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Fire Season Effects on Flowering and Seed Germination of Longleaf Pine (Pinus palustris) Sandhill Grasses

Permanent Link: http://ufdc.ufl.edu/UFE0021054/00001

Material Information

Title: Fire Season Effects on Flowering and Seed Germination of Longleaf Pine (Pinus palustris) Sandhill Grasses
Physical Description: 1 online resource (51 p.)
Language: english
Creator: Shepherd, Benjamin J
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2007

Subjects

Subjects / Keywords: fire, flowering, longleaf, poacea, reproduction
Interdisciplinary Ecology -- Dissertations, Academic -- UF
Genre: Interdisciplinary Ecology thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Longleaf pine savannas are among the most exploited and species-rich communities outside the tropics, with a significant proportion of that diversity occurring at the ground-layer. These communities evolved with frequent (1-5 yr), low-intensity fire and some species may require a specific season-of-burn to elicit sexual reproduction. I experimentally tested the month-of-burn effects on aspects of sexual reproduction for five grass species: percentage of seed-bearing plants, seed-bearing stems per area and plant, floret and seed production per stem, and seed germination. Months-of-burn include winter burns (February 2005), early spring burns (April 2005), early lightning-season burns (May 2005), and late lightning season burns (July 2005). Burns were conducted in longleaf pine sandhills regularly (1-6 yr) maintained with fire for the previous two decades and sustaining an assemblage of ecologically desirable grasses. None of the species showed consistent responses across all variables, though several species showed greater percentages of seed-bearing plants after lightning-season burns. Similarly, germination percentages were not consistent across species, but at least one species had greater germination in response to lightning-season burns. These results suggest that land maintaining a variable fire season should maintain a full complement of ground-layer richness.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Benjamin J Shepherd.
Thesis: Thesis (M.S.)--University of Florida, 2007.
Local: Adviser: Miller, Deborah L.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2009-08-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2007
System ID: UFE0021054:00001

Permanent Link: http://ufdc.ufl.edu/UFE0021054/00001

Material Information

Title: Fire Season Effects on Flowering and Seed Germination of Longleaf Pine (Pinus palustris) Sandhill Grasses
Physical Description: 1 online resource (51 p.)
Language: english
Creator: Shepherd, Benjamin J
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2007

Subjects

Subjects / Keywords: fire, flowering, longleaf, poacea, reproduction
Interdisciplinary Ecology -- Dissertations, Academic -- UF
Genre: Interdisciplinary Ecology thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Longleaf pine savannas are among the most exploited and species-rich communities outside the tropics, with a significant proportion of that diversity occurring at the ground-layer. These communities evolved with frequent (1-5 yr), low-intensity fire and some species may require a specific season-of-burn to elicit sexual reproduction. I experimentally tested the month-of-burn effects on aspects of sexual reproduction for five grass species: percentage of seed-bearing plants, seed-bearing stems per area and plant, floret and seed production per stem, and seed germination. Months-of-burn include winter burns (February 2005), early spring burns (April 2005), early lightning-season burns (May 2005), and late lightning season burns (July 2005). Burns were conducted in longleaf pine sandhills regularly (1-6 yr) maintained with fire for the previous two decades and sustaining an assemblage of ecologically desirable grasses. None of the species showed consistent responses across all variables, though several species showed greater percentages of seed-bearing plants after lightning-season burns. Similarly, germination percentages were not consistent across species, but at least one species had greater germination in response to lightning-season burns. These results suggest that land maintaining a variable fire season should maintain a full complement of ground-layer richness.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Benjamin J Shepherd.
Thesis: Thesis (M.S.)--University of Florida, 2007.
Local: Adviser: Miller, Deborah L.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2009-08-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2007
System ID: UFE0021054:00001


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FIRE SEASON EFFECTS ON FLOWERING A ND SEED GERMINATION OF LONGLEAF PINE ( Pinus palustris ) SANDHILL GRASSES By BENJAMIN J. SHEPHERD A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2007 1

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2007 Benjamin J. Shepherd 2

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ACKNOWLEDGMENTS A great number of people contributed their knowledge, criticisms, suggestions, physical labor, and/or moral support thr oughout the duration of this proj ect. Amanda Stevens and the Jackson Guard staff provided information and fi res necessary to embark in this study. The University of Florida-Milton campus provided space to store material for this study. The Department of Wildlife Ecology and Conservation and Environmental Horticulture Departments provided transportation and equipment, respec tively. The School of Natural Resources and Environment afforded me the opportunity to study at the University of Florida. A special thanks goes to my committee memb ers whom have been able to endure this project and myself. My advisor, Dr. Debbie Mi ller, provided shelter on several occasions and assisted in field observations. Dr. Miller al so has provided tremendous editing and technical support. Dr. Mack Thetford helped tremendously with SAS and seed germination trialsfor that I am ever thankful. Duri ng this project, Dr. Jack Putz has offered his knowledge of fire ecology and editing prowess, which has ultimately made me a better writer and scientist. Dr. Doria Gordon provided her knowledge of Eglin Air Force Base and community ecology. Several peers have assisted in refining the scope of this study, pr ovided assistance in the field, and have proven invaluable during times of need. First, Tanya Alvarez deserves much praise for her field assistance and contributions to the project, among which there are too many to name. Jennifer Dupree and Josiah Raymer, co lleagues in the School of Natural Resources and Environment, contributed numerous collection days to this study. Brett Williams, fire ecologist at Jackson Guard, has proved to be a wonderful resource and great friend while I was living in Milton, FL. I also thank those who have im parted their academic and world philosophies throughout my tenure at the University of Florida. 3

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TABLE OF CONTENTS page ACKNOWLEDGMENTS...............................................................................................................3 LIST OF TABLES................................................................................................................. ..........6 LIST OF FIGURES.........................................................................................................................7 ABSTRACT.....................................................................................................................................8 CHAPTER 1 FIRE IN THE SOUTHE ASTERN UNITED STATES............................................................9 Research Hypothesis............................................................................................................ ...11 2 EFFECTS OF BURN MONTH ON FL OWERING AND SEED PRODUCTION BY LONGLEAF PINE SANDHILL GRASSES..........................................................................14 Methods..................................................................................................................................15 Species and Site Selection...............................................................................................15 Vegetation Sampling.......................................................................................................16 Seed Sampling.................................................................................................................17 Statistical Analysis..........................................................................................................1 7 Results.....................................................................................................................................18 Percent SBS.....................................................................................................................18 SBS Density.....................................................................................................................18 SBS per Plant...................................................................................................................18 Floret and Seed Production per SBS...............................................................................19 Discussion...............................................................................................................................19 Fire Season Effects on Charac teristics of SBS Production.............................................19 Fire Season Effects on Flor et and Seed Production........................................................22 3 FIRE SEASON EFFECTS ON SEED GERMINATION OF LONGLEAF PINE SANDHILL GRASSES..........................................................................................................29 Introduction................................................................................................................... ..........29 Methods..................................................................................................................................31 Species Selection.............................................................................................................31 Seed Selection and Germination.....................................................................................31 Statistical Analysis..........................................................................................................3 2 Results.....................................................................................................................................33 Discussion...............................................................................................................................33 4 CONCLUSIONS AND IMPLICATIONS FOR GROUND-LAYER RESTORATIONIN FLORIDA SANDHILLS........................................................................................................38 4

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APPENDIX A CLIMATE NORMALS FOR NICE VILLE, FL FROM 1971-2000......................................40 B BURN HISTORY OF EG LIN AIR FORCE BASE...............................................................41 LIST OF REFERENCES...............................................................................................................42 BIOGRAPHICAL SKETCH.........................................................................................................51 5

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LIST OF TABLES Table page B-1 Burn history for longleaf pine ( Pinus palustris ) sandhills on the western range of Eglin Air Force Base..........................................................................................................4 1 6

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7 LIST OF FIGURES Figure page 1-1 Fire frequency in Florida...................................................................................................13 2-1 Map of Eglin Air Force Base (EAFB) in northwest Florida..............................................24 2-2 Mean percent ( 1 SE) of plants pr oducing at least one seed-bearing stem (a) Sporobolus junceus (b) Schizachyrium scoparium (c) Andropogon ternarius (d) Aristida mohrii and (e) Aristida purpurascens after different months-of-burn in 2005...................................................................................................................................25 2-3 Mean ( 1 SE) seed-bearing stems (SBS) per area (a) Sporobolus junceus (b) Schizachyrium scoparium (c) Andropogon ternarius, (d) Aristida mohrii and (e) Aristida purpurascens after different months-of-burn in 2005..........................................26 2-4 Mean ( 1 SE) seed-bear ing stems (SBS) per plant (a) Sporobolus junceus (b) Schizachyrium scoparium (c) Andropogon ternarius, (d) Aristida mohrii and (e) Aristida purpurascens after different months-of-burn in 2005..........................................27 2-5 Mean ( 1 SE) production of floret and seed per seed-bearing stem (a) Sporobolus junceus (b) Schizachyrium scoparium (c) Andropogon ternarius, (d) Aristida mohrii, and (e) Aristida purpurascens after different months-of-burn in 2005.................28 3-1 Mean ( 1 SE) germination (a) Sporobolus junceus (b) Schizachyrium scoparium (c) Andropogon ternarius, (d) Aristida mohrii, and (e) Aristida purpurascens after different months-of-burn....................................................................................................36 3-2 Mean ( 1 SE) germination (a) Schizachyrium scoparium (b) Andropogon ternarius and (c) Aristida purpurascens after different months-of-burn..........................................37 A-1 Monthly precipitation and temper ature means for Niceville, FL (1971-2000), including average monthly precipit ation (a) 2004 and (b) 2005 seasons..........................40

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Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science FIRE SEASON EFFECTS ON FLOWERING A ND SEED GERMINATION OF LONGLEAF PINE ( Pinus palustris ) SANDHILL GRASSES By Benjamin J. Shepherd August 2007 Chair: Deborah L. Miller Major: Interdisciplinary Ecology Longleaf pine savannas are among the most exploited and species-rich communities outside the tropics, with a significant proportion of that diversity occurring at the ground-layer. These communities evolved with frequent (1-5 yr), low-intensity fire and some species may require a specific season-of-burn to elicit se xual reproduction. I experi mentally tested the month-of-burn effects on aspects of sexual reprod uction for five grass species: percentage of seed-bearing plants, seed-bearing stems per area and plant, floret and seed production per stem, and seed germination. Months-of-burn include winter burns (February 2005), early spring burns (April 2005), early lightning-season burns (May 2005), and late lightning season burns (July 2005). Burns were conducted in longleaf pine sa ndhills regularly (1-6 yr) maintained with fire for the previous two decades and sustaining an as semblage of ecologically desirable grasses. None of the species showed consistent respon ses across all variables, though several species showed greater percentages of seed-bearing plants after lig htning-season burns. Similarly, germination percentages were not consistent across species, but at least one species had greater germination in response to lightning-season burns. These results suggest that land maintaining a variable fire season should maintain a full complement of ground-layer richness. 8

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CHAPTER 1 FIRE IN THE SOUTHEAS TERN UNITED STATES Fire is an important component of plant communities worldwide (Kozlowski & Ahlgren 1974; Whelan 1995; Pyne et al. 1996). In the sout heastern United States, frequent (1-5 yr), lowintensity fires maintain longleaf pine ( Pinus palustris Miller) savannas by suppressing oak trees and shrubs (Glitzenstein et al 1995; Frost 2006) and by stimulating flowering of ground-layer plants through short-term increases in light and nutrient availability (Christensen 1977; Platt et al. 1988; Outcalt 1994; Hier s et al. 2000). These fire-maint ained longleaf pine savannas are among the most species-rich communities outside the tropics, with a large majority of that diversity at the ground-layer (Walker & Peet 1983; Peet & Allard 1993). In addition, these communities maintain a high leve l of endemism (Hardin & White 1989). Conservation and restoration of longleaf pine habitat is therefore a bi ological priority. Due to landscape fragmentation and vigorous fi re suppression for the majority of the 20 th Century, remnant stands of longleaf pine today account for less than 3% of their historic range and only 0.2% are maintained with frequent fires (Frost 2006). In the absence of fire, fireintolerant trees and shrubs readily succeed into the sub-canopy of longleaf ecosystems; effectively shading-out ground-layer plants and longleaf pine recr uits. Continued indefinitely, fire suppression alters community dynamics in longleaf ecosystems by reducing ground-layer richness and thus the likelihood of frequent, low-intensity fire (Glitzenstein et al. 1995; Beckage & Stout 2000; Kaplan 2005). Gr ound-layer restoration is therefore essentia l to restoring the historic fire regime in longleaf communities wh ere fire has been suppressed. Unfortunately, many desirable native ground-layer plants in Fl orida have low seed production and viability (Pfaff & Maura 2000), reducing the frequency of recruitment into the ground-layer. Nevertheless, longleaf pine commun ities evolved under a fairly specific fire regime and several 9

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plant species may require seasonally-specific bur ns to enhance sexual reproduction (Platt et al. 1988), thus creating the potential for greater establishment of plants at the ground-layer. Historically, lightning and Native Americans were the principal agents of fire in longleaf savannas (Robbins & Myers 1992; Frost 2006). Native Americans burned primarily in fall and winter months (October-February) to reduce fuel and drive game, while lightning fires occurred most readily between spring and summer mont hs (May-August; Fig. 1-1) when thunderstorms and lightning are frequent and spring droughts create tinder dry fuel (Komarek 1964; Robbins & Myers 1992). Consequently, the season-of-burn is considered a significant ecological force affecting the sexual reproduction of many plant speci es in longleaf pine savannas (Platt et al. 1988; Brewer & Platt 1994; Sparks et al. 1998; Hiers et al. 2000). In cent ral Florida, fires between May and August (i.e., lightning-season) enhance flowering st em production and the number of flowers per stem for wiregrass ( Aristida stricta Michx.; Streng et al. 1993; Outcalt 1994), an abundant bunchgrass in th e eastern longleaf range. Si milarly, Brewer & Platt (1994) noted that golden aster ( Pityopsis graminifolia (Michx.) Nutt.) increased flowering stem production after lightning-season fires in a longleaf pine community in north Florida. If enhanced sexual reproduction is an adaptation of pl ants to lightning-season fire, then examining flowering responses to varying months of burn may illustrate the ecological signif icance of fire season and the potential for land managers to enhance sexual reproduction for a suite of groundlayer plants in longleaf pine communities. While lightning-season fire is known to enhance the production of flowering stems for several plant species, few studies have examin ed the month-of-burn on seed effects on seed germination of longleaf pine sa vannas grasses. The month-of -burn may also enhance seed germination for ground-layer species. Christ ensen (1977) observed temporary increases in 10

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nutrient availability for 4 to 6 mo after lightning -season fires in longleaf sa vannas, but noted that nutrient availability 6 mo after burning declined to levels consistent with unburned sites. Similarly, Brewer and Platt (1994) suggested that an increase in sexual reproduction by forbs is a strategy evolved to exploit favorable environmenta l conditions following lightning-season fire in longleaf pine savannas. As such, conditions resu lting from lightning-season fire (i.e., increased nutrient availability) may enhance sexual reproduc tion of some grass species and, as a result, may also improve seed germination for these species. Grasses are ideal species to test the monthof-burn effects on characteristics of sexual reproduction. They comprise significant proporti ons of the total ground cover in longleaf pine savannas and are the principal fuels sustaining low intensity fire in the ecosystem (Peet & Allard 1993; Outcalt 1994; Mulligan & Kirkman 1998). Furthermore, numerous grass species worldwide have evolved life-history strategies that reflect the local fire regime (Curtis & Partch 1950; Daubenmire 1968; Howe 1994; Whelan 1995; Bond & Wilgen 1996). Less known is the response of grass species to different months of burn in longleaf pine communities, especially the western extent of longleaf pine where wiregrass is not the predominant ground-layer fuel (Rodgers & Provencher 1999). Research Hypothesis I tested the month-of-burn eff ects on characteristics of sexual reproduction to determine if ecologically important grasses, which sustain fire in longleaf pine communities of northwest Florida, respond favorably to fires that mimic the natural occurrence of lightning. This study examines the following hypotheses: Fire stimulates sexual reproduction in a suit e of longleaf pine sandhill grass species. Flowering differs among mont h-of-burn and is greatest af ter lightning-season fires. 11

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Flowering stem production varies with monthof-burn and is greater after lightning-season fires Seeding potential (callus producti on per stem) differs among mont h-of-burn and is greatest after lightning-season fires. Seed production is greatest in sites burned during the lightning-season and differs among month-of-burn. Germination differs among month-of-burn a nd is greatest after lightning-season burns. 12

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0 100 200 300 400 JFMAMJJASOND MonthAnnual lightning-fire frequency Figure 1-1. Fire frequency in Florida. [Reprinted with permission from Tall Timbers Research Station. Komarek, E.V., Sr. 1964. The natural history of lightning. Proc. Tall Timbers Fire Ecology Conf. 4:169-197.] 13

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CHAPTER 2 EFFECTS OF BURN MONTH ON FLOW ERING AND SEED PRODUCTION BY LONGLEAF PINE SANDHILL GRASSES Longleaf pine ( Pinus palustris Miller) savannas are a fire-evolved ecosystem of the southeastern United States that historically bur ned at low-intensity every 1-5 yr (Frost 2006). Lightning is the natural agent of fi re in this ecosystem, typically occurring in the peak lightningseason (May-August) after spring droughts create tinder dry ground-laye r fuels that ignite readily (Komarek 1964). Native Americans also burned longl eaf pine savannas, but did so typically in fall and winter months to drive game and to e xploit predictable weathe r conditions (Robbins & Myers 1992; Frost 2006). These fire-maintained longleaf savannas are am ong the most species rich communities outside the tropics (Walke r & Peet 1983; Peet 2006), maintaining a large proportion of the endemic species in the sout heast U.S. (Sorrie & Weakley 2005; ch. 3). Unfortunately, the extent of longleaf pine ha s declined by more than 97% since European colonization and only 0.2% is regularly maintain ed with fire (Frost 2006). Conservation of longleaf pine habitat is therefore a priority for many public and private land managers. In longleaf pine savannas, fire suppresses fi re-intolerant trees and shrubs from succeeding into the sub-canopy. In addition, fire increase sh ort-term nutrient availa bility (Christensen 1977), surface soil temperatures (Hultert 1988) and the growth and sexual reproduction of numerous ground-layer plants (Pla tt et al. 1988; Streng et al. 1993; Brewer & Platt 1994; Outcalt 1994; Hiers et al. 2000). In th e absence of recurrent fire, fi re-intolerant trees and shrubs establish in the sub-canopy; reduc ing the cover and richness of ground-layer plants that sustain fire (Walker & Peet 1983; Gilliam et al. 1993). Where ground-layer plants have been locally extirpated due to vigorous fire suppression, co llection from donor site s may facilitate ground14

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layer restoration by providing an adequate source of seed. Unfortunately, many desirable ground-layer plants in longleaf pine savannas have poor s eed production (Pfaff & Maura 2000). Lightning-season fires enhance flowering stem production of numerous ground-layer plants in longleaf pine commun ities (Platt et al. 1988; Streng et al. 1993; Outcalt 1994; Hiers et al. 2000). If seed production is correlated with flowering stems, then lightning-season fire may be a major ecological force driving sexual re production and ground-layer maintenance (Robbins & Myers 1992; Brewer & Platt 1994). Few publis hed studies have examined flowering stem production and seed production of ground-layer speci es after fire, especially in the western extent of longleaf pine. Moreover, effects of different months-of-burn on sexual reproduction are lacking in these communities. Thus, littl e is known of the potential to enhance seed production in donor sites by conducting prescribed burns of a particular season. The purpose of this study was to examine sexual reproduction after different months-ofburn for grass species in a longleaf pine comm unity of northwest Florida. The following questions were examined: (1) what are the differen ces in percent of plants producing at least one seed-bearing stem for each species after various months-of-burn, (2) what are the differences in seed-bearing stem production per plant and per area for each species after various months-ofburn, and (3) how many seed are produced by each species af ter various months-of-burn? Methods Species and Site Selection The species studied are co mmon components of northwest Florida sandhills (Rodgers & Provencher 1999): Schizachyrium scoparium (Michx.) Nash var. stoloniferum (Nash) J. Wipff. (little bluestem); Andropogon ternarius Michx. (splitbeard bluestem); Sporobolus junceus Michx. (pineywoods dropseed); Aristida mohrii Nash (Mohrs threeawn); and, Aristida purpurascens Poir. (bottlebrush threeawn). S. scoparium and A. mohrii are endemic to the 15

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southeastern United States while the remaining three species occur throughout the eastern half of the U.S. S. scoparium is the dominant ground-layer specie s in fire-maintained sites across western EAFB. All five species are warm-season (C 4 ), fall-flowering bunchgrasses except for S. scoparium which is a (C 4 ) highly rhizomatous, sod-forming grass. Flowering occurs between October and December for all species except S. junceus, which flowers between September and November. Typically, seed disarticulation occurs within two months of flowering. Study sites were located in mature, longleaf pi ne sandhills at Eglin Ai r Force Base (EAFB) in northwest Florida (30 N, 86 W; Fig. 2-1). This area has been managed with prescribed fire for the past several decades. The prescribed fire regime has been one of frequent fire (1-6 yr) conducted between late February and late July (Table C-1). Study sites were randomly chosen from areas having burned in winter (February 2005), early spring (April 2005), early lightning-season (May 2005), and late lig htning-season (July 2005). Five to seven replicates were selected for each burn month. Crite ria for site selection were: (1) fire-maintained longleaf sandhills >0.1-ha in western EAFB; (2 ) a ground-layer consisting of fire-following grass species (see Lemon 1949; Hodgkins 1958); (3) excessively drained sands of the Lakeland series (Overing et al. 1995); (4) l ittle evidence of mechanical disturbance; and, (5) a fire regime consistent with the study season of burn (Table B-1). Plant nomenclature follows that of the Inte grated Taxonomic Information System (2007). Vegetation Sampling Vegetation sampling was used to determine th e percent of plants (population of ramets) producing seed-bearing stems (SBS), the number of SBS per plant, and the density of SBS per area of each species after five different months-of-burn. All sa mpling was carried out between October and December 2005. To determine the percent of seed-bearing plants, the presence/absence of at least one seed-bearing st em was recorded for the nearest plant of each 16

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species at 10 randomly located points within each 0.1-ha site. Basal area was calculated for each plant and the number of SBS were counted and harvested from the plant base. If SBS were absent, the nearest seed-bearing plant of that species was located and characterized using the methods previously described. Du e to the rhizomatous nature of S. scoparium SBS were counted in 0.125-m 2 (20-cm radius) sub-plots and basal area was not calculated. Concurrently, ten 3x15m transects were randomly placed within each site and the number of SBS recorded of each species. Due to high abundance, SBS of S. scoparium were counted in 1x15m transects I nested in each of the 3x15m transects used for th e other species. SBS were air-dried at room temperature (24C) for 2-wk and then stored in brown paper bags at room temperature for an 8mo after-ripening period. Seed Sampling Numbers of seeds were quantified from SBS to examine differences in seed production for the five species after various months-of-burn. For SBS harvest in fall 2005 (described above), seeds were recorded from 10-20 randomly sele cted stems per site and species. Where disarticulation had occurred on th e SBS, the node of disarticulat ion was considered to bear a floret and was thus described as measure of potential seed production. Statistical Analysis The percent of plants with SBS, SBS per area, and SBS per plant were analyzed for months-of-burn using separate one-way Proc GLM test in which month-of-burn was the treatment factor (SAS Institute Inc. 1988). Orthogonal linear contrasts were performed on Spring 2004 burns versus all other months-of-burn; results are reported in text. Arcsin-square root transformations of percen t data and the inverse of SBS counts were used to meet assumptions of normality and homogeneity of variances (Zar 1998). Differences among means were separated by Tukeys HSD post-hoc when treatments were significant ( p < 0.05). Results 17

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are expressed as means ( 1 SE). Mean basal ar ea of plants did not influence the number of SBS and was therefore not considered as a covariate for analysis. Results Percent SBS Different months-of-burn revealed significant sp ecies-specific differences with respect to the percent of plants producing at leas t one SBS (Fig. 2-2). Percent SBS of S. junceus plants (Fig. 2-2a) was significantly greater for late lightning-season burns than winter (February) burns. For S. scoparium percent SBS was significantly lower afte r winter burns than lightning-season burns (Fig 2-2b). In comparison, there were no significant differences for the percent SBS of A. terarius after different months-of-burn (Fig. 2-2c). When comparing am ong different monthsof-burn, percent SBS of A. mohrii was significantly lower (i.e., 0) after late lightning-season burns than other months-of-burn in 2005 (Fig 2-2d). Lastly, A. purpurascens showed no significant differences to percent SBS after different months -of-burn in 2005 (Fig. 2-2e). SBS Density High variance over month-of-burn for all specie s meant few significant differences in SBS density (Fig. 2-3), though results indicate that SBS density after differe nt months-of-burn was species-specific. S. junceus (Fig. 2-3a), S. scoparium (Fig. 2-3b), A. mohrii (Fig. 2-3d), and A purpurascens (Fig. 2-3e) showed no significant differences to SBS density as a result of 2005 burns. In comparison, SBS density of A. ternarius was significantly lower after winter burns than late lightning-season burns (Fig. 2-3c). SBS per Plant Differences in SBS per plant did not show a consistent pattern with respect to the season of burn (Fig. 2-4). S. junceus (Fig. 2-4a), S. scoparium (Fig. 2-4b), A. ternarius (Fig. 2-4c), and A. purpurascens (Fig. 2-4e) again showed no significant differences to SBS stems per plant as a 18

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result of different months-of-burn conducted in 2005. In comparison, SBS per plant of A. mohrii were significantly lowest after late lightningseason burns, similar be tween spring and early lightning-season burns, a nd highest after winter burns (Fig. 2-4d). Floret and Seed Production per SBS When comparing floret production per SBS of S. junceus (Fig. 2-5a), A. ternarius (Fig. 25c), A. mohrii (Fig. 2-5d), and A. purpurascens (Fig. 2-5e), floret production was not significantly different among the months-of-bur n. In contrast, floret production of S. scoparium was higher in lightning-season bur ns than winter burns, or sp ring burns of 2004 and 2005 (Fig. 2-5b). Lastly, showed no significant differences in floret production Changes in seed production by species in each burn month did not show a consistent pattern with respect to seasonof-burn (Fig. 2-6); how ever, seed production trends emulated those of floret prodution. Though several sp ecies had higher producti on after lightning-season burns, S. junceus (Fig. 2-6a), A. ternarius (Fig. 2-6c), A. mohrii (Fig. 2-6d), and A. purpurascens (Fig. 2-6e) showed no significant differences in seed production to different months-of-burn, In contrast, S. scoparium showed trends emulating floret production, with significantly higher seed production after lightning-season burns in comparis on to winter burns and early spring burns (Fig 2-6b). Discussion Fire Season Effects on Charac teristics of SBS Production In my study, changes in flowering characterist ics of dominant grass species varied with respect to month-of-burn. The pattern for greater percent of seed-bearing plants in response to lightning-season burns is consistent with those reported previous ly for ground-layer plants in longleaf pine savannas (Platt et al. 1988; Outcalt 1994; Hiers et al. 2000). Similarly, these results are in accordance with several studies reporting enhanced flowering in response to 19

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lightning-season burns for bluestem grasses in tallgrass prairies of the Midwest United States (Curtis & Partch 1950; Howe 1995). Likewise, some field observati ons indicate that bluestems flower profusely in response to lightning-season burns conduc ted in longleaf pine savannas (Lemon 1949; Rodgers & Provencher 1999). Some species, however, showed little change in percent seed-bearing plants as a result of lightning-season burns, w ith high percentages across all burn treatments. Moreover, the percent of seed-b earing plants of at l east one grass species ( A. mohrii) declined in response to lightning-season burns The decline in flowering stems of this species contrast sharply with th e observed flowering response of A. stricta to lightning-season burns.These results suggest that fire season effects on the percent of seed-bearing plants are species-specific among the five grass species. Despite significant differences in the percent of seed-bearing plants for three of five grass species after different months-of-burn, I detected significantly different SBS densities for just one species after the different months-of-burn. Si milarly, just one of five grass species produced significantly different numbers of SBS per plant after different months of burn. For 4 of 5 species, SBS density varied considerably and was greatest after late li ghtning-season burns. Extreme variability after late lightning-season burn s was the result of a 4-folod increase in SBS density within one burn site. At the plant level, SBS production fo r 4 of 5 grass species was not significantly different as a result of different months-of-burn. A. mohrii, however, showed marked changes in SBS production per plant in re sponse to burns conducted in early spring and the lightning-season. Consequent ly, variation in SBS producti on is not consistent across different months-of-burn or among species, although the majority of species responded favorably to burns conducted in the early spring and lightning-season. Unexpectedly, several characteristics of SBS producti on declined precipitously in A. mohrii with respect to lightning20

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season. Hiers et al. (2000) reported similar declines in flowering stem production of this species as a result of lightning-season burns. Declines in SBS production are then not surprising as several species in longleaf pine communities expl oit a broad range of life-history strategies adapted to different environmental pressures. In longleaf pine savannas, literature exam ining the effect of seasonal burning has suggested that enhanced post-fire flowering is an evolved adapta tion to lightning-season fires (Platt et al. 1988; Brewer & Pl att 1994), which may be reflected across a large proportion of the plant community (Platt et al. 1991). Such st udies, however, are too few and encompass just a small suite of the native species able to sustain fi re in longleaf communities. More recent studies suggest that observed flowering patterns in response to burni ng might reflect a dependence on fire rather than the season of burning (Kirkman et al. 1998; Hier s et al. 2000). In general, burning removes litter from the ground-layer, which subsequently provides greater light availability at the soil surface (H ulbert 1988). In turn, greater light availability increases soil temperatures and stimulates flowering (Gill 197 5; Hulbert 1988). Christensen (1977) also observed that, in comparison to unburned sites, soil nutrients were significantly greater for 4 to 6 mo following burning in longleaf pine savannas. Thus, enhanced flowering in lightning-season treatments may reflect the temporary increase in available nutrients the subsequent fall, while nutrient availability in spring and winter burn tr eatments likely subsides to pre-burn conditions by the fall flowering period. Burns conducted during these months remove aboveground biomass (Myers 1990), reduce sub-canopy density (Robbins & Myers 1992), increase short-term nutrien t availability (Christensen 1977), and increase light irradiance at the soil surface (Hulbert 1988). Different months-of-burn resulted in specie s-specific differences with resp ect to SBS characteristics. 21

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Burns conducted in early spring and during the lightning-season enhanced th e percent of seedbearing plants of S. scoparium and S. junceus. Similar results were observed in longleaf pine savannas where growing season or lightning-season burns e nhanced flowering and SBS production of ground-layer plants (Platt et al. 1988; Streng et al. 1993; Out calt 1994; Hiers et al. 2000). Surprisingly, no seed-beari ng plants were observed of A. mohrii after late lightningseason burns. In addition, fewer samples (plants) of A. mohrii were found after late lightningseason burns than any other month-of-burn or species. Percent of seed-bearing plants of A. ternarius and A. purpurascens were not influenced by differe nt months-of-burn, with high (> 90%) numbers of seed-bearing plants observed across the months-of-burn. Fire Season Effects on Flo ret and Seed Production Although abundant seed production is expected in sites where flowering is also abundant (Platt et al. 1988; Outcalt 1994) the number of florets and seed were consistent across the different months-of-burn for each species. Furtherm ore, the numbers of seeds were correlated to the numbers of florets produced within each mont h-of-burn and species; how ever, seed shatter of S. junceus resulted in dramatic differences in the reported proportion of seeds and florets. Increased floret and seed production in S. scoparium were the result of lightning-season burns. Seed production is a dynamic process requiring successful pollination, fertilization, and seed development (Walker & Silletti 2006). While th e numbers of florets and seeds were counted from the entire inflorescence of each sample, it is possible that greater fl oret and seed production are the result of greater inflorescence length or increased branching of the inflorescence. In this study, none of the species showed c onsistent responses across variables; however, burns conducted in early spring and the lightning-season improved se veral SBS characteristics of some species. Therefore, land management may rely on a month or season-of-burn to enhance SBS characteristics for a particular species. Beca use not all species responde d to similarly to the 22

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month-of-burn, however, maintaining a variable fire season should maintain a full complement of ground-layer richness (Hiers et al. 2000). 23

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Figure 2-1. Map of Eglin Air Force Base (EAFB) in northwest Florida. The study sites were all located in the western range of EAFB. 24

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Burn Month a) b ) b ab ab b0 10 20 30 40 50 60 70 80 90 100February April May July a a ab b0 10 20 30 40 50 60 70 80 90 100February April May July b a a a0 10 20 30 40 50 60 70 80 90 100February April May Julyc) d) e) 0 10 20 30 40 50 60 70 80 90 100February April May July 0 10 20 30 40 50 60 70 80 90 100February April May July Figure 2-2. Mean percent ( 1 SE) of plants producing at least one s eed-bearing stem for (a) Sporobolus junceus (b) Schizachyrium scoparium (c) Andropogon ternarius, (d) Aristida mohrii and (e) Aristida purpurascens after different months-of-burn in 2005. Significant differences (ANOVA, p < 0.05) are indicated with different letters. The numbers of reps varied du e to preexisting differences in species abundance for each month-of-burn. Therefor e, the total number of reps for each month-of-burn ranges from a minimum of n = 3 to a maximum of n = 10. 25

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a) b) Burn Month 0 20 40 60 80 100 120 140 160February April May July 0 5 10 15 20 25 30 35 40 45February April May July a ab ab b0 1 2 3 4 5 6 7 8 9 10February April May July 0 2 4 6 8 10 12 14 16 18 20February April May July 0 5 10 15 Figure 2-3. Mean ( 1 SE) seed-bearing stems (SBS) per area for (a) Sporobolus junceus (b) Schizachyrium scoparium (c) Andropogon ternarius, (d) Aristida mohrii and (e) Aristida purpurascens after different months-o f-burn in 2005. Significant differences (ANOVA, p < 0.05 ) are indicated with different letters. The total number of reps for each month-of-burn was n = 5. Note that scales on the various panels are different. Note also that stems of S. scoparium were determined in 15m 2 transects while stems of other species were determined in 45-m 2 transects. Note differences in scale for the various panels. 20 25 35 40February April May July c) d) e) 30 26

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Burn Month b) a) 0 5 10 15 20 25February April May July 0 1 2 3 4 5 6 7 8 9 10February April May July 0 1 2 3 4 5 6 7 8 9 10February April May July a b b c0 2 4 6 8 10 12 14 16 18 20February April May July 0 1 2 3 4 5 6 7 8 9 10February April May Julyc) d) e) Figure 2-4. Mean ( 1 SE) seed-bearing stems (SBS) per plant for (a) Sporobolus junceus (b) Schizachyrium scoparium (c) Andropogon ternarius, (d) Aristida mohrii and (e) Aristida purpurascens after different months-o f-burn in 2005. Significant differences (ANOVA, p < 0.05) are indicated with diffe rent letters. The numbers of reps varied due species-specific di fferences in SBS production for each monthof-burn. Therefore, the total number of reps for each month-of-burn ranges from a minimum of n = 4 to a maximum of n = 10. Note differences in scale for the various panels. 27

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Burn Month Figure 2-5. Mean ( 1 SE) production of flor et and seed per seed-bearing stem for (a) Sporobolus junceus (b) Schizachyrium scoparium (c) Andropogon ternarius, (d) Aristida mohrii and (e) Aristida purpurascens after different months-of-burn in 2005. Significant differences (ANOVA, p < 0.05) are indicated with different letters. The numbers of reps varied due species-specific differences in SBS production for each month-of-burn. Therefor e, the total number of reps for each month-of-burn ranges from a minimum of n = 2 to a maximum of n = 10. Note differences in scale for the various panels. 0 20 40 60 80 100 120 140 160February April May July A A B B a a b b0 10 20 30 40 50 60February April May July Floret Floret seed Seed 60 0 10 20 30 40 50 60February April May July Floret Floret Seed Seed 0 10 20 40 50February April May July 30 60 0 10 20 30 40 50February April May July Floret Seede) d) c) a) b) 28

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CHAPTER 3 FIRE SEASON EFFECTS ON SEED GERM INATION OF LONG LEAF PINE SANDHILL GRASSES Introduction Fire plays an essential role in determining the structure and function of plant communities worldwide (Daubenmire 1968; Whelan 1995; Bond & Wilgen 1996; Pyne et al. 1996). In the southeastern United States, longleaf pine ( Pinus palustris ) savannas are maintained by frequent (1-5 yr), low-intensity fire sustained by ground-layer fuels (Frost 2006). Fire removes aboveground biomass, thus increasing light availability and temperat ure at the soil surface (Christensen 1975; Hulbert 1988). Moreover, fi re increases short-term (4-6 mo) nutrient availability for ground-layer plan ts (Christensen 1977). As a re sult, ground-layer plants often increase growth and sexual reproduction after fire (Platt et al. 1988; Brewer & Platt 1994; Hiers et al. 2000). The ground-layer in these fire-m aintained communities are also among the most species-rich communities outside the tropics (Walker & Peet 1983; P eet & Allard 1993). Due to habitat fragmentation and vigorous fi re suppression, the range of longleaf pine has declined by more than 97% sin ce European colonization and only 0.2% is regularly maintained by fire (Frost 2006). During the prolonged absen ce of fire, fire-intoler ant trees and shrubs succeed into the sub-canopy and competitively re duce ground-layer fuels and longleaf pine recruits (Glitzenstein et al. 1995; Varner et al. 2005). Without adequate ground-layer fuel, fire is neither sufficient-nor-frequent enough to ma intain longleaf pine savannas (Peet 2006). Therefore, maintaining ground-layer populations is essential to the fire regime, habitat quality, and species richness of longleaf pine communities. Consequently, longleaf pine restoration is dependent on thinning fire-i ntolerant trees in the canopy and establishing adequate ground-layer 29

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fuel in sites where fire has been actively s uppressed (Robbins & Myers 1992; Streng et al. 1993; Glitzenstein et al. 2001; Provencher et al. 2001; Walker & Silletti 2006). Direct seeding is the most viable and ec onomical method for starting new populations in sites where the ground-layer has been locally exti rpated (Guerrant 1996; Gl itzenstein et al. 2001; Walker & Silletti 2006). Considerations fo r establishing new populations of ground-layer species should include: (1) similarity between habitat conditions of the donor site and restoration site; (2) proximity between the donor site and rest oration site; and, (3) quality of seed from the donor site. Fortunately, several public and private land managers maintain large tracts of longleaf pine with frequent ground-layer fires (A lavalapati et al. 2006; Compton et al. 2006). For example, land managers of Eglin Air For ce Base (EAFB) in northwest Florida have prescribed burned longleaf pine savannas for more than two decades (Appendix; Table C-1). These fire-frequented sites are composed of de sirable ground-layer species whose seed may be harvested and used to establish new ground-layer populations in adjacent, species-poor sites of EAFB. Unfortunately, native ground -layer species in longleaf pi ne savannas have poor seed production and viability (Pfaff & Gonter 1996; Yarlett 1996), thus hindering the ability to establish a dominant ground-layer during the initial stages of restoration. Longleaf pine communities evolve d under a regime of frequent fire, naturally occurring between May and August (lightning-season) wh en thunderstorms and lightning are frequent (Komarek 1964; Chen & Gerber 1990; Robbi ns & Myers 1992). Increased and more synchronous flowering (Platt et al 1988; Robbins & Myers 1992; Brewer & Platt 1994; Outcalt 1994), and increased seed production (Streng et al. 1993; Outcalt 1994), are considered adaptations of some ground-layer sp ecies to the peak lightning-seas on of the southeastern United States. While studies have reported the m onth-or-season-of-burn effects on flowering 30

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characteristics of several ground-layer species (P latt et al. 1988; Streng et al. 1993; Brewer & Platt 1994; Outcalt 1994; Hiers et al. 2000), few studies have reported differences in seed germination of ground-layer spec ies after different months-ofburn in these fire-maintained communities. Thus, it is not known whether lightning-season burns have an influence of seed germination nor on the potential of ground-layer plan ts to establish in longleaf pine savannas. Grasses are an ideal species to assess the months-of-burn effects on seed germination. They are a dominant component of the ground c over and the primary fuel source in longleaf communities (Myers 1990; Walker & Silletti 20 06). In addition, grasses worldwide have evolved life-history strategies th at often reflect adaptations to the local fire regime (Curtis & Partch 1950; Kucera &; Bond & Wilgen 1996). The purpose of this study was to examine seed germination after different months-of-burn for gr ass species in a longleaf pine community of northwest Florida. The following question was exam ined: what are the differences in percent of seed germinating for each speci es after various months-of-burn? Methods Species Selection The species studied are domina nt perennial grasses in sandhills in northwest Florida (Rodgers & Provencher 1999): Schizachyrium scoparium (Michx.) Nash var. stoloniferum (Nash) J. Wipff. (little bluestem); Andropogon ternarius Michx. (splitbeard bluestem); Sporobolus junceus Michx. (pineywoods dropseed); Aristida mohrii Nash (Mohrs threeawn); and, Aristida purpurascens Poir. (bottlebrush threeawn). A fu rther description of each species and sites from which seeds were collected is previously re ported (Chapter 2). Seed Selection and Germination Seeds of the five species were collected from seed-bearing stems after different months-ofburn in longleaf pine sandhills of EAFB, as prev iously reported (Chapter 2). Germination was 31

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conducted on 9 x 1.5 cm Petri dishes with two pieces of saturated (4 ml deionized water) Whatman No. 5 filter paper with 25 seeds; there we re three replicates per treatment (burn month) per species (n =75). Petri dishes were placed on trays and incubated for 1 mo in Percival seeds incubators under 12:12 li ght: dark photoperiod at 30C: 20C. Prior to treatment, seeds were surface-sterilized for 15 min in 3% sodium hypoch lorite solution (Essah et al. 2003) and rinsed three times with deionized water. Additionally, S. junceus and S. scoparium seeds were cold stratified at 5C for 30 and 14 d, respectiv ely (Glitzenstein et al. 2001; AOSA 2004). Germination was considered as the emergence of the radicle and was characterized almost daily for 1 mo. A second germination trial was conducted 1 mo after completion of the first trial when mold was discovered on 38% of the seeds in the fi rst trial. A surfactant (Ivory liquid soap) was added to the 3% sodium hypochlor ite solution and seeds were clean ed using methods previously mentioned. Surfactants reduce surface tension of sodium hypochlorite and may coat the seed more thoroughly, especially on highly pubescent seeds such as Andropogon ternarius and Schizachyrium scoparium Seed groups were additionally treated using two sprays of 29.5 ml/7.5 L (v/v) fungicide (Daconil; tetrachloroisophthalo nitrile) in a hand-held spray bottle. Similar incubation methods were conducted for the second germination trial. Statistical Analysis The percentage germination was arcsine-squa re root transformed prior to one-way Proc GLM tests with the months-of-burn as the treatm ent factor (SAS Institute Inc. 1988; Zar 1998). Differences among means were separated by Tukeys HSD post-hoc when treatments were significant ( p < 0.05). 32

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Results In the first trial, most of the species showed patterns indicat ing seed germination dependence to a month-of-burn, but high variance rendered these response s non-significant (Fig. 3-1). However, late lightning-s eason burns resulted in significantly greater seed germinating for A. ternarius than winter burns (Fig. 3-1c). Germination of A. mohrii was not significantly different among months-of-burn (Fig. 3-1d), in cluding no observed seed germination for the early lightning-season treatment a nd the lack of seed to test seed germination of the late lightning-season treatment. Lack of germination is of interest because this particular species is endemic to longleaf pine sandhills and likely evolved with fire. A. purpurascens produced the highest percentage germination among all species, but showed no significant preference to any particular month-of-burn (Fig. 3-1e). Three species ( S. scoparium A. ternarius, and A. purpurascens ) were tested in the second trial due to a lack of s eed for the other species ( S. junceus and A. mohrii). Again, lightningseason fires appeared to result in higher seed germination of all species, but in this trial the pattern was significant only for A. purpurascens (Fig. 3-2). This species showed higher germination after late lightning-season burns than winter burns or early spring burns (Fig. 3-2e). Discussion The two trials conducted demonstrate that germin ation of at least 2 of the 5 grass species, and potentially all 5 species, is fire-season depe ndent. Low germination rates (< 30% for most) may suggest that more seeds would be required to fully elucidate these patterns. Successful germination is dependent on a complex associ ation of physiological processes and optimal environmental conditions (Bewley 1997). Th eses interactions are further compounded by differences among site conditions, year-to-year climate differences, and even differences between individuals within a species (Fenner 198 5). The presence of deeply dormant seed is 33

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common of species associated with fire-evolved communities, especially in California chaparral and fynbos communities of Sout h Africa (Keeley & Bond 1997). Smoke generated from fires induces and/or enhances germination of many spec ies in these communities and is considered an evolved adaptation to the local fire regime (Keeley 1981, 1991). In comparison, seed dormancy issues are not readily apparent in species associ ated with fire-evolved l ongleaf pine savannas of the southeastern U.S. (Walker & Silletti 2006). Low germination is typical of grasses wo rldwide (Blake 1935; Green & Curtis 1950; Grime et la. 1981; Cook 1985; Brys et al. 2005). Germination percentages are highly variable across a suite of ground-layer species in longleaf pine savannas, ranging from 0% to greater than 80% under a variety of field and laboratory conditions (Pfaff & Gonter 1996; van Eerden 1997; Glitzenstein et al. 2001; Pfaff et al. 2002). Previous re ports indicate that germination percentages of many desirable gra sses are consistently lower than other guilds associated with longleaf communities (Pfaff & Gonter 1996; Hiers et al. 2000; Glitzenstein et al. 2001; Walker & Silletti 2006). Indeed, germination percentages of grass species ranged from 0% to 64% under laboratory conditions during my study. The mean germination percentage of desirable grasses (i.e., S. junceus, S. scoparium and A. ternarius ), however, ranged between 0% and 28%. These germination percentages are in accordance with va lues reported by Seamon et al. (1993), Outcalt (1994) and Pfaff & Gonter (1996 ), who also found low (< 30%) germination percentages of a suite of grass species associated with longleaf pine Similarly, Glitzenstein et al. (2001) reported germination percentages as low as 5% for S. scoparium which correspond to low germination percentages (0 to 7.5%) found of S. scoparium in my study. Similarl y, season-of-burn did not influence germination percentages for a suit e of ground-layer plants in longleaf pine 34

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communities (Glitzenstein et al. 2001), but germin ation trends reported in my study at least suggest a pattern of higher germinat ion after lightning-season burns. Many grasses of fire-evolved ecosystems re ly heavily on clonal reproduction (Briske & Richards 1995), often forming dense sods fr om rhizomes and stolons. In comparison, bunchgrasses form via tiller production and are gene rally assumed to rely on recruitment from seed (Liston et al. 2003). Ther efore, species may also exhibit differences in seed germination based on different life history st rategies. Germination percenta ges found in this study, however, were consistently low among species exhibiting both clonal growth and t iller production. High germination percentages of A. purpurascens are consistent with Pfaf f and Gonter (1996) and Haddock (2005), who reported that this grass depends entirely on recruitment from seed and exhibits ruderal qualities (e.g., rapid germination). Little emphasis has been placed on seed research in the southeastern U.S., especially with respect to burning native grasses. While depe ndence on fire seasonality is well understood in Aristida stricta germination responses are less well unde rstood. Population establishment of desirable ground-layer plants is dependent on viable seed produced during the current or previous years growing seasons due to the lack of a persistent soil seed bank in dominant and ecologically beneficial grass species (Cohen et al. 2004). These data suggest that seed germination is species-specific and significantly enhanced by light ning-season fires for at least two species ( A. purpurascens and A. ternarius ) in longleaf pine sandhills of northwest Florida. Therefore, increased establishment of ground-laye r populations from existing plants may benefit from fires burned at different times during the lightning-season. 35

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a ) b ) c ) d ) e ) Burn Month a a a a0 5 10 15 20 25 30 35 40February April May July a a a a0 1 2 3 4 5 6 7 8 9 10February April May July a ab ab b0 5 10 15 20 25 30 35 40February April May July a a a0 1 2 3 4 5 6 7 8 9 10February April May July a a a a0 10 20 30 40 50 60 70 80February April May July Figure 3-1. Mean ( 1 SE) germination of (a) Sporobolus junceus (b) Schizachyrium scoparium (c) Andropogon ternarius (d) Aristida mohrii and (e) Aristida purpurascens after different months-of-burn. Significant differences (ANOVA, p < 0.05) are indicated with different letters The numbers of samples varied due species-specific differences in the number of seed produced by each species after different months-of-burn. Therefore, the total number of reps for each months-ofburn ranges from a minimum of n = 5 to a maximum of n = 7. Note that means and SEs represent non-transformed data. Note also that scales on the various panels are different. denotes month-of -burn was removed from analysis due to small sample size (n = 1). 36

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a) b) c) Burn Month a a a a0 2 4 6 8 10 12 14 16 18 20February April May July a a a a0 5 10 15 20 25 30 35 40February April May July a ab b b0 10 20 30 40 50 60 70 80February April May July Figure 3-2. Mean ( 1 SE) germination of (a) Schizachyrium scoparium, (b) Andropogon ternarius and (c) Aristida purpurascens after different months-of-burn. Significant differences (ANOVA, p < 0.05) are indicated with different letters. The numbers of samples varied due species -specific differences in the number of seed produced by each species after different months-of-burn. Therefore, the total number of reps for each months -of-burn ranges from a minimum of n = 4 to a maximum of n = 6. Note that means and SEs represent non-transformed data. Note also that scales on the various panels are different. 37

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CHAPTER 4 CONCLUSIONS AND IMPLICATIONS FOR GROUND-LAYER RESTORATION IN FLORIDA SANDHILLS In the southeastern U.S., fire-maintained longleaf pine remnants are among the most species-rich communities outside the tropics (Hardin & White 1989; Peet & Allard 1993). Unfortunately, longleaf pine habitat has declined by at least 97% since European colonization and only 0.2% is regularly maintained with fire (Frost 2006). Ground-layer fuels are characteristically absent or not readily able to sustain low-intensity fires in sites where fire has been vigorously suppressed from longleaf pine communities. Therefore, establishment of ground-layer fuels is considered a biological priority for the persistence of the local fire regime and health of longleaf habitat. Many desirable native ground-layer plants in Florida have low seed production and viability (Pfaff & Maura 2000), t hus making ground-layer establishment difficult. Nevertheless, longleaf pine communities evolved under a fairly specific fire regi me, with highest frequency of lightning-ignited fires in May and June (Fig. 11). Thus, several plant species may require a relatively narrow fire regime to enhance sexual re production (Platt et al. 1988) and successfully establish from seed. Few studies have investigated the months-of-burn effects on ecologically important grass species. Therefore, studies ev aluating differences in sexual repr oduction after different months-of-burn are important for consideration of ground-layer establishment. For purposes of this study, true unburned controls di d not exist because longleaf pine savannas evolved under frequent fire and EAFB regularly maintains their longleaf pine communities with fire (Brewer & Platt 1994; Compton et al. 2006 ). I considered the fire season effects on flowering characteristics of longl eaf pine sandhill grasses a better indicator of the ecological significance of fire than the e ffects of fire vs. no fire. 38

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Results of my study suggest that not all of these domi nant grass species respond consistently to month-of-burn. First, several species res ponded to lightning-season burns by producing a greater percentage of seed-bearing plants, while one species showed a significantly lower percentage of seed-bearing plants after lig htning-season burns. Furthermore, differences in the months-of-burn did not affect the percenta ge of seed-bearing plants for two species, as they produced high percentages across all months -of-burn. Thus, the hypot hesis that lightningseason burns increase flowering percent is spec ies-specific. Likewise none of the species showed consistent production of seed-bearing stem s (SBS) per area and plant, with 4 of 5 species showing no differences with respect to month-of -burn. Tests of floret and seed production per stem revealed considerable variation among speci es and months-of-burn and 4 of 5 species again produced no differences with respect to month-ofburn. For each of these tests, significance was not consistent across variables, suggesting that inadequacies in one variable may be overcome by another variable. Similarly, tests of seed ge rmination were not consistent among species and ranged from 0% to 64%, including germinati on percentages from 0 to 28 for ecologically important grass species. In this study, none of the species showed c onsistent responses across variables; however, burns conducted in early spri ng and the lightning-season improve d several SBS characteristics for some species. Therefore, land management may rely on a month or season-of-burn to enhance SBS characteristics for th ese particular species in rest oration and seed donor sites. Because not all species responded to similarly to the month-of-burn, however, maintaining a variable fire season should maintain a full comp lement of ground-layer richness (Hiers et al. 2000). 39

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APPENDIX A CLIMATE NORMALS FOR NICE VILLE, FL FROM 1971-2000 0 10 20 30 40 50 60 70Janu a ry February Ma r ch Apr i l May June J ul y Aug u st September October N ove m b e r De ce mberMonth 0 5 10 15 20 25 30Temperature (C) Mean Precipitation 1971-2000 Observed Precipitation 2004 Mean Temperature 1971-2000 a) 0 10 20 30 40 50 60 70Ja n ua r y Fe b r u a ry Mar ch April Ma y June J u ly August Septem b e r October November Decemb e rMonth 0 5 10 15 20 25 30Temperature (C) Mean Precipitation 1971-2000 Observed Precipitation 2005 Mean Temperature 1971-2000 b) Figure A-1. Monthly precipit ation and temperature means for Niceville, FL (1971-2000), including average monthly precipita tion for (a) 2004 and (b) 2005 seasons. 40

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APPENDIX B BURN HISTORY OF EG LIN AIR FORCE BASE Table B-1 Burn history for longleaf pine ( Pinus palustris ) sandhills on the western range of Eglin Air Force Base. Spring 2004 907 E 4/8/2004 5/24/2003 4/16/2000 2/1/1993 Burn Treatment Burn Site Burn History 704 B 4/10/2004 /1/1988 702 E 5/4/2004 4/26/2003 2/24/1998 2/1/1994 2/1/1987 2/1/1977 ebruary 2005 /1/1995 /1/1992 704 A 2/26/2005 2/9/2002 1/26/2000 2/1/1995 2/1/1992 2/1/1986 5 904 D 4/13/2005 1/8/2003 3/2/1999 2/1/1993 2/1/1988 ay 2005 3/2/1999 5/1/1998 2/1/1993 2 106 B 4/27/2004 4/27/1998 2/1/1991 F 104 D 2/4/2005 2/9/2002 2/2/2000 2 2 April 200 703 B 4/6/2005 4/23/2002 1/25/2000 1/1/1996 2/1/1979 903 C 4/9/2005 1/21/2001 2/1/1993 2/1/1987 M 5285 D 5/14/2005 5/4/2004 3/20/2000 1/1/1996 2/1/1993 2/1/1979 July 2005 704 E 7/24/2005 3/24/2001 2/23/2001 2/12/1996 2/1/1994 41

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LIST OF REFERENCES Abrahamson, W. G. 1984. Species responses to fire on the Florida Lake Wales Ridge. American Journal of Botany 71:35-43. Alavalapati, J. R. R., G. A. Stainback, and J. R. Matta. Longleaf pine re storation: Economics and policy. Pages 403-412 in S. Jose, E.J. Jokela, a nd D.L. Miller, editors. The longleaf pine ecosystem: ecology, silviculture, and restor ation. Springer, New York, New York. Association of Official Seed Analysts. 2004. Rules for testing seeds. Las Cruces, NM, USA. Beckage, B. and I. J. Stout. 2000. Effects of repeated burning on species richness in a Florida pine savanna: A test of the intermediate disturbance hypothesis. Journal of Vegetation Science 11 :113-122. Blake, A. K. 1935. Viability and germination of seeds and early life history of prairie plants. Ecological Monographs 5:405-460. Bond, W. J. and B. W. van Wilgen. 1996. Fire and Plants. Chapman & Hall, London, UK. Brewer, J. S. and W. J. Platt. 1994. Effects of fire season and herbivory on reproductive success in a clonal forb, Pityopsis graminifolia (Michx.) Nutt. Journal of Ecology 82:665-675. Briske, D. D. and J. H. Richards. 1995. Plan t responses to defolia tion: a physiologic, morphologic and demographi c evaluation. Pages 635-710 in Bedunah, D.J., and R.E. Sorebee (eds). Wildland plants: physiol ogical ecology and developmental morphology. Society for Range Management, Denver, CO. Brockway, D. and C. E. Lewis. 1997. Long-term effects of dormant-season prescribed fire on plant community diversity, structure, and pr oductivity in a longleaf pine wiregrass ecosystem. Forest Ecology and Management 96:167-183 Brockway, D. G., R. G. Gatewood, and R. B. Pari s. 2002. Restoring fire as an ecological process in shortgrass prairie ecosystems: initial eff ects of prescribed burning during the dormant and growing seasons. Journal of Environmental Management 65:135-152. Chakravarty, T., J. G. Norcini, J. H. Aldrich, and R. S. Kalmbacher. 2001. Plant regeneration of creeping bluestem ( Schizachyrium scoparium (Michx.) Nash var. Stoloniferum (Nash) J. Wipff) via somatic embryogenesis. In V itro Cellular & Developmental Biology-Plant 37:550-554. Chen, E. and J. F. Gerber. 1990. Climate. Pages 11-34 in R.L. Myers and J.J. Ewel, editors. Ecosystems of Florida. University of Central Florida Press, Orlando. Christensen, N. L. 1977. Fire and soil-plant nut rient relations in pine-wiregrass savanna on the coastal plain of North Carolina. Oecologia 31 :27-44. 42

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Christensen, N. L. 1981. Fire regimes in S outheastern ecosystems. Pages 112-136 in H.T. Mooney, T.M. Bonnicksen, N.L. Christensen, J.E. Lotan, and W.A. Reiners, editors. Fire regimes and ecosystem processes. USDA Fo rest Service General Technical Report, Washington, DC. Cohen, S., R. Braham, and F. Sanchez. 2004. Seed bank viability in disturbed longleaf pine sites. Restoration Ecology 12:503-515. Compton, V., J. B. Brown, M. Hicks, and P. Pe nniman. Role of public-private partnership in restoration: A case study. Pages 413-430 in S. Jo se, E.J. Jokela, and D.L. Miller, editors. The longleaf pine ecosystem: ecology, silvicultu re, and restoration. Springer, New York, New York. Copeland, T. E., W. Sluis, and H. F. Howe. 2002. Fire season and dominance in an Illinois Tallgrass prairie restorati on. Restoration Ecology 10:315-323. Curtis, J. T. and M. L. Partch. 1950. Some factors affecting flower production in Andropogon geradi Ecology 31:488-489. Daubenmire, R. F. 1968. Plant communities: a te xtbook on plant synecology. Harper and Row, New York. Denslow, J. S. 1985. Disturbance-mediated coex istence of species. Pages 307-323 in S.T.A. Pickett and P.S. White, editors. The ecology of natural disturbance and patch dynamics. Academic Press, San Diego. Ehrenreich, J. H. and J. M. Aikman. 1963. An ecological study of the effect of certain management practices on native prairie in Iowa. Ecological Monographs 33 :113-130. Essah, P. A., Davenport, R., and M. Tester. Sodium influx and accumulation in Arabidopsis Plant Physiology 133:307-318. Fenner, M. 1985. Seed Ecology. Chapman & Hall, London, UK. Frost, C. C. 2006. History and future of the longl eaf pine ecosystem. Pages 9-42 in S. Jose, E.J. Jokela, and D.L. Miller, editors. The longl eaf pine ecosystem: eco logy, silviculture, and restoration. Springer, New York, New York. Gill, A. M. 1975. Fire and the Australia n flora: a review. Australian Forestry 38:4-25. Gilliam, F. S. and W. J. Pla tt. 1986. Effects of long-term fire exclusion on tree species composition and stand structure in an old-growth Pinus palustris (longleaf pine) forest. Plant Ecology 140:15-26. Gilliam, F. S., B. M. Yurish, and L. M. Goodwin. 1993. Community composition of an old growth longleaf pine forest: Relation to soil texture. Bulletin of the Torrey Botanical Club 120:287-294 43

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BIOGRAPHICAL SKETCH Benjamin James Shepherd was born in Orlando, Florida on July 1, 1982. He grew up in Winter Park, Florida and often escaped to near by springs and beaches. While attending Winter Park High School, Ben competed in rowing and was elected team captain his senior year. His success in rowing garnered the atte ntion of several universities. Eventually, he chose to row for the University of Wisconsin-Mad ison. In Spring 2001, Ben helped Wisconsin capture a national championship. He frequently explored the Wi sconsin landscape while attending college and eventually volunteered at Curtis Prairiethe olde st restored prairie in the United States. At Curtis Prairie, Ben conducted an independent plant study descri bing species associations among the community and decided to further pursue acad emics. In 2004, Ben received a B.S. degree in biological aspects of conservation and a concen tration in Environmenta l Studies. He began graduate school at the Univers ity of Florida in January 2004 in the School of Natural Resources and Environment and received his degree in August of 2007. He now works for an environmental science and engineering company. 51