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Linkages among Vegetative Substrate Quality, Biomass Production, and Decomposition in Maintaining Everglades Ridge and Slough Vegetative Communities

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Linkages among Vegetative Substrate Quality, Biomass Production, and Decomposition in Maintaining Everglades Ridge and Slough Vegetative Communities
Creator:
LEWIS, CHRISTOPHER G.
Copyright Date:
2008

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Biomass ( jstor )
Biomass production ( jstor )
Everglades ( jstor )
Lignin ( jstor )
Nitrogen ( jstor )
Nutrients ( jstor )
Plant tissues ( jstor )
Soils ( jstor )
Species ( jstor )
Vegetation ( jstor )
City of Delray Beach ( local )

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University of Florida
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University of Florida
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Copyright Christopher G. Lewis. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
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5/31/2006
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436098728 ( OCLC )

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LINKAGES AMONG VEGETATIVE SU BSTRATE QUALITY, BIOMASS PRODUCTION, AND DECOMPOSTION IN MAINTAINING EVERGLADES RIDGE AND SLOUGH VEGETATIVE COMMUNITIES By CHRISTOPHER G. LEWIS 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 2005

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Copyright 2005 by Christopher G. Lewis

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This thesis is dedicated to God and my family: particularly my father, who has strengthened my endeavors as a novice scie ntist, and ameliorated the many hardships I have encountered along my chosen path. I must also thank Dr. Mark Clark, who has provided guidance and support; as well as in sight into complex, scientific conundrums that would puzzle even the most brilliant minds.

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ACKNOWLEDGMENTS I would like to thank God, my family, and my committee members (Dr. Mark Clark, Dr. Joseph Prenger, and Dr. Donald Gr aetz) for the support th ey have graciously lent me throughout my graduate career at the Un iversity of Florida. I would also like to thank the following graduate students: Eric Jorczak (Golden Corral rules!), Patrick Inglett, and Dr. Kanika Sharma for their advice in all matters scientific.

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v TABLE OF CONTENTS page ACKNOWLEDGMENTS.................................................................................................iv LIST OF TABLES............................................................................................................vii LIST OF FIGURES.........................................................................................................viii ABSTRACT....................................................................................................................... ix CHAPTER 1 INTRODUCTION AND SITE CHARACTERIZATION............................................1 2 VEGETATIVE SUBSTRATE QUALITY...................................................................5 Introduction................................................................................................................... 5 Hypotheses....................................................................................................................9 Materials and Methods.................................................................................................9 Field Methods........................................................................................................9 Laboratory Methods..............................................................................................9 Results........................................................................................................................ .10 Discussion...................................................................................................................11 3 VEGETATIVE BIOMASS PRODUCTION..............................................................17 Introduction.................................................................................................................17 Hypotheses..................................................................................................................20 Materials and Methods...............................................................................................20 Field Methods......................................................................................................20 Tall and short ridge biomass........................................................................20 Slough biomass............................................................................................21 Laboratory Methods............................................................................................21 Results........................................................................................................................ .22 Biomass, Plant Density, and Leaf Turnover: Ridges..........................................22 Sloughs................................................................................................................23 Discussion...................................................................................................................23

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vi 4 DECOMPOSITION....................................................................................................29 Introduction.................................................................................................................29 Hypotheses..................................................................................................................33 Materials and Methods...............................................................................................33 Field Methods......................................................................................................33 Litterbags......................................................................................................34 Standing dead decomposition.......................................................................34 Laboratory Methods............................................................................................37 Litterbags......................................................................................................37 Standing dead decomposition.......................................................................38 Results........................................................................................................................ .38 Litterbags.............................................................................................................38 Standing Dead Decomposition............................................................................40 Discussion...................................................................................................................43 Litterbags.............................................................................................................43 Standing Dead Decomposition............................................................................46 5 SYNTHESIS AND CONCLUSIONS........................................................................48 LIST OF REFERENCES...................................................................................................53 BIOGRAPHICAL SKETCH.............................................................................................58

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vii LIST OF TABLES Table page 1-1 Relative ranking of hydroperiod and flow ra te for each of the four main study sites.......................................................................................................................... ...4 2-1 Fractionation of neutral detergent fi ber and acid detergent fiber methods................8 2-2 Residual fiber production for different vegetative communities within Shark River Slough, Everglades.........................................................................................11 3-1 Vegetative community characteristics for ridge vegetative communities at the four study sites.........................................................................................................23 3-2 Vegetative community characteristic s for slough vegetative communities at the four study sites.........................................................................................................24

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viii LIST OF FIGURES Figure page 1-1 Four study areas in Shark River Slough, located in Water C onservation Area 3A (3A) and Everglades Nati onal Park (ENP), Florida.............................................1 2-1 Sequential extraction technique used in this study to determine vegetative substrate quality for ridge a nd slough community vegetation...................................7 2-2 Substrate quality values for ridge and slough vegetation.........................................12 2-3 Ratios of C:N and N:P for various sp ecies of ridge and slough vegetation.............13 3-1 Profile of study site showing tall ri dge, short ridge, and slough vegetative communities.............................................................................................................18 4-1 Litterbag experiment showing (a) litterbag structure (b) litterbag arrangement on PVC poles and (c) deployment in th ree ridge and three slough vegetative communities at each study site.................................................................................35 4-2 Standing dead decomposition experime nt showing (a) PVC pipe arrangement within ridge vegetative communities at each of the four study sites, and (b) PVC pipe structure showing at tachment of individual C. jamaicense leaves...................36 4-3 Decomposition of E. cellulosa and C. jamaicense at the four study sites during the experiment................................................................................................................39 4-4 Mass decay rates for E. cellulosa and C. jamaicense litterbags collected from ridge and slough vegetative communities in Shark River Slough during 2002-2003.......40 4-6 Temporal variation for % residual fiber content, C:N, and N:P values for standing dead C. jamaicense at each of the four sutdy sites...................................................42 5-1 Hypothetical Everglades landscape mor phology if no variation in mesotopography existed.......................................................................................................................4 8 5-2 Current landscape morphology show ing variation in ridge and slough mesotopography and vegetation...............................................................................49

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ix 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 LINKAGES AMONG VEGETATIVE SU BSTRATE QUALITY, BIOMASS PRODUCTION, AND DECOMPOSTION IN MAINTAINING EVERGLADES RIDGE AND SLOUGH VEGETATIVE COMMUNITIES By Christopher G. Lewis May 2005 Chair: Mark W. Clark Major Department: Soil and Water Science Shark River Slough contains topographydefined ridge and slough vegetative communities characteristic of the central Everglades. It also contains a vegetative mosaic characterized by extensive monos pecific stands of sawgrass ( Cladium jamaicense Crantz) interspersed with open water sloughs, and wet prairies containing fl oating and emergent macrophytes and periphyton. Soil elevation ha s a significant influence on the vegetative community. It is important to understand fact ors that may influence soil elevation, such as soil accretion rates, in order to maintain the current vegetative mosaic and ensure success of Everglades restoration efforts. These factors include vegetative substrate quality, biomass production, and organic matter decomposition that may indirectly affect soil accretion rates and vegetative community structure. However, quantitative information describing the importance of thes e factors in maintaining topography-defined landscapes is scarce in the scientific literature.

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x The primary objective of our study was to provide insight on this issue in Everglades ridge and slough vegetative communities. Biomass and residual fiber production were significantly greater for ri dge vegetative communities than for slough communities monitored during 2001-2004. Aver age dry-weight biomass production was 3493.4 + 174.3 g/m2/yr (ridges) and 1177.0 + 261.3 g/m2/yr (sloughs). Residual fiber production in ridges and sloughs was 282.3 + 38.0 g/m2/yr and 45.0 + 9.7 g/m2/yr, respectively. A litterbag experiment to determine species and community effects on decomposition rates was also performe d. Species-specific differences ( C. jamaicense and Eleocharis cellulosa ) in decomposition were greater than site-specific differences (ridge vs. slough). Litterbags cont aining ridge vegetation ( C. jamaicense ) decomposed slower than bags containing slough vegetation ( E. cellulosa ) due primarily to differences in vegetative substrate quality. As a result, faster decompositi on may be expected to occur in slough vegetation. This resu lt, combined with greater biomass production in ridges, may be responsible (at least in part) for th e current soil-elevation differences between ridge and slough vegetative communities, in the Shark River Slough ecosystem.

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1 CHAPTER 1 INTRODUCTION AND SITE CHARACTERIZATION The Florida Everglades is a vast subtr opical wetland that formed approximately 5000 years ago, through a process of sea level rise and peat accretion, in a limestone depression. South of Lake Okeechobee, Sh ark River Slough is the major drainage pathway for the Everglades (Fig. 1-1). It is a broad, shallow river approximately 200 km long and 40-60 km wide, that transports wa ter from wetlands north of Everglades National Park (ENP) to the Gulf of Mexico. Shark River Slough consists of a distinct vegetative mosaic. This mosaic includes extensive stands of Cladium jamacense (sawgrass) and other emergent macrophytes ; interspersed with openwater sloughs containing floating macrophytes and wet prai ries containing floa ting leaf macrophytes, emergents, and periphyton (Herndon et al., 1991; Doren et al., 1997). The central Everglades includes topography-defined landscapes such as the ridge and slough communities of central Shark River Slough. The terms ridge and slough represent elevation differences of the peat soil surface; C. jamaicense stands cover the higher peat ridges, and the lower elevation sloughs ar e characterized by openw ater, emergent, and floating leaf macrophytes ( Eleocharis cellulosa and Nymphaea odorata , respectively). Current evidence indicates extensive degradation of ridge and slough plant communities, compared to historic accounts. According to McVoy and Crisfield (2001), the historic ridge and slough landscape was composed of a peat-underlain mosaic of dense sawgrass ridges, with soil elevations 0.5 m higher than adjacent openwater sloughs.

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2 3A1 3A2 ENP1 ENP2 3A1 3A2 ENP1 ENP2 Figure 1-1. Four study areas in Shark Rive r Slough, located in Water Conservation Area 3A (3A) and Everglades Na tional Park (ENP), Florida Although this elevation difference may seem minimal, it was important in maintaining ecological homeostasis in the pre-drainage Everglades. This difference in mesotopography, in addition to seasonal variat ions in water level, allowed sloughs to remain wet throughout the year and allowed ridges to be exposed intermittently during dry months. Wildlife and ve getation adapted to this hydr ologic region and vegetative mosaic, and many aquatic species depended on the continuous inundation of sloughs for survival during severe droughts (McVoy and Crisfield, 2001). South Florida has experienced rapid populat ion growth, causing alterations in the regionÂ’s water quality and quantity; which ha s led to a decline in the environmental quality of aquatic and terrestrial ecosystems. This decline is of increasing concern to the public, and to regulatory and scientific co mmunities (McCormick and Stevenson, 1998). Of greatest concern is the ecological condition of Everglades National Park (ENP), which

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3 many believe has degraded considerably (F rederick and Spalding, 1994; Hoffman et al., 1994; Loftus and Eklund, 1994; Rader and Richardson, 1994). In response, the Comprehensive Everglades Restoration Progr am (CERP) was developed to identify critical restoration components that will attempt to restore predisturbance conditions to ENP. These components, however, are not well understood. Therefore, success of this multiyear initiative will depend on availability of scientific data to understand the interaction of vegetation, hydropattern, and so il accretion within th e Shark River Slough region of the Everglades. The overall objective of this study was to provide this information. Our study had three main objectives, each related to soil accre tion: vegetative substrate quality, biomass production, and decomposition. Our first objective was to determine plant tissue quality differen ces between ridge and slough vegetative communities. Our second objective was to determine differences in vegetative biomass production between ridge and slough communities. Our third objective of this study was to determine the effect of plant tissue quality and envir onmental condition on plant litter decomposition. Background, methods, and result s are discussed separately for each objective. Study Area The study was conducted in Shark River Sl ough (Florida) (Fig. 1-1) at four study sites. At each study site, ridge and slough vegetative communities were characterized using transects (each 150-200 m in length) . These study sites (3A1, 3A2, ENP1, and ENP2) were chosen based on hydropattern acces sibility and represen tative condition of ridge and slough vegetative community. A brief description follows.

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4 Site 3A1, the northernmost site , was assumed to be flow intact and less affected by barriers to water flow than th e other sites to th e south (Table 1-1). Reduced hydroperiod and water depths, however are characteri stic of this site. McVoy (personal communication) suggested that th is site best represents pr edisturbance ridge and slough landscape morphology. Site 3A2 has significan tly reduced flow rates due to damming effects of Tamiami Trail to the south. In c ontrast, ENP1 is flow impaired, primarily due to its location south of Tamiami Trail a nd east of the L-67 canal extension. The proximity of ENP1 to water management stru ctures explains the sh allow water depth. Hydroperiod at this site is less than 3A1 and 3A2, but longe r than ENP2. Site ENP2 is located farther south from Tamiami Trail than the ENP1 site, and has the highest flow rate of any of the sites. However, hydroperiod at Site ENP2 is the shortest of all sites surveyed (often resulting in water levels well below the soil surface in slough vegetative communities). Table 1-1. Relative ranking of hydroperiod and flow rate for each of the four main study sites Site Hydroperiod Flow Rate 3A1 2 2 3A2 1 4 ENP1 3 3 ENP2 4 1 * Smaller numbers indicate longer hydroperiods and faster flow rates

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5 CHAPTER 2 VEGETATIVE SUBSTRATE QUALITY Introduction Interactions among vegetative carbon input s, organic soil accretion, soil elevation change, and hydropattern suggest that autoct honous mechanisms may play an important role in the formation and maintenance of the vegetative mosaic found in Shark River Slough. Ecological changes (including mesotopogr aphical differences in soil elevation) may be affected by vegetative substrate qua lity, an autocthonous forcing function thought to affect soil accretion rate s in the Everglades. Although changes in soil accretion (resulting from local deposition of vegetation with different tissue compositions) may seem insignificant at first, the significan ce of these changes may manifest itself on a larger scale. For example, vegetative community shifts from one dominant species to another accompany concomitant changes in vegetativ e substrate quality. Davis (1991) observed that a shift from native sawgrass stands to th ick stands of cattail re sulted in a doubling of net primary productivity. Such a shift can a ffect soil accretion rate s by altering the type of plant tissue that is deposited onto the pe at soil surface, and may alter ridge and slough soil elevation differences. Therefore, quan tifying the relationsh ip between vegetative substrate quality and soil accretion to determ ine how forcing functions have changed, and how anthropogenic control mechanisms might better be managed, is critical to the Everglades restoration effort.

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6 Vegetative substrate quality relates to th e availability of organic compounds and associated nutrients in plant tissue. It also pl ays an important role in affecting the rate at which microbial populations can catabolize pl ant litter substrates, thereby affecting decomposition rates. The carbon-containing st ructural composition of Everglades plant tissue affects the decomposition of residual tissue once it reac hes the peat soil surface. Nutrient ratio characteristics such as C:N or N:P values ar e an important component of vegetative substrate quality, and, the amount an d type of organic compounds and their recalcitrance (resistance to decomposition) are also important substrate quality components regulating decomposition. The mo st recalcitrant organic structural compounds, contained within the residual fibe r fraction, are the primary regulators of vegetative substrate quality. Lignin is the most abundant aromatic polymer present in soils and one of the most recalcitrant organic structural compounds especially under anaerobic conditions (Criquet et al., 2000). The biological functions of li gnin and other organic structural components of plant tissue are to give vasc ular plants the rigidity and st ructural support they need to remain upright, and to provide protection against microbial att ack (Hammel, 1997). Ridge vegetation is likely to contain more residual fibe r than slough vegetation due to shallower water depths which provide rela tively less buoyancy. Conversely, labile plant tissue components such as sugars and starches are likely to be more abundant in slough vegetation, as a percent of tota l plant tissue, due to deeper water which reduces the need for structural support. Commonly used methods to determine ligni n content in plant material are based upon the hydrolysis of cellulose with 72% H2SO4 (also known as the Klasson method)

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7 (Rowland and Roberts, 1999). Standard methods (AOAC methods 932.01 and 949.04; Association of Official An alytical Chemists, 1990) recommended for lignin content determination based on the Klasson method are labor intensive and time consuming (Rowland and Roberts, 1999). In contrast, the neutral detergent fiber (NDF) and acid detergent fiber (ADF) methods provide a stra ightforward approach to determining fiber and are the methods used in this study (Fi g. 2-1). The sequential NDF-ADF extraction is recommended by Mould and Robbins (1981) be cause it improves di ssolution of cell wall proteins and minimizes influence of conde nsed tannins on detergent fiber residuals (Terrill et al. 1994), which ma y alter the recoveries of re sidual fiber and lignin (Rowland and Roberts, 1999). Increasing Recalcitrant Fiber Content Starch Hemicellulose Cellulose “Lignin” Increasing Recalcitrant Fiber Content Increasing Recalcitrant Fiber Content Starch Hemicellulose Cellulose “Lignin” Figure 2-1. Sequential extraction technique used in this study to determine vegetative substrate quality for ridge a nd slough community vegetation

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8 In this study, “residual fibe r content” of plant tissue is functionally-defined lignin, material that is highly refractory, yet may c ontain impurities that prevent it from being strictly lignin. Likewise, ADF and H2SO4 detergent fiber (H2SO4DF) are, for the purpose of this study, functionally-defined hemicellu lose and cellulose, respectively. The ADF solution dissolves plant structural compounds such as hemicellulose, leaving behind a fibrous product containing cellu lose, lignin, and ash (Table 2-1). To quantify residual fiber, detergent fiber resi dues are treated with 72% H2SO4 to remove all cellulose and any residual hemicellulose (Rowla nd and Roberts, 1994). Plant tissue soluble carbohydrate content is estimated by NDF measurements, wh ich have been successf ul in liberating the more labile carbohydrate and pr otein components of Everglad es plant tissue (Rowland and Roberts, 1999) (Table 2-1). Table 2-1. Fractionation of Neutral Detergent Fiber and Ac id Detergent Fiber methods (Rowland and Roberts, 1999) NDF Plant Fraction ADF Neutral Detergent Soluble Fraction Soluble Protein Lipids Starch Soluble Carbohydrates Pectin Insoluble Protein Hemicellulose Acid Detergent Soluble Fraction Neutral Detergent Fiber Fraction Cellulose Lignin Lignified Nitrogen Ash Acid Detergent Fiber Due to the recalcitrant nature of lign in under anaerobic conditions, this compound comprises a significant fraction of wetland soil organic matter and can influence soil

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9 accretion rates. Structural differences observed in ridge and slough vegetation suggest differences in plant tissue recalcitrant fiber content (vegetative substrate quality), thereby affecting decomposition rates. As a resu lt, mesotopography of the soil surface would vary according to dominant vegetation type and recalcitrant fiber content of vegetation. Several hypotheses were formulated to i nvestigate the possibl e connection between vegetative substrate quality and soil accretion rates in the Everglades. Hypotheses Ridge vegetation has less soluble car bohydrates (determined by NDF soluble fractions) and more hemicellulose, ce llulose, and lignin (determined by ADF soluble, H2SO4DF soluble, and residual fiber fr actions, respectively), as a percent of plant tissue, than slough vegetation. Residual fiber production is greater at Sites 3A1, ENP1, and ENP2 due to vegetation at these sites requiring mo re buoyancy from the surrounding water column. Litter nutrient quality, in the form of C/N and N/P ratio, is lower in slough vegetative communities than in ridge vegetative communities, because water column availability of nutrients is greater in slough vegetative communities. Materials and Methods Field Methods Dominant plant species found in ridge and slough communities were collected and analyzed for substrate quality. Live plan t leaves were collected by hand during the sampling periods which were Novemb er 2002, January 2003, March 2003, and November 2003. Plant material was stored in 4-liter plastic bags and placed in a cooler until returned to the laboratory for anal ysis of TC, TN, TP, and residual fiber. Laboratory Methods Plants were dried at 40oC for at least 48 hours. Plan t samples were then ground to 1 mm fragments using a Wiley Mill. Anal ysis of total carbon a nd total nitrogen was

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10 determined using a Carlo-Erba NA 1500 CNS Analyzer (Carlo Er ba Strumentazione, Milan, Italy ) . Total phosphorus was determined using acid digestion of ashed tissue, and analyzed using colorimetric procedures (Method 365.4; USEPA, 1993). Neutral detergent fiber, ADF, and percent residual fiber wa s determined using an Ankom 200 Fiber Analyzer (Ankom Technology Corp., 1998a). Residual fiber production was calculated as a fraction of total vegetative biomass production at each study s ite (Chapter 3). Comparison of mean values was performe d on all data using a Tukey-Kramer HSD (honestly significant difference) test to determine statistical significance. Results Residual fiber content of ridge vegetation ( C. jamaicense ) was, on average, greater than slough vegetation. Furthermore, residua l fiber varied more so than NDF and H2SO4DF among slough vegetation (Fig. 2-2). The labile fiber fraction (NDF) of vegetation occurring in slough commun ities was greater than that for Cladium jamaicense , the only species analyzed in ridge communities (Fig. 2-2). Slough vegetation contained a greater NDF fraction, as a percenta ge of plant tissue, than C. jamaicense . Among slough vegetation, aci d detergent fiber (ADF) and 72% sulfuric acid detergent fiber (H2SO4DF) fractions, which roughly estimate hemicellulose and cellulose content, respectivel y, were highest in Rhyncospera tracyi , Eleocharis cellulosa , and Panicum hemitomon . Acid detergent fiber and, to a lesser extent, H2SO4DF were relatively high in C. jamaicense when compared to most species of slough vegetation. Ridge vegetative communities produced si gnificantly greater amounts of residual fiber than slough communities (Table 2-2). Mean values were 238.2 + 38.0 and 45.0 + 9.7 g residual fiber/m2/yr, respectively for ridges a nd sloughs within each study site.

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11 Table 2-2. Residual fiber pr oduction for different vegetativ e communities within Shark River Slough, Everglades Site Community type Residual fiber production (g/m2/yr) Ridge 231.9 ± 35.5 3A1 Slough 70.1 ± 11.1 Ridge 244.5 ± 34.7 3A2 Slough 30.7 ± 14.8 Ridge 250.2 ± 45.7 ENP1 Slough 21.3 ± 6.9 Ridge 226.1 ± 36.2 ENP2 Slough 57.8 ± 6.05 *Values represent mean (+ 1 standard deviation) C ladium jamaicense C:N values were greater th an those for slough vegetation (Fig. 2-3). C:N values were si gnificantly greater than those for Utricularia spp ., B. caroliniana , N. odorata , and Crinum americanum . Slough vegetation containing high H2SO4DF fractions usually were characterized by high C:N values, although there was considerable variation among most slough vegetation. Significant differences in N:P values occurred between species of slough vegetation (Fig. 2-3). Crinum americanum had significantly lower N:P values than B. caroliniana , R. tracyi , and P. hemitomon . Discussion Different amounts of NDF, ADF, H2SO4DF, and residual fiber in vegetation comprising ridge and slough communities were observed in this study. Plants requiring more buoyancy from the surroundi ng water column, such as Nymphoides aquatica , Nymphaea odorata , Utricularia spp. , and Bacopa caroliniana, had fewer carboncontaining structural components such as hemicellulose, cellul ose, and lignin. In ridges where C. jamaicense was the dominant species, water depths were constantly less than in

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12 0% 20% 40% 60% 80% 100%Cladium jamaicense Panicum hemitomon Eleocharis cellulosa Rhyncospera tracyi Utricularia spp. Nymphoides aquatica Nymphaea odorata Bacopa caroliniana Crinum americanum 0 1 2 3 4 5 6 7 8 9 NDF ADF H2SO4DF Residual Fiber% Residual Fiber % of Plant Tissue 0% 20% 40% 60% 80% 100%Cladium jamaicense Panicum hemitomon Eleocharis cellulosa Rhyncospera tracyi Utricularia spp. Nymphoides aquatica Nymphaea odorata Bacopa caroliniana Crinum americanum 0 1 2 3 4 5 6 7 8 9 NDF ADF H2SO4DF Residual Fiber NDF ADF H2SO4DF Residual Fiber% Residual Fiber % of Plant Tissue Figure 2-2. Substrate qualit y values for ridge and slough vegetation. Values for top graph represent mean (+ 1 standard deviation) residual fiber content of vegetation. Cladium jamaicense represents the only species of ridge vegetation surveyed.

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13 0 10 20 30 40 50 60 70 80 90 100Cladium jamaicense Panicum hemitomon Eleocharis cellulosa Rhyncospera tracyi Utricularia spp. Nymphoides aquatica Nymphaea odorata Bacopa caroliniana Crinum americanum C:N N:P 0 10 20 30 40 50 60 70 80 90 100Cladium jamaicense Panicum hemitomon Eleocharis cellulosa Rhyncospera tracyi Utricularia spp. Nymphoides aquatica Nymphaea odorata Bacopa caroliniana Crinum americanum C:N N:P C:N N:P Figure 2-3. Ratios of C:N and N:P for variou s species of ridge and slough vegetation. Values represent mean (+ 1 standard deviation). Cladium jamaicense represents the only species of ridge vegetation surveyed adjacent slough communities, and morphology of this plant species provides for significant above water biomass. As a result, more structural support was likely needed to compensate for the lack of water support. Another explanation for the higher levels of ADF, H2SO4DF, and residual fiber in C. jamaicense is that this species would be more prone to oxidative fungal and terrestrial macroinvertibrate degradation, generally absent from the water column of sloughs. This is attributable to aero bic grazing organisms which prefer labile energy sources, estimat ed by NDF measurements, over more complex

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14 compounds, resulting in lower NDF fractions, and higher ADF, H2SO4DF, and residual fiber fractions of C. jamaicense leaves. Based on field observations, P. hemitomon stems were found to be much more rigid than those for other species of slough vegetation; therefore, it was expected that this species would contain more residua l fiber. This was confirmed; P. hemitomon had the highest ADF, H2SO4DF, and residual fiber fractions of all sampled slough vegetation. Furthermore, subsequent biomass tagging e xperiments (Chapter 3) revealed that P. hemitomon , and to a lesser extent, E. cellulosa , were often found intact and standing for up to two months post-sampling. In cont rast, floating macrophytes and submerged vegetation such as N. odorata, N. aquatica , and B. caroliniana were rarely found intact after several months post-sampling. This suggests that, upon senescence, P. hemitomon and E. cellulosa would likely remain standing for l onger periods of time than floating or submerged macrophytes. This attribute coul d result in leaching of nutrients by rain which may serve to reduce degradability as pl ant material reaches the soil water interface in slough communities. Vegetative composition may have influen ced the residual fiber production at each site. The term “wet prairie” is used to describe slough communities containing a relatively high percentage of emergent vegetation, such as E. cellulosa, R. tracyi , and P. hemitomon (Loveless, 1959), relative to floati ng leaf vegetation. Based on field observations, the amount of emergent vegeta tion growing in 3A1 and ENP2 sloughs was much greater than the emergent vegetati on comprising ENP1 and 3A2 sloughs. Thus, wet prairie-type sloughs surveyed in this study would include those at Sites 3A1 and ENP2, due to greater emergent content in these areas.

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15 Emergent vegetation in wet prairie-type sloughs woul d require a greater amount of support from carbon-containing structural components and would likely have higher residual fiber contents th an floating macrophytes ( N. odorata and N. aquatica ) or submerged macrophytes ( B. caroliniana and Utricularia spp.). Nowhere is this more evident than at ENP2, where emergent c ontent was highest, and water depths were shallowest of all sites (Table 1-1). Ther efore, soil accretion w ould likely occur to a greater extent in slou ghs at Sites 3A1 and ENP2, than in sloughs at Sites 3A2 and ENP1. The C:N values for slough vegetation such as Eleocharis cellulosa, P. hemitomon, R. tracyi, and N. aquatica were not significantly di fferent than those for C. jamaicense . Therefore, it would seem that microbial d ecomposition of the aforementioned species of slough vegetation would be similar to that for C. jamaicense based on C:N values alone. However, the results for residual fiber conten t indicate that ridge vegetation may be more recalcitrant than slough vegetation. These data, in addition to C:N values, suggest C. jamaicense leaf substrates may provide greater carbon limitation and increased structural resistance to microbial decomposition, when submerged, than slough vegetation. Therefore, it is unlikely that ridge vegetati on would decay faster th an slough floating or submerged macrophytes which, on average, ha d lower C:N values and residual fiber contents. This is supported by the scientific lite rature. Decay rates generally increase with higher N content (Kaushik and Hynes, 1971; Suberkropp et al. 1976; Triska and Sedell, 1976). Plants with lower C:N values will decompose faster th an those with higher C:N (Tam et al., 1990; Merril and Cowling, 1996). The relatively high N:P values observed fo r submerged and aquatic vegetation in this study is likely due to extreme P limitati on and potentially more available N in slough

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16 vegetative community water columns. The N:P value of 38.5 for C. jamaicense reported by Ross et al. (2001) is similar to that of 34.2 obtained for the same species in this study. In contrast, E. cellulosa N:P values reported by the Sout h Florida Terrestrial Ecosystem Lab (44.9, 46.2, and 48.7) were higher than th e measured value of 37.8 in this study indicating a lesser degree of P limitation at our sites. Differences in N:P values between ridge and slough vegetation are likely due to possible variations in water column N cont ent, not P content, which does not vary considerably in the central Everglades. Eleocharis cellulosa and C. jamaicense are insensitive to P content, which in low P areas, may give these species a competitive advantage (Ross et al., 2001). As much as 64% of nitrogen immobilized in ridge and slough plant tissue can result from nitrogen fi xation (van der Valk and Attiwill, 1984; Woitchik et al. 1997). Differences in leaf chemical composition between ridge and slough vegetation affect rates of nitrogen immobi lization in leaf substr ates (Pelegri et al. 1997) and may also explain differences in N:P values. These findings indicate a potentially strong feedback mechanism between the greater amounts of recalcitrant fiber in ridge species than that of slough species. In summary, relative to the hypotheses, ridge vegetation contained fewer labile components and greater amounts of recalcitran t material than slough vegetation. Percent residual fiber content was al so greater in ridge vegetation than in slough vegetation, which suggests ridge vegetation offers lower quality substrates to microbial communities than slough vegetation. Lastly, C:N values were lower in sl ough vegetation than in ridge vegetation; however, there wa s no clear trend in N:P va lues among slough vegetation.

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17 CHAPTER 3 VEGETATIVE BIOMASS PRODUCTION Introduction In recent years, satellite images and aer ial photography suggest th at the Everglades ridge and slough pattern is bei ng altered. According to Mc Voy and Crisfield (2001), soil accretion influenced the strong a lignment of ridges and sloughs to historic flow paths, thereby helping to maintain the directional pa ttern of landscape feat ures. Currently, there is a trend toward less directional, more ra ndom landscape patterns. For example, when contrasted against historic accounts of pre-drainage c onditions (McVoy and Crisfield, 2001), recent observations taken at the four study sites indicate definite changes in present-day patterns of ridge and slough vegetation. Where dykes and canals have compartmentalized the landscape, the extent and shape of ridge vegetation has been altered. Slough vegetative communities are also changing, from hist orically openwater tracts filled with Nymphaea odorata and Nymphoides americanum to wet prairies dominated by Panicum hemitomon and Eleocharis cellulosa ; moreover, some sloughs have even changed to ridge-type vegetation dominated by Cladium jamaicense . In addition to vegetation changes within slough communities, distinct short stature and tall stature C. jamaicense zones were observed within ri dge communities in 3 of the 4 sites surveyed (Fig. 3-1). Because C. jamaicense plant height differed between the four study sites, it was difficult to determine an accurate average height difference between short and tall stature ridge co mmunities. In general, short stature plants tended to have

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18 heights above the soil surface of less than 175 cm , and tall stature plants tended to have heights greater than 175 cm. Figure 3-1. Profile of study site showing tall ridge, short ridge, and slough vegetative communities. Measurements presented at 5 m intervals. Five nested measurements every 10m along transect are summarized as standard deviation along soil and bedrock contours. Changes in vegetation may lead to a concomitant loss in soil mesotopography (McVoy and Crisfield, 2001) due to possibl e feedback mechanisms between soil accretion rates and plant community. This hypothesized deterioration of the historic vegetative mosaic would suggest that the ridge and slough plant community may be lost in the future; therefore, it is critical to understand the role of vegetative biomass production and community structure in maintain ing these communities. Due to different biological requirements and adap tations of wetland plants wi th respect to hydropattern, it is hypothesized that whole community bioma ss production is related to local hydrologic -300 -200 -100 0 100 200 300-1 0 0 -9 5 -90 -85 -80 -75 -70 6 5 6 0 -55 -5 0 -4 5 4 0 -3 5 -3 0 -2 5 -2 0 -1 5 -10 -5 0 5 1 0 1 5 20 2 5 30 35 40distance along transect, mheight or depth, cm limstone bedrock soil water depth vegetation Tall Ridge Short Ridge Slough

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19 regime. More specifically, it is believed that the heterogene ity of soil elevation at the ridge and slough landscape scale is closely rela ted to differences in vegetative biomass production rates that reinforce soil elevation differences. Factors that influence the ridge and slough landscape patt ern have been the subject of much research (Davis and Ogden, 1974; David, 1996; Busch et al., 1998). For example, Davis (1994) reported a community sh ift from wet prairie/slough to sawgrass ridge during a 15-21 year sampling period ; furthermore, he found that slough communities had decreased from 64% to 29% cover in one Shark River Slough plot. Recently, scientists have noted scale depe ndencies in vegetation patterns (Davis and Ogden, 1994). It has been hypothesized that different relationships may emerge when vegetation is studied at differe nt spatial scales. Another hypothesis is whether vegetation pattern and processes can be understood statistically without reference to spatial position or configuration (Davis a nd Ogden, 1994). However, while much is known regarding species occurrence and distribution in the Ev erglades, biomass production rates in ridge and slough vegetative communities are not well understood. Most research concerning the ridge and slough vegetative communities in the Everglades has centered on determining the impo rtance of environmental factors such as hydrologic regime. Of these, water quality and quantity, distribu tion, and timing have been of most scientific interest due to the anthropogenic manipulation of hydrology and increases in nitrogen and phosphorus loads in surface waters as a result of agriculture in the Everglades watershed. However, it is impor tant to note that re storation efforts may not be successful if based on research data for these parameters alone; it is likely that hydrologic and water quality conditions will not completely be restored to predrainage

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20 conditions. Therefore, research is needed to also understand the role of biomass production in determining and maintaining ve getative distribution in the Everglades. Variations in plant density and distribu tion of vegetation in the Everglades are thought to affect wetland soil organic matte r and can influence so il accretion rates. Moreover, plant density differences observe d in ridge and slough vegetative communities suggest differences in biomass production rate s. As a result, mesotopography of the soil surface would vary according to dominant ve getation type and the amount of vegetation being produced per year. Several hypotheses we re formulated to i nvestigate the possible connection between vegetative biomass pr oduction and soil accre tion rates in the Everglades. Hypothesis Due to the greater size attained by C. jamaicense when compared to the surveyed slough species, biomass production rates are greater in tall stature ridge communities than in short stature ridge communities and sloughs. Materials and Methods Field Methods Tall and short ridge biomass Two methods were used to estimate biomass production in ridge vegetative communities. Leaf turnover rate and plant density determinations were made during January 2003, March 2003, November 2003, and February 2004. In November 2002, seven permanent 1 m2 quadrats were established in tall and short stature ridge communities at each of the four study sites, with the exception of site 3A2, which did not have a short stature ridge. Within each quadr at two plants were selected randomly and live leaf turnover rate was determined by securing a plastic “zip tie” around the youngest C. jamaicense shoot. During subsequent Marc h 2003, November 2003, and February

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21 2004 sampling events, a new, different co lored zip tie was secured around each new shoot produced by the plant, and total number of new shoots was recorded. During each sampling, plant density and number of live l eaves for each individual within the seven quadrats was counted. Seven whole C. jamaicense plants were randomly harvested from tall and short ridges at each of the four study sites during ea ch sampling trip to determine average plant and leaf weight. Ridge bi omass production was determined by multiplying live leaf turnover rate by number of plants per square me ter within tall and short stature ridge communities. Slough biomass Slough turnover rate was determined using methods similar to those for ridges. Five permanent 0.25 m2 quadrats were established at each of the four main sites. Due to the physiological differences between ridge vegetation and slough vegetation, new shoots in slough quadrats were tagged with ribbon, not plastic zip ties, to prevent structural damage to the plant. In contrast to m onotypic ridge communities, emergent and floating macrophyte species were tagged within slough quadrats. Slough biomass samples were obtained by sampling five randomly thrown 0.25 m2 quadrats and collecting the vegetation within each quadrat . All plants, including peri phyton, were harvested from each quadrat at the soil-water interface. Determination of slough biomass production was identical to that for ridge biomass. Laboratory Methods Ridge and slough vegetation was collected from each site during the sampling periods. Vegetation samples were separated according to species and growth stage (live, standing dead, litter). All plant material from each site was placed into individual paper bags and dried at 40oC for at least 48 hours. After dr ying, plant samples were weighed

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22 then ground to 1 mm fragments using a Wiley Mill. Comparison of mean values was performed on all data using a Tukey-Kramer HSD (honestly significant difference) test to determine statistical significance. Results Biomass, Plant Density, and Leaf Turnover: Ridges Mean biomass production ranged from 1094.6 ± 13.4 g/m2/yr (ENP1) to 3487.4 ± 280.6 g/m2/yr (ENP2) in short ridge communities, and from 3667.7 ± 225.0 g/m2/yr (3A2) to 5656.2 ± 100.9 g/m2/yr (ENP1) in tall ridge commun ities (Table 3-1). Mean tall ridge biomass production was significantly grea ter than short ridge biomass production at Sites 3A1 and ENP1. There were no significan t differences between tall and short ridge biomass production at ENP2, however the tr end indicates greater biomass production rates in tall ridges at this site. Mean tall ridge leaf production was significan tly greater than shor t ridge live leaf production at Site ENP1 (Tab le 3-1). Mean tall ridge leaf production was not significantly different than s hort ridge leaf production at Sites 3A1 and ENP2, however, the trend indicates greater live leaf producti on rates in tall ridges at these sites. Live plant density was significantly greater in tall ridge vegetation than in short ridges at Sites 3A1 and ENP1 (Table 3-1). The greatest difference between mean tall and short ridge live plant density occurred at EN P1, where live plant density at tall ridges was more than 2 times that of short ridges (544.9 + 40.2 g/m2 vs. 213.4 + 8.8 g/m2). No significant difference in plant density was obs erved at Site ENP2, though tall ridges at this site contained more biomass, on average, than that of short ridges. There was no significant difference in mean live leaves per plant and leaf mass between tall and short ridge communities (Table 3-1). However, the trend suggests tall ridge communities

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23 contained, on average, a greater number of la rger live leaves per individual than short ridge communities. Table 3-1. Vegetative community characteristics for ridge vegetative communities at the four study sites Site Ridge community stature Live plant density (g/m2) Live leaf production (new leaves/yr) Biomass production (g/m2/yr) Live leaves per plant Leaf mass(g) Short 389.2 ± 109.5 6.4 ± 1.5 2486.7 ± 160.9 3.6 ± 1.2 6.8 ± 1.6 3A1 Tall 591.6 ± 11.0 7.3 ± 1.7 4295.2 ± 19.0 4.3 ± 1.7 6.5 ± 0.4 3A2 Tall 397.4 ± 102.8 9.2 ± 2.2 3667.7 ± 225.0 5.2 ± 2.6 9.2 ± 2.2 Short 213.4 ± 8.8 5.1 ± 1.5 1094.6 ± 13.4 2.9 ± 1.2 5.3 ± 0.9 ENP1 Tall 544.9 ± 40.2 10.4 ± 2.5 5656.2 ± 100.8 5.9 ± 2.3 6.6 ± 0.5 Short 506.9 ± 200.4 6.9 ± 1.4 3487.4 ± 280.6 3.5 ± 1.3 4.1 ± 1.8 ENP2 Tall 535.7 ± 230.9 7.0 ± 1.8 3765.6 ± 420.2 4.6 ± 1.9 6.1 ± 2.1 *Values represent mean (+ 1 standard deviation) Sloughs Slough biomass production varied consid erably among sites (Table 3-2). Production at site 3A1 was significantly great er than at Sites 3A2 and ENP1. Slough biomass production ranged from 663.7 + 213.7 g/m2/yr (ENP1) to 1683.5 + 266.1 g/m2/yr (3A1). Slough vegetative production at the southernmost site, ENP2, was also significantly greater th an at Sites 3A2 and ENP1. Site ENP2 biomass production was slightly less than 3A1 biomass production (1515.7 + 158.7 g/m2/yr and 1683.5 + 266.1 g/m2/yr, respectively), but the difference was not statistically significant. Plant density and percent live leaf turnover rates followed a pattern similar to that for total slough biomass production (Table 3-2) . Site 3A1 containe d significantly more vegetation, per square meter, than Sites 3A2 and ENP1. Mean live l eaf turnover rates at Sites 3A1 and ENP2 were significantly greater than those at Site ENP1.

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24 Table 3-2. Vegetative community characte ristics for slough vegetative communities at the four study sites Site Plant density (g/m2) Live leaf turnover per mo. (%) Total slough biomass production (g/m2/yr) 3A1 332.3 ± 58.9 42.2 ± 6.7 1683.5 ± 266.1 3A2 212.3 ± 18.3 33.2 ± 16.0 844.9 ± 406.6 ENP1 199.4 ± 41.7 27.7 ± 8.9 663.8 ± 213.7 ENP2 308.7 ± 125.9 40.9 ± 4.3 1515.7 ± 158.7 *Values represent mean (+ 1 standard deviation) Discussion Site differences in biomass production between tall and short ridge vegetative communities, and between ridge and slough comm unities, were often significant and may be partially explained by envi ronmental factors. Environmen tal influences are typically large in spatial scale and establish the general features of the ecosystem, such as tropical hardwood hammocks, coastal fringing mangr oves, and the Taylor and Shark River Sloughs (DeAngelis and White, 1994). The ex tent to which environmental factors influence ecosystem development in these areas is related to the fre quency of a particular environmental forcing function, as well as th e synergistic effects of both environmental and biological factors. Empi rically, the best approach to addressing the extent to which environmental factors control ridge and slough vegetative composition and structure involves experimental determination of inunda tion tolerances and fi re resilience (Daoust and Childers, 1999). An alternate, less labor intensive, approach involves using biomass productivity to help explain how species co exist in the ridge and slough landscape mosaic (Daoust and Childers, 1999). Biomass production is thought to vary acco rding to soil mesotopography (Craft and Richardson, 1993, Gleason and Stone 1994), a term describing peat elevation differences between ridge and slough vegetative mosaics of the Everglades. Prior to its portioning by

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25 dykes and canals, rainfall pattern, temperatur e, and fire were th e likely principal environmental factors influencing ridge a nd slough vegetative community development and biomass production in the Shark River Slough. The importance of fire and hydropattern as controlling factors for biomass production has recently been recognized (Dor en et al. 1997). Fire events followed by flooding are reported to reduce sawgrass sta nd density (Herndon et al. 1991). Short ridges, when present, may have been exposed to fire more recently than tall ridges within the same site. Similarly, an incomplete burn within a single ridge community may account for the difference in stand density, and subsequent biomass production, between tall and short ridge communities at sample site s. Steward and Ornes (1975) suggest that different regions within the same ridge comm unity have different regrowth potentials. For example, if a complete burn occurred w ithin a ridge, sawgrass height differences within the same community may have emerge d due to greater regrowth potentials of certain groups of culms, resu lting in different biomass produc tion rates. This difference in maturity is also supported by the fact that flower stalks are observed to a greater extent in tall ridge communities. Fewer stalks are reported in less mature short ridge communities (Steward and Ornes, 1975). Another possible explanation for the differences in biomass production between tall and short ridge communities is that fire tends to burn only the tops of sawgrass and not the live culm formed by inner leaf bases (Herndon et al., 1991). The remaining live shoots within the culm have variable hei ghts depending on the conditions of the burn. A flood following a fire is likely to kill or stunt the growth of short, live sawgrass shoots if the live portions are completely submerged for a sufficient length of time. Tall ridges

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26 may have emerged as a result of these plan ts having longer pre-fire live shoot lengths, which would allow for maturation of certain individuals during high water (Herndon et al., 1991). However, based on observations, fire would likely burn tall ridge communities to a greater extent than short ridge communities b ecause tall ridges were observed at slightly higher peat elevations than s hort ridges. Short ridges were generally proximal to slough communities, which are underlain by saturated peat throughout the majority of the year. As a result, peat underlying shor t ridges would be saturated to a greater depth than peat underlying tall ridges, thereby pr otecting short ridge communities from fire events. This would select for a uniform ridge community di fferent from the unique tall and short ridge communities observed at sites 3A1, ENP1, and EN P2. Thus, it is unlikely that fire was controlling stand density and bi omass production at these sites, but may be a controlling factor at 3A2, a site that lack ed a short ridge community. In addition to environmental factors, bi ological factors are also important as controlling mechanisms of biomass production. It is thought that biomass production in the Everglades and, more specifically, Shar k River Slough, may be strongly influenced by characteristics of soil accre tion rates and peat composition. Slight differences in soil mesotopography within the same ridge community may allow some areas of the ridge to remain inundated for longer periods of time, especially during the dry season. As a result, there is sufficient water in these areas to maintain the growth of certain stands of sawgrass and not others. According to He rndon et al. (1991), sawg rass grows best in sites that are subject to inundati on periods longer than 6 months.

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27 Peat composition differences underlying ri dge vegetation may also help explain differences in biomass production between ta ll and short ridge communities at ENP1. Sawgrass is known to be less pr oductive in sites u nderlain by peat with high marl content (Brewer 1996). During measurements of EN P1 slough communities, we noticed distinct marl bands in the rooting depths of soil cores taken at this site. We also observed that short ridge communities at ENP1 fringed adjacent, periphyton-laden slough communities closely, and were likely partia lly underlain by the same ma rl soil underlying the slough. Tall ridges at ENP1 were patchy and located d eep within short ridges, and may have been less exposed to marl soils than the fringing short ridge comm unity. Observed differences in biomass production rates between tall and s hort ridges at ENP1 are partially supported by Brewer (1996), who suggests sawgrass is mo re productive in pure stands growing in peat soils than in stands growing in marl soils with other species. Measurements of biomass productivity in ridge and slough areas of the Everglades are limited. Daoust and Childer s et al. (1998) reported biom ass production rates in ridge communities as high as 3620 g/m2/yr, which is similar to the 3493 g/m2/yr for tall and short ridges combined in this study. In c ontrast, the mean measured slough biomass production rate of 1177 g/m2/yr in this study was higher th an that reported by Daoust and Childers (1998) (522 g/m2/yr). Mean slough biomass production at ENP1 (approximately 664 g/m2/yr) was most similar to the value reported by Daoust and Childers (1998), although mean slough biomass production varied up to three-fold among sites (Table 32). In support of this, species type and abundance are known to vary to a greater extent in slough communities than ridge communities (Loveless, 1959). Therefore, it is likely that

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28 our measured differences in slough biomass production rates may be attributable to differences in sample site selection. On average, ridge biomass production was significantly greater than slough biomass production when averaged at all sites (3493.4 + 174.3 g/m2/yr vs. 1177.0 + 261.3 g/m2/yr). The greatest difference between ridge and slough biomass production occurred at ENP1, where, on average, tall ridges pr oduced 8.6 times more biomass per year than slough communities at this site. The findings of this study agree with Gunderson and Loftus (1993) who suggested that biomass production is greater in sawgrass marshes (ridges) than in sloughs. Fu rthermore, relative to the hypotheses, biomass production was greater in tall ridge vegetative communitie s than in short ridge or slough vegetative communities.

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29 CHAPTER 4 DECOMPOSITION Introduction Organic matter decomposition is a process that occurs in all ecos ystems, but, in the Everglades, is slower than in upland e nvironments (Qualls and Richardson, 2000). Organic matter decomposition is important to soil elevation and nutrient turnover and cycling (Kurka et al., 2000) and is affected by the physical and chemical composition of organic matter, microbial community, and nutri ents. The two primary factors affecting decomposition rate in the Everglades are vege tative substrate quality and environmental condition. Substrate quality is influenced by nutrient content and recalcitrance of plant tissue which influences decomposition rates by limiting or enhancing microbial catalysis of the plant tissue (litter) s ubstrate. Environmental conditions regulating decomposition include temperature, pH, moisture, and the pr esence or absence of oxygen. In the case of ridge and slough vegetative communities, both vegetative substrate quality and environmental condition may be influencing decomposition rates. We found that it was important to determin e vegetative substrat e quality of ridge and slough vegetation (above water and below wa ter) since ridge biomass appears to stay lodged within the canopy for an extended period of time under aerobic conditions and, when submerged, undergoes a second phase of decomposition under anaerobic conditions. Ridge vegetative communities reta in dead biomass in a standing dead phase much longer than most vegetative communities in the central Everglades. The significance of this is not clear, but standing dead C. jamaicense biomass exists in an

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30 aerobic zone during this phase. As a result, this plant material is prone to nutrient leaching which could have an effect on the overall decomposition rate and amount of recalcitrant material that makes it to the soil. Litter decomposition is important as it relates to the availability of carbon compounds and associated nutrients for micr obial utilization. Of the many factors influencing litter decomposition, the impor tance of nitrogen, phosphorus, and lignin content (Johnson et al., 1995; Berg et al., 1998a) and C/N ratio (Berg et al., 1998b) have received greater scientific attention. Genera lly, nutrient enrichment in soil increases decomposition rates (Hackney et al. 2000; Newm an et al. 2001) but not always (Rybczyk et al., 1996). When nutrients such as phosphorus become limiting, decomposers use more energy in the form of enzyme production to acqui re nutrients needed for their metabolic functions. As microbes use more energy for phosphorus acquisition, they have less available for carbon oxidation and, consequent ly, decomposition rates slow down. For phosphorus to be re-released or mineralized to the soil, the C/P ratio should be less than 200:1 (Schlesinger, 1991). Therefore, as stated earlier, litter decomposition is directly linked to nutrient content and phosphorus availability. Nitrogen content expressed as C/N ratio or lignin/N ratio can be used as a predictor of litter decomposition rates (M elillo et al., 1982; Sinsaba ugh et al., 1993; DeBusk and Reddy, 1998; Carreiro et al., 2000). The presence of exogenous nitrogen may reduce the importance of initial nitrogen content of the li tter with respect to decomposition rates. Similarly, additions of nitr ogen may slow down decompos ition rates by inhibiting the production of certain enzymes required to break down lignin (Carreiro et al., 2000). In

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31 such a case, the rate of d ecay would depend on lignin content of the litter. However, litter with a higher nitrogen content expressed as lignin/ N ratio decomposes faster, particularly labile substrates (Taylor et al., 1989). In s upport of this, data have shown that nitrogen and other nutrients control deca y rates during the first phase of decay when mass loss is less than 30%. Also, the com position of carbon compounds within the litter is also influential on decomposition rates, with initial lignin and cellu lose content of plant matter shown to be related to mass loss (Sinsabaugh et al., 1991). Lignin is the most abundant aromatic polymer present in soils and one of the most recalcitrant plant tissue components especially under anaerobic condi tions (Criquet et al., 2000). Lignin gives vascular pl ants the rigidity and structural support needed to remain upright, and provides prot ection against microbial attack (Hammel, 1997). Lignocellulose, another abundant organic polym er, is also a component of plant tissue and it is composed of approximately 25% lignin (Donnelly et al., 1990). Lignin and cellulose interact to form a sheath around the cellulose fibers of plant tissue, thus slowing decomposition rates (D onnelly et al., 1990). Cellulose generally degrades two to five times fast er than lignin, but degradation is still slower than that for non-lignocellulosic organic matter (Ford, 1993). The recalcitrant lignocellulosic matrix is formed as the labile components of litte r are decomposed, and lignin and cellulose decomposition is slowed (Mellilo et al., 1982, 1989). Lignin and cellulose decomposition can be primed, however, by the addition of ne w substrates to the otherwise recalcitrant organic matter (Donnelly et al., 1990). Conditions favorable for lignin decomposition include warm temperatures and high litter moisture, oxygen availability, and palatability

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32 of litter to microorganisms (Hammel, 1997). Also, lignin content may differ temporally depending on climatic conditions (DeBusk and Reddy, 1998). Mesotopographical differences in soil el evation affected by litter decomposition rates can lead to large-scale ecological change s, such as vegetative community shifts. In turn, vegetative community shifts can affect decomposition rates and may alter ridge and slough soil elevation differences. For exampl e, litter quality is thought to exhibit the greatest variation accord ing to plant species and growth stage. Therefore, vegetative community shifts from E. cellulosa dominated sloughs to C. jamaicense dominated ridges, or vice-versa, may slow decompos ition rates by affecting litter recalcitrance and/or litter production. Substrate age and growth stage may also play roles in affecting decomposition rates, as well as substrate location on the pl ant. Generally, the olde r substrates are likely to contain higher amounts of recalcitrant mate rial and lower amounts of N and P. While the younger, standing dead substrates retained on living plants and the older, litter substrates submerged below the water surface both undergo leaching and oxidative decomposition, these processes occur to a great er extent in the younger leaves. Due to the relative scarcity of nutri ents in older substrates, gr eater amounts of exogenous N and P would be required for microorganisms to meet their ideal nutrient ratios before further decomposition would occur. Furthermore, the concomitant increase in plant recalcitrance exhibited in old vegetative substrates woul d further slow decomposition. Thus, in order to estimate decomposition rates and, ultim ately, soil accretion in the Everglades, biological factors regulating these processes must be understood in order to make

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33 technically-based decisions regarding land and water management in the entire affected South Florida ecosystem. Hypotheses Due to relatively shallow water depths and increased oxygen availability in ridge vegetative communities, C. jamaicense and E. cellulosa litter decomposition rates are greater in ridge vegetative communities than slough communities. Cladium jamaicense contains a greater residual fiber fraction than E. cellulosa (Fig. 2-1), and therefore deco mposes at a greater rate. Values of C:N and N:P for C. jamaicense and E. cellulosa will decrease proportionately with exposure time, as microbes immobilize substrate and watercolumn nutrients. Percent residual fiber, an estimate of plant recalcitrance, will increase proportionately with exposure time, as more labile sources of C are leached away or consumed by microorganisms. Values of C:N, N:P, and residual fiber for standing dead C. jamaicense will display similar trends to those for litter bag-deployed vegetation. Standing dead C. jamaicense is exposed to environmental conditions longer than litterbagdeployed vegetation; therefore, leaching of C, N, and P will occur to a greater extent in standing dead C. jamaicense . Materials and Methods Field Methods Litter decomposition rates were determined by measuring the mass loss of standing dead vegetation collected from ridge and slough communities. Litterbag and standing dead decomposition experiments were us ed to estimate both environmental and biological effects on decomposition rates. In addition, all plant mate rial obtained from litterbag and standing dead decomposition e xperiments was analyzed for TC, TN, TP, and plant recalcitrance. Descriptions of the methods follow.

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34 Litterbags Recently dead standing biomass from C. jamaicense (representing dominant ridge biomass) and E. cellulosa (representing dominant slough bi omass) was collected during November 2002. Biomass was dried at 40oC and cut into 3 inch-long segments. Approximately 10 g of dried C. jamaicense or 6 g of dried E. cellulosa was placed into 6 cm x 6 cm litterbags with 1 mm mesh diameter. Litterbags were deployed in the field on January 2003. At each deployment locati on, two one-inch diamet er PVC poles were erected approximately two meters apart from one another and were driven down into the peat in order to maintain stability. F our sets, each with 3 nylon mesh litterbags containing litter from the same species, were affixed to each pole with a length of twine (Fig. 4-1). Litterbags were tucked and cove red by the local flora to maintain litterbag submergence. Three replications (144 litt erbags) were deployed in ridge and slough vegetative communities at each site dur ing November 2002 to estimate environmental effects on decomposition rates and differences in substrat e quality between species. Litterbags were harvested after January 2003, March 2003, and November 2003, representing 41, 105, and 365 days of exposure, respectively. During collection, litterbags were shaken firmly in the water to remove epiphyton contaminati on. After shaking, lit terbags were placed into a ziplock bag and cooler for transportation to the laboratory. Standing dead decomposition To investigate standing dead decomposition of C. jamaicense we had to replicate the environmental conditions in which decomp osition occurred, while still being able to quantitatively sample. The method developed is essentially an upright litter pack method

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35 Figure 4-1. Litterbag experiment showing (a) litterbag structure (b) litterbag arrangement on PVC poles and (c) deployment in thr ee ridge and three slough vegetative communities at each study site Ridge Slough C. jamaicense E. cellulosa a b c

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36 Figure 4-2. Standing dead decomposition expe riment showing (a) PVC pipe arrangement within ridge vegetative communities at each of the four study sites, and (b) PVC pipe structure showing attachment of individual C. jamaicense leaves allowing environmental moisture, leaching, and photodegradation conditions to occur while creating opportunities for harvest and measurement. To implement this method, 75 living C. jamaicense leaves (just prior to standing dead phase) were harvested from plants b a

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37 along each of the transects at each site. On each leaf, two marks approximately 50 cm apart were made in the midsection of the leaf. Fifteen leaves were then attached to a 5 cm diameter PVC pipe with twine (Fig 4-2). Along each transect, five pipes with 15 leaf blades each were nestled within the tall-stature sawgrass in a manner to represent a typical standing dead leaf. In order to provide an initial value for sequential mass loss calculations, 3 leaves were harvested from each PVC pipe during early November 2002. Three additional leaves were harvested from each PVC pipe after 41, 105, and 365 days of exposure to ambient conditions at each of the four study sites. Af ter leaf selection from each pipe, the 50 cm section was cut out of the leaf and used fo r mass loss and analytical analyses. Leaf sections were placed in a ziplock bag and c ooler for transportation to the laboratory. Laboratory Methods Litterbags The plant material remaining inside each litterbag was placed into a paper bag and dried at 400C. After drying for at least 48 hours, pl ant material was weighed to determine mass remaining after the elapsed exposure time. Subsamples for substrate quality analysis were prepared by placing the contents of three C. jamaicense litterbags and three E. cellulosa litterbags into two separa te paper bags. Each paper bag was a composite of either three ridgedeployed or three slough-depl oyed litterbags at each of the four study sites (a total of 48 composite s per site) (Fig 4-1). Composite samples were ground to 1 mm fragments using a Wiley M ill. Analysis of total carbon and total nitrogen was determined using a Carlo-Erba NA 1500 CNS Analyzer (Carlo Er ba Strumentazione, Milan, Italy ) . Total phosphorus was determined using acid digestion of ashed tissue, and analyzed using colorimetric procedures (Method 365.4; USEPA, 1993). Percent residual

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38 was determined using an Ankom 200 Fibe r Analyzer (Ankom Technology Corp., 1998a). Comparison of mean values was performe d on all data using a Tukey-Kramer HSD (honestly significant difference) test to determine statistical significance. Standing dead decomposition Each of the three leaves harvested per PVC pipe, per sampling event, were individually weighed after drying. After wei ghing individual leaves , a composite sample was prepared by combining the three leaves harvested per PVC pipe. All leaves harvested from PVC pipes were analyzed in the laboratory for TC, TN, TP, and residual fiber using analytical and statis tical methods similar to those for litterbag experiments. Results Litterbags Decomposition occurred to the greatest exte nt at ENP2 (Fig. 4-3). The amount of plant material remaining in litterbags was signi ficantly less at this site, regardless of species. The greatest difference in mean decay rates between the ridge and slough deployment occurred for E. cellulosa litterbags but the difference was not significant (Fig. 4-4). Cladium jamaicense decay rates at the remaining sites varied from 0.0008 g/d (ridges) to 0.0007 g/d (sloughs). Eleocharis cellulosa decay rates were between 0.0021 and 0.0018 g/d for ridge and slough deployments, respectively. There was no significant difference in mean C:N relative to deployment site; however C:N was less for slough deployments of C. jamaicense -containing litterbags (Fig. 4-5). In contrast to l ack of significant difference be tween sites, there was a highly

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39 0 20 40 60 80 100 120 050100150200250300350400 3A1 3A2 ENP1 ENP2 0 20 40 60 80 100 120Exposure time (d)% Mass RemainingEleochariscellulosa Cladiumjamaicense 0 20 40 60 80 100 120 050100150200250300350400 3A1 3A2 ENP1 ENP2 0 20 40 60 80 100 120Exposure time (d)% Mass RemainingEleochariscellulosa Cladiumjamaicense Figure 4-3. Decomposition of (a) E. cellulosa and (b) C. jamaicense at the four study sites during the experiment. Values represent mean (+ 1 standard deviation). a b

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40 y = 98.079e-0.0021xy = 98.032e-0.0018xy = 95.755e-0.0008xy = 94.922e-0.0007x0 20 40 60 80 100 120 050100150200250300350400 Ridge Cla Slough Cla Ridge Ele Slough EleExposure time (d)% Mass Remaining (d) y = 98.079e-0.0021xy = 98.032e-0.0018xy = 95.755e-0.0008xy = 94.922e-0.0007x0 20 40 60 80 100 120 050100150200250300350400 Ridge Cla Slough Cla Ridge Ele Slough Ele y = 98.079e-0.0021xy = 98.032e-0.0018xy = 95.755e-0.0008xy = 94.922e-0.0007x0 20 40 60 80 100 120 050100150200250300350400 Ridge Cla Slough Cla Ridge Ele Slough Ele Ridge Cla Slough Cla Ridge Ele Slough EleExposure time (d)% Mass Remaining (d) Figure 4-4. Mass decay rates for E. cellulosa and C. jamaicense litter collected from ridge and slough vegetative communities in Shark River Slough during 20022003 significant difference in C:N values between species. Eleocharis cellulosa , on average, had lower C:N values than C. jamaicense -containing litterbags. The greatest difference in residual fibe r content occurred between species (Fig. 4-5). After one year of deployment, E. cellulosa bags deployed in sloughs were significantly lower in residual fiber conten t than litterbags deployed in ridges. Conversely, residual fiber cont ent was not significantly di fferent between ridge and slough deployments of C. jamaicense litter. Standing Dead Decomposition Standing dead decomposition rates of C. jamaicense showed similar trends to decay rates of litterbag plant material; residual fiber content increased linearly with

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41 0 20 40 60 80 100 120 140 160 180 200 050100150200250300350400 Ridge Cla Slough Cla Ridge Ele Slough Ele 0 2 4 6 8 10 12 14 16 0 20 40 60 80 100 120 140N:P % Residual Fiber C:NExposure Time (d) 0 20 40 60 80 100 120 140 160 180 200 050100150200250300350400 Ridge Cla Slough Cla Ridge Ele Slough Ele 0 2 4 6 8 10 12 14 16 0 20 40 60 80 100 120 140N:P % Residual Fiber C:NExposure Time (d) Figure 4-5. Temporal variation for % re sidual fiber content, C:N, and N:P for E. cellulosa and C. jamaicense litter deployed in ridg e and slough vegetative communities. Values represent mean (+ 1 standard deviation).

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42 0 2 4 6 8 10 12 14 16 18 20 0 20 40 60 80 100 120 0 20 40 60 80 100 120 050100150200250300350400 3A1C 3A2C ENP1 ENP2Exposure Time (d)N:P % Residual Fiber C:N 0 2 4 6 8 10 12 14 16 18 20 0 20 40 60 80 100 120 0 20 40 60 80 100 120 050100150200250300350400 3A1C 3A2C ENP1 ENP2Exposure Time (d)N:P % Residual Fiber C:N Figure 4-6. Temporal variati on for % residual fiber content, C:N, and N:P values for standing dead C. jamaicense at each of the four sutdy sites . Values represent mean (+ 1 standard deviation).

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43 exposure time (Fig. 4-6). Residual fiber increas es were observed to be greater in standing dead C. jamaicense than litterbag-deployed C. jamaicense . No leveling off in residual fiber decay rates was observed. Mean C:N valu es decreased with exposure time at Sites 3A1 and 3A2; however, an increase in C: N was observed at Sites ENP1 and ENP2. Discussion Litterbags Regardless of litter type (s pecies) or location of deployment (ridges and sloughs), litterbags deployed at site ENP2 had cons istently higher and si gnificantly different decomposition rates than those at the other study sites to the north. This can be attributed to the fact that ENP2 had the shortest hydroperiod of all site s, and therefore likely had the greatest oxygen exposure. The increased oxygen availability at this site may have increased the rate of carbon structural compound breakdown, but also may have allowed for the growth of white rot fungi and other microbial decomposers that are capable of degrading lignin in the presence of oxygen (Benner et al. 1984). Moreover, ridges and sloughs comprising the remaining sites were inundated longer than those at ENP2, and litterbags at these sites likely remained shielded from oxidative ca tabolism to a greater extent. This has significant implications with respect to so il accretion processes th at are capable of reinforcing elevation differences between ridge and slough vegetative communities at each study site. As expected, litter mass decreased with exposure time. Regardless of species content, litter decayed at a slightly faster rate when deployed in ridge communities; however, after one year of exposure, no si gnificant difference wa s observed. If both C. jamaicense -containing and E. cellulosa -containing litterbags were to remain exposed

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44 beyond 1 yr, plant material contained within litterbags deployed in ridge communities would be expected to decay toward an asympto tic value at a significantly faster rate than that deployed in slough communities, due to lo nger hydroperiods in slough communities. Eleocharis cellulosa contained within litterbags decayed at a significantly faster rate than C. jamaicense . Decay rates observed for ri dge and slough deployment of C. jamicense litter were slightly lo wer than the 0.0012 g/d valu e reported by Harris et al. (1995); however, Newman et al. (2001) reported rates as low as 0.0003 g/d. The observed decay rate differences observed between C. jamaicense and E. cellulosa litter may be due to tissue characteristics. For exam ple, plant material C:N values and residual fiber content, two important regulators of decomposition, va ried with exposure time. The C:N values for C. jamaicense litter were initially great er than those containing E. cellulosa . This suggests that C. jamaicense litter may have initially provided greater nitrogen limitations to microbial decomposers than E. cellulosa litter. In support of this, De Busk (1996) suggests microbial decompos ers colonizing high C:N ratio substrates may depend on the water column for nutrients , thus slowing decomposition. This would occur to a lesser extent in sloughs, due to gr eater water depths and nitrogen fixation. Cladium jamaicense C:N values reported in this study are similar to those reported previously in the scientific literature. C:N values reported in a mesocosm study by Corstanje (personal communicatio n) ranged from 66 to 91 for C. jamaicense litter under submerged conditions. The observed C:N values in this study were slightly higher (65120), in part due to seasonal and site varia tions in water depth, as our litterbags were submerged the majority of the year. While C. jamaicense C:N values fluctuated little between 0 and 110 d, they remained higher than E. cellulosa C:N values throughout the

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45 experiment. As a result, nutrien t limitations may have decreased C. jamaicense litterbag decomposition. Several authors report that as much as 64% of nitrogen immobilized in leaf litter can come from nitrogen fixation (van der Walk and Attiwill, 1984; Woitchik et al. 1997). Differences in leaf chemical composition affect rates of nitrogen im mobilization in leaf substrate (Pelegri et al. 1997). Decay rates generally increase with higher N content (Kaushnik and Hynes, 1971; Suberkrop et al. 19 76; Triska and Sedell, 1976). Plants with lower C:N values will decompose faster than plants with higher C:N (Tam et al. 1990; Merril and Cowling, 1996). Intere stingly, there was a slight in crease in C:N ratio from 0 to 150 d of exposure time in litterbags containing E. cellulosa . This increase may have been due to a prominent leaching phase in E. cellulosa litter, as this trend was not observed in C. jamaicense litter. This observa tion may have suggested C. jamaicense litter was more resistant to leaching than E. cellulosa litter in this study. The amount of initial residua l fiber contained within C. jamaicense and E. cellulosa -containing litterbags may have also affected decay rates. There was a pronounced increase in residual fiber observed between 0 d and 41 d of exposure for both species of litter, suggesting an increase in recalcitrant litter after 41 d. Although, residual fiber content was expected to increase with exposure time, it significantly decreased from 41 d to 105 d of exposure in both species of litter. This may have been caused by inorganic carbon contamination of the litterb ags, which seems most plausible in slough communities, where deeper water exposes vegetation to greater CaCO3 precipitation. Also, following one year of deployment, residua l fiber contents tended to converge for all species in ridge community deployments. Th is suggests that the dominant vegetation in

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46 ridges ( C. jamaicense ) and sloughs ( E. cellulosa ) have similar recalcitrant litter after one year of decomposition. Standing Dead Decomposition The greater increase in percent residual fiber observed in standing dead C. jamaicense may be a direct result of oxygen expos ure; however, leaching from rainfall and photodegradation may have also contribut ed to the measured increase in residual fiber. Furthermore, catabolic energy yields for bacteria using electron acceptors other than oxygen are generally low; therefore, gr owth rates of microbial decomposers are reduced in anaerobic conditions (Westerm ann, 1993; Reddy and DÂ’Angelo, 1994). In contrast to C. jamaicense -filled litterbags, standing dead C. jamaicense is constantly exposed to oxygen and therefore available for aerobic decomposers such as white rot fungi. For example, fungal colonization under aerobic conditions can breakdown certain carbon compounds (such as lignin) that ar e otherwise recalcitrant under anaerobic conditions and typically app ear in the residual fracti on after fiber analysis. Site differences observed in residual fiber content after 1 yr of exposure may have been attributable to small-scale differences in ridge deployment type or microclimate within sites. PVC pipes were deployed in tall ridges at all sites, but minor variations in ridge vegetative structure or microclimate may have affected residual fiber dynamics. For example, pipes were observed to be s ubmerged at 3A1 after 41 d of exposure as a result of unusually high water at this site, which may account for the lower residual fiber content. Site ENP2 was the driest site; therefore, probably ne ver attained depths sufficient to submerge quivers and slow decomp osition. Fluctuations in C:N, particularly at ENP1 and ENP2, were likely due to incr eased N leaching in pipes deployed at these sites, possibly a result of an environmenta l factor such as small-scale rain events.

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47 In summary, relative to the hypotheses, Cladium jamaicense decomposed significantly slower than E. cellulosa. Furthermore, Cladium jamaicense and E. cellulosa decomposition rates were greater in ridge vegetative communities than in slough vegetative communities. As a result, litter inputs to ridge vegetative communities would decompose faster than the same litter deposit ed in slough communities. Also, the extent to which litter inputs are prone to nutr ient leaching, oxidati on, and photodegradation would be less in submerged plant material th an standing dead plant material. Because of this, litter that stays lodged above the wa ter surface for extended periods of time may have the potential to accrete more soil than submerged litter. The C:N values decreased with exposure time and N:P values increased with exposure time for both species of submerged litter and standing dead vegetati on. Percent residual fiber increased with exposure time.

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48 CHAPTER 5 SYNTHESIS AND CONCLUSIONS Hydroperiod is a major factor influenc ing the development of ridge and slough vegetative communities in the central Evergl ades. In addition, vegetative substrate quality, biomass production, and decomposition also affect topography-based vegetative structure as related to their impact on soil accretion. For example, if ridge and slough vegetative communities had identical soil topogr aphy, variations in hydroperiod would be minimal and monospecific stands of vegetati on would dominate the landscape (Fig. 5-1). However, this does not occur, as the intera ction of the above components promotes the soil heterogeneity observed in ridge and slough vegetative communities (Fig. 5.2). Figure 5-1. Hypothetical Everglades la ndscape morphology if no variation in mesotopography existed

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49 Figure 5-2. Current landscape morphology showing variation in ridge and slough mesotopography and vegetation Environmental factors that regulate thes e components are not well understood and the success of Everglades restoration attempts will depend on the availability of scientific data addressing linkages among them. Ridge and slough vegetative communities were evaluated in this study to determine the relationship between ve getative substrate quality, biomass production, and soil accretion. Ridge vegetation, on average, contai ned significantly greater amounts of more recalcitrant plant tissue per year than ad jacent slough vegetative co mmunities at each of the four study sites (Fig. 5-2). This suggests that greater ra tes of soil accretion occur in ridge communities based solely upon differenc es in biomass production rates. However, differences between ridge and slough bioma ss production occurred within sample sites, including complete dieback within certain ar eas of ridge communities. This indicates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ridge Slough Slough C:N: 33 Residual Fiber: 3.8% Total Production: 1177 g/m2/yr Decay Rate: 0.734 g/yr Ridge C:N: 68 Residual Fiber: 6.8% Total Production: 3493 g/m2/yr Decay Rate: 0.294 g/yr

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50 that the vegetative community structure was in flux which needs to be considered in data interpretation. For example, transition zones grading from slough community to a short ridge community, and from short ridge to ta ll ridge community, may reflect ridge and slough landscape forming processes. Close obs ervation of their transition zones have provided some additional insight for processe s responsible for clona l establishment and feedback mechanisms regulating Everglades vegetative communities. The potential for sediment accreti on variation within slough vegetative communities, although not as great as th at between ridges and sloughs, may be significant in maintaining vegetative structure in the Everglades. Sediment accretion in sloughs at Sites 3A1 and ENP2, which cont ained higher percentages of emergent vegetation, such as E. cellulosa and P. hemitomon , would be greater than that at the other two sites due to higher biomass and residua l fiber production rate s. This was not unexpected. According to Loveless (1959), E. cellulosa probably adapted to fluctuating water levels occurring in the post-drainage Everglades, as evident by its presence at sites 3A2 and ENP2 that had relatively long and shor t hydroperiods, respectively) (Table 1-1). Like E. cellulosa , P. hemitomon is tolerant of long periods of inundation and attains its greatest density in sloughs with shorter hydrop eriods. In support of this, the greatest percentage of P. hemitomon was observed at Site ENP2, whic h was the driest site in this study. Panicum hemitomon dominance within ENP2 may result from the fact that this species emerges early after fire (3 to 4 da ys) and flowers prolif ically following droughts (Loveless, 1959). As a possible result of the above c onsiderations, elevation differences and sediment accretion rates between slough communities at Sites 3A1 and ENP2 and

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51 their adjacent ridge communities, might be expe cted to be less than those at Sites 3A2 and ENP1. Soil accretion and maintenance of vegetati ve community structure is not solely a function of biomass production. Decomposition of plant tissue is also an important regulator of vegetative commun ity structure. Decomposition rates were greatest at ENP2; as a result, plant tissue making it to the so il surface at this site would not persist as long as plant tissue deposited at other sites. Although Site ENP2 contained the second most productive slough vegetative community, increased oxygen exposure and shorter hydroperiod at this site would decrease se diment accretion by enhancing decomposition. In contrast, sloughs at other sites, where hydroperiod was less variable, may have been less affected by oxidative catabolism of ne wly deposited plant tissue substrates and decomposition rates were less affected. Ho wever, greater biomass and residual fiber production rates, combined with a greater perc entage of highly recalc itrant plant species at ENP2, may counteract the effects of increased oxygen e xposure and decreased soil accretion. While litter decay rates at Sites 3A1, 3A2, and ENP1 were similar, differences between values for C. jamaicense and E. cellulosa litter were highly significant which may help explain the elevation differences observed in this study between ridge and slough vegetative communities. Cladium jamaicense -dominated ridges undergo more oxidative degradation than slough vegetati ve communities, and greater decomposition might be expected. However, the recalcitrant substrate quality of C. jamaicense prevents it from decomposing faster than E. cellulosa , and, as a consequence, its litter persisted at the soil surface longer than that for E. cellulosa .

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52 Increased leaching from rainfall and phot odegradation might occur to a greater extent in ridge vegetative communities , because a significant fraction of C. jamaicense biomass exists in the standing dead phase in ridge locations, more so than any species of slough vegetation. Upon lit terfall, material would have lost the majority of soluble forms of N and P and simple structural carbon compounds (NDF) to leaching and/or leaf shatter, which may serve to increase recalci trance. Litter in sloughs, where water flows are minimal and depths are greater, would be less prone to N leaching than P leaching due to the relative abundance of N in the su rrounding water column and less leaf shatter (destruction of plant material from rainfall) . This would allow decomposers of slough vegetation to catabolize slough litt er faster than ridge litter. Because biomass production and vegetative substrate quality showed significant differences between ridge and slough community type, the results of this study provide useful insight on factors important for maintaining and restoring vegetative communities in the Shark River Slough region of the Ever glades. Biomass produc tion rates, nutrient and residual fiber contents, and mass d ecay rates measured for ridge and slough vegetation are useful in predicting change s that occur as a re sult of anthropogenic alterations in hydrology or nut rient loading to the system. Changes in vegetative composition in response to an thropogenic hydrologic alterations may result in the inability to maintain ridge and slough soil to pography and vegetative mosaic. The results of this study, when used in conjunction w ith sediment profile data, flow data, and historical accounts of ridge and slough landscape patterns will improve management strategies aimed at restoring pr e-drainage vegetative mosaics.

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53 LIST OF REFERENCES Ankom Technology Corporation. 1998a. Method for determining Acid Detergent Fiber, Neutral Detergent Fiber and Crude Fibe r, using the Ankom Fiber Analyzer. Ankom Technology Corporation, 14 Turk Hill Park, Fairport New York 14450, USA. Benner, R., S.Y. Newell, A.E. Maccubin, and R.E. Hodson. 1984. Relative contributions of bacteria and fungi to rates of degrada tion of lignocellulosic detritus in salt-marsh sediments. Appl. Environ. Microbiol. 48, 36-40. Berg, B., Jansson, P-E., Meentenmeyer, V., and Krantz, W. 1998a. Decomposition of tree root litter in a climatic transect of coniferous forests in northern Europe: A synthesis. Scand. J. For. Res. 13, 402-412. Berg, M.P., Kniese, J.P., Zoomer, R., and Verhoef, H.A. 1998. Long-term decomposition of successive organic strata in a nitrogen saturated Scots Pine forest soil. For. Ecol. Mgt. 107, 159-172. Brewer, J.S. 1996. Site differences in th e clone structure of an emergent sedge, Cladium jamaicense . J. Aquatic Bot. 55, 79-91. Busch, D.E., Loftus, W.F., and O.L. Bass, Jr. 1998. Long-term hydrologic effects on marsh plant community structure in the southern Everglades. Wetlands 18, 230241. Carreiro, M.M., Sinsabaugh, R.L., Repert, D.A., Parkhurst, D.F. 2000. Microbial enzyme shifts explain litter decay re sponses to simulated nitrogen deposition. Ecology 81, 2359-2365. Craft, C.B., and C.J. Richardson. 1993b. Peat accretion and N, P, and organic C accumulation in nutrient rich and unenriched Everglades peatlands. Ecol. Appl. 3, 446-458. Criquet, S., Farnet, A.M., Tagger, and S ., LePetit, J. 2000. Annual variations of phenoloxidase activity in evergreen oak litte r: Influence of certain biotic and abiotic factors. Soil Biol. Biochemistry 32, 1505-1513. Daoust, R.J., and D.L. Childers. 1998. Quantifying aboveground biomass and estimating net aboveground primary production fo r wetland macrophytes using a nondestructive phenometric technique. J. Aquatic Bot. 62, 115-133.

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54 Daoust, R.J., and D.L. Childers. 1999. Controls on emergent macrophyte composition, abundance, and productivity in freshwater Everglades wetland communities. Wetlands 19, 262-275. David, P.G. 1996. Changes in plant commun ities relative to hydrologi c conditions in the Florida Everglades. Wetlands 16, 15-23. Davis, S.M. 1991. Growth, decom position, and nutrient retention of Cladium jamaicense Crantz and Typha domingensis Pers. in the Florida Everglades. J. Aquatic Bot. 40, 203-224. Davis, S.M., and Ogden, J.C., 1994. Everglades : The ecosystem and its restoration. St. Lucie Press, Delray Beach, FL. De Angelis, D. L., and P. S. White. 1994. Ec osystems as products of spatially and temporally varying driving forces, ec ological processes, and landscapes: A theoretical perspective. In Davis, S.M. and Ogden, J.C. (eds.) Everglades: The Ecosystem and Its Restoration. St. Lu cie Press, Delray Beach, FL, Ch.13. DeBusk, W.F. 1996. Organic matter tur nover along a nutrient gradient in the Everglades. Ph.D. Dissertation. Univer sity of Florida. Gainesville, FL. DeBusk, W.F., and Reddy, K.R. 1998. Turnover of detrital organic carbon in a nutrientimpacted Everglades marsh. Soil Sci. Soc. Am. J. 62, 1460-1468. Donnelly, P.K., Entry, J.A., Crawford, D.L., and Cromack, K.C., Jr. 1990. Cellulose and lignin degradation in forest soils: Response to moisture, temperature, and acidity. Microb. Ecology 20, 289-295. Doren, R.F., Armentano, T.V., Whiteker, L.D ., and Jones, R.D. 1997. Marsh vegetation patterns and soil phosphorus grad ients in the Everglades ecosystem. J. of Aquatic Bot. 56, 145-163. Frederick, P.C., and Spalding, M.G. 1994. Factors affecting reproductive success of wading birds (Ciconiformes) in the Evergl ades ecosystem. In Davis, S.M. and Ogden, J.C. (eds.) Everglades: The Ec osystem and Its Restoration. St. Lucie Press, Delray Beach, FL, pp. 659-692. Gleason, P.J. and P. Stone. 1994. Age, origi n, and landscape evoluti on of the Everglades peatland. In S.M. Davis and J.C. Ogden (e ds.) Everglades: the Ecosystem and its Restoration. St. Lucie Pre ss, Delray Beach, FL, p.149-198. Gunderson, L.H., and Loftus, W.F. 1993. The Everglades. In Martin, W.H., Boyce, S.G., and Echternacht, A.C. (eds.) Bi odiversity of the Southeastern United States/Lowland Terrestrial Communities . John Wiley and Sons, New York, pp. 191-255.

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55 Hackney, C.T., Padgett, D.E., and Posey, M.H. 2000. Fungal and bacterial contributions to the decomposition of Cladium and Typha leaves in a nutrient enriched and nutrient poor areas of the Ev erglades, with a note on ergos terol concentrations in Everglades soils. Mycol. Res. 104, 666-670. Hammel, K.A. 1997. Fungal degradation of lig nin. In Cadisch, G. and Giller, K.E. (eds.) Driven by Nature: Plant Litter Qua lity and Decomposition. University Press, Cambridge, UK, pp. 33-45. Harris, T., T. Williges, K.A., and Zimba, P.V. 1995. Primary productivity and decomposition of five emergent macrophyt e communities in the Lake Okeechobee marsh ecosystem. Ergebnisse der Limnologie 45, 63-78. Herndon, A., Gunderson, L., and Stenberg, J. 1991. Sawgrass ( Cladium jamaicense ) survival in regime of fire and flooding. Wetlands 11, 17-28. Hoffman, W., Bancroft, G.T., and Sawicki, R. J. 1994. Foraging habitats of wading birds in the Water Conservation Areas of the Fl orida Everglades. In Davis, S.M. and Ogden, J.C. (eds.) Everglades: The Ec osystem and Its Restoration. St. Lucie Press, Delray Beach, Fl, pp. 585-614. Kaushik, N.K., and Hynes, H.B.N. 1971. The fate of dead leaves that fall into streams. Arch. Hydrobiol. 68: 465-515. Kurka, A.M., Starr, M., Heikinheimo, M., and Salkinoja-Salonen, M. 2000. Decomposition of cellulose strips in relation to climate, litterfall nitrogen, phosphorus and C/N ratio in natural boreal forests. Plant and Soil 219, 91-101. Lee, J., and Carter, V. 2001. U. S. Geological Survey Fact Sheet, Vegetative Resistance to Flow in the Florida Everglades . Loftus, W.F., and Eklund, A. 1994. Long-term dynamics of an Everglades small fish assemblage. In Davis, S.M. and Ogden, J.C. (eds.) Everglades: The Ecosystem and Its Restoration. St. Lucie Press, Delray Beach, FL, pp. 461-484. Loveless, C. M. 1959. A study of the vege tation in the Florida Everglades. Ecology 40, 1-9. McCormick, P.V., and Stevenson, R.J. 1998. Periphyton as a tool for ecological assessment and management in the Florida Everglades. J. Phycol. 34, 726-733. McVoy, C., and Crisfield, E. 2001. White Paper, The Role of Water Flow and Sediment Flows in the Everglades Ridge and Slough Landscape . Mellilo, J.M., and Aber, J.D. 1982. Nitrogen and lignin control of hardwood leaf litter decomposition dynamics. Ecology 63, 621-626.

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56 Mellilo, J.M., Aber J.D., Linkins, A.E., Ricca, A., Fry, B., and Nadelhoffer, K.J. 1989. Carbon and nitrogen dynamics along the d ecay continuum: Plant litter to soil organic matter. Plant and Soil 115, 189-198. Merril, W., and E.B. Cowling. 1966. Role of nitrogen in wood deterioration: amounts and distribution of nitrogen in tree stems. Can. J. Bot. 44, 1550-1580. Mould, E.D., and C.T. Robbins. 1981. Evalua tion of detergent analysis in estimating nutrient value of browse. J. Wildl. Mgt. 45, 937-947. Newman, S., Kumpf, H., Lang, J.A., a nd Kennedy, W.C. 2001. Decomposition responses to phosphorus enrichment in an Everglades slough. Biogeochemistry 54, 229-250. Pelegri, S.P., Riveria-Monroy, V.H., and Twiley, R. 1997. A comparison of nitrogen fixation (acetylene reduction) among three species of mangrove litter, sediments, and pneumatophores in south Florida, U.S.A. Hydrobiologia 356, 73-79. Rader, R.B., and Richardson, C.J. 1994. Res ponse of macroinvertibra tes and small fish to nutrient enrichment in the north ern Everglades. Wetlands 14, 134-146. Reddy, K.R., and E.M. DÂ’Angelo. 1994. Soil processes regulating water quality in wetlands. pp. 309-324. In Mitsch, W.J. (ed.) Global wetlands: old world and new. Elsevier Science, Amsterdam. Ross, M.S., Ruiz, P.L., Reed, D.L., Mickler, E., Stockman, D., Oberbauer, S, and Stone, P. 2001. Report to Everglades National Park, Assessment of Marsh Vegetation Responses to Hydrological Rest oration in Shark Slough, Everglades . Rowland, A.P., and J.D. Roberts. 1994. Lignin and cellulose fractionation in decomposition studies using acid-deterge nt fiber methods. Commun. Soil Sci. Plant Anal. 25 (3&4), 269-277. Rowland, A.P., and J.D. Roberts. 1999. Evaluation of Lignin and Lignin Nitrogen Fractionation Following Alternative Dete rgent Fiber Pre-treatment Methods. Commun. Soil Sci. Plant Anal. 30 (1&2), 279-292. Rybczyk, J.M., Garson, G. and Day, J.W. 1996. Nutrient enrichment and decomposition in wetland ecosystems: models, analyses, a nd effects. Current Topics in Wetland Biogeochemistry 2, 52-72. Sinsabaugh, R.L., Antibus, R.K., and Linkins, A. E. 1991. An enzymatic approach to the analysis of microbial activity during plant litter decomposition. Agriculture, Ecosystems, and Environment 34, 43-54.

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58 BIOGRAPHICAL SKETCH I have always been enthusiastic about the biological sciences. This passion led me to pursue a graduate career at the University of Florida. I comple ted my Bachelor of Science degree in the field of Interdisciplin ary Ecology at the Univer sity of Florida in August 2000. In Fall 2001, I began my graduate program at the University of FloridaÂ’s Soil and Water Science Department. I comple ted my Master of Science degree in May 2005.