Report on successional relationships of selected plant communities

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Report on successional relationships of selected plant communities


Subjects / Keywords:
City of Lakeland ( local )
Hammocks ( jstor )
Plant communities ( jstor )
Soils ( jstor )

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Source Institution:
University of Florida
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All applicable rights reserved by the source institution and holding location.
Resource Identifier:
002436763 ( ALEPH )
AME1927 ( NOTIS )

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University of Florida

This study of the plant communities of the University of Florida
Conservation Reserve was begun in December, 1939. I am much
indebted to J. Speed Rogers for the interest and encouragement
he 'gave toward the initiation and completion of my dissertation
on this subject which was published in July, 1942. My interest in
plant communities and their succession in Florida has been con-
tinuous since then, but field work on the Reserve was limited largely
to irregular observations until September 1951, when permanent
quadrats were set up on selected sites. I regret that permanent
quadrats were not constructed in 1939 when my studies began.
I can only say that I then had no idea that I would remain in this
general area nor did I know that I would have any opportunity to
continue this study on the Reserve.

Permanent quadrats are set up in the following manner and in-
volve the following considerations:
1. Size-Inasmuch as trees and shrubs were the main vegetation
studied all quadrats are at least 100 x 100 feet. One, 160 x 160
feet, was made because it contained many large and widely
spreading live-oaks.
2. Location-The location of quadrats was chosen by estimat-
ing examples of typical communities as exemplified at their
time of classification given by Laessle, 1942. Wherever such
examples were satisfactorily represented within one of the
four inviolate areas of the Reserve, they were so located,
but two, one in a mature live-oak hammock, and one a black-
pine and fetterbush flatwoods, are located in non-inviolate
areas. The quadrats are clearly marked and designated as


3. Marking-Concrete posts measuring 4 x 4 inches and 3 feet
long were set at the corners of each quadrat, leaving the
upper foot above ground level. Where the quadrats were
located at considerable distance from obvious reference
points, bearings and measured distances were taken from
such obvious reference points as road or fence intersections.
These data were recorded and plotted on a map of the Re-
4. Mapping and vegetation-In order to get a fairly accurate
map of the woody species within the quadrats the area was
laid off in twenty foot squares by running twine at twenty
foot intervals from two adjacent sides to their opposite sides.
The approximate position of each plant was then mapped
using different symbols for each species. When the diameter
breast high was an inch or more this D. B. H. was recorded
to the nearest inch, either within the symbol or close enough
to it, to indicate definitely to which symbol the figure refers
(Fig. 4). This should enable one to record, not only of the
rate of growth of each tree, but also of those which succumb
and new invaders as well. I have not decided how often it
will be advisable to re-map these quadrats, but time inter-
vals for profitable re-evaluations will no doubt vary in differ-
ent sites having variable rates of succession.
5. Herbaceous vegetation-Only lists of the more important
herbaceous species and vines were made. This data is omit-
ted in this reoprt.
6. Soil profiles-One soil profile was made from a recorded cor-
ner of each quadrat. A soil auger was used to get this record
Ito a depth of four feet No subsequent comparisons have
yet been made as six years is probably much too short a time
to yield any recognizable changes.
7. Photographs-Photographs of each quadrat were made from
recorded positions, (Figs. 1 and 2). Dated negatives are in
my files.

P Quadrat 1
This quadrat, measuring 160 feet per side, is located in what I
classified as xeric or live-oak hammock (Laessle, 1942: 36) and has


I 4.

-1L1 .1111b PRIULUgidjJ11 Was LURUIL 110ll 11 Lilt: Uj~lU7"llldL PUbi~l~l as
the above, in October 1956. In addition to the great increase of Spanish-moss,
notice the increase in the height of the myrtle-oaks, laurel-oaks are now evident
just to the right and left of the center.


not been burned since 1936. Prior to this time fire had been of
almost yearly occurrence. Tabulation of the principle tree species
in D. B. H. is given in Table 1 below.


D.B.H. Live- Laurel- Myrtle- American- Slash- Swamp Longleaf-
inches oak oak oak holly pine red-bay pine

< 1 4 44 very 4 2 2 1
1 2 37 12 1 1 0 0
2 0 20 3 5 0 0 0
3 1 11 0 1 0 0 0
6 6 0 0 0 0 0 0
7 4 0 0 0 0 0 0
8 4 0 0 0 0 0 0
9 7 0 0 0 0 0 0
10 5 0 0 0 1 0 0
11 6 0 0 0 0 0 0
12 0 0 0 0 0 0
3 5 0 0 0 0 0 0
14 4 0 0 0 0 0 0
15 3 0 0 0 1 0 0
17 3 0 0 0 0 0 0
18 1 0 0 0 0 0 0
20 1 0 0 0 0 0 0
25 1 0 0 0 0 0 0
27 1 0 0 0 0 0 0
31 1 0 0 0 0 0 0

The number of individuals falling into each D.B.H. is given under the
species name at the top of each column. Young cabbage-palms, (Sabal pal-
metto) were abundant but are omitted here as none had trunks of breast height.

Some speculation regarding the history of this site before fire
protection was initiated in 1935 seems appropriate. There are
some very large longleaf-pine stumps present and some of the
larger live-oaks must be at least one hundred years old. These
facts, plus the fact that the hammock is roughly circular in shape
rather than the typically rectangular outline characteristic of culti-
vated fields, makes it seem unlikely that the area was ever cleanly
cultivated. The low widely spreading branches of the live-oaks,
(Fig. 1), indicate that these trees underwent early growth either in


the open or under a rather open canopy. Either of these conditions
may have been created well over a hundred years ago when the
region was first lumbered. This part of Florida was fairly well
settled in Bartram's time (Bartram, 1791). It seems likely that the
site had been subject to fires from both lightning and man for a
very long time, and that the dominant vegetation was once long-
leaf-pine with an understory of small live-oaks (Quercus virginiana)
and myrtle-oaks (Q. myrtifolia).1 Even before the cutting of the
pines it is probable that occasional very severe fires occurred, kill-
ing most live and myrtle-oaks to the ground, but leaving the larger
longleaf-pines unharmed. Sprout growth from the oaks would
grow until another fire. Once-in-a-while, due to chance, a live-oak
would attain such size and thickness of bark to be fire resistant
enough to reach maturity. Many of the present live-oaks bear fire
scars. .
Analysis of Table 1 shows that the more fire susceptible species,
especially laurel-oaks (Q. laurifolia), have invaded the site in great
numbers. Increment borings of the largest laurel-oaks showed them
to be about twenty years old, or to have existed just about the length
of time since the last fire. There is no evidence that any of this
species are from sprout growth. An attempt to date the last se-
vere fire by counting the rings that have accumulated in the over-
growth of the partially healed-over fire faces of the live-oaks failed
because of the difficulty of recognizing growth rings in this species.
One of the most puzzling aspects of the quadrat is why the live-
oaks are not reproducing. In good seed years, the ground is almost
covered with viable live-oak acorns. Lack of sufficient light under
the thick canopy might be considered the critical factor, however,
there are a number of openings in the canopy which receive at
least one-half full sunlight, still there is no live-oak reproduction
here. Perhaps the answer lies in the severity of root competition?
Another question which arises is the paucity of holly, (Ilex opaca)
and complete lack of magnolia, (Magnolia grandiflora) and other
components of the mesic hammock (Laessle, 1942 :37) in compari-
son to the large number of recently invading laurel-oaks. This I
believe to be due to chance, as mature laurel-oaks are abundant in
the nearby mesic hammocks bordering the St. Johns River, while
mature trees of holly and magnolia are both farther away and fewer

Nomenclature follows Small, 1933.


in number. The presence of swamp red-bay (Tamala pubescens)
normally a swamp of bayhead species, in such a well drained site
;' l,!i.i- Observations at the Reserve show that other charac-
teristically hydric species as swamp-maple, r-ite, i rubrum) and
whitebay it\ s.i J.eli virginiana) are invading drier sites than those
in which they are usually found. I believe that their usual restric-
tion to hydric situations is primarily due to their susceptibility to
fire rather than their need for abundant water. It ,,-e tl. I,_ l-lay
(Tamala borbonia), a characteristically mesic hammock species,
would be more likely to invade this site. I believe it would, other
factors being equal, but the swamp red-bays are abundant in a
nearby bayhead only five hundred feet away, while mature red-
bays are at least a mile distant.

40- 40

20- -20

20 40 60 80 100 120 140 160
Figure 3. This profile includes a strip about twenty-five feet wide along the
N. W. side of Quadrat No. 1. Small sprouts of myrtle-oak, small cabbage-
palms and vines are omitted. Numerals are in feet. Sketched October, 1956.

Quadrat 2
This quadrat is in what was classified as the Pinus australis-
Quercus cinerea Association (Laessle, 1942: 35). When my first
study of the Reserve was made, this site contained numerous live-
oaks, the larger only five to six feet tall. Next to Quadrat 1 above,
this shows more rapid successional change than any other of my per-
manent quadrats. Here the soil is similar to that of Quadrat 1,
Blanton fine sand. The topography is also similar, being surrounded
by slightly lower longleaf-pine flatwoods, except on the east, where
it merges with scrubby flatwoods (Laessle, 1942:29-30). The fol-
lowing Table was derived from the mapped quadrat Fig. 4.



S-Serenoa repens B-Bacchoris holimifolia NE.
O-Pinus australis R-Rhus copollinum
O-Quercus virginiona A-Tamola pubescens
P- Padus virginian D- Diospyros virginiana
3-Quercus myrtifolio K- Comphora comphora
C -Quercus chapmanni c-Cerothamnus pumilus
L-Quercus laurifolia Also nearby- Sobino silicicolo, but this
W-Quercus cinerea was not of fruiting size
T-Quercus laevis Numerals in or by symbols indicate
X-Sabal palmetto D.B.H. in inches

Figure 4. Map of Quadrat No. 2 showing the approximate position and
D.B.H. of trees and shrubs. Clump outlines rather than individual stems are
used for the root-sprouting wax-myrtle. The smaller squares measure twenty
feet per side.

In addition the following species, all with a D.B.H. of less than
one inch were: Cerothamnus pumila-11 clumps, Diosypros virginia-
14 small stems all within a radius of twenty feet and probably all


sprouts from a single root system, Rhus copallinum- 7 stems, prob-
ably root clones, Tamala pubescens -1, Camphora camphora -1,
Serenoa repens -12 small clumps, Quercus chapmanii -1, Sabal
palmetto -1.

D.B.H. Longleaf Live- Black- Laurel- Bluejack Turkey-
inches) pine oak cherry oak oak oak

< 1 0 321 10 2 20 4
1 0 60 0 0 1 0
2 0 30 2 1 0 0
3 1 3 1 1 0 0
4 4 0 0 0 0 0
5 6 0 0 0 0 0
6 2 0 0 0 0 0
7 6 0 0 0 0 0
8 5 0 0 0 0 0
9 9 0 0 0 0 0
10 9 0 0 0 0 0
11 4 0 0 0 0 0
12 3 0 0 0 0 0

Table 2 is deceptive in the apparently great number of live-
oaks-most stens are root clones.2 Further analysis shows that
longleaf pine have not reproduced since the last fire about 20 years
ago, or shortly thereafter. One can easily visualize that this quadrat
would, in the continued absence of fire, develop into something

SAs most observers in this region have no doubt noticed, live-oak is a very
heterogeneous species and, in my experience, even genetically identical speci-
mens are markedly modified morphologically in different environments. A num-
ber of years ago I transplanted from the Reserve scrub a typical example of the
strongly revolute margined, strong veined form, which Small named Q. gem-
inata, to a mesic hammock near Gainesville, Florida. All leaves formed in
the new habitat were nearly flat with scarcely revolute margins. An additional
observation as to the plasticity of the some of its varieties occurred in the study
of my permanent transect in the longleaf-pine flatwoods (Laessle, 1942:48).
Dwarf live-oak [Q. minima (Sarg.) Small] was once common in this habitat.
When my transect was mapped in 1951 examples of this species were absent,
but there were scattered small live-oaks up to six or eight feet tall. In April,
1956, a severe fire killed all this vegetation to the ground. On a visit to this
spot on October 1956, there were new sprouts from the burned root-stocks.
All showed the characteristic toothed leaves of Q. minima, while the charred
six to eight foot stems of what could only fit Q. virginiana before the burn,
were still sticking up from the same rootstocks. So, in my opinion, Q. minima
is merely a fire and flatwoods ectotype of a freely root-sprouting variety of
Q. virginiana.


similar to Quadrat 1 except that there would be a marked telescop-
ing of stages-exemplified by some laurel-oak being as large as the
largest live-oak.
The naturalized species camphor, (Camphora camphora), while
scattered, is apparently destined to become an important element
in the development of the Reserve's hammocks-providing that
fire is eliminated. The same may be said for most of the northern
and central Florida.
It is my belief that the small blue-jack oaks and turkey-oaks in
this quadrat will soon succumb to the severe competition for light,
water, etc., which, while severe now, will become increasingly so
in the future. Why invading laurel-oaks do not occur in as large
number as found in Quadrat 1 is not apparent to me. The proximity
of seed trees of this species is certainly as favorable here as it is
Many of these quadrats show very little successional change at
this time. A quadrat in the sandhills Longleaf-pine-Turkey-oak
Association, (Laessle, 1942: 30) showed practically no evidence of
invading species except five sand-pine (P. clausa). The larger two
had a D. B. H. of five inches. Some small magnolia were noticed
in nearby portions of the sandhills, outside the quadrat. In order
to get some sort of estimate of their rate of invasion, an area much
larger than my quadrat, but including it, was sampled by walking
in parallel lines spaced one hundred feet apart and counting invad-
ing species fifty feet to each side of these lines. As ground cover
was very sparse, and larger vegetation widely spaced, I feel certain
that no invading species over a foot tall was missed. An area of
roughly thirteen acres was covered in this manner, and the follow-
ing number of invading species recorded: Sand-pine-35, mag-
nolia-5, black-cherry-2, Chapman's-oak-2, wild-olive, (Amarolea
americana)-1, cabbage-palm-1 (small), camphor-1. Live-oak
is not considered an invader, as small trees and sprout growth are
characteristic of this association even when burning is frequent.
All of the invaders, except the cabbage-palm, are intolerant of fire
and would not occur in a longleaf-pine-turkey-oak community ex-
posed to the almost annual burning which has obtained in Florida.
The southern portion of this thirteen-acre area is within about
a quarter of a mile north-east of a mesic hammock containing many
mature magnolias. It was noticed that four of the five invaders
of this species were in the southern half of the area. The nearest


mature sand-pines were about the same distance south of the area.
No mature camphor trees are known to occur within at least a mile,
but as the pits of this species and of the black-cherry are trans-
ported by birds, their migration to this area is understandable. The
peculiar thing, in the light of the very rapid invasion of the laurel-
oaks in Quadrat 1, is that no laurel-oaks have invaded here, though
mature trees of this species are abundant within a third of a mile
to the south. I have no doubt that many laurel-oak acorns have
been transported to the area, probably more of them than magnolia
seed. Laurel-oak is frequently one of the first invaders in the long-
leaf-pine-turkey-oak (generally Lakeland soils) around Gainesville.
I am aware of no environmental factor which would prevent the
establishment of this species on the Reserve's Lakeland soils unless
some critical element is lacking. No significant difference in either
the macro nor micro-elements found in Blanton fine sand, the
series of soil in Quadrat 1, and Lakeland of the same texture, was
apparent in (Gammon et al, 1953). In fact there was often more
variation in these elements in examples of the same series than in
selected examples from the two series. Analyses of soil samples
from the Reserve might give more conclusive information.
The demonstrated ability of magnolia to become established on
the excessively drained poor sands of the Reserve's sandhills does
not seem so surprising when it is realized that is common in the
dunes of western Florida (Kurz, 1942). It is apparently tolerant to
both strong light and deep shade, and is able to sur\ hi \ ith meager
amounts of those nutritional elements generally required in plant
nutrition, but its rate of growth is much retarded in poor soils.
Reports on successional studies from other quadrats of the Re-
serve must await more conclusive changes in vegetation. Changes
in soil profiles will no doubt lag behind vegetational changes for
variable lengths of time but I hope that at least some of these will
be evident during whatever time is allowed me to continue this
A number of scattered observations concerning plant succession
on the Reserve seem worthy of presentation. During the twenty
years of fire protection there has been a surprisingly rapid spread
of red-maple from its former confinement to river swamps to the
flatwoods, particularly to those portions adjacent to the swamps.


The absence of fire has also permitted a considerable extension of
the bayhead flora, especially loblolly-bay (Gordonia lasianthus), to
the moister portions of the flatwoods. This substantiates my hy-
pothesis (Laessle, 1942: 103), that in the absence of fire, bayhead
species would invade the lower, more moist portions of the flat-
woods. There is also increasing substantiation of my opinion that
the drier portioti, o the flat\\; i:ds are being: inv added bv hammock
species-particularly i\ e-oak, although a number of magnolia and
swamp red-bay have been observed growing well in this habitat.
The magnolias are doing much better here, as individuals, than
in the sandhills. A number of trees six to seven feet tall were ob-
served here, while the largest sandhill specimens are scarcely three
feet tall.
Unless fire or some unnatural disturbances take place, the Re-
serve's quadrats should not only yield definite information regard-
ing the stages of plant succession on most of the soil series of pen-
insular Florida, but should also yield a fairly accurate measure of
the rate of these changes. I expect that, as invading species reach
seed bearing size or age, the rate of succession should accelerate,
not only because of the increased number of seed produced, but
also because of soil changes which should also accelerate as more
and more invaders modify the areas. As succession progresses the
sharp ecotones between the predominantly fire climax communities
obtaining when I first studied the Reserve should become broader
and less clear cut. Indeed this tendency is already apparent in
some areas. I do not expect that, even within a thousand years,
the vegetation will become homogeneous throughout including the
better drained areas of flatwoods, sandhills, hammocks and scrub.
I believe that a mesophytic hardwood climax would develop in all
these situations. I am a supporter of the polyclimax concept. It
does not seem possible, for instance, that soils derived from de-
posits of nearly pure sand could ever support a flora even approxi-
mating that derived from limestone, or limy materials such as the
shell mounds at Orange Point (Laessle, 1942: 59-60). Observations
of almost undisturbed calcareous climax hammocks to the west and
southwest of Gainesville show them to have considerable numbers
of such trees as box-elder (Negundo negundo), hammock-maple
(Saccharodendron floridanum) and Shumard's-oak (Q. shumardii),


in addition to the species characteristic of the sandy mesophytic
hammocks of the Reserve. The calcareous hammocks also have a
noticeably higher component of deciduous elements than do any
of the sandy hammocks observed in the northern and central parts
of peninsular Florida. Such observed floristic differences, while
in part probably influenced by the higher pH of the calcareous soils,
are no doubt also influenced by the generally richer and more
clayey nature of these soils.
The effects of chance will be more pronounced in the early veg-
etational changes following both fire climaxes and secondary suc-
cessions. This is particularly obvious when one considers the com-
parative scarcity and generally widely separated stands of most
of the climax associations-both on the Reserve and in most of
peninsular Florida.
1791. Travels through North and South Carolina, Georgia, East and West
Florida. Philadelphia.
1953. Physical, spectographic and chemical analyses of some virgin Florida
soils. Univ. of Fla. Ag. Exp. Sta., Tech. Bull. 524.
1942. Florida dunes and scrub, vegetation and geology. Fla. Geol. Surv.,
Geol. Bull. 23, Tallahassee, Fla.
1942. The plant communities of the Welaka area, with special reference to
correlations between soils and vegetational succession. Univ. of Fla.
Publication. 4(1).
1933. Manual of the southeastern flora. Science Press Printing Co., Lan-
caster, Pa.

Quart. Journ. Fla. Acad. Sci., 21(1), 1958.