 * 4-1 Sh Q >1 Q 4-1 4« 4-1 o n

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31 Extractable 1g -nay be somewhat higher after burninq, at least at sits 1. Burning increased extractable K in both types of" soli samples at site 1 bat the increase was statisticall/ significant only for the R a dland soil. At site 2 th = re was a decrease in K after burning. This may result fro
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C3APTSR 17 DISCUSSION Fire-caused Losses _of _y_utrients ln= of the most obvious effects of fire is the removal of organic matter, Nutrients are also lost by volatilization or oarticulate amissions. Numerous studies have af+emotod to measure taese losses in several Scinds of ecosyst : 2>s, Tn Drescribed birning situations it is possible to sample standing croos before and after the fire, as was done in this study. Wita wildfires the approach has usually been to compare standing crops in the burned area vi*-h nearby unburned analogs (e.g. ~rier 1975). Spatial heterogenei^ :y of fuels mi the collectiag of oostbnra ash rose rrobl^T.s for field stidies (Paison 1980). 7 or example, in a li^h*prescribed birn in southeastern coastal plain nine forest, Binstock (1978) and Kguyen (1978) measured higher mean values of mass and nutrients after the burn than before. In a study of fire in heather ecosystems in England 'vans and Mien (1971) gave up on field measurements and performed artificial barns in the laboratory. This rsorssents the other common approach to measuring losses during ^ires. Simulated burning has been done both as open ignition or in a muffle furnace. The alditional accuracy in measuring 82

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S3 losses, however, is at the expense of the realism of. the burning conditions. Table 12 presents the average mass balance for th c four burns in this study along with data c rom several other southeastern pinelands and a few other ecosystems. The table does not include examples of slash burning (e.g. Garwood and Jackson 1975, Pwel et al. 19«1). Comparisons raust be temnerei with a degree of caution because methodologies an5 conventions differ somewhat among the studies. Ii sone cases the fuel represents onl7 the forest floor (litter) and in others litter *Rd vegetation. T ": .-> studies by Hou?h (19R1), Kodaiaa and Van Lear f1?3n), Pich^r et al. (193?), Debano and Conrad (1978), and Trier Ml?' 7 * involved fieLd sampling of ash, Debano and Conrad vacuumel the litter and ash in their stuiv of chaDarral. Hough picked no tha ash "bv hand" and stated that sos? ash was not collected. The study by flough (1981) ieals with the situation most similar to the *iami Pock 5idge oinelands. The overstory was mixed stands of slash and longleaf Dines with relatively iense understories dominated bv l£££S.2i E^oens (saw nalastto) and Ilex glabra (gallberrv) . The fuel consumption in the Long Pine Key burns was within tha range of the other pineland burns (Table 1 2> , The lower consuaption (both absolute and percentage) in three of the oth=r southeastern oineland burns is due to high moisture content of the lower lavers of the forest

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84 CO

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85 "OIIO •H u O U i e >.« " 10 -H i-H fH -O -I -I O O O .il 01 in C T3 C -I £ (0 -H O >i (0 » c c io c C 10 0) U 10 > JZ r* m
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86 floor (Sweeaay and Biswell 1961) , wildfires under extreme conditions :in of course Lead to very large losses (Grior 1975) , irasslani fuels (Lloyd 1971, Christensen 1977) also have high percentage consumption rates. The losses of 8 seem, for all oractical purposes, to be proportional to losses of total mass. Hough (198 1) developed a regression eguation to describe the loss of *! i?. prescribed barns: S (kj/ha) = -10.55 + 0,0071 (J) where X is the loss of mass in k^/ha. The jean 8 concentration in the fuel of these stands is abo'Jt 0.75"' (Hough 1982), la a field study not included in Table 12, ^leanedson et al. (1963) found losses of 30T of mass ?,.nd 31* of H after prescribed burning of ponderosa pine litter. r ?. a lab stu3y knight (1966) burned conifsr fores 1 ^loor samples in a muffle furnace and found losses of 3 Q and 2 " ? for mass mi V, respectively, at 300°C and 53 and 64'? at 600°C. Tq Lab studies on southeastern pine litter in which fael samples were simplv ignited, De^ell and Palston (197^) recorded losses of 71? of the mass and 58^ of N while Le'-ris (1975) founl lasses of 39 and 56% for mass and !?, respectively. Ta these relatively cool burns most of the V was lost as iinitrogen gas. Fires may also result in losses o c the so-called ash elements (Cliytoa 1975, Table 12), However, under raost

PAGE 95

87 circumstances it is not possible to show statistically significant Losses by preburn anl postburn sampling (e, g, this study an3 Pishter et al. 198?). The magnitude of these losses as oresentei in much of the literature is likely to be ovarastima ted. In field studies it is difficult to sample the ash. When small plots are burned, and especially i c samples of fuel are burned in laboratory settings, there is no opportunity for the particulate matter to settle back 3own on the sampled area. Significant amounts of nutrients in particulate flatter are carried away from saall burns (Smith ani Powes 197*, Evans and Mien 1971), Tn :nore extensive burns much of the particulate fraction of smoke will return lirectly to the ground. Some of the particulate emissions are deposited on the canopy and are returned to the forest floor by the first rain after the burn. Ther« is also a tendency to consider any loss reported in the literature as real while gains after burning are ignored (e.g. 3oarner 1982). For examole, the increase of 25? in the amount of *lg reported bv Debano and Tonra2 (1978, Table 12) makes the loss of 155 of K seem of guestionable significance. The ash element most likel7 to be lost by volatilization is S, which is volatilized at temperatures above 500°c. in what arorooably the two hottest fires listed in Tabl1? (chaparral and the 2ntiat wildfire) the percentaae of K lost was higher than that of any other ash element. This wa~ also true of the lab simulations on heather.

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pq The ash lepositel on the soil surface is subject to erosion losses oa sloped tarrain, but not in South Florida. 9ach of the minaral conteit of the ash is easilv leached into the soil by rainfall (Allen 1964, Lewis 1974, ~hristensen 1977). Recently burned ecosvstems may experience losses to groundwater, however these losses s°em to be very small for coastal plain pinelands (Boerner and Foraan 1932, Richter et al. 1982), In Long Pine Key the iiijh soil organic matter content should give the soil a high option exchange capacity and P should be guic^lv immobilized by the abundint 3a. The rapid recovery o* the vegetation also acts as a sink for the nutrients released by the fire (see below) . Mthough the losses of nutrients (other than N) in the barns in thi, study were not statistically significant it is certain that some losses did occur, "oK=v a r, even if on-assumes a loss of 10% of the standing crop o^ the ash elements, tiase losses could be replaced by orecipitation inputs over the period of a burning rotation, 3. r ^-6 yr. Annual deposition of N, P, K, Ca, and ?!g in bulk precipitation in northcentral Florida is about 1-1. '4, 0.1, 0,3-0.6, 1-1,5, aad 0.2 g/m 2 respectively ("endry and Brezonik 193), Siekerk et al. 1979). Depending upon the estimate of 'J input by precipitation, this may or may not replace the substantial loss of H because losses ranged from 1.4-2.2 g*m-2*yr~* when averaged over the timo sines the previous fira.

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or, Tt is to be expected that nutrient losses should more or less egual inputs in ecosystems that have a long his+ory of frequent burning. In fact, fire may be a mechanism by which nutrient-poor ecosystems prevent the accumulation of nutrient capital. Several ajents of biological N-fixation could aid in recovery of N lost through burning. Although several herbaceous lagumas are common (e.g. Cassia spo, , Crotalaria Eumila) they ara not likely to fix significant amounts (Pundel 1981). kvsiloma latisi llgua is a leguminous tree, hut it is not common enough in pinelands to aid much nitrogen. Jilii guaila has a blue-green algal endophvt^ that fixes * (Lindblad 198U) . Sirica cerifera, an actinomycete-nodalated shrub, has substantial bio-rsass in much of Lonj Pin? Key (including site 2) and raav fix appreciable mounts of v, in a northern Plorila slash oinplantation Permarr and Fisher (1983) estimated that ^. cerifera niti a crown covec of 8* fixed 1, 1 g N*m2 *yr _1 . Sonsymbiotic ^ fixation by soil microorganism s in forest ecosystems has often proved to be a rather minor source of ^* relative to oreclpitation inputs (rjepkema 197°). Jorgensen and ffells (1971) found indications o^ increased soil acetylene reliction activity in burned loblollv pine olots compared to inburned controls. A later study by Jorgensen (1975) did aot support this finding and found ?r-fixation rates of < 0. 1 g*m2 + yr-». Vance et al. (1981) found even

PAGE 98

90 lower rites (0,01 g*a" 2 *yr-») and no effect of long-term prescribe;! burning in oak-hickory forest. In a orairi? site, DuBois and Kapustka (1983) aeasured 0.8 g*a-2*vr-* of nonsyabiotio V-fixation, about half of which was due to cyanobacterii. 31ue-green algae are not found in acid coastal plain soils (Jurgensen and Davey 1958) but they are coaaon in ciccuaneatral soils (~ranhall and Senriksson 1^*9) and abound oi ths oolitic limestone of the Siaai Rock p id7=. I ran an acetylene reduction assay on a few sanpl^s of rorl' from the stuly area and found aeasursable rates a f ter ?& hr of incubatioi. 2rude calculations indicate ? rates on t '-. order of 0.1 g*B~ 2 *yr-i. It would seem that fixation by various taxi plus precipitation inputs over a burnina rotation could easily account for tha losses of *T recorded for the experimental fires, Postfire _gecoyerv In the ^iaai Sock Ridge pinelands virtually all recoverv of understock species is by vegetative jeans rather than by seedling reproduction. This is fairly coaaon in ecosysteas that experience high fire frequencies. Abrahaiason (1983a) found very little change in species composition after fires in several pi n?-loainated plant coaniunities in sout hcentral "loriia. Boarner (1981) aLso note! relatively little change in species coaposition in burned areas of the Mew Jersev Pine Barrens.

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91 This is Li contrast to situations, often where fires are of lower frequency bat higher intensity, in which there is a distinctly oostburn flora. The large number of herbaceous annuals that appear after chanarral fires is a dramatic example (Chri stensen and ifuller 1975). The degree to which species changes result from burning depends in part on the severity of the fire, In -jack pine communities, fires during the Iry summer months consume the upoer organic layers of tie soil, whereas fires during the moister spring do not. Siioe species with shallow regenerative organs 3 ?^ eliminated by ground firas, numerous postffra disturbance species like Fpilobium (fireweed) become established after summer fires (Ohaann and Grigal 1981). Even thoujh recoverv in the roc* ridga pin°lands is vegetative, there are differences among the different growth forms in the rate of recovery, F'erbs and palms regrow very quickly, reaching their preburn dry masses within 1 yr. The monocots (jraaiaoid herbs and palms) and ferns hav= protected meristams that are seldom damaaed by ^ires, brasses are *ell known for their rapid regrowth aft>er top removal (gilion and Lewis 1962, Daubenmire 1963) . The recovery of iicots (whose buds are usually killed) recruires the activation of previously inactive morist^ms or *:he production 3? adventitious buds, whether they be on rhizomes, roots, or the base of stems; woody dicots take longer than larbaoeous dicots to show regrowth, "owev^r, a

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9? study by Hough (1965) in Georgia found that Serenoa reoens only reached 55T of its preburn aass 1 yr after burning whereas Tlax Tlabra, a hardwood, returned to 70% of its preburn l?v=L. This is somewhat anomalous because the preburn vegetation had been unburned for 15 vr and there should have been considerable stem bioaass. 5. reDgns was found to have greater cover 1 yr after a burn than before the barn in i stuiy by Abrahamson (1980b). This agrees mors closely with ay findings in the rock ridge pinelands. ^v 1 vr after the experimental burns, 110-190 g/m 2 of regrowth vegetation appeared in the burned plots, This is a fairly large amount in relation to some other postburn recoveries, Ons year after a prescribed burn in the New Jersey Pine 3arrens the regrowth of herbs, shrubs, and oak sprouts was 113 g/m 2 (Boeraer 19°1), In jack nine stands buraed by wildfires in Minnesota the vegetation recover^ range! from 2 1-13 1 g/a 2 after one complete growing season (Dhsann and 3rigal 1931) . The rerovsry of photosynthetic capacity is ev^n more rapid than tie recovery of biomass because hardwoods oroduce leaves iaoc3 ripilly than support tissues. In the four burns in Long Pine Key the recovery of ohotosynthetic tiss'i<=s (sum of herbs, palms, and hardwood leaves) was 53-937 of the preburn amount at the end o^ 1 yr, T he first vear recoverv of hardwood leaves alone ranged from 32-68* of the initial quantities. The rapid recovery of photosynthetic surface is

PAGE 101

93 also founl after fires in other South Florida slash pine ecosystems. Saaly flatwools with an understory of grasses, ?_• £2£LD.§r !• li.§.bra, an ^ several ericaceoas sr> e cies regained froi 57-83? of their original cover within a year after burning (Abrahamson 1984a). ^f f 3Ct_2f_S9ason_2f _Pnrnina_on_nardwood_Pecojrory Several stadias in southern U. S. pinelands have shown that presoriDed burning during the growing season kills back a greater percentage of hardwood stems and larger hardwood stems than iorman t-season fir^s (~haiken 1 9 S 2 ; Ferauson 1957, 1961; Lotti et al. 1969; 3render anrl Cooper 1968; Langlon 1981|. Tn the present study all understorv hardwood steins were Kille? by the fires regardless of season. This is because fiere were no stems with basal diameter? > 7 en and the burns w?re very even an 3 complete. Of greater interest, therefore, is the relative recovery of these hariwoods (by sprouting) following burns at different seasons. The pattern of sprout recoverv after burns at different seasons parallels, in general, that of topkilling: greater recovery after winter burns than summer burns. 'erauson (1961) in east Texas found, however, that although summer (August) burns tilled back more hardwood stems than winter (December) burns, the sprouts resulting from these burns were larger and mora numerous than those produced bv late

PAGE 102

91 winter (''ebriarylate *arch) or spring (late April-way) barns. Different measures of recovery have been used in different stiiies. The iata roost commonly reported are isnsity of steas (sprouts) ani cover, with sprout height occasionally givaa. Only rarely is bioraass (as used in this stulv) or sois measure of volume used, Densitv alone can be a misleading measure because topkilled hardwoods usually proiuce several sprouts, and therefore burning appears to increase har3wood density, but not necessarily biomass or total leaf acea, Results of a long-term study of prescribed burning in South ~aroliaa coastal plain loblolly pine stands have been reported after 13 (Lotti at al. 1960) , 20 (L°wis an* STarshbarger 1976), and 30 yr (Langdon 1981) of treatment?. The burning treatments, begun in 19'-i6 ani 1°S1, include annual burns and oeriodic burns (> 3 yr interval) ir hoth summer ani winter ani bienaial summer burns. Summer burns ace conductei as soon after June 1 as conditions permit ani the winter burns after December 1. Interpretation of the results is not entirely straightforward because the treatments vara sampled at different postburn ages, However, it is claar that summer burns result in reduce* hardwood ~3v?r relative to winter burns done at ths same freguency. The reduction is due to a combination o^ increased moctallty and less vigorous regrowth, T n fact.

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95 biennial sumaar burning is more effective than annual winter burning at reusing the number of stems and crown cover of woody undergrowth when the longer recovery period is accounted fee. The annual summer treatment virtually eliminated w->ody plants < 12.5 cm dbh. It is unlikely that th=? Long ?ina Key pinelands could burn more frequently than once every 2 yr, even on the aost productive si*-es. Th° periodic suner burning in the South Carolina study reduced the cover of woody plants relative to winter burning in st>its of prr>lucing a greater number of st°ms (Langdon 19S1), In Louisiana Srelen (1975) found that plo'-s that had been burned by six biennial Julv burns had less cov^r of hardwoods (iticlu3ing *I£ica cerifera and Phus cogallina) than plots birnel in *arch or lay. Hodgkins (1953) in Alabama found a greater recovery of shrubs and vines after ? single January burn than a singl? August burn. Hughes an 1 Knox (1964) followed the recovery of Tie* glabra after a series of three annual burns conducted in January, April, Juns, August, aid Octsber. Thev reported sorout density, height, and cov^r. 5ven after three burns all treatments showed an increase in number of stems relative to the initial nuib?r. All burning treatments also resulted in a decrease in average stem heights. Cover, which mav be the b?st single measure of the three measures the^ reported f or assessing recovery, was decreased for all months exceo 1 -. April, Jun? and August burns gave the greatps* decreases in

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or, cover ant! August and October barn plots ha-? tha shortest sprouts, Rised on the available data it would anoear that the recovery of bioaass was least after the August burns, followed by Juna and October. There are two frequently suggested explanations for this seasonal effact af fires, which can be described as the physical and the physiological. The physical explanation ; s based on the fact that summer fires are "hotter", because of higher ambient temperatures and often drier fuel conditions. The higher imbiant temperatures mean that the vegetation itself is warmer and, therefore, that less heat is r^auired to raise tha tissue to a Lethal temoerature (Pvram 1948, Rare 1961). Rare (1965a) demonstrated that it took about 50% longer for a torch flame aoplied to a lonqleaf nine trunk to raise tha temoerature of the cambium to ^0'" when the initial temperatura was near instead of 1 s °C. This irgument is aostly applied to topkilling of strain but it ear. be applied agually well to the degree of damage to the rootstock, A fire when the initial temperature of the soil and rootstacc is high should kill more tissue so tha* less nutrient reserves and fewer buds are available for r^ooverv, In subtraoical South Florida pinelands the temperature difference batwean summer \ n d wintar is less than that fonn* at higher latitudes. Lotti et al. (1960) reported amtiier. 4 temperature liffarences of about 1^.5°C in South Carolina. Summer and winter burning conditions in east Texas differed

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Q7 by about 19°(Ferguson 1961) . The dif f erences for the two pairs of burns in rock ridge pineland «er a 11.5 and B°n, The other explanation is that th* plants in question are physiological, lv nor? susceotible to heat injurv and less able to recover by sprouting a certain tines of the year Hare 1961), These times of year are of course related to the phenology of the plant rather than the calendar date. Susceptibility to topkilliag in particular should be higher during th<* active growing season than durinq the dormant season, particularly in deciduous species, Numerous studies examining the ability of hardwoods to resprout following top-removal or girdling orovid= evidpr_c=> for seasonal fluctuations in the ability of plant to recover, independent of anv fire-temperature effects, 9enger (1953) and Hare (19M) reviewed the literature or. effect of season on coooicing. They conclude that cutt-inq at the time of most active growth in the spring or earlv summer generally results in the poorest recovery of deciduous hirdvoois, and winter cutting results in most vigorous sprouting. All the hardwoods of interest in the ttiaai VozY, Hidge pineland are evergreen or nearlv so. T t might be exoected that evergreen species, since they naintain leaves that can photosvn thesire throughout the year, might b? sore stressed by winter topkilling relative to dormant deciduous species.

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Longhurst (1956) observed sprouting ability of two evergreen an! two deciduous species of California oaks cut at different times of the vear. Re suggested that the evergreaa species were lass sensitive to season of cutting than the deciduous species, although by two years after cutting thsr* appeared to be no seasonal differences among the species in the number of stumps with > 5 sprouts, Juniper (a conifer) cut at various times throughout the vear in Texas has less sprout biomass a year after cutting in lata 'lay-August than the c n st of the year (Schuster and George 1969). In South Florida, coppicing of erotic, evergreen Suralv^us species, in terms of survival, of rootstocks aid height and biomass of sprouts, was stronglv influenced bv month of cutting and was lowest in August (Pockwood et al, 1984), With 3, ULilldis the biomass of sprouts, although lowest after cutting in August, was depressed for traes cut in the entire JulyOctober period, Variation in the ability to recover after topkilling is usuallv attributed to differences ia available carbohydrate reserves in the regenerating organ. Deciduous trees generally s*iow i decline and minimum in belowgro'ind carbohydrates during the period of leaf enlargement. This is the cisa with two deciduous oak species in western Florida that showed minima in Aoril and May floods e 4 al. 1959). !b»37?r root carbohydrate levels returned to fairly high levels by June or July, well within the summer fire

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perioi. Sv^rgrs^n species seem to have lowest reserves later in tha year. §§E§H2i I£2S.Q.§ (admittedly no 4 a hardwood) had lowest available carbohydrate lsvels in the rhizome in June and July (Hough 1965) . II ex 2l3tE3: * n Georgia has lower carbohydrate concentrations in its rhizomes daring Jane, August, and October than Januarv or April (Hughes and Knos 196U). Evidence that carbohydrate reserves determine the potential capacity of hardwoods to recover from topkilling is not overly convincing. Sanger (1953) speculated that the resorouting :>!: sweetgum may be regulated by the hormonal balance of ta2 plant or by photoperiod because he did not find a good correlation between sprouting vigor and carbohydrate concentration. » study bv Jones and T.aude (1960) c oun? the least sprouting of Ad_enostom§_ f asriculat ut (chaaise) after cutting in **ay when the carbohydrate content of the roots was relatively high. Although carbohydrate reserves may show a seasonal pattern that is in a general way similar to sprouting ability, it is prefer*bl a to conduct catting experiments to determine dir=ctlv the variation in recovery ability. Tn many pLne-hardwoo3 situations, the temperature and physiological factors operate concurrently to result in less recovery after summer fires than winter fires. Tn subtropical pinelands it is likely that both these factors are not as Lnflaential because ambient temperatures show

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100 less seasonal fluctuation and the species are evergreen, Individual fire characteristics can therefore more °asilv override the influence of season. Fuel moisture conditions in South Florida follow a seasonal pattern that can lead to "cooler" fires during the wet season (summer) than the dry season (winter). The significantly lower hardwood recovery after the early *arch burn than tha September burn in site 2 is due, at least in part, to a large difference in fire temperatures, Tn this case the lo*er fuel moisture resulted in higher f i r c temperatures luring th^ cooler season. A similar phenomenon has been reported in the regeneration of heather in Scotland. Hilar and "files (1970) found that Calluna IS.ili£i.§ regenerated better after cutting in the spring than the autumn, but better after burning in autumn than sntln, This was apoarently due to drier conditions in the sprins resulting in mora severe burns, It is possible, however, that a physioloaical mechanism was involve! as well in tha poor recovery of the hardwoods after the dry season burn at site 2. Fven though the available evidence indicates that sprouting abilitv and carbohydrate reserves of evergreen species reach a minimum in the summer, some of the hardwoods were beginning stem elongation at the time of the M .arch burn and may hav~ been especially sisceptible.

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101 Frequently burned ecosystems, often nutrient-r>oor ecosystems, must contend with relativelv large pulses o* nutrients released in laachable or easily mineral \ zable form in the ash. One mechanism that reduces *he losses of this material is the exchange processes and other chemical reactions that hsid the nutrients in tha soils. Another mechanism whereby nutrients are immobilized within the ecosystem is uptake by the postfire plan* community. Nutrients contained in plan 1blora.ass are not so subi = ct *o leaching or rmo p f losses as thosp in the soil. This can K a considered a general response of ecosystems to listurbanoe (iarfcs and Borman 1972, Vitousek and Seiners 1975) whether the disturbance is fira, logging, insect defoliation, a tc. It has even been suggested that the rapid growth of sD:i?/j ephemerals in temperate deciduous forests is r^spnnsibl c or picking up natriants that otherwise might be leached and lost from tha system (duller and Borman 1976, Blank et al. 1989). Pegrawti vegetation after disturbance mav also reduce nutrient losses by other mechanisms. For Q :carapl ri , avapotranspiratiDn decreases the amount of water moving through tha system and thereby reduces leachino loss (Roernar anl "onann 1982). ''egrowth of svmbiotio T-firers can also serve to replace some of the *? lost through volatilizatiDn,

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10? The resprouting mode of racovary may be particularly aivantageous in nutrient-poor ecosystems, such as nost pinalands, because the established root systems fane 3 possibly stored carbohydrates) allow more raoid initial uotake of nutrients than recovery by seedling regeneration (Chapin and 7an Cleve 1981). In this study the recovery of understory ve-retation di^s after 1 yr averaged 47^ of the original amount. This would represent a substantial amount of nutrients even if nutrient concentrations were the same in regrowth bioanss as. in the oreburn vagatation. flowever, the higher nutrient concentrations of young tissues (except Ca) mean the immobilization of nutrients was more raoid thin biomass accumulation during the first year. At the end of 1 vr of recovery the average standing crops of nutrients in vegetation as a percent of initial standina crop vac 62* r or 5, 60% for ?, 55* for T, 46* for Ca , and 56^ for ig, Only Ca, which is ur.likelv to b3 limiting in this situation, was not substantially higher than bionass, Tt is likely that some of the nutrients in the retTrowth vegetation are translocate! from belowgronnd parts, but by 1 yr they probably represent net uptake by the plants. The sprouting habit anl the pattern of rapid growth bv herbs and paLms and then hardwoods would se Q i to ma v . c this nutrient-pooc system particularly well-alapted to relatively frequent fices. The guicVgrowth by th° understory

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103 vegetatioa should capture the pulse of nutrients released hy fire and suDs^qnant decomposition. The turnover of the understory vegetation (through litter production) in the order (from fastest to slowest) herbs, palms, and larger hardwoods should then gradually release nutrients that can be taken up ay the pine overstorv as well as the understory vegetation. Tf the fire frequency were to be drasticallv decreased, the eliaination of the herbaceous understorv would reduce the ability of the system to retain nutrients after fires. Under a very high fire frequency the herbaceous exponent of the understorv vegetation would increase at the expense of the woody sDecies. ^he rapid recovery of lerbiceous species would presuiaablv be able to retain the nutrients released in smaller but more frequentpulses* Summarv_and_CoQclusions The «iami Rock Sidge pineland is a floristicallv and ecologically distinctive ecosystem that is perpetuated ^y frequent fires. The ecosystem itself may be considered endangered because only a few thousand hectares of the original arei are maintained in a natural condition, and most of the rest has been irrevocably altered. The oianh oomiunity contains several endemic taxa, many if which ar? found in the study plots. ^ver 128 species were pr°se*it in the plots, Including almost 50 shrubby hardwood species.

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f}tt 3 get tarda scibra was the dominant shrub in terms of biomass at both site?. The shrub layer also included three Dalas and a cycid, The remainder of the species w^re herbs, with grasses contributing most to biomass. The burns were backing fires that gave good fuel consumption (> 70S) except for the wet season burn in site 2 where high fuel moisture reduced consumption to about 50 1 *. Ml the fires completely top.ki.lled the understory vegetation with little immediately visible damage to the overstorv. There was little mortality of understory shrubs, but most o* the pines < 7 :u dbh in the site 2 dry season burr, plo 4 were dead at the end of 1 vr. Fire temperatures were hotter in the site 1 wet season and the site 2 dry season burns than the other burns. The burns consumed about 1 ^g/m 2 of organic master except in the site 2 Iry season burn where about 1.5 kg/m z burr.oi. Nitrogen losses ranged from 5.7-9,5 i/ia 2 , The V loss can easily be replaced by meteorological inputs and symbiotic and nonsymbiotic fixation during the period of a 3.5-6 vr burning rotation. Losses of cations (K, Ca, Sg) and P were too small to be detected by preburn and postburn sanplicq, except for one burn where the loss of K was significant, The 78-95 g/a 2 of ash deposited on the soil surface include ! up to 20 g/m 2 of Ca, The soil oft was still elevated 1 vr after the burns in soite of initial soil r>H > 6.0,

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105 The regro*th of the nn'lerstorv vegetation, essentially all by sprouting, was quit? rapid. The recovery of nutrient standing crops was faster than biomass because of elevate:? nutrient concentrations in the regrowth tissues, "erbs and pains began to grow immedia tely after the burns aad reached preburn biomiss levels by 1 yr. In some cases the herb arH shcub nutrient standing crops were not significantly different from preburn amounts at 2 mo postburn. Hardwood, whose sprouts appeared later, reached 18-39? of initial biomass ani higher levels of nutrients by 1 vr. The recovery of biomass by the total understory vegetation was 27-63% but ths recovery of photosvnthet icallv active tissues (herbs, pains, and hardwood leaves) was an impressive ^B-gS*. The raoii vegetative recovery of the understory vegetation probably aids in the retention of the large pulse of nutrients released by the fires. The litter present 1 yr after burning consisted mostly of vegetation killel in the burns, the heavier pir^ litter that was not consumed in the burns, and the accumulation of postburn pine litterfall, which was 305-UUtt g/m ? . Meedlefall (2U0-326 g/m 2 ) made up the bulk of the litterfall. Pine litter constitutes the maior portion of the fuel mass. In the year following burning there was vigorous reproductive activity by the herbs (including several

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10<5 endemic taxa) but little flowering by the hardwoods, "ip^ seedling reproduction was greatly favored bv wet season burning before the early autumn seedfall, Even though there were no differences in the degree o^ topkilling aaong the four burns or in the recovery of herbs and palms, there were striking differences in the amount of hardwood recovery at the <=>nd o F 1 yr» However, in one oair of burns the hardwoods in the wet season burn plot rocov^re^ lass than those in the dry season burn plot and in the other pair the opposite occurred. I conclul* that the season of burning has less imoac 4 on hardwood recovery than the specific conditions f os-neci a 1 , lv fuel moistnra) ua3er which a burn occurs. The physical and physiologicaL factors that influence response to fire show Ihss seasonal, variation ia subtropical ?lori^a •'ban a + higher latitudes. The dry season burn at si^e 2 was 7er» hot because a r3latively large amount of irv ~u Q l burned. The paired *et season burn had lower fire temperatures because highsr fa=l moisture limited combustion, ev Q n though ambient temperature was higher. Conseguentlv there was significantly less hardwood recovery after the Irv season burn. Natural area management requires making decisions about the desired stat3 of the natural area and how that stite is to h= maintained, As nonnicks?n and Stone (1982) point on*-, in natural areas where the ecosystem has bren altered by human in terf 3r?n:s , simply reintroducing natural processes

PAGE 115

107 (such as wet season fires) may not be the way to return to natural conditions. Before natural orocesses (or prescribed imitations thereof) can operate successfully, the svstem must be returned to its original state. In the case of the rock ridge pinelands in Everglades National Parh the hardwoods may have been less important anl the herb layer better developed before interference during the last few decades. To return to these conditions may require more extreme measures than have been attempted bv nark managers in the past. Natural fires may have occurred every 3-5 yr in grassy pinaland with scattered small hardwoods. But th Q same fire regime todav may do nothing to reduce the amount of hardwoods found after logging an3 a period of fire suppression. To reduce the hardwoods to their original level may require the use of hot fires followed bv very frequent huraing. Once a condition considered aoprooriate is attained the natural fire regime can be reinstated. There is also, unfortunately, uncertaintv about the natural fire regime. The importance of lightning fires is obvious, and it is generally assumed that potential ignitions show the same pattern today as they Sid in the past. The role of indigenous people in increasing fir* freguency ani changing the season of burning is, however, less easily evaluate!. rjpper and lower limits to fire frequency caa be inferred from the time it takes for the

PAGE 116

103 andamic harbicaoas plants to be shaded out by the shrubby vegetation and the time it takes for sufficient ^uel to accumulate, respectively. Reasonable estimates might be 10-15 yr and 2-3 yr. One potential way to address the question of season of burning is to examine the response of individual species to different fire regimes. Tn particular, plants endemic to rock ridge pinelands shoal 1 show life history characteristics attuned to th> 3 natural occurence of fires, but this has not been studied. Pine seedling establishment is obviously aided bv a vet season barn the year of i good seed cron, although this event need only occur vary infrequently. In lieu 3f a firm decision on what the natural fire regime was, a conservative approach to orescribei burning seeas wise. Tha rocfc ridge pinelaads recover viaorouslv after wet or dry season fires and, as long as fires ar^ frequent enough (maybe every 3-7 yr) to prevent further development of iardwoods, the characteristic herbaceous flora should flourish. Wet season lightning fires must have occurred natarally, but it is possible that the pnderaic flora evolved under conditions that included frequent drv season fires set by indigenous people. By aaintainir.a diversity in the frequency and season of burning there is less likeliiood of inadvertantly eliminating certain species. It may turn out that fire management plans will be dictated more bf the need to discourage the widespread

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109 invasion of the pinelands by the exotic hardwood, Echinus terebin thif oLins, than by the desire to encourage native species, Hith luck, however, these two objectives can he mat with the same actions.

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TjTyijf? ftTHp w CI' T 'P n \brihimson, 3, 3, 1934a, Post-fice rscovatv o c "lorit'? L?Ae Wales Silge vegetation. American Journal o f Botar.v 71:9-21, ^brahamson, 7. (3. 1984b. Species responses to firs on th:» Florida Like Miles Bidgs, American Journal of Sotanv 71:35-43. *hlgren, I. *., and C, F, Ahlgcen. 1960, Ecological affects of focest fires. Botanical Review 2 C : £i83c 31. »lerand?r, T. R, 1967, (Florida) limastone: 48: 363-357, A tropical hammock on *-he «iaai a twenty-five year studv. Rcol Alexander, ?. ?,., and 7. P. Dickson III. 1972. Vagetatioul changes in the National Key Deer Refuge TT , Quarterly Journal of the Florida Academy of Science 35:35-96. Ul?r., S. F. 1964. Chemical asperts of haather burning. Journal oi Applied ^cologv 1:347-368, Anonymous. 1977. Individual/simultaneous determinations of nitrogen in/or phosohorus in BD acid digests, Industrial method nunbor 39-7u*/b + . Technicon Industrial Systems, Tarrytown, Sew York, USA. Arno, S, F,, and K. fl, Snerk, 1977. A method for determiniaj fire history in coniferous forests in the nountiin *fast. United States Forest Service General Technical Report INT-&2, Intermountain Forest and Rang* Sxperiaiant Station, Ogden, Utah, USA, Avecy, S. R., and L. L. Loope. 1930a. "pjemic tara in the flora of 5outa Florida, South Florida Research Center Report r-558. United States National Park Service, Uoaestaai, Florida, USA. Avery, S. S. , ani L. L. Loope. 1930b. Plants of Fverglades National Park: A preliainary checklist of vascular plants. South p lorida Research Center Report T-57^, Unitai Stites National Park Service, Homestead, Florida, US^, 110

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111 Bancroft, L. 1975. ^ira aanagement in p vergladas National Park. Fire wanagemant 3 7 ( 1) : 1 8-21 . Bancroft, », L, 1971. Fir? management, in Everglades National ?art Pages 1253-1259 in ?. ". Linn, suitor. Proceedings of th.2 first conference on scientific research Ln the national parks. United States National a ark S?rvice rransactioas and Proceedings Series Number 5, Washington, DC, OSA. 3instock, D, A, 1978, Effects of a prescribed winter burn on anion nutrient budgets in the Santee Experimental forest watershed ecosystem, Dissertation. Ou v e Bniversitf, Durham, North Carolina, USA. Blank, J. L., R, K. Olson, and P. H. Vitousek, 1980, Nutrient lptafce by a diverse spring ephemeral community, Oecologia »7:?6-98, B^erner, ?. *. m J. 1981. 'or^st structure dynamics following wildfire and prescribed burning in the M °w Terse? Pile Barrens. American Midland Saturalist 105:321-333. Boomer, 5. 5. J. 1982. Fire and nutrient cycliri in temperate ecosystems. BioScience 32:187-192. Boerner, 5. E. J., and P. T. *T. Forman. 1982. Bydrologic and minani budgets of Mew Jersey D ine Barrens upland forests following two intensities of fire. Canadian Journal of Forest Research 12:5D3C 10. Boncicksen, r. ». , and E. Z. Stone. 1982. Managing vsgetatioa within U.S. national parks, Environmental Management 6:109-122. Iradley, J, V, 1975, Freaze probabilities in Florida. Institute of Food and Agricultural Sciences Bulletin 777P, University of Florida, Gainesville, Florida, USA, Brender, F. 7., and R. w. Cooper. 1968. Prescribed burning in ~2orjia piedmont lobLollv stands, Journal of Forestrv 66:31-36 Brown, A, A,, and K, P. Davis, 19 7 3. Forest fire: control and use. Second edition. Rc3 raw-Bill , v ew York, » T ew York, PSA, Byram, 3« 9. 19^8. Vegetation temperature and fire damage in the southern pines, nnited States Forest Service? "irControl «!Dtes 9(4):3U-36.

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112 ^haiken, L, 5. 1952. Annual sumner fires kill hardwood rootstocks, United States Forest Service Pesaarch Hot? 19, Southeastern Forest experiment Station, Asheville, fforth Carolina, USA. 'hanin, F. S., IT, an! K. Van Cleve. 1981. n lan J nutrient absorption an! retention under differing fire regimes. ''ages 391-321 in T. A. ^ooney, T. w. Bonnicksen, N. I,. ChristansBQ , J. S. Lotaa, and R". A. P^in^rs, editors. Fire regises and ecosystem properties, United States Forest Service General Technical Report WO-2^, 3ashingtoa, DC, us A, rhristensen, H. L. 1977. 'ire ana soil-plant nutrient relations in a pine-wiragrass savanna on the coastal plain of 3orti Carolina. Oecologia ^1:27-au. Ihristensan, B. L, 1981, Firs regimes in southeastern ecosystems. Pages 112-136 in '•*. A. Focney, T. v . Bonnicksea, N. i. Christensan, J. ?. Lotan, ^ii r ". A. Peiners, editors, ^ire recimes and ecosystem orooertUnited States Forest Service General Technical Fennrt 30-26, Washington, DC, USA. 'hristensen, S. L. and C. Ff. Jfuller. 197^. ?f c ects of fi on factors controlling plant growth in Ad^ngs^ma chaparral,, Ecological Monographs '45:29-55, "layton, 7. luring a . 22:162-165 1976. forest fi Sutrient gains to adjacent ecosvst^Ts : an evaluation, "3r = s*: Science "ok?r, W, 3, 1935. Vegetation of the Bahama Islands, Pages 185-270 in G. 3. Shattuck, editor. The Bahama Fslands. Hacaillan, N°w York, Tew York, USA. :onover, W, J. 1980, Practical nonparaaetric statistics, Second edition. wilev, 'lew York, Vew York, USA. ooke, C, W, 19'45. Oeologv of Florida, Geological Bulletin lumbar 29, Florida Geological Survey, Tallahass?a, Florida, PSA, rorrell, D. S. r and «. B. Correll. 1982. ^lora of the Bahama Acrhip2lago, J, Crarcer, Vaduz, West '"eriranv. Iraighead, F. G. , Sr. 1971. The trees of South Florida. Univarsit/ of Miami Press, Coral Gables, 'lorida, r'SA, iraighead, p. C. , Sr. 1974. Uammocks of South 'Lorida. Pages 53-50 in P, J, GlBasoa, editor, Environments of South Florida,, Memoir 2, Miami Geological Societv, '1iami, Florida, USA.

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113 Craighead, F. C, Sr. , and 7, C, Gilbert. 1962. The affects of hurricane norma on the vegetation of southern Florida. }uarterly Journal of the ^lorida Academy of Science 25: 1-29. Critchfield, 3. 7. 197U. laneral climatology. Third edition. Preti tice-Sall, Fnclewood Cliffs, Hew j^ s?Vr USA. OauDenraire, ?. 1968, ^cologv of fire in grasslands. Advances in Geological Research 5:209-266. Davis, J. Ff, 19U3. The natural features of southern 'lorida. Geological Bulletin 25, Florida Geological Survey, Tallahassee, Florida, ISA, neBano, L. ?. , and C. F. Conrad. 197B. The effect of p i r=> on nutrients ia a chaaarral ecosvstem. Fcologv 59:4 89-!* 97. ^ebell, n. 3., and C. ff. Falston. 1970. Felease of nitrogen oy burning light forest fuels, Soil Science Society of. America ?roceedinqs 30:936-938. DuSois, J, 9. , aid L. A. Kapustka, 1933. Pioloqical nitrogen influx, in an Ohio relict prairie. Am^ricj'n. Journal of lotany 70 : g-i6, Fgler, F. 5. 1952. Southeast saline ^vergia les vegetation, Florida, and its management. Tegeta^io xc.tn "pcro 4 ani ""a 3:213-265. ?vans, 3, 2, , amd S, F, Allen, 1971, Nutrient losses in smoke nroduced during heather burning. Oikos 22:1"9-l r a. Fverglades National Park, 1979. Fire management plan, Fverglades National Park, Onited States National Park Service, lomestead, Florida, nsA. Fwel, J., c, Berish, B, Brown, N, Price, and J, Paich, 1981. Slash and burn innacts on a Costa F.ican wet ^or^s*site, Foology 52:816-829. "erguson, F. R. 1957. Stem-kill and sprou^ini following prescribed fires in a pine-hardwood stand in Texas, Journal of Forestry C 5:Q26-U29. Ferguson, F, 9, 1961. Effects of prescribed fire on anderstorjr stens in pina-hardwood stands in Texas. Journal of Forestrv 59:356-359, Floyd, A. G. 1966. effect of fire unon we^d seeds in the wet s~ler5phyll forests of northern New South Wales, Australia! Journal of Botany 14:243-256.

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11 '4 barren, *, H, 19U3, Effects of fire on vegetation of tbe southeastern Jnited States. Botanical Review 9:617-65'4, Sentry, 8. Z. 1^75. Hurricanes ia South Florida. Page^ 73-31 in ?, J, jlsason, editor, Environments of South Florida, "eajDir 2, Siami ideological Societv, ??iarai, Florida, 7SA. Iranhall, (7, , ani B, Hanriksson, 1969, Nitrogen-fixing blue-green algae in Swedish soils. Cikos 20:175-179. Srelen, Ef, ?., 1975, Vegetative response to twelv° vears o^ seasonal Earning on a Louisiana longleaf pine site. Onited Stites Forest Service Research Note SD-1 Q 2, Southern Forest Experiment Station, New Orleans, Louisiana, 'ISA, Srier, C. Z. 1975. wildfire effects on nutrient listribution and leaching in a coniferous ecosvstem, Canadian louraal of "orest "esearch 5:599-607. Hire, R, Z, 1961, Heat effects on living plants, Belted States Forest Service Occasional Paper 1R3, Southern Forest Fxperiaent Station, New Orleans, Louisiana, VS\ , Hare, R. C. 196^a. Bark surface and cambium temperatures in simulated forast fires. Journal of Forestry 53: <*37-$40, flare, F. C. 1965b. Contribution of bark to fire resinta*c^ of southern tr = es. Journal of Forestry 63:248-251. Harper, D . 1. 1927. -latural resources of southern Flori1.ru Florida Seological Survey Annual Report 18:25-206, Harshberger, 7. 3. 191U. The vegetation of South Florida south of 270331 north, exclusive of the Florida K^vs, Transactions of the Wagner ?ree Institute of Science 7:51-189. Garwood, Z. B. , and S. n. Jackson. 1975. Atmospheric losses of four plant nutrients during a forest fire, Australiai Forestry 38:92-99. Heinselman, l, L, 1^73, Fire in the virgin for-sts of the boundary Waters Canoe Area, Minnesota. Quaternary Research 3:329-382, Hendry, C. D., and P. L. Erasonik. 1930. Chemistry of precipitation at lainesvilie, Florida, Environmental Science and Technology 1£: 343-81*9.

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115 Filmon, J, Vr *ad C, E» Lewis. 1962. Effect of burning on South Florida range. United states Forest Service Station Piper 1U6, Southeastern 'orest Experiment Station, asheville, North Carolina, USA. rtobbs, P. 7., 7. e. ?. Currall, an? C. H. Giminghanu 1984. The U3 2 ->£ ' Thermo-olor' ovrometers in the study of heath fire behaviour. Journal of Ecology 72:2*11-250. fodgkins, B, J. 1958, Effects of fire on undergrowth yegetatioa in upland southern nine forests. ^colonv 39:36-^6. Usffaeister, J. ?. , K. 3. Stockman, and FTG. Suiter. 1957. Wiami Liaastone of Florida and its Recent Bahamian counterpart. Geological Society of America Bulletin 73:175-190. Holdridge, L. . R. 19'47. Determination of vorli plant formations from simple climatic -lata, Science 105:367-363. Sough, W, !\, 1955. Palmetto and gallberrv regrowth following a winter prescribed burn. Research Paper "31, Georgia Psrest Research Council, lacon, Georgia, USA, Hough, W. A. 1931. Tmoact of prescribed fire on understory and forest floor nutrients, United States "ores1 -. Service Research Jote SF-393, Southeastern Forest ~xperii3nt Station, "sheville, North Carolina, US^, Rough, 7. A. 1932. Phytomass and nutrients in the understory ani forest floor of slash/longleaf nine stands. Forest Science 28:359-372. Ffughes, B, Ft,, ail F. E, Knar, 1 Q 6U. Response of gallberrv to seasonal burning. Unitel States forest Service Research ^ote SF-21, Southeastern Forest Experiment Station, Asherille, North Carolina, USA. Jones, M, B, , ind Ft, H, Laide, 1959, Relationship between sprouting in ohamise and the physiological condition o~ the plant. Journal of Range Management 13:210-21*4, Jorgensen, I. R, 1975. nitrogen fixation in forested coastal oliln soils, United States Forest Service Research ?aner SF-130, Southeastern "orest Experiment Station, Ashaville, North Carolina, USA. Jorgensen, J. P., and Z. G. Wells. 1971. Apparent nitrogen fixation in soil influenced by prescribed bnrninq. Soil Science Society of America Proceedings 35:395-319.

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115 Jurgensen, •*., !?, , and C, B, Oavey. 1969. Nitrogen-fixing blue-green algae in acid fnrest and nursery soils, ranariian Journal af microbiology 14:1179-1181. ^aaley, J, F» , and S, , C, Keel '/. 198 1. Post-fire regeneration of southern California chaoarrai. American Journal of Botany 68:524-530. yf^etchum, D. 3., and J. 5. Bethune. 1963. of Soutd Florida slash oine. Journal Fire resistance of ""orestr^ 61:529-530. F. lammed son, J. 0, , A. H, Srhultz, H. Jennv, and E, B, Bisvoll. 1962. Effects of prescribed burning of forest litter on total soil nitrogen. Sail Science Society of America Proceedings 26:200-202. FClukas, R, S, 1973, Sontrol burn activities in Svercrladcs National Park. Proceedings of the Tall "imhers "ire Ecology "onfar3uC9 12:397-U2B, Knight, 3. 1966. Loss of nitrooen from the fores 4 -, floor by burning, Forestry Chronicle 42:149-152. £odama, H. E. , ani D. H. Van Lear. 1°S0. Prescribed burning nl nutrient cvcling relationships in young lobloll7 nine plantations. Sou+hern Journal of Anoliel Forestrv 1:113-121, ^oziowski, r. T. , ana 1 F . P . Ahlgren, editors. 197'4. "ire and ecosystems, Academic ^ress, *r = y York, '*^w York, "Sy. Lamb, A. ", A. 1^73, ^ast growing timber trees of the lovlani tropics numbar 6: Pinus Cari^baaa, volume 1. Onit of Tropical Silviculture, Department of Forestrv, Oxford, England. ^tangdon, 3. 1. 1963. Pange of South Florida slash ni n -=. Journal oE Forestry 61:384-385. Langdon, 0. 5. 1991. Some effects of prescribed fire on undarstory vegetation in loblollv pine stanls. Paies 143-153 in 3. 57. Wood, alitor. Prescribed fires and wildlife in Southern forests. Belle B. Baruch ^ores 4 -. Service Institute of Clemson Bniversity, Georgetown, South Carolina, USA. Leighty, ?. ;,, *. H. Gallatin, J. L, *alcolm, and ?, B, Smith. 19*5. Soil associations of Bade County, "lorida. Tircular S-77&, Agricultural Experiment Station, Bniversitf of Florida, Gainesville, Florida, BSA.

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ir Lewis, C, E., and T. J. Hacshbargec. 1976. Shrab and herbaceous vegetation after 29 years of prescribed burning in the South Carolina coastal plain. Journal of Range Sanageaeat 29:13-18, Lewis, ?. "!. 197U. Effects of fire on nutrient movement i\ a South Carolina pine forest. Ecology 55 : 1 1701 1 o -7 , Lewis, 17. E. 1975. Effects of forest fires on atmospheric loads of soluble nutrients, Pages 833-RU6 in F, G, Uowell, J, B, Gentry, and "», h, Smith, editors. mineral cycling ii southeastern ecosystems. National Technical Information Service, Springfield, Virginia, USA. Liniblad, P. 1934. Diversion between c2U2-reduction an.'i heterocyst fraguency in a cycad root, °age 511 in C, Veeger mi Sf, E. Newton, editors. Advances in nitron?. fixation research. M artinus Uijhof f /Junk , The TJ agu~, Netherlands. Little, E. L. , Jr., ar.d K. E. norma n. 195Ua. Slash, pin^ (Ei.H!l§ iikllttli) f including South Florida slas^ pine: nomenclature and description. United States Forest Service Station Paper 35, Southeastern Forest Experiment Station, \sheville, North Carolina, USA. AfLlttle, '-' L» , Jr., and K, », Dorman, 1°54b. Slash o* (Si°!i§ ll.H2t.jikk) ' its nomenclature and varieties. Journal of Forestrv r 0:918-923. Lloyd, 3 , S. 1971, Effects of fire on the chemical stat' of herbaceous communities of the Derbyshire Dales. Journal of Ecology 59:25 1-273. Long, R. if. 197a. Origins of the vascular *lora of southern 'lorida, Pages 28-35 in P. J, Gleason, editoi Environments of South Florida. Memoir 2, Siaai Geological Society, Miami, Florida, USA. Long, 5, U. , and D. Lakela. 1971, a flora of tropical Florida. University of Siaai Press, Coral Gables, Florida, USA, Longhurst, ff. If. 1956. Stump sprouting of oaks in response to seasonil cutting, Journal of Range Management 9:194-196. Loope, L, L,, D, . H, Black:, S. Black, and G, S, Avary. 1979. Distribution and abundance of flora in limestone rocklan! pine forests of southeastern. Florida. South Florida Pesearch Tenter Report T-5U7, United States National Park Service, homestead, Florida, USA,

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113 Loope, L. L. r and 7. L. Dunevitz, 1991. Imoact of ^ire arzlusioa m3 invasion of Schinus terebint hi folios on linieston? rockland pine forests of southeastern Florida. South Florid Research Tenter Raport T-645, [Jaited States National Park Sarvir:?, Homestead, Florida, ?SA. Lotti, T,, ?.. A. Klawitter, ard S. P. LeGrande, I960, Prescribed burning for understory oon^rol in loblolly pine stands of the coastal plain. United States Forest Service Station Paper 115, Southeastern Forest Experiment Station, \sheviile, North Carolina, OS*. Lackhoff, 3. A. 1964. The natural distribution, growth ia^ botanical yariatioa of Pinus caribaea and its cultivation in South \frica, Annale Iniversiteit van Stallenbosc'39: 1-160. Mar?h, F, W. 19*9. Empire 'Drestc The pine fores'eview 23: 13-37. :h *arks, P, L. 1979. ^aparaat fire-stimulated germination o £ E-kus iZ.°^.kO.S seeds. Bulletin of the Torrev Botanica 1 Club 106T5T-42. Sarks, P, L. , and ?, FT, Bormann, 1972. ^evegetation following forast cutting: mechanisms for return to steady-state nutrient cycling. Science 176:91<»-915, Hat co-Dado. 1979. Toninreiensive development aaster "Ian for net ronolitm Dade Countv. letro-badc lanninT Peoartaent, Jiaiai, "lorida, T7SA. filler, S, 9,, aod J. ^iles. 1970, Regeneration of heather (^lILlilL I!lkli£i§ (!») 3nll) at different ages and seasons in north-east Scotland. Journal of Aoplied Ecology 7:51-50, "itchell. Jr., and n. Ehu; 1979. • r o c e d u r used by the University of Florida Soil Testing and Analytical Research Laboratories. Soil Science Pesearch Report 79-1, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, Florida, USA. '"ooney, H. A., T. n, Bonnicksen, N, L. Christenson, J. F. Lotan, aid S. i\ . D einers, editors. 1931. ^ire r 3 3ii^and ecosvotem properties. United States Forost Service Seneral Technical "eport WP-25, Washington, DC, 'ISA. Puller, P. 5T. , and ler, P. $. , and F. X. Bormann. 1978. i.£Y.5.t roniim a_H£ricanum Ker. in energy dynamics of a northern hardwood forest Science 193:1126-1128. 1978. Pole of energy flov an^ nutrient ecosvst°m,

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119 Nguyen, P. 7ao. 1979. Effects of a prescribed winter baton cation nutrient budgets of the Santee "roerimen'-al Forest watershed ecosystem. Dissertation.. Duke Sniversitv, nurham. North Carolina, NSft. Ohmann, L, F,., ail n, F, Gcigal, 1991, Contrasting vegetation responses following two forest fires in northeastern Minnesota, American Nidland fataralist 106:5U-6(4. Olmsted, T. :., L. L, Loope, and C. Hilsenbeck, 1°9Qa, Tropical hardwood hammocks of the interior Iverrrlades National Park and Hig Cypress National Preserve, South Florida Research Center Report T-60U, United States National Park Servioe, Homestead, Florida, as?, ?l3ste3, T. Z. t L. L. Loope, and ?. F. Sints. 1990b. A survev anl baseline analvsis of aspects of the vegetation of Taylor Slough, Everglades National ^arlf. Sou*h Florida Research Center Report T-596, Unitei States National Park Service, Homestead, "loriia, HSA. y Olmsted, I. :., H, 3, Robertson, Jr., J, Johnson, and 0. L, Bass, Jc. 1993. The vegetation of Long Pine Kev, Everglades National Park. South Plorida Fesearch Center Report SF5C-83/05, United States National Park S^rvic^, fomestea^., Florida, USA. Paraar, m . \. , and D . F. Fisher. 1993. Nitrogen fixation and az^r=tion bv wax: nyrtle (*y_£.icT_ cerifera) ic slash nine Pi?.!! sLliottii) plantations. Forast~Fcology an •I Nanageaent 5:39-U6. Phillips, H. s. 1940, b trooical hammock on the Jtiaai (Florida) limestone. Ecology 21:166-175. Porter, C. L. , Jc. 1967. Composition and prod'ictivitv of a subtropical prairie. Ecology 43:937-9U2. Pritchett, W. L. 1979. Properties and management of forest soils. John ?iley and Sons, New York, New York, ^SA. Eaison, R, J. 1990, \ review of the role of fire in nutrient cycling in Australian native f orests, and of aethodolDgv for studying the fire-nutrient interaction, Rustraliai Journal of Ecology 5:15-21. P.ichter, D, 0, , Z. «. Palston, and W, F. "arms. 1992, Prescribe! firs: effects on water quality and fore^ 4 : nutrient cycling. Science 215:661-663,

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120 Piekerk, H. , S. \. Jones, L, R, M orris, and n. a, Pratt, 1979iTylrol^y and water guality o^ three small lower coastal plain forested watersheds, Soil and "roo Scie'io? Society of Florida, Proceedings 38:105-111. Robertson, 3, 3,, Jr. 1953. A survev of the effects o^ fire in F/erglades Sational Park. United States National Park: Service, Homestead, Florida, ISA, Robertson, 7. 9., Jr. 1954. Everglades ?ires--past, present aid future. Everglades Natural History 2:9-16, Robertson, 7. B«, Jr. 1962. Fire and vegetation in th, W\ , ani S. C, Eowes, 197U. Loss of some elemt in fly-as!i during old-field burns in southern Ontario. Canadian Journal of Soil Science 54:215-224, nts

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121 Ksoii Conservation Service. 1959, Soil survey of Dads Sounty, FLDriia. United States Department of Agriculture, Washington, DC, USA, Soil Survey Staff. 1975. Soil taxonomy: a basic system of soil classification for mating and interpreting soil surveys. Agriculture Handbook U35, United States Department of Agriculture, Washington, DC, HSA, //Squillace, A. . E. 1966. Geogranhic variation in slash oina. <* Forest ScLsnca Ponograph 10:1-56. Sweeney, 1. 3. , and 3. H. Biswell. 1961. Quantitative studies dc th = removal :>f litter and duff bv fire under controlled conditions. Fcology '42:572-575. Swin3al, B, F. , Z. A, ffollis, II T , L. F. Conde, and J, F, Smith. 1978. Aboveground. li vp biomass o^ slash pine? trees in natural stands. IMPACT Report 1(1), Intensive Management Practices Assessment Center, University o £ Florida, Gainesville, Florida, rJSA, Taylor, D. L. 1980. Fire history and man-induced fire problems In subtropical South Florida, Pages 63-68 in Unitsd States Porest Service General Technical "enort R1-81, Ro-lcy fountain Forest and Range Sxoeriment Station, "ort Sollins, Colorado, ISA. Taylor, 0. L. 1931. 'ire historv and fire records f or Svsrglades National Pare, 1948-1979. South Florida Research Tenter Report T-619, United States * T ation?.l Par*: Service, Homestead, Florida, nSA. Taylor, D. L. , and A. Herndon. 1981. Tmoac 4 o* 22 yaars o c fir= on uiiarstory hardwood shrubs in slash nine communities within Fvarglades National °ark. South Florida Research Center Report T-640, United States National ?ark Service, Homestead, Florida, HSA. ^Tebeau, C. w, 1968, *an in the Miami Prass, Coral Sables, "1 Fvergladas, University of orida, ^SA. Tjegkama, J, 0, 1979, Nitrogen fixation in forasts of Central Massachusetts. Canadian Journal of Botany 57:11-16, ft Tomlinson, 9. B. 1980. The biology of trees native to tropical 'lorida, P. B. Tonlinson, Harvard 'orest, Petersham, Massachusetts, USA.

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12? rcalinson, P, P., and ?. C, Craighead, Sr. 197?. Growthring studies on the native trees of sub-tropical Florida, Pages 39-51 in A. K. S. Shouse and 1. Yamis, editors. 'asearch tranis in plant anatomv. Tata *cGraw-Rill, 'Tew Dehli, Tnlia, 7ance, S. D. , G. S. Henderson, and 0. S. Flevins. 1983. Nonsvmbiotio litrog^n fixation in an oak-hickory forest following long-term prescribed burning. Soil Science Society of America Journal 47:134-137. 7itousefc, P. 1., and W. A. Seiners. 1975. Fcosvstem suoc?ssioi an 1 , nutrient retention: a hypothesis, BioScience 25:376-381. Wad = , D, !>, 1983, Pire management in the slash nine ecosystem. Pages 203-227 in 3. L. Stone, editor. The managed slash pine ecosystem. School of Forest Resources ?.nd Conservation, University of Florida, f?ainesvill = , Florida, 7SA. Wide, D., J, Ewai, and c . Hofstettar. 1 Q 30, ''ire in Sooth p lorida ecosystems. United States Forest Service General Technical Rsrort SE-17, Southeastern Forest Experiment Station, Asheville, North Carolina, USA. Wells, C, 3, 1971, Fffects of prescribed burning on soil chemical properties and nutrient availability. Pa-ien sf;_97 fj Prescribed burning symposium nroc==dinns, Southeastern Forest ""xperiment Station, Asheville, Sorth Carolina, TSA. Vanger, K, P, _ 1953, The sprouting of swaatgum in relation to season of rutting and carbohydrate content. Plant Physiology 28:35-49, Shite, ?. S. 1979. Pattern, Drocess, and natural disturbance in vegetation, Botanical "eview 'J5: 72 cl -2 r!n . Woods, ?. F., H. C. Harris, and F. F. Caldwell. 1959. Sonthlv variations of carbohydrates and nitrogen in roots of sandhill oaks and wiregrass. Ecology 40:?9?-?95. Wright, H, A,,, aai A, . », Pailev, 1992, Eire ecology; nnited States and southern Canada. ^iley, ^ew York, "ev York, USA.

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APP2NDIX A VA511LA9. PIANT PAX A PPES3NT ;sj STfjpy PL^TS

PAGE 132

Table 13. Vascular plant species found in the study plots. Nomenclature follows Avery and Loope (1980b) . Woody vines are included with hardwoods. Site 1 Site 2 Taxon Wet Dry season season burn burn plot plot Wet Dry season season burn burn plot plot HERBS Ferns Anemia adiantifolia Pteridium aquilinum var. caudatum Pteris longifolia var. bahamensis Thelypteris kunthii Dicots Acalypha chamaedri folia Agalinis purpurea Angadenia sagraei Asclepias tuberosa ssp. rolf sii Aster adnatus Aster dumosus Ayenia euphrasii folia Borreria terminalis ( Spermacoce verticillata ) Buchnera floridana Carica papaya (exotic, postburn weed) Cassia aspera (exotic) Cassia deeringiana Cassytha f iliformis Centrosema virginianum Chamaesyce adenoptera Chamaesyce pinetorum Chaptalia dentata Chiococca parvifolia Cirsium horridulum Crotalaria pumila Cynanchum blodgettii Desmodium lineatum Dyschoriste oblongifolia var. angusta Echites umbellata 124

PAGE 133

Table 13. continued 125 Site 1 Taxon Wet Dry season season burn burn plot plot ciliosa var. heteromorpha Sachsia polycephala Samolus ebracteatus Scutellaria havanensis Solidago chapmanii Solidaqo stricta Stillingia sylvatica ssp. tenuis Tephrosia florida Tragia saxicola Vernonia blodgettii Site 2 Wet Dry season season burn burn plot plot Erechtites hieracifolia Eupatorium capillifolium Galactia sp. Galium hispidulum Hedyotis nigricans var. f ilifolia Heterotheca graminifolia var. tracyi Hyptis alata var. stenophylla Ipomea tenuissima Jacquemontia curtisii Liatris gracilis Mecardonia acuminata Melanthera parvifolia Mikania scandens Passif lora suberosa Phyllanthus pentaphyllus var. f loridanus Physalis pubescens (postburn weed) Physalis viscosa Piriqueta caroliniana var. tomentosa Poinsettia pinetorum Polygala grandiflora Rhynchosia reniformis Ruellia caroliniensis ssp.

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Table 13. continued 126 Site 1 Taxon Wet Dry season season burn burn plot plot Monocots Andropogon cabanisii Aristida spp. Cladium jamaicensis Dicanthelium sp. Dichromena floridensis Digitaria spp. Muhlenbergia capillaris Panicum spp. Paspalum setaceum Rhynchospora globularis Schizachyrium gracile Schizachyrium rhizomatum Schizachyrium semiberbe Scleria ciliata Sorghastrum secundum Tripsicum floridanum Site 2 Wet Dry season season burn burn plot plot SHRUBS Cycads Zamia pumila Palms Coccothrinax argentata Sabal palmetto Serenoa repens Hardwoods Ardisia escallonioides Baccharis glomeruli flora Bumelia reclinata var. reclinata Bumelia salicifolia Byrsonima lucida Callicarpa americana Chrysobalanus icaco Chrysophyllum oliviforme

PAGE 135

12.7 Table 13. continued Site 1 Site 2 Wet Dry Wet Dry season season season season burn burn burn burn Taxon plot plot plot plot Citharexylum fruticosum * * Coccoloba diversifolia * * Colubrina arborescens * * * Crossopetalum ilicifolium * * * Croton linearis * * * Dodonaea viscosa var. linearis * * * * Eugenia axillaris * * * Eupatorium villosum * * Exothea paniculata * Ficus citrifolia * * * * Forestiera segregata var. pinetorum * * Guapira discolor * * * * Guettarda elliptica * * * * Guettarda scabra * * * * Ilex cassine * * Ilex krugiana * * * * Jacquinia keyensis * Lantana depressa * * * * Lantana involucrata * * * Licania michauxii * * * Lysiloma latisiliqua * * Metopium toxiferum * * * * Morinda royoc * * * * Myrcianthes f ragrans var. simpsonii * Myrica cerifera * * * * Myrsine floridana * * * * Persea borbonia * * * Psidium longipes * * * * Psychotria nervosa * Quercus virginiana * * * Randia aculeata * * * * Rhus copallina * * * * Schinus terebinthifolius (exotic) * * Simarouba glauca * Smilax auriculata * * * * Smilax bona-nox * Tetrazygia bicolor * * * *

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Table 13. continued Toxicodendron radicans Trema micrantha Vitis aestivalis Vitis munsoniana 128 Site 1 site 2 Wet Dry Wet Dry season season season season burn burn burn burn Taxon plot plot plot plot

PAGE 137

P.PPENOIX B sr\ l 70I*H CROPS OF D?Y MASS \ND NrJTHIESfrS Tha following table? show the standing crop? of drv mas? and nutrients (5, P, K, Ca, and M cr) before burning, immediately after burning, and at 2, 7, and 12 mo after burning, Tie immediate postburn vegetation is tha 4 : nart of the initial 7?aetation not consumed by tha c ire, but is actually \^\\ and is part of the understory litter. v^lu^s are means with standard errors in parentheses. Sample si-res are n = 2U and a = 12 for dry mass at site 1 and site 2, respectively. ?or all nutrient standing crops n = a. differences betwean sampling periods were t'stei by one-var s^07 ; \ and ffallec-Ouucan multiple comparisons (* = 100, sis Institute Inc. 1332) on log 10 transform?d data. Sampling periods with tha same superscript are no 4 : significantlv different.

PAGE 138

.Q r-v o * coo o o a* — i o ( ),-»,_( .-tooooo -». -p o c 3 C o fl (fl 4-1 (1) 5 o -h m y > n ^o o CD 0> I l» l l \o . co o *r — — in in . —t rvt o o ~~^— . . n ma — i (ncooj — ^ o m ry o o •0 — O u — O — o CO a o u o Cn C •H C to 4-1 en w e >i M O (a -~ ~ *r w <-* CD *G ~* -» O • O O «J _ n

PAGE 139

131 O H Q, C U Xi c o (d CO >i U o u o c C (0 4J tn en w (0 e >i Q CJ\ CN H (N CJ\ O fl (N *n VfN^^^HOO — . o t7< voh ir»f-«\o cn cm o m rn o vo >-• « in in co o oomo r*p-or-^m cm * •* ^ r* ja — « (N p» . . . go VO rH CM V r* O \D o rm c* ** in xi o o u cn U in cm . . *h -~ O CM O ^ o tn • oo r»o • v co enni 1 co us h —i c^ rci o c tn on o o o a; |— i to •& H w z O ±j u x:

PAGE 140

132 J3 J *•_ i O — •» < ' *-* >fi *-4 o O O w O — < 4J O r-t Cu c u c o CO ~ ry o — . •h*O00 o O ' ~* ~i *0 ^ I I o o — a, o u en c C 03 -P W tfi en g >< p. Q <-\ Eh tt — » *H O ON T • . CM . ' o n — *

PAGE 141

133 Xt — (1 ( • — 13 .a tor* r-t i oao in > — © m — . • — £ J3 +1 o rH c C o 01 (13 0) CO >i M u — i"> ig i -« o v ' O -h 3D NO O — GO O «mn o r~ ~ — o oo . o rt . . C* CN o> o o> a, o u c •rH TJ C (0 +J cn en CO e Q ^ o — — m — — — .^-— . Jrt ^ o

PAGE 142

134 \£ *T r-t IH < • J3 J i (N in o — _ itj t^ m — o • .Q +) rH a c n XI c o ca a) en +J 3; •a • rjs ca a o u c H C 03 +1 en C E a *j -J CO M „

PAGE 143

135 -p o c u a o CO 10 1 u to Cu o u o en c •H c -p c (U Cn O u +J •H a in -OO -
PAGE 144

136 a> t m ^h ^ o " w21 iS *" "" -° II «rO OfNCD —* o II ft i [to ^ ja » o fl -« — O f J3 n ffl ro -P o c M £} C (fl (0 G) W J3 . . H3 oo -h m \o *G P* -H [fl o u c •H c (0 4-1 W — in i«i i »-< .a to o ro C a; Cn -P H Q

PAGE 145

137 o h a c u c o w i U M O &) c H C (0 -P CO c QJ o u 4-) CN rH En — «j _ a r•
PAGE 146

138 3 u o Xi a a o jG o o o o o o o o o «r oo us -P o H C M c o (0 (0 (1) lO o o a* o XI r* ^ ^ »o v vo o w a: o o rO o -~ ~i OMhi o > e .u 71

PAGE 147

>1 u T3 o u u Cn c •H C 03 +J to 139 -u o -h a c M c o to ra (1) CO O .a — O — I I I — — vo — o r» <"t HOIOH O 1 ^ ,, v o ( O — tfl 3 JC ft CO o Pa *> la)

PAGE 148

140 -p o cu c u ja a o w rtj 3J > E 4J

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141 •P O C u G O Cfl fC 0) >1 u CO a o u u Cn C H TS C nj -P CO 3 M O CO O A A — -^ o r* ri i ~ XI X} I (H O — — . ~< *r — o o ri i o ^h — ^r o i i o rt ionoo U r~ ~ m . v I ^ . if) o o i-( w
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142 I O CD -» ~ \D J2 -p o H Cu C u X! G O W nj
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143 IO — ~~ •4-1 O rH c u £1 G O CO RJ fl r~ -a O ^h CT» J3 — . -• O \D -* M H III CO a, o U Cn C •H TJ C (TJ -P io cn in ,

PAGE 152

144 (TJ .Q « O • J o a u a A G O E up J —

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145 -Q Si r~* Si .—«•-(«* ja o ^ -p o <-\ a, c u X! C en to a; w >i u U -. CJ -. _ Si a a Si — — o* to • • — ortyj • J — o o ™ • ja — tj en a. o S-l o c -H C

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14 6 — "TOO — -p o c u a A c o 03 mofl -.(NO — .^H o • — . *» o vo u> ** o o ~~ fN OM (V h — WO — — r* ^o r* -o J3 . . . _ — r* *r o r~ U TJ TJ tw a o u c -H C (13 -P U3 e D H U H fO U oovn — . ( vi a.

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147 \S lA — — ID J3 P> O o ino rr* avoir *r o vo o -«»o oo' -P iH ft c M 3 X> C o en
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149 n^vo <3 — .2 o rH c u c o w ia
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150 o c u p ja c o QJ W +J en ft O u o &1 c •H a id •4-1 Cfl (1) C m • • o rtOON(NO — O \0 <-l — m'^ n "J « ^ 1 X -° O ^" O* o ^ m o 13 O O O * .0 •IN «Hffl( t «n o -^ m ( Hi O > S jj — wlwlui U u CO

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151 p o H c u a c o m 0) _o o .a . — — c* u o H3 o u C •H c m . o o • . <* -* CD -* O ^H — » •H en a) c 2

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152 10 N J) a o a, c u £t C O m 0} w +J (U 5 U OD — — — . C* CO -on •rj — u3 — < O
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153 u Of-b j m a • m j jj -P r-\ a c n £1 C en 03 0) — . (N ~H O I I I I u u III — . — o — O * O -H — ~ • J J o S-l CJ Cn c H C (C -P CO rg — _ _ « n o me -HO -~ •H c 2 oa — < ualw 4J u x

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BID35APHICAL SKETCH James B, Snyler receive! a B.S, in biology from Ursinus College in 2d llejaville, Pennsylvania, and an M . \. in botany froa ths Oaiyersity of North Carolina, Chapel Fill. After teaching botany for a year at "oravian College in 3ot.hleh.en, Pennsylvania, ha entered the fTniversity of Florida, Tn "ay 198*i he begins araployaen t as research biologist at Big Cypress NatiDaal Preserve, He and wife Jear. ar° the oroni parents Df t#o daughters. 15U

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I certify that I have read this study and that in ay opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, a: a dissertation for the degree of Doctor of Philosophy. / / Joan J, Ewel, Chairman -'Professor of Botany I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. OtsTf J do*es Associate Professor of 3otany I certify that I have read this study and that in my opxnion it conforms to acceptable standards of scholarly presentation and is fully adeguate, in scope and quality, as a dissertation for tae degree of Doctor of Philosophy. Walter S, Judd /7 Associate Professor of Botany 1 certify that 1 have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adeguate, in scope and quality, a: a dissertation for tae degree of Doctor of Philosophy. of Soil Science

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This dissertation was submitted to the Graduate Faculty of the Department of Botany in the College of Liberal Arts and Sciences and to the Graduate Scnool, and was accepted as partial fulfillment of the requirements for the degree of Doctor of Philosophy. August 1984 _ Dean for Graduate~StudIes~and Eesearch

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UNIVERSITY OF FLORIDA 3 1262 08553 2207


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