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SPATIAL AND TEMPORAL PATTERNS OF BIOGEOCHEMICAL CYCLING OF NITROGEN IN A NUTRIENT-IMPACTED SUBTROPICAL WETLAND

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SPATIAL AND TEMPORAL PATTERNS OF BIOGEOCHEMICAL CYCLING OF NITROGEN IN A NUTRIENT-IMPACTED SUBTROPICAL WETLAND
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2008

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Enzyme activity ( jstor )
Microbial biomass ( jstor )
Nitrogen ( jstor )
Nutrients ( jstor )
Soil quality ( jstor )
Soil science ( jstor )
Soil temperature regimes ( jstor )
Soils ( jstor )
Vegetation ( jstor )
Wetlands ( jstor )

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University of Florida
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8/8/2002
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SPATIAL AND TEMPORAL PATTERNS OF BIOGEOCHEMICAL CYCLING OF NITROGEN IN A NUTRIENT-IMPACTED SUBTROPICAL WETLAND By KATHRYN J. BARCH A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2002

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ACKNOWLEDGMENTS I would like to thank my advisor, Dr. J. R. White, and the members of my committee, Drs. K. R. Reddy and D. A. Graetz for all of their assistance, patience, and guidance in the development of my research and the writing of this work. Dr. J. Prenger, Mr. M. Fisher, Mr. R. Corstanje, and Ms. M. Seo are greatly appreciated for their hard work in the field, laboratory help, and continual support throughout this project. A special thanks to Ms. Y. Wang and the many friends in the Wetland Biogeochemistry Lab for all of their laboratory assistance, and Mr. R. Corstanje for all of his statistical help. Most of all, I would like to express my deepest thanks to my family and friends, especially Missy and Keisha, for their emotional support throughout this journey. This research was funded, in part, by a grant (R-827641-01) from the U.S. Environmental Protection Agency and the St. Johns River Water Management District. Financial assistance was provided through the Hydrologic Sciences Academic Cluster by Dr. Jimmy Cheek, Dean for Academic Programs. ii

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TABLE OF CONTENTS page ACKNOWLEDGMENTS..................................................................................................ii ABSTRACT.........................................................................................................................v CHAPTER 1 INTRODUCTION.........................................................................................................1 Problem Statement.........................................................................................................8 Goal and Objectives.......................................................................................................9 2 METHODS AND MATERIALS.................................................................................12 Study Area...................................................................................................................12 Field-Sample Collection..............................................................................................14 Spatial Study.........................................................................................................14 Temporal Study.....................................................................................................18 Laboratory Analyses....................................................................................................19 Microbial Biomass Nitrogen (MBN)....................................................................21 Potentially Mineralizable Nitrogen (PMN)..........................................................22 Arginine Ammonification (Arg-N).......................................................................24 Denitrification Enzyme Assay (DEA)..................................................................25 Additional Experiments........................................................................................26 Statistical Analysis.......................................................................................................27 3 RESULTS AND DISCUSSION..................................................................................28 Spatial Distribution of Select Nitrogen Indicators Related to Phosphorus-Loading Impacts...........................................................................................................28 Soil and Detritus Characterization........................................................................28 Microbial Biomass Nitrogen.................................................................................30 Potentially Mineralizable Nitrogen.......................................................................34 Denitrification Enzyme Activity...........................................................................41 Comparisons of Nitrogen Processes.....................................................................50 Spatial Sampling Discussion.................................................................................53 Temporal Responses of Select Nitrogen Indicators Related to Phosphorus-Loading Impacts...........................................................................................................56 Sampling...............................................................................................................56 Microbial Biomass Nitrogen.................................................................................57 iii

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Potentially Mineralizable Nitrogen.......................................................................64 Arginine Ammonification.....................................................................................82 Denitrification Enzyme Activity...........................................................................92 Temporal Sampling Summary............................................................................104 4 SUMMARY AND CONCLUSIONS..........................................................................107 APPENDIX SPATIAL AND TEMPORAL SAMPLING DATA..................................115 LIST OF REFERENCES.................................................................................................125 BIOGRAPHICAL SKETCH...........................................................................................135 iv

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v Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science SPATIAL AND TEMPORAL PATTERNS OF BIOGEOCHEMICAL CYCLING OF NITROGEN IN A NUTRIENT IMPACTED SUBTROPICAL WETLAND By Kathryn J. Barch August 2002 Chair: Dr. J. R. White Department: Soil and Water Science Wetlands function as a sink or source for nutrients, depending on the biogeochemical characteristics within the wetland and the rate of nutrient input. Excess N within a system can lead to eutrophication of aquatic systems by causing imbalances in nutrient ratios. Impacts from agricultural runoff into wetlands have led to changes in vegetative communities; to microbial activities; and to increased levels of soil nutrients, especially P. Changes associated with total P were evaluated by examining their effect on shifts in vegetative communities and soil quality, within the Blue Cypress Marsh (BCM). Specifically, indicators associated with the rates of biogeochemical cycling of N were investigated. The objectives of this research were 1. To determine the spatial patterns of microbial biomass nitrogen (MBN), potential mineralization of organic N (PMN) and denitrification enzyme activity (DEA) within impacted and unimpacted regions of the (BCM) and 2. To examine the temporal responses in MBN, PMN, DEA, and arginine ammonification (Arg-N) within impacted and unimpacted regions of BCM.

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Detritus and soil samples (0-10 cm) were collected from impacted and unimpacted regions along a nutrient gradient established during preliminary sampling originating from surface water inflows. Samples were analyzed for pH, bulk density, PMN, DEA, MBN, total C, N, and P. Soil total P concentrations averaged 850 + 170 mg kg -1 and 640 + 80 mg kg -1 in the impacted and unimpacted regions, respectively. Significant differences ( < 0.05) existed between regions and vegetative communities for PMN, extractable NH 4 + and DEA. Mean values of PMN in detritus from the impacted and unimpacted regions were 150 + 120 mg kg -1 d -1 and 81.5 + 35.4 mg kg -1 d -1 , respectively. Extractable NH 4 + values in detritus for impacted and unimpacted regions averaged 360 + 450 mg kg -1 and 200 + 210 mg kg -1 , respectively, suggesting greater N availability in P-enriched areas. The detrital layer was found to be seasonally influenced ( < 0.05) regarding PMN, extractable NH 4 + , microbial biomass N (MBN), and DEA rates. The substrate quality may have influenced PMN rates between sites. Higher PMN activity was found to be associated with lower C/N values. Overall, nitrogen cycling in this 8,000 ha wetland has increased as a function of increased P loading. The BCM revealed evidence of ecosystem recovery in the Southwest region. The unimpacted region did not significantly differ from the Southwest region, where nutrient loading ended 20 years ago. However, the Northeast region, where nutrient loading ended 10 years prior, still had significantly higher N turnover rates, suggesting continued effects from previous P loading. Increased release rates of inorganic N from detritus may have implications for water quality for the adjacent St. Johns River. vi

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CHAPTER 1 INTRODUCTION Nitrogen is an important element in natural systems, functioning as a major component of all living things. The conversion of nitrogen into its various forms is necessary to maintain the large biological nitrogen requirement of plants and microbes. Nitrogen limitation within a system can lead to a reduction in growth due to the high N demand. Excess N, on the other hand, can lead to eutrophication and degradation of the biodiversity in an aquatic system by causing nutrient-ratio imbalances (Flite et al., 2001;Gustafson and Wang, 2002; Howard-Williams, 1985). In wetlands, N inputs are primarily from anthropogenic sources, precipitation, and biological N 2 fixation. Nitrogen is present in organic and inorganic forms with most in organic forms as detrital tissue and soil organic matter in wetland soils. The dissolved inorganic forms, ammonium (NH 4 + ), and nitrate (NO 3 ), are available for plant and microbial uptake. Most of inorganic N is found in wetlands as NH 4 + , which is preferred by plants in the soil solution (Howard-Williams and Downes, 1993; Mitsch and Gosselink, 1986). Wetlands function as a sink or source for nutrients depending on the biogeochemical characteristics within the wetland and the rate of nutrient input. Inorganic N concentrations in surface and porewater are reduced through nitrification and denitrification, ammonia volatilization, and plant uptake. Therefore low levels of inorganic N can be maintained in the water column, resulting in reduced transport through the wetland into adjacent aquatic systems. The rates and contribution of each 1

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2 process in soil and water column of wetlands vary because a variety of environmental factors such as temperature, pH, and nutrient availability (Mosier and Schimel, 1993). Three major factors are involved in influencing water quality in wetlands: hydrologic factors, vegetation factors, and soil factors. The dominant factor, hydrology, can affect vegetative communities, microbial activity, and the biogeochemical cycling of nutrients in the soil (Johnston, 1991; Mitsch and Gosselink, 1986). Hydrologic conditions significantly affect nutrient cycling and availability based on dissolved oxygen concentrations in the water column. Accumulation of organic matter in flooded wetland soils allows the establishment of anaerobic soil conditions with a high oxygen demand. Oxygen consumption creates distinct soil layers: (1) a thin aerobic surface layer and below (2) a thicker permanent anaerobic layer. Aerobic conditions at the soil-floodwater interface are maintained by diffusion of O 2 from the overlying water column. Wetland plants contribute to the transport of O 2 into the soil, specifically in the root zone. The aerobic-anaerobic interface in the soil controls the biogeochemical cycling of N in wetlands because N is a redox element (Figure 1-1) (Howard-Williams and Downes, 1993; Mortimer, 1942; Patrick, 1982; Tobias et al., 2001). Organic N is converted to inorganic N (NH 4 -N) by the process of ammonification or mineralization within both the aerobic and anaerobic soil layers. This is the ultimate step in organic N mineralization and is microbially mediated by extracellular enzymes (Figure 1-2) (Bonde et al., 2001). The rate-limiting step for these processes is the final hydrolysis (deamination) of organic N through microbial activity. Therefore, rates of N mineralization can significantly correlate to microbial biomass and the activity of microorganisms (Alef and Kleiner, 1986; Hopkins et al., 1994; Williams and Sparling,

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3 NH4+NO2Aerobic Soil LayerAnaerobic Soil Layer OO22 AerobicSoil FloodwaterInterfaceAerobicWater column NH4+NO2Aerobic Soil LayerAnaerobic Soil Layer OO22 AerobicSoil FloodwaterInterfaceAerobicWater column Figure 1-1. Aerobic-anaerobic interface in flooded soils and sediments. 1988). Nitrogen mineralization rates are also limited by temperature and O 2 availability. Higher temperatures have been found to increase net N mineralization rates. A doubling of the mineralization rate occurs with a 10C increase in temperature, commonly called the Q 10 of a reaction (Atlas, 1984; Gale et al., 1992; Marion and Black, 1987). Mineralization rates are the highest in the aerobic zone at the soil surface layer and along the root zone, and decrease with depth as microbial communities shift from aerobic to facultative and obligate anaerobes (Hauck, 1979; Patrick, 1982). Low N requirements of anaerobic microorganisms result in elevated levels of NH 4 + under anaerobic conditions. Nitrification is also diminished in an anaerobic environment allowing the buildup of NH 4 + . Ammonium is therefore readily available for plants and microorganisms in the anaerobic wetland soil. Oxidation of NH 4 + NO 3 , a process known as nitrification, occurs in three zones: water column, aerobic soil layer, and the aerobic region of the rhizosphere (Howard-Williams and Downes, 1993). Autotrophic bacteria mediate the two-step nitrification process involving the oxidation of NH 4 + to NO 2 and NO 2 to NO 3 . Environmental conditions (i.e., pH) can influence the activity of these bacteria, therefore

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4 NH 1 1 1 2 11 1 1: PMN: rate f (A,B,C)2: Arg-N: rate f (C) 2 NH4+-N C A B Large OrganicN CompoundsSmall OrganicN Compounds Dissolved OrganicN CompoundsDeaminationNH 1 1 1 2 11 1 1: PMN: rate f (A,B,C)2: Arg-N: rate f (C) 2 NH4+-N C A B Large OrganicN CompoundsSmall OrganicN Compounds Dissolved OrganicN CompoundsDeamination1: PMN: rate f (A,B,C)2: Arg-N: rate f (C) 1: PMN: rate f (A,B,C)2: Arg-N: rate f (C) 2 NH4+-N C A B Large OrganicN CompoundsSmall OrganicN Compounds Dissolved OrganicN CompoundsDeamination 2 2 NH4+-N C A B Large OrganicN CompoundsSmall OrganicN Compounds Dissolved OrganicN CompoundsNH4+-N C C A B Large OrganicN CompoundsSmall OrganicN Compounds Dissolved OrganicN CompoundsA A B B Large OrganicN CompoundsSmall OrganicN Compounds Large OrganicN Compounds Large OrganicN CompoundsSmall OrganicN Compounds Dissolved OrganicN Compounds Dissolved OrganicN CompoundsDeamination Figure 1-2. Mineralization rates determined by potentially mineralizable nitrogen (PMN) and arginine ammonification (Arg-N). regulating the rate of NO 2 and NO 3 production. Dissolved O 2 and NH 4 + availability are the primary regulators of the nitrification process (Henriksen and Kemp, 1988). The supply of NH 4 + in the aerobic soil layer in wetlands is controlled primarily by the flux of NH 4 + from the anaerobic soil layer as a result of concentration gradients between the two layers (Mitsch and Gosselink, 1986; Patrick and Reddy, 1976). Nitrate produced by nitrification diffuses down into the anaerobic soil layer under a concentration gradient where it becomes reduced to N 2 gas according to Fick’s Law (Figure 1-3). The nitrification process is therefore tightly coupled to denitrification, which can occur simultaneously with nitrification in wetland soils (Firestone and Davidson, 1989; Tobias et al., 2001). Nitrification-denitrification has been shown to be a major pathway of managing nitrogen cycling processes and nutrient enrichment for organic soils (Kemp et al. 1990).

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5 NH4+NO2-NO3OO22 AerobicSoil-FloodwaterInterfaceAerobicWater column N2Organic NAerobic Soil Layernaerobic Soil Layer 1NO2-NO3-NO3-N2ON2 5 6 1N Fixation 3 2Mineralization**Immobilization 4Ammonia Volatilization 5Nitrification 6Denitrification**Org N 1 2 2Org N 2 3 NH4+NH4+NH3 4 NH4+ 1 NH4+NO2-NO3OO22 AerobicSoil-FloodwaterInterfaceAerobicWater column N2Organic NAerobic Soil Layernaerobic Soil Layer 1NO2-NO3-NO3-N2ON2 5 6 1N Fixation 3 2Mineralization** 2Mineralization**Immobilization 4Ammonia Volatilization 5Nitrification 6Denitrification**Org N 1 2 2Org N 2 3 NH4+NH4+NH3 4 NH4+ 1 Nitrogen Cycle Nitrogen Cycle A A Figure 1-3. Nitrogen cycle in wetland soils. (** Nitrogen processes focused on in this study). Nitrate reduction in wetlands is the major N removal mechanism and denitrification is the dominant process (Reed et al., 1988, USEPA, 1988). The absence of O 2 , the presence of available C, temperature, soil moisture, pH, presence of denitrifiers, soil texture, and the height of the water column influence the rate of denitrification, NO 3 to N 2 . The optimum pH range for denitrification is 6.0 to 8.5 (Reddy and Patrick, 1984). As the temperature increases in the system, denitrification rate will also increase due to an increase in microbial activity. Soil moisture affects the aeration of the soil and in turn the redox potential of the soil. Facultative anaerobic bacteria use NO 3 as a terminal electron acceptor in the absence of O 2 (Eh: 200-300 mV) (Patrick and Jugsujinda, 1992). Facultative anaerobic bacteria through the utilization of enzymes control denitrification rates during the reduction process. The maximum rate of NO 3 reduction can be quantified through enzyme activity in the soil (Tiedje, 1982; Veldkamp et al., 1999). Wetlands can be partly saturated or continuously flooded throughout most of the year. Therefore, O 2 (electron acceptor) is limiting in the surface layer of the soil and in

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6 turn organic matter (electron donor) builds up in the system. Under these conditions, NO 3 is the greatest limiting factor for denitrification. Therefore, NO 3 will control the size and activity of the denitrifier microbial populations. An increase in denitrification in flooded soils can be linked to an increased concentration of NO 3 into the system (Jacobson and Alexander, 1980; Luo et al., 1998). Denitrification can therefore be used as an indicator for determining the area impacted by NO 3 loading (White and Reddy, 1999). Nitrate respiration is the use of NO 3 as an electron acceptor in breaking down C compounds in the soil system. If the C content of the system is increased, there will be a similar increased response in the denitrification capacity of the soil. Wetland soils are generally high in organic C and low in O 2 , which leaves NO 3 as the limiting factor of denitrification. Vegetation community type(s) can influence the quality of detrital material and the rate of organic C decomposition. For example, Typha domingensis has been found to decompose more rapidly than C. jamaicense (Davis, 1991). Microbial populations can be limited by soil P instead of N in some wetland ecosystems (White and Reddy, 1999). Therefore, in these cases, additions of P into the system can increase microbial activity. An increase in inorganic N release from the soil was found to be related to increased total P (White and Reddy, 2000). Eutrophication from P inputs can increase turnover rates of inorganic N from soil and detritus, potentially stimulating plant growth (White and Reddy, 2000). Fire can play an important role in the modification and evolution of wetland ecosystems. Three basic effects to the environment, which occur due to fire, are the direct response of heat on plants and soil; the removal of litter and the creation of new

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7 microclimates; and the transfer and availability of nutrients. Soil nutrient concentrations are altered by fire, although these alterations are quite variable (Smith et al, 2001). Changes in vegetation form and productivity and in soil microorganism activity due to fire also can lead to alterations in soil properties. Additionally, a thick organic layer on the soil surface can be effective in insulating the underlying soil from high temperatures, therefore limiting changes in the soil profile (Raison, 1979). Studies have shown that soil nutrient levels (NH 4 -N, NO 3 -N, PO 4 -P, Ca, Mg, and K) increase after a fire for mineral soils, although this is largely restricted to surface soil (Kutiel and Shaviv, 1993; Marion et al., 1991), while others find no enrichment (Laubhan, 1995). Nutrients can also be lost through volatilization, leaching, and/or ash particles during the fire (Marion et al, 1991; Turner et al., 1997). Fire increases pH significantly due to ash additions and in turn can influence phosphorus availability and increase N volatilization in the soil. The pattern and magnitude of changes in soil inorganic N are influenced by both site factors and fire behavior (Boerner et al., 2000). Prior studies suggest that changes in litter volume and microclimate initially have a larger impact on N mineralization than fire behavior (Webb et al., 1991). The severity of a fire is regulated by the fuel load, water content of the soil, and vegetation (Jensen et al., 2001). At low fire intensity, stimulation of microbial growth may result due to increased nutrient availability (Singh et al., 1991). However, some changes in the soil chemical environment may limit microbial growth some period after a fire (Raison, 1979). Mineral nitrogen (NH 4 -N) was found to be greater in the soil surface layers following a burn and increased with fire severity in grasslands. Much of the NH 4 -N released to soils

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8 is thought to originate from changes in the forms of N due to heat (Romanya et al., 2001). Increased mineralization of organic N after heating soils has also been reported by other authors (Serrasolsas and Khanna, 1995). The release of NH 4 -N is suggested to orginate from the decomposition of N-containing organic matter and from soil minerals. This is supported by the fact that soil NH 4 -N does increase after a fire after the elimination of ammonifying organisms from the heat (Raison, 1979). Other studies have found decreases in NH 4 -N and NO 3 -N concentrations with greater fire severity (Marion et al, 1991). Post-fire increases in soil nitrate depended greatly on vegetation type with grasslands having higher nitrate increases than shrublands with fire severity (Romanya et al., 2001). Overall, effects from fire and existing environmental conditions in the field are compounded making the cause of changes in soil properties difficult to discern (Raison, 1979). Problem Statement Determining the soil quality of any ecosystem can be challenging, especially when it comes to the diversity of landscapes with in a system. Focusing on specific biogeochemical properties within the soil can lead to a more efficient and inexpensive method of determining the soil quality of the system. Wetlands play a critical role in removing contaminants and can reflect the stability of the surrounding communities. Wetland systems receive inflows from uplands as they occupy low-lying areas in the landscape. Changes of the soil quality of wetlands can therefore indicate possible disturbance in the upland community. Biogeochemical processes in wetlands will reflect these changes before they are noticeable as shifts in suites of higher organisms. Therefore, biogeochemical properties can provide an early sign of changes in the ecological status of the system (Reddy and D’Angelo, 1997).

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9 Soil quality refers to the combination of physical, chemical, and biochemical properties in evaluating three basic function: (1) productivitythe ability of the soil to enhance plant and biological productivity; (2) environmental qualitythe ability of the soil to filter, buffer, and transform material to protect the environment from pollution; and (3) degradationthe capacity of the soil to function as part of a mature, self-sustaining ecosystem (Doran and Parker, 1994; Doran and Safley, 1997; Leirs et al., 2000; Pankhust et al., 1997; Yakovchenko et al., 1996). Indicators of soil quality have not been previously established due to the broad range of soil indicators as well as the disagreement over which indicators should be analyzed (Doran and Safley, 1997). Biochemical properties have been found to be more sensitive to environmental stress and have the largest impact on degradation (Yakovchenko et al., 1996). Emphasis, however, must be made that these are only “indicators” (i.e. not direct measures of soil health), which determine if the soil is functioning normally (Pankurst et al., 1997). Exclusively for this study, emphasis was placed on indicators associated with the biogeochemical processes of N (Table 1-1). This focus will lead to a greater understanding of the response in N processes affected by historic nutrient loading and changes in vegetation communities and soil quality. Goal and Objectives The overall goal of the project was to develop indicators of eutrophication to aid in the determination of the soil quality of wetlands. The main objective was to determine the biogeochemical N processes affected by nutrient loading and vegetative communities and measure the rates of these processes along the P-impacted gradient. As well as, to observe differences in biogeochemical N processes between impacted and unimpacted regions of the marsh due to the termination of two surface water and nutrient inflow

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10 points 10 and 20 years before this study. Specific objectives of this research are the following: 1. Determine the spatial pattern of microbial biomass N (MBN), potential mineralization of organic N (PMN) and denitrification enzyme activity (DEA): Between the impacted and unimpacted regions of the Blue Cypress Marsh (BCM) and The vegetative communities associated with each region. It is hypothesized that nutrient enrichment will increase these biogeochemical N processes in relation to differences in soil quality due to shifts in vegetative communities. 2. Examine the temporal responses in MBN, PMN, DEA, and arginine ammonification (Arg-N): Between the impacted and unimpacted regions of BCM and The vegetative communities associated with each region. It is hypothesized that nutrient loading will lead to differences in seasonal patterns of these biogeochemical nitrogen processes due to changes in soil quality by shifts in vegetative communities.

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11 Table 1-1. Biogeochemical indicators within the soil profile associated with N processes. (DEA = denitrification enzyme activity, PMN = potentially mineralizable nitrogen, and Arg-N = arginine ammonification.) IndicatorNitrogen process Primary regulatorsDEANO3N20Presence of denitrifiersAvailability of nitrate (NO3-) Absence of oxygenAvailability of carbonPMNComplex Organic N NH4 + Microbial biomass NOxygen availabilityC/N ratio of substrateArg-NDissolved Organic N NH4 + Oxygen availabilit y C/N ratio of substratePresence of arginine dihydrolase

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CHAPTER 2 METHODS AND MATERIALS Study Area The research site is located in the headwater area of the St. Johns River in east-central Florida (Figure 2-1). This region is composed of 8,000 ha of freshwater marsh wetlands within the Blue Cypress Marsh Conservation Area (BCMCA) of the Upper St. Johns River Basin Project. The marsh receives inflows from Fort Drum Marsh Conservation Area (FDMCA) to the south, and historically received surface water inflows from the surrounding agriculture lands from two breaks in the levee surrounding the marsh. One break occurred at the Southwest corner of the marsh until the 1980s and the other levee break existed in the Northeast corner, allowing surface water inflows and nutrient loading until the early 1990s. This area within the BCMCA was chosen as a study area because of the (1) formation of gradients from impacted areas at inflow areas to pristine regions in the interior, (2) multiple input points for pollutants with data on the flow, water quality and upstream land uses for each source, and (3) abundance of supplementary ecological data for the area managed by the St Johns River Water Management District (SJRWMD). The vegetative species are predominantly made up of sawgrass stands and maidencane flats, but also contains significant areas of shrub swamp, flag marshes, cattail marshes, and deepwater slough communities. Rainfall is recorded at two hydrologic monitoring stations within the marsh, handled by the SJRWMD. As well as a 50-year 12

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13 Blue C yp ress Marsh Figure 2-1. The location of the Blue Cypress Marsh Conservation Area.

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14 record of stage data for the Blue Cypress Lake, which is hydrologically connected to the marsh. Field-Sample Collection Spatial Study Three regions, Northeast, Southwest, and Blue Cypress Trail (BCT), were selected within the BCM to provide a range of soil nutrient properties, including impacted and unimpacted areas (Figure 2-2). The unimpacted sites were selected based on their location in the interior or low nutrient impacted area of the marsh (BCT). Sites were chosen within the unimpacted region following the direction of water flow from the interior of the marsh north towards the adjacent Blue Cypress Lake (Figure 2-3). The sites selected from the impacted areas of the marsh followed along the proposed nutrient gradient, which was established from preliminary sampling in January 2000. Preliminary sampling examined only the soil characteristics extending from the historic surface water inflow locations in both the Southwest and Northeast corners of the marsh. Laboratory soil analysis produced a total P gradient, which extended from the two surface water inflow regions (i.e., Northeast and Southwest) into the interior of the marsh (Figure 2-4). Detritus and soils samples (0-10 cm) were collected from within the Northeast and Southwest impacted regions, following the total P gradient (Figure 2-3). This sampling design would allow the determination of changes in biogeochemical N processes associated with total P. The detritus layer represents the most current impacts (< 3 years), while the soil samples (0-10 cm) signify nutrient impacts of a greater time scale (10-20 years) (Reddy

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15 Figure 2-2. Map of the regions sampled within the BCM for the spatial study.

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16 Figure 2-3. Maps displaying the layout of sampling sites within each region for the spatial study.

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17 Northeast Corner Southwest Corner BCM Northeast Corner Southwest Corner Northeast Corner Southwest Corner Northeast Corner Southwest Corner Northeast Corner Southwest Corner BCM Figure 2-4. Total phosphorus gradient within the Blue Cypress Marsh. (Map credited to the SJRWMD.)

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18 et al., 1999). Forty soil samples along with corresponding detrital samples were obtained from each of the three regions for the spatial study (9/12/00-9/26/00). Each soil sample was made up of two soil cores, which were combined to make a representative sample. The soil samples were taken with a 10 cm ID aluminum core tube and the detritus hand gathered within a 625 cm 2 region on the soil surface. When collecting detritus, an outline of a square measuring 25 cm by 25 cm was used to measure the area to be sampled. A nested sampling plan was used in all three areas, with samples taken at 1.5, 15, 75, and 750 meters apart, to provide the most efficient sample spacing (Burrough, 1991) (Figure 2-3, 2-4). This sampling distribution was applied in order to construct reliable semivariograms for the final phase of the overall BCM project. Temporal Study Within each of these same three spatial sampling regions, two sites were selected for additional temporal sampling based on stands of vegetation as well as total P. Within the Northeast region, sites containing Typha sp. and Cladium vegetative communities were selected. For the BCT region, sites were chosen containing Cladium and Panicum stands. The two sites within the Southwest region contained Typha sp./Myrica and Typha/Cladium/Salix communities, as no pure stand of one vegetative community existed. Each of these six sites was designated by number with 1 and 2 occurring in the Northeast region, 3 and 4 found in the BCT region, and 5 and 6 within the Southwest region. Within each of these sites, three sub-plots were arranged linearly and ran in the north to south direction except for site 6, which extended west to east. These sub-plots were labeled A, B, and C and measured 2 by 2 meters (Figure 2-5). Plot A was the western most sub-plot for all sites except for site 6, where A was found to the north of both B and C. Four soil and detrital samples were randomly taken from each 2 by 2

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19 meter plot within each site. These four soil cores and detrital samples were combined to make a representative sample for each sub-plot. Therefore, each site had three soil and detrital samples giving a total of 18 soil and 18 detrital samples for all three regions combined. Redox probes were placed extending into the sampling area from the corner of sub-plot A for all sites at 5, 10, 20, and 30 cm depths. Soil temperature probes were also located in the same corner of sub-plot A within each site just below the soil surface (i.e., 2-3 cm). Soil samples as well as corresponding detrital samples were collected from these six sites for the temporal study (3/28/01, 6/5/01, 7/26/01, 9/25/01, 12/5/01, 1/29/02). The soil samples were taken with a 10 cm ID aluminum core tube and the detritus hand gathered as before within a 625 cm 2 region on the soil surface. Samples were transported on ice and stored in sealed containers for use in laboratory procedures. Laboratory Analyses All samples were analyzed for basic physicochemical properties: pH, bulk density, and total C, N, and P. Measurements of pH were done using a 1:1 DDI soil slurry on an ORION SA 720 pH meter (Fisher Scientific, Fair Lawn, NJ). Bulk density was calculated on a dry soil weight basis. Total C and N contents of detritus and soil were determined on dried, ground samples using a Carlos-Erba NA-1500 CNS Analyzer (Haak-Buchler Instruments, Saddlebrook, NJ). Total P was analyzed on samples following combustion (ashing) at 550C for 4 h in a muffle furnace and dissolution of the ash in 6 M HCl (Anderson, 1976). The digestate was analyzed for P by an automatic ascorbic acid method (Method 365.4, USEPA, 1993).

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20 Figure 2-5. Map of the site locations and sub-plot design used for the temporal study, illustrated here for the BCT region.

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21 Microbial Biomass Nitrogen (MBN) The fumigation-extraction method was used in measuring MBN (Brookes et al, 1985, Horwath and Paul, 1994). This laboratory procedure provides information about the metabolic efficiency of the microbial population and may be an indicator of changes in soil properties along the gradient (Jordan et al., 1995; Yoshikawa and Inubushi, 1995). The transformation and storage of nutrients are regulated by soil microbial biomass (Bohlen et al., 2001; Martens, 1995). A significant relationship has been shown between microbial biomass and the amount of mineralizable nutrients in soils (Powlson and Jenkinson, 1981). For all of the samples, an approximate wet soil equivalent of a 0.5 g dry weight sample was weighted out in duplicate labeled 50-mL polypropylene centrifuge tubes (one sample is fumigated and one sample is not fumigated). For the fumigated sample set, in a fume hood, approximately 0.5 mL of chloroform (Fisher Scientific, Fair Lawn, NJ) was added to each centrifuge tube. The tubes were placed into a vacuum desiccator with a beaker containing about 60 mL of chloroform and several boiling chips. A vacuum was created in the desiccator until the chloroform reaches a boil in the samples and the beaker. Air was then allowed to reenter the desiccator by opening the value on the lid of the desiccator. This evacuation procedure was repeated four times. After the fourth vacuum cycle, the top valve of the desiccator was closed. The samples were incubated in the vacuum desiccator in a fume hood for 24 hours. After 24 hours, the valve at the top of the desiccator was opened in the fume hood to allow air to reenter. Air was allowed to reenter about seven times to remove as much chloroform from the samples as possible. For the extraction procedure, both the non-fumigated control samples and the fumigated samples followed the same procedure. To each tube, 25 mL of 0.5 M K 2 SO 4

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22 was added. The tubes were placed on a reciprocating shaker for one hour. The sample supernatant was vacuum filtered into 20-mL HPDE scintillation vials using Whatman #42 filter paper and stored at 4C until digestion and analysis. For the digestion procedure, 10 mL of each 0.5 M K 2 SO 4 sample extract was subjected to Kjeldahl-N digestion (Bremner and Mulvaney, 1982). Digestion repeats and spikes were made for 10% of samples and one blank per digestion set. A range of NH 4 -N standards were prepared (0-10 mg NH 4 -N/L) using 1000 mg NH 4 -N/L (ppm) and 10 mL of 0.5 M K 2 SO 4 . One scoop of Kjeldahl salt catalyst (K 2 SO 4 and CuSO 4 ) (about 0.6 g) and 2 mL concentrated H 2 SO 4 were added to each digestion tube. The tubes were placed in the digestion block where the starting temperature is 125C. After two hours, the temperature was increased to 150C and again to 280C after five hours. After six hours, the temperature was set to 380C and glass funnels were placed on top of the tubes to allow the recirculation of sulfuric acid fumes. The digestion continued for about 2-3 hours until the samples were clear. While the samples were still warm, 20 mL of distilled deionized (DDI) water were added to the tubes and vortexed thoroughly. The digestate was poured into labeled 20-mL HPDE scintillation vials for storage at room temperature until analysis. The TKN in the sample disgests were determined using a Technicon TM Autoanalyzer (Method 351.2, USEPA, 1993). Microbial biomass nitrogen was determined by subtracting the TKN of the controls from the fumigated samples. A combined extraction efficiency factor (Kn) value of 0.54 was used with the final TKN values in determining total microbial biomass nitrogen (Brookes et al, 1985). Potentially Mineralizable Nitrogen (PMN) The PMN rate is best described as an anaerobic waterlogged incubation at 40C (Keeney, 1982; Sarathchandra et al., 1989; Tiedje, 1982; Williams and Sparling, 1988).

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23 Potentially mineralizable N measures the release rate of NH 4 + from the decomposition of large into small and eventually dissolved organic N compounds. The rate-limiting step(s) for this process involves the microbial enzyme activity associated with the break down of the larger organic N compounds (Bonde et al., 2001). Anaerobic conditions allow the following: (1) only measurements of NH 4 + are needed, (2) use of higher temperatures allowing faster N release under shorter incubation times, (3) representation of typical flooded wetland soil conditions, and (4) reduction in water loss from the sediment (Patrick, 1982). The PMN rates were determined for all detritus and soil samples. An approximate wet soil equivalent of a 0.5 g dry weight sample was weighed out into 50-mL glass serum bottles (incubated set) and into 50-mL centrifuge tubes (control set). To each glass bottle, 5 mL distilled deionized (DDI) water was added. The bottles were sealed with butyl rubber stoppers and aluminum crimp tops. The headspace was replaced with O 2 -free N 2 gas (purged for about 5 minutes). The bottles were stored in an incubator in the dark at 40C 2C for 10 days. The temperature of the incubator was recorded during the incubation period. Simultaneous to day 0 of the incubation period, 25 mL of 2.0 M KCl was added to the control set tubes, and the tubes were placed in reciprocating shaker for 1 hour. The tubes were then centrifuged at 4000 g for 10 minutes. The sample supernatant was vacuum filtered into 20-mL HPDE scintillation vials using Whatman #41 filter paper and stored at 4C until colorimetric analysis of NH 4 -N using a Technicon TM Autoanalyzer (Method 365.1, USEPA, 1993). After the 10 day incubation period, the bottles were removed and 20 mL of 2.0 M KCl was injected into each bottle using an outlet needle. The bottles were placed in a reciprocating shaker for 1 hour.

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24 After shaking, the bottle caps were removed and the soil and extract was transferred into labeled 50-mL centrifuge tubes. The tubes were then centrifuged at 4000 g for 10 minutes. The sample supernatant was vacuum filtered into 20-mL HPDE scintillation vials using Whatman #41 filter paper and stored at 4C until colorimetric analysis of NH4-N using a Technicon TM Autoanalyzer (Method 365.1, USEPA, 1993). Potentially mineralizable nitrogen was calculated by subtracting the NH 4 -N value of the controls from the NH 4 -N value of the incubated samples with the result divided by time (10 days). Arginine Ammonification (Arg-N) Arginine ammonification rates have been used to estimate the activity of microorganisms present in the soil (Alef and Kleiner, 1986). This method measures the microbial activity or more precisely the extracellular enzyme activity involved in the final step of organic N mineralization, deamination (Franzluebbers et al., 1995; McLatchey and Reddy, 1998; White and Reddy, 2001). Therefore, arginine ammonification does not include the rate-limiting step(s) as PMN. Arginine ammonification rates were to be determined for detritus and surface soil samples from the temporal study. An approximate wet soil equivalent of a 0.5 g dry weight sample was weighed out into 50-mL glass serum bottles (incubated set) and into 50-mL polypropylene centrifuge tubes (control). To each glass bottle, 5 mL distilled deionized (DDI) water was added. The bottles were sealed with butyl rubber stoppers and aluminum crimp tops. The headspace was replaced with O 2 -free N 2 gas (purged for about 5 minutes) and 2 mL of Arginine-N (1.01 mg N/mL) was added. The loading rate applied to each bottle was approximately 4070 mg N/kg dry soil. The bottles were stored in a shaker incubator in the dark at 30C 2C for 4 hours. After the 4 hour incubation period, the bottles were removed and 10 mL of 2.0 M KCl was added to the control tubes

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25 and incubation bottles. The samples were placed in a reciprocating shaker for 1 hour. After shaking, the soil and 2 M KCl extract were transferred into 50 mL centrifuge tubes and centrifuged at 6000 rpm for 10 minutes. The sample supernatant was vacuum filtered into 20 mL HPDE scintillation vials using Whatman #41 filter paper and stored at 4C until colorimetric analysis of NH 4 -N using Technicon TM Autoanalyzer (Method 365.1, USEPA, 1993). Denitrification Enzyme Assay (DEA) Denitrifiers produce enzymes for the utilization of NO 3 as a respiratory electron acceptor where NO 3 is abundant and O 2 is low. Furthermore, soils with a high rate of DEA either have or recently had increased levels of NO 3 (White and Reddy, 1999). Denitrification enzyme activity may therefore be used as an indicator of recent NO 3 loading. This method observes the maximum rate of NO 3 reduction for the enzymes already present in the soil. An approximate wet soil equivalent of a 0.8 g dry weight sample was placed into a glass serum bottle. To each bottle, 5 mL of distilled deionized (DDI) water was added that had been purged with N 2 gas (Grade 5.0) for about 10 minutes. The bottles were sealed with butyl rubber stoppers and aluminum crimp tops. The headspace was evacuated (20psi vacuum for about 15 seconds) and purged with N 2 gas (Grade 5.0) for about 15 minutes with exhaust needle being inserted 1 minute after N 2 gas. After purging, approximately 14% of the headspace was removed from each bottle and was replaced by an equal volume of acetylene gas (C 2 H 2 ). The bottles were placed on a reciprocating shaker for 1 hour to allow the acetylene gas to thoroughly mix with the sample. Eight mL of solution containing 0.411 g KNO 3 , 0.729 g C 6 H 12 O 6 -C L -1 , and 2 g L -1 choloramphenicol (an enzyme production inhibitor) were added to each bottle and

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26 samples were placed on the shaker in the dark at 25C (time zero). Headspace was sampled after 30 minutes, 1 hour and 2 hours with the pressure (KPa) measured at time 1 (30 minutes). Nitrous oxide production was measured using a Shimadzu Gas Chromatograph equipped with an Electron Capture Detector (ECD). A Bunsen absorption coefficient of 0.544 for N 2 O at 25C was used to adjust for N 2 O dissolving in the aqueous phase (Tiedje, 1982). Additional Experiments DEA may be used as an indicator of recent nitrate loading in wetland soils; for that reason, two soil samples (Northeast and BCT) were used to determine DEA as a function of nitrate addition. Soil sample slurries were prepared in triplicate consisting of approximately 30 g wet weight of soil and 60 mL of distilled deionzied water (DDI), when taking into account the moisture content of the sample. A total of 24 soil sample slurries were divided into 4 groups of nitrate spike concentrations, 0, 50, 500, and 1250 mg L -1 were incubated in a shaker at 25 C for 30 days. Three times a week the soil slurries received 1 mL spike of the corresponding nitrate concentration. After which, the slurries were analyzed for DEA and the porewater for DOC, NO 3 -N, SRP, and NH 4 -N. Nitrogen mineralization rate methods provide an indication between the quantity of microbial biomass and the activity of microorganisms. Investigating PMN rates as a function of time and temperature will display trend(s) of microbial activity in the soil. The influence of temperature on PMN was determined for two soils from the Northeast and BCT regions at 20, 30 and 40C. Nitrogen mineralization rates were also observed at 40C over at 2, 5, and 10 day incubation periods.

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27 Statistical Analysis Statistical analysis for the spatial data was performed using JMP 3.1 (SAS Institute, Inc.). Spatial distribution of nitrogen processes between sites and vegetative communities were tested using a one-way ANOVA model. Statistically significant differences (p < 0.05) were further analyzed with Tukey Kramer multiple comparisons. The data for each parameter was log transformed and the outliers were removed to produce a data set, which met homogeneity of variances and normality test required for statistical comparison. The nonparametric method of Spearman’s rank correlation coefficients was employed to test for interactions between specific parameters using non-transformed data. To assess the importance of seasonality in the temporal study as well as the interaction between the sites over time, a MANOVA of repeated measures using Pillai’s Trace Criterion Test (SAS Institute, Inc.) was conducted to find significant (p < 0.1) results. The data for each parameter were log transformed and the outliers were removed required for statistical comparison. For illustration purposes only, elliptical figures were created using JMP 3.1 (SAS Institute, Inc.) to show relationships between parameters in the marsh. Non-transformed data were used for the diagrams. The size of the ellipse is an approximate measure of the confidence limits for the impacted and unimpacted sites, but is not useful for statistical comparisons.

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CHAPTER 3 RESULTS AND DISCUSSION Spatial Distribution of Select Nitrogen Indicators Related to Phosphorus-Loading Impacts Historic nutrient loading into the marsh from adjacent agricultural lands has created enrichment areas of P near the inflows in the Northeast and Southwest regions in relation to the interior within the BCT region. The spatial distribution of biogeochemical N process rates, specifically PMN and DEA, have been effected by this nutrient loading, in part, due to changes in vegetative communities and soil quality. Vegetative communities surrounding the inflow areas have progressively shifted towards more invasive species including Typha sp., Salix and Myrica. Different plant communities can affect soil N transformations indirectly by microbial activity through detrital quality and quantity (Steltzer and Bowman, 1998; Griffiths et al, 1998; Klingensmith and Van Cleve, 1993). Therefore, variations in soil quality may occur between the impacted and unimpacted sites due to these changes in vegetation. The spatial study was to examine the differences in MBN, PMN, and DEA between (1) the three regions and (2) the vegetative communities associated with each region. Soil and Detritus Characterization Bulk density for soil samples (0-10 cm) within each of the three regions, Northeast, BCT, and Southwest, averaged 0.066, 0.067, and 0.073 g cm -3 , respectively (Table 3-1). Bulk density was not calculated for detritus samples. Total C and N were not found to be significantly different ( < 0.05) between the three regions for both the 28

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Table 3-1. Selected physiochemical properties of detritus and soil samples collected from the spatial sampling (9/12/00). Data are mean values (n = 40) with one standard deviation. MBN PMN NH4+ mg N kg-1SoilNortheast522 37531.5 21.7188 99BCT527 23060.5 12.7132 44.7Southwest550 21247 12.7147 64DetritusNortheast1007 731160 77.3565 392BCT958 83180.9 32.1198 210Southwest800 498125 113199 433mg N kg-1 d-10.00329 0.00226DEA mg N20-N kg-1 hr-10.0017 0.001320.0121 0.00759 Total PTotal C Total NpHBulk density mg kg-1g cm-3SoilNortheast847 213467 13.229.8 5.535.84 0.430.066 0.018BCT643 82.2465 6.327.8 2.395.51 0.130.067 0.014Southwest860 109465 7.3424.2 1.896.25 0.620.073 0.011DetritusNortheast921 309419 14.218.6 6.85BCT530 133449 21.411.9 3.49Southwest766 287474 13.813.3 4.12 g kg-1 29

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30 soil and detritus layers. There was no significant difference ( < 0.05) in total P content between detritus and the soil layer (0-10 cm). Due to the mixture of vegetative species in the sampling regions, especially within the Southwest region, vegetative groupings were established in order to simplify the analysis (Table 3-2). Pure stands of Typha sp., Cladium, and Panicum remained labeled as such. Communities having Typha sp. present as well as other species, including Salix and Myrica, were designated as a Typha sp/woody mix. Sampling areas dominated by Cladium but also including Salix, Myrica, etc. were labeled as Cladium/woody mix. Those communities having both Typha sp. and Cladium or mixed species not including Typha, Cladium or Panicum were grouped into the Other category. Microbial Biomass Nitrogen Microbial biomass N averaged 533 + 281 mg N kg -1 and 921 + 687 mg N kg -1 for the soil and detritus layers respectively, combining all three regions (Table 3-1). This decrease in microbial biomass N with depth may be because of the lower availability of C to support microbial communities (Williams and Sparling, 1988; Franzluebbers et al., 1995). For both the soil and detrital layers, MBN was not found to be significantly different ( < 0.05) between the three regions, even when taking into account vegetative communities (Figure 3-1, 3-2). Therefore, increased availability of P within the impacted regions may only have increased heterotrophic activity, not the size of MBN. Although, it has been shown that long-term P loading (i.e., months to years) has brought about an increase in microbial activity as well as an increase in size of the microbial pool (White and Reddy, 2000).

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31 Table 3-2. Vegetative groupings established to simplify the spatial and temporal analysis due to the mixture of vegetative species in the sampling regions, especially within the Southwest region. RegionVegetative GroupingOriginal Vegetative CommunityNortheastTypha sp.Typha sp.CladiumCladiumTypha sp./woody mix Typha sp., Salix Cladium/woody mix Cladium, Salix OthersHyacinth, Polyganum Nymphaea, SloughBCTCladiumCladiumPanicumPanicumSouthwestTypha sp.Typha sp.Typha sp./woody mix Typha sp., Salix, MyricaCladium/woody mix Cladium, Salix, MyricaOthersSalix, Myrica, Royal Fern, Cephalanthus

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32 02004006008001000NortheastBCTSouthwestMBN(mg N kg-1) Soil aaa 02004006008001000NortheastBCTSouthwestMBN(mg N kg-1) Soil aaa 02004006008001000NortheastBCTSouthwestMBN(mg N kg-1) Soil aaa 02004006008001000NortheastBCTSouthwestMBN(mg N kg-1) Soil aaa 040080012001600NortheastBCTSouthwestMBN(mg N kg-1) Detritus aaa 040080012001600NortheastBCTSouthwestMBN(mg N kg-1) Detritus aaa 040080012001600NortheastBCTSouthwestMBN(mg N kg-1) Detritus aaa 040080012001600NortheastBCTSouthwestMBN(mg N kg-1) Detritus aaa Figure 3-1. Microbial biomass N within the soil and detrital layers for all three regions, Northeast, Southwest, and BCT. Bars represent the means ( + 1 SD) of samples (n=40) collected from the respective sampling locations. Contrasting letters above the bars represent differences in significant values ( < 0.05).

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33 020040060080010001200PCTT/WMC/WMOVegetationMBN (mg N kg-1) Soil aaaaaa 020040060080010001200PCTT/WMC/WMOVegetationMBN (mg N kg-1) Soil aaaaaa 020040060080010001200PCTT/WMC/WMOVegetationMBN (mg N kg-1) Soil aaaaaa 020040060080010001200PCTT/WMC/WMOVegetationMBN (mg N kg-1) Soil aaaaaa 0400800120016002000PCTT/WMC/WMOVegetationMBN (mg N kg-1) Detritus aaaaaa 0400800120016002000PCTT/WMC/WMOVegetationMBN (mg N kg-1) Detritus aaaaaa 0400800120016002000PCTT/WMC/WMOVegetationMBN (mg N kg-1) Detritus aaaaaa 0400800120016002000PCTT/WMC/WMOVegetationMBN (mg N kg-1) Detritus aaaaaa Figure 3-2. Microbial biomass N for the soil and detritus layers with respect to vegetative communities, P = BCT Panicum, C = NE, BCT Cladium, T = NE, SW Typha sp., T/WM = NE, SW Typha sp./Woody Mix, C/WM = NE, SW Cladium/Woody Mix, and O = NE, SW Others. Data are mean values (+ 1 SD) from the respective sampling locations (n=40). Contrasting letters above the bars represent differences in significant values ( < 0.05).

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34 Potentially Mineralizable Nitrogen Potentially mineralizable N measures the release rate of NH 4 + from the decomposition of large into small and eventually dissolved organic N compounds. The rate-limiting step(s) for this process involves the microbial enzyme activity associated with the break down of the larger organic N compounds (Bonde et al., 2001). Anaerobic incubation conditions for PMN permit the use of higher temperatures allowing faster N release under shorter incubation times and represent typical flooded wetland soil conditions. Differences, however, may arise between conditions within the lab and the field. Exposure of the soil surface to the atmosphere will increase the release of inorganic N due to contact with O 2 than would be observed under anaerobic conditions. Sampling periods within March, May and possibly June may have had several sites where the soil surface was not covered by water. Greater inorganic N release would be expected because of the larger aerobic N mineralization rates as compared to N mineralization under anaerobic conditions (Patrick, 1982). However, only the top exposed layer of detritus would likely experience aerobic N mineralization because of the high demand of O 2 within organic soils. Potentially mineralizable N averaged 121 + 74 mg N kg -1 d -1 and 46 + 16 mg N kg -1 d -1 for the detritus and soil layers, respectively combining all three regions (Table 3-1). Others have also observed a decrease in PMN with depth in anaerobic (White and Reddy, 2000) and aerobic soils (Franzluebbers et al., 1995; Hossain et al., 1995; Humphrey and Pluth, 1996; Lavermaan et al., 2000). These PMN rates are similar to rates found in impacted regions of the Everglades (WCA-2A), which had rates of 34 mg N kg -1 d -1 and 126 mg N kg -1 d -1 for 0to 10-cm soil depth and detritus, respectively (White and Reddy, 2000). Extractable NH 4 + concentrations decreased with depth as well,

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35 averaging 322 + 411 mg N kg -1 and 156 + 76 mg N kg -1 for all three regions within the detritus and soil layers, respectively (Table 3-1). The decrease of PMN and extractable NH 4 + with depth through the soil profile may be because of the distribution of the MBN. With respect to the detrital layer, PMN rates did not exhibit a trend with distance from the two surface water inflow points (distance = 0) in the impacted regions along the total P gradient, as well as along the flow path of water from the interior of the marsh north towards Blue Cypress Lake within the unimpacted BCT region (Figure 3-3, 3-4). This suggests a decrease in nutrient loading since the discontinuing of surface water inflows into the system (White and Reddy, 2000). In the detrital layer, PMN and extractable NH 4 + concentrations were found to be significantly higher ( < 0.05) in the Northeast region than the BCT and the Southwest regions (Figure 3-5). Within the soil, PMN rates were significantly different ( < 0.05) between all three regions, with the BCT region having the highest activity. However, extractable NH 4 + concentrations within the soil were significantly higher ( < 0.05) for the Northeast and Southwest regions than the BCT region (Figure 3-6). The distribution of PMN rates and extractable NH 4 + concentrations between regions should be related to MBN, as N mineralization is mediated by soil microbial activity; however, MBN was not significantly different between the three regions. Total P concentrations found within the detritus layer followed the same spatial pattern as PMN and extractable NH 4 + ( < 0.05). However, contrary to PMN rates within the soil, total P was found to be higher ( < 0.05) within both the Southwest and Northeast regions than the unimpacted BCT region (Figure 3-7). To clarify, the figures that illustrate N processes or measurements associated with vegetation type have combined all similar vegetative communities regardless of region.

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36 4.04.55.05.56.00200400600800100012001400Distance (m)ln(PMN) (mg N kg-1d-1) Northeast 4.04.55.05.56.00200400600800100012001400Distance (m)ln(PMN) (mg N kg-1d-1) Northeast 4.04.55.05.56.00200400600800100012001400Distance (m)ln(PMN) (mg N kg-1d-1) Northeast 4.04.55.05.56.00200400600800100012001400Distance (m)ln(PMN) (mg N kg-1d-1) Northeast 4.04.55.05.50200400600800100012001400Distance (m)ln(PMN) (mg N kg-1d-1) Southwest 4.04.55.05.50200400600800100012001400Distance (m)ln(PMN) (mg N kg-1d-1) Southwest 4.04.55.05.50200400600800100012001400Distance (m)ln(PMN) (mg N kg-1d-1) Southwest 4.04.55.05.50200400600800100012001400Distance (m)ln(PMN) (mg N kg-1d-1) Southwest Figure 3-3. Potentially mineralizable N rates measured along the sampling transect from the inflow points (distance = 0) in the Southwest and Northeast regions for the soil layer. Points represent the natural log values of the samples (n=40) collected from the sampling regions.

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37 0246020040060080010001200Distance(m)ln(PMN) (mg N kg-1d-1) BCT 0246020040060080010001200Distance(m)ln(PMN) (mg N kg-1d-1) BCT 0246020040060080010001200Distance(m)ln(PMN) (mg N kg-1d-1) BCT 0246020040060080010001200Distance(m)ln(PMN) (mg N kg-1d-1) BCT Figure 3-4. Potentially mineralizable N rates measured along the sampling transect from the direction of water flow (distance = 0) in the BCT region for the detrital layer. Points represent the natural log values of the samples (n=21) collected from the sampling regions.

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38 04080120160200240NortheastBCTSouthwestPMN (mg N kg-1d-1) Detritus bba 04080120160200240NortheastBCTSouthwestPMN (mg N kg-1d-1) Detritus Detritus bba 04080120160200240NortheastBCTSouthwestPMN (mg N kg-1d-1) Detritus Detritus bba 04080120160200240NortheastBCTSouthwestPMN (mg N kg-1d-1) Detritus Detritus bba Detritus Detritus bba 0100200300400500NortheastBCTSouthwestExt. NH4+ (mg N kg-1) Detritus bba 0100200300400500NortheastBCTSouthwestExt. NH4+ (mg N kg-1) Detritus bba 0100200300400500NortheastBCTSouthwestExt. NH4+ (mg N kg-1) Detritus bba 0100200300400500NortheastBCTSouthwestExt. NH4+ (mg N kg-1) Detritus bba Figure 3-5. Potentially mineralizable N and extractable NH 4 + concentrations within the detrital layer for all three regions, Northeast, Southwest, and BCT. Bars represent the means ( + 1 SD) of samples (n=40) collected from the respective sampling locations. Contrasting letters above the bars represent differences in significant values ( < 0.05).

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39 020406080NortheastBCTSouthwestPMN (mg N kg-1d-1) Soil cba 020406080NortheastBCTSouthwestPMN (mg N kg-1d-1) Soil Soil cba 020406080NortheastBCTSouthwestPMN (mg N kg-1d-1) Soil Soil cba 020406080NortheastBCTSouthwestPMN (mg N kg-1d-1) Soil Soil cba Soil Soil cba 01000200030004000NortheastBCTSouthwestExt. NH4+(mg N kg-1) Soil baa 01000200030004000NortheastBCTSouthwestExt. NH4+(mg N kg-1) Soil Soil baa 01000200030004000NortheastBCTSouthwestExt. NH4+(mg N kg-1) Soil Soil baa 01000200030004000NortheastBCTSouthwestExt. NH4+(mg N kg-1) Soil Soil baa Soil Soil baa Figure 3-6. Potentially mineralizable N and extractable NH 4 + concentrations within the soil layer for all three regions, Northeast, Southwest, and BCT. Bars represent the means ( + 1 SD) of samples (n=40) collected from the respective sampling locations. Contrasting letters above the bars represent differences in significant values ( < 0.05).

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40 030060090012001500NortheastBCTSouthwestTP (mg kg-1) Detritus bba 030060090012001500NortheastBCTSouthwestTP (mg kg-1) Detritus Detritus bba 030060090012001500NortheastBCTSouthwestTP (mg kg-1) Detritus Detritus bba 030060090012001500NortheastBCTSouthwestTP (mg kg-1) Detritus Detritus bba Detritus Detritus bba 020040060080010001200NortheastBCTSouthwestTP (mg kg-1) Soil aba 020040060080010001200NortheastBCTSouthwestTP (mg kg-1) Soil Soil aba 020040060080010001200NortheastBCTSouthwestTP (mg kg-1) Soil Soil aba 020040060080010001200NortheastBCTSouthwestTP (mg kg-1) Soil Soil aba Soil Soil aba Figure 3-7. Total P concentrations within the detrital and soil layers for all three regions, Northeast, Southwest, and BCT. Bars represent the means ( + 1 SD) of samples (n=40) collected from the respective sampling locations. Contrasting letters above the bars represent differences in significant values ( < 0.05).

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41 Therefore, the descriptive spatial analysis for vegetative communities associated with each region includes the region name before the species type to identify the location and differentiate between vegetative communities. Within the Northeast, Typha sp. communities had higher PMN rates and extractable NH 4 + concentrations ( < 0.05) for the detrital layer than the Southwest (Cladium/Woody Mix) and BCT (Panicum and Cladium) communities (Figure 3-8). For the soil, BCT (Panicum and Cladium) and Southwest (Typha sp.) communities had greater PMN rates ( < 0.05) than other vegetative communities, especially Typha sp. communities within the Northeast (Figure 3-9). Extractable NH 4 + concentrations were not significantly different ( < 0.05) between vegetative communities within the soil. The PMN activity associated with vegetation type therefore coincided with the distribution of PMN between impacted and unimpacted regions. Within the impacted regions, detrital PMN activity was the highest within the Northeast region, corresponding to the high activity found in Typha sp. communities in the Northeast region. Changes in C/N values for detritus between regions due to differences in vegetative communities may also have played a role in establishing PMN rates (Figure 3-10) (Chen and Stark, 2000; Nadelhoffer et al., 1991; Stelzer and Bowman, 1998). Higher PMN activity was found to be associated with lower C/N values occurring primarily in the Northeast region. Denitrification Enzyme Activity Within the soil layer, DEA averaged 0.0057 + 0.0037 mg N 2 0-N kg dry soil -1 h -1 combining all three regions (Table 3-1). These DEA values are significantly lower than rates found in impacted regions of the Everglades (WCA-2A), which had rates of 2.69 mg N 2 0-N kg dry soil -1 h -1 for the surface soil (0-10 cm) (White and Reddy, 1999). In the

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42 050100150200250PCTT/WMC/WMOVegetationPMN(mg N kg-1d-1) bbab 050100150200250PCTT/WMC/WMOVegetationPMN(mg N kg-1d-1) bbab 050100150200250PCTT/WMC/WMOVegetationPMN(mg N kg-1d-1) bbab 050100150200250PCTT/WMC/WMOVegetationPMN(mg N kg-1d-1) 050100150200250PCTT/WMC/WMOVegetationPMN(mg N kg-1d-1) bbab 050100150200250PCTT/WMC/WMOVegetationPMN(mg N kg-1d-1) bbab 050100150200250PCTT/WMC/WMOVegetationPMN(mg N kg-1d-1) bbab 050100150200250PCTT/WMC/WMOVegetationPMN(mg N kg-1d-1) 0200400600800PCTT/WMC/WMOVegetationExt. NH4+(mg N kg-1) abbb 0200400600800PCTT/WMC/WMOVegetationExt. NH4+(mg N kg-1) abbb 0200400600800PCTT/WMC/WMOVegetationExt. NH4+(mg N kg-1) abbb 0200400600800PCTT/WMC/WMOVegetationExt. NH4+(mg N kg-1) 0200400600800PCTT/WMC/WMOVegetationExt. NH4+(mg N kg-1) abbb 0200400600800PCTT/WMC/WMOVegetationExt. NH4+(mg N kg-1) abbb 0200400600800PCTT/WMC/WMOVegetationExt. NH4+(mg N kg-1) abbb 0200400600800PCTT/WMC/WMOVegetationExt. NH4+(mg N kg-1) Figure 3-8. Potentially mineralizable N and extractable NH 4 + concentrations for detritus with respect to vegetative communities, P = BCT Panicum, C = NE, BCT Cladium, T = NE, SW Typha sp., T/WM = NE, SW Typha sp./Woody Mix, C/WM = NE, SW Cladium/Woody Mix, and O = NE, SW Others. Data are mean values ( + 1 SD) from the respective sampling locations (n=40).

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43 020406080100120PCTT/WMC/WMOVegetationPMN(mg N kg-1d-1) aabbbb 020406080100120PCTT/WMC/WMOVegetationPMN(mg N kg-1d-1) aabbbb 020406080100120PCTT/WMC/WMOVegetationPMN(mg N kg-1d-1) aabbbb 020406080100120PCTT/WMC/WMOVegetationPMN(mg N kg-1d-1) aabbbb 020406080100120PCTT/WMC/WMOVegetationPMN(mg N kg-1d-1) aabbbb 020406080100120PCTT/WMC/WMOVegetationPMN(mg N kg-1d-1) aabbbb 020406080100120PCTT/WMC/WMOVegetationPMN(mg N kg-1d-1) aabbbb 020406080100120PCTT/WMC/WMOVegetationPMN(mg N kg-1d-1) aabbbb Figure 3-9. Potentially mineralizable N rates for the soil layer with respect to vegetative communities, P = BCT Panicum, C = NE, BCT Cladium, T = NE, SW Typha sp., T/WM = NE, SW Typha sp./Woody Mix, C/WM = NE, SW Cladium/Woody Mix, and O = NE, SW Others. Data are mean values ( + 1 SD) from the respective sampling locations (n=40). Contrasting letters above the bars represent differences in significant values ( < 0.05). Figure 3-10. Potentially mineralizable N associated with C/N concentrations for impacted and unimpacted regions within the detritus layer. Ellipse size for illustration purposes only (represents the 0.8 confidence limits).

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44 soil layer, DEA was found to be significantly higher ( < 0.05) within the unimpacted BCT region than the Southwest and Northeast regions (Figure 3-11). Greater PMN rates also occurring in the BCT region may influence DEA within the soil because of the availability of extractable NH 4 + for nitrification. With regards to the soil, no simple trend with distance was revealed with respect to DEA rates from the two surface water inflow points in the impacted sites. For the Northeast and Southwest regions, DEA rates were not shown to decrease with distance from either inflow point (distance = 0) along the total P gradient (Figure 3-12). The total P gradient was found to extend into the marsh decreasing in concentrations with distance. This high spatial variability of DEA was also apparent in the BCT or unimpacted region along the flow path of water from the interior of the marsh north towards Blue Cypress Lake (Figure 3-13). High spatial variability associated with DEA has also been noted by other studies (Christensen et al., 1990a; Duncan and Groffman, 1994; Forlorunso and Rolston, 1984; Myrold, 1988; Parkin, 1987; Reddy and D’Angelo, 1994). This demonstrates that NO 3 concentrations, associated with nutrient loading, are not present at high levels at the impacted regions, as inflows have recently been curtailed. Denitrification rates for the BCM are likely related to nitrification processes in the water column driving NO 3 to diffuse into the anaerobic sediment for denitrifiers. Concerning the descriptive spatial analysis for vegetative communities associated with each region for the soil, BCT (Panicum and Cladium) vegetation had higher DEA rates ( < 0.05) than other vegetative communities within the Northeast and Southwest regions (Figure 3-14). Denitrification enzyme activity associated with vegetation therefore similarly follows the distribution of DEA between impacted and unimpacted

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45 00.0050.010.0150.020.025NortheastBCTSouthwestDEA(mg N20-N kg-1h-1) Soil bab 00.0050.010.0150.020.025NortheastBCTSouthwestDEA(mg N20-N kg-1h-1) Soil bab 00.0050.010.0150.020.025NortheastBCTSouthwestDEA(mg N20-N kg-1h-1) Soil bab 00.0050.010.0150.020.025NortheastBCTSouthwestDEA(mg N20-N kg-1h-1) Soil bab Figure 3-11. Denitrification enzyme activity within the soil layer for all three regions, Northeast, Southwest, and BCT. Bars represent the means ( + 1 SD) of samples (n=40) collected from the respective sampling locations. Contrasting letters above the bars represent differences in significant values ( < 0.05). regions. Higher DEA activity was found within the BCT region corresponding to the high DEA activity for BCT Panicum and Cladium communities. Changes in soil quality, including C/N values, between regions due to shifts in vegetation may have partially influenced the spatial variability of DEA. Wetland soils have the capacity to reduce high NO 3 concentrations if available in the system (Flite et al., 2001; Howard-Williams and Downes, 1993; Jacobson and Alexander, 1980; Luo et al., 1998; Reddy et al., 1980b). Often NO 3 is the limiting factor for denitrification in wetlands, therefore controlling microbial biomass size and the activity of the denitrifying microorganisms. To explore this denitrification capacity, different loading concentrations of NO 3 were added to duplicate soil samples to demonstrate possible changes in DEA rates (Figure 3-15). Additions of NO 3 over an extended incubation period (i.e., 30 days) can allow for the synthesis of new enzymes

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46 -8.0-7.0-6.0-5.0-4.00200400600800100012001400 Southwest ln(DEA) (mg N2O-N kg-1d-1) Distance (m) -8.0-7.0-6.0-5.0-4.00200400600800100012001400 Southwest Southwest ln(DEA) (mg N2O-N kg-1d-1) Distance (m) -8.0-7.0-6.0-5.0-4.00200400600800100012001400 Southwest Southwest ln(DEA) (mg N2O-N kg-1d-1) Distance (m) -8.0-7.0-6.0-5.0-4.00200400600800100012001400 Southwest Southwest ln(DEA) (mg N2O-N kg-1d-1) Distance (m) Southwest Southwest ln(DEA) (mg N2O-N kg-1d-1) Distance (m) -8.0-7.0-6.0-5.00200400600800100012001400Distance (m) Northeast ln(DEA)(mg N2O-N kg-1d-1) -8.0-7.0-6.0-5.00200400600800100012001400Distance (m) Northeast Northeast ln(DEA)(mg N2O-N kg-1d-1) -8.0-7.0-6.0-5.00200400600800100012001400Distance (m) Northeast Northeast ln(DEA)(mg N2O-N kg-1d-1) -8.0-7.0-6.0-5.00200400600800100012001400Distance (m) Northeast Northeast ln(DEA)(mg N2O-N kg-1d-1) Northeast Northeast ln(DEA)(mg N2O-N kg-1d-1) Figure 3-12. Denitrification enzyme activity rates measured along the sampling transect from the inflow points (distance = 0) in the Southwest and Northeast regions for the soil layer. Points represent the natural log values of the samples (n=18,13) collected from the sampling regions.

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47 -7.0-6.0-5.0-4.0-3.002004006008001000Distance (m) BCT ln(DEA) (mg N2O-N kg-1d-1) -7.0-6.0-5.0-4.0-3.002004006008001000Distance (m) ln(DEA) (mg N2O-N kg-1d-1) -7.0-6.0-5.0-4.0-3.002004006008001000Distance (m) BCT ln(DEA) (mg N2O-N kg-1d-1) -7.0-6.0-5.0-4.0-3.002004006008001000Distance (m) ln(DEA) (mg N2O-N kg-1d-1) -7.0-6.0-5.0-4.0-3.002004006008001000Distance (m) BCT ln(DEA) (mg N2O-N kg-1d-1) -7.0-6.0-5.0-4.0-3.002004006008001000Distance (m) ln(DEA) (mg N2O-N kg-1d-1) -7.0-6.0-5.0-4.0-3.002004006008001000Distance (m) BCT ln(DEA) (mg N2O-N kg-1d-1) -7.0-6.0-5.0-4.0-3.002004006008001000Distance (m) ln(DEA) (mg N2O-N kg-1d-1) Figure 3-13. Denitrification enzyme activity rates measured along the sampling transect from the direction of water flow (distance = 0) in the BCT region for the soil layer. Points represent the actual values of the samples (n=16) collected from the sampling region. 00.0050.010.0150.020.025PCTT/WMC/WMOVegetationDEA (mg N2O-N kg-1h-1)bbbbaa 00.0050.010.0150.020.025PCTT/WMC/WMOVegetationDEA (mg N2O-N kg-1h-1)bbbbaa 00.0050.010.0150.020.025PCTT/WMC/WMOVegetationDEA (mg N2O-N kg-1h-1)bbbbaa 00.0050.010.0150.020.025PCTT/WMC/WMOVegetationDEA (mg N2O-N kg-1h-1)bbbbaa Figure 3-14. Denitrification enzyme activity for the soil with respect to vegetative communities, P = BCT Panicum, C = NE, BCT Cladium, T = NE, SW Typha sp., T/WM = NE, SW Typha sp./Woody Mix, C/WM = NE, SW Cladium/Woody Mix, and O = NE, SW Others. Data are mean values ( + 1 SD) from the respective sampling locations (n=40). Contrasting letters above the bars represent differences in significant values ( < 0.05).

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48 stimulated by the enhancement of microbial activity within the system. This boost in enzymes can lead to increased denitrification activity within the soil (Luo et al., 1996; Paavolainen et al., 2000; White and Reddy, 1999). An increase in DEA may be a valuable indicator of recent NO 3 loading and for determining the extent of the impact of nutrient additions (White and Reddy, 1999). For these soils, NO 3 may not be a limiting factor because of historic nutrient-impacts to the system as compared to the availability of soluble-C (Luo et al., 1996, 1998). This may explain why soils with additions of lower NO 3 concentration (i.e., B and C) had higher DEA rates than soils with greater NO 3 concentrations (D). However, considerable amounts of dissolved organic C were found in the pore water for these samples. Although redox was not measured for these soil samples, conditions may have favored the dissimilation of NO 3 to NH 4 + . This pathway is favored by low redox and high organic C content, often found in wetland habitats (Howard-Williams and Downes, 1993). High concentrations of NO 3 have also been found to inhibit denitrification despite the availability of soluble-C (Luo et al., 1996; Sherr and Payne, 1981). Possible diversity within the microbial community in the Northeast region may be another factor responsible for the range of denitrification rates, despite additions of NO 3 in the soil slurries. Overall, the denitrification capacity was visibly greater for those soil samples receiving NO 3 additions, shown by higher DEA activity, than the samples representing the DEA activity within the marsh (i.e., A). Therefore, revealing low concentrations of NO 3 present in the marsh due to the discontinuing of surface water inflows within the impacted regions.

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49 0.0000.0010.0020.0030.00400.511.52Time(h) 450a 450b 450c 450d DEA (mg N2O-N kg-1d-1) 0.0000.0010.0020.0030.00400.511.52Time(h) A B C D DEA (mg N2O-N kg-1h-1) Northeast 0.0000.0010.0020.0030.00400.511.52Time(h) 450a 450b 450c 450d DEA (mg N2O-N kg-1d-1) 0.0000.0010.0020.0030.00400.511.52Time(h) A B C D DEA (mg N2O-N kg-1h-1) Northeast 0.0000.0010.0020.0030.00400.511.52Time(h) 450a 450b 450c 450d DEA (mg N2O-N kg-1d-1) 0.0000.0010.0020.0030.00400.511.52Time(h) A B C D DEA (mg N2O-N kg-1h-1) Northeast 0.0000.0010.0020.0030.00400.511.52Time(h) 450a 450b 450c 450d DEA (mg N2O-N kg-1d-1) 0.0000.0010.0020.0030.00400.511.52Time(h) A B C D DEA (mg N2O-N kg-1h-1) Northeast 0.0000.0020.0040.0060.0080.01000.511.522.5Time (h) A B C D DEA (mg N2O-N kg-1h-1) BCT 0.0000.0020.0040.0060.0080.01000.511.522.5Time (h) A B C D DEA (mg N2O-N kg-1h-1) BCT 0.0000.0020.0040.0060.0080.01000.511.522.5Time (h) A B C D DEA (mg N2O-N kg-1h-1) BCT 0.0000.0020.0040.0060.0080.01000.511.522.5Time (h) A B C D DEA (mg N2O-N kg-1h-1) BCT Figure 3-15. Denitrification enzyme activity rates associated with different loading concentrations of NO 3 where A = 0 mg KNO 3 /L, B = 50 mg KNO 3 /L, C = 500 mg KNO 3 /L, and D = 1250 mg KNO 3 /L. Points represent the means of samples (n=3) from one soil sampling location within the Northeast and BCT regions.

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50 Comparisons of Nitrogen Processes A significant correlation (p < 0.05) was found for MBN vs. total P for the detrital and soil layers (r = 0.33; 0.19) (Table 3-3), suggesting that historic P-loading might have had an effect on microbial biomass quantity and activity (White and Reddy, 2000). The PMN rates, when combining all three regions, were significantly correlated (p < 0.05) with MBN (r = 0.40), DEA (r = 0.68), total P (r = -0.30) and total C (r = 0.22) in the soil layer. For detritus, MBN (r = 0.35), extractable NH 4 + (r = 0.47), total P (r = 0.63), and total N (r = 0.64) were significantly correlated (p < 0.05) with PMN (Table 3-3). Extractable NH 4 + concentrations for all three regions combined were significantly correlated (p < 0.05) with MBN (r = 0.34), total N (r = 0.20), and total P (r = 0.20) in the soil layer. Within the detritus layer, PMN (r = 0.47), total P (r = 0.52), and total N (r = 0.65) were significantly correlated (p < 0.05) with extractable NH 4 + (Table 3-3). Under low O 2 conditions, typical of wetland soils rich in organic matter, the conversion of NH 4 + to NO 3 is severely limited. Therefore, the end product of PMN, extractable NH 4 + , can be used as an excellent indicator of N mineralization rates in flooded soils (Ross et al., 1995; White and Reddy, 2000; Williams and Sparling, 1988). Total P was significantly correlated (p < 0.05) with PMN rates for the detritus layer revealing an increase in inorganic N release with an increase in total P (White and Reddy, 2000). A significant correlation (p < 0.05) was found for extractable NH 4 + concentrations with total P within the soil and detritus layers respectively. This implies a relationship between inorganic N availability and total P suggesting an increase in microbial decomposition with increased soil total P, which has also been noted by others (DeBusk and Reddy, 1998; White and Reddy, 2000). A significant correlation (p < 0.05)

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51 Table 3-3. Spearman’s Rho correlation coefficients for parameters from detritus and soil samples from the spatial sampling (n=120). Values in bold type are significant at p < 0.05. was found for DEA vs. PMN (r=0.74) and DEA vs. total P (r = -0.47) within the soil (Table 3-3). Lower total P concentrations found within the unimpacted region therefore coincides with high DEA for the BCT sampling locations. Vegetation, therefore, may be more of a controlling factor of DEA rates than the direct influence of P-loading into the marsh. When comparing N processes between the soil and detrital layers, it is important to note that the activity rates and nutrient concentrations are not measurements based on area distributions. However, these measurements do provide a way of assessing the N processes associated with nutrient and vegetative components between the three regions. Converting concentrations into mass equivalents involved using the moisture content for the sediment to determine the amount of dry soil or detritus taken from the field. For the soil, conversion factors for each of the parameters were calculated by the dry weight SoilMBNPMNDEAExt. NH4 +Total CTotal N PMN 0.409 DEA0.189 0.685 Ext. NH4 +0.337 0.104 0.084 Total C -0.220-0.224 -0.198-0.052 Total N-0.0330.131-0.087 0.203 0.115 Total P 0.186-0.298-0.4700.196 0.072-0.076 DetritusMBNPMN Ext. NH4 +Total CTotal N PMN 0.354 Ext. NH4 +0.010 0.470 Total C-0.1410.0590.099 Total N 0.3590.6400.651 0.187 Total P 0.3390.6310.5180.2430.891

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52 being divided by the surface area of the soil core (0.00785 m 2 ). Conversion factors for all parameters with respect to detritus were found by dividing the dry weight of sample by the surface area sampled (0.0625 m 2 ). In finding the percentage of microbial biomass and N processes within the soil and detritus layers associated with each region, the detritus or soil mean was divided by the sum of detritus and soil associated with each parameter by region. Taking into account areal rate comparisons, the Northeast region had a greater quantity of detritus than BCT and the Southwest regions. There was, as well, a slight change in MBN and total C within the detritus layer. When quantified based on mass, the Northeast region had more MBN and total C than the BCT and Southwest regions (Table 3-4); however, when comparing concentrations, the three regions were not significantly different regarding MBN and total C ( < 0.05). Also, PMN rates were considerably higher on a mass scale for detritus within the Northeast sampling locations than the other two regions. With regards to vegetation, the Northeast Typha sp. detritus had more PMN, MBN, and extractable NH 4 + when measured by mass than other communities. For the soil layer, on an areal or mass basis, BCT Panicum was shown to have higher PMN rates as well as increased MBN and extractable NH 4 + concentrations. Changes with total C occurred within the soil layer as well. The Southwest region had a higher mass of total C than the BCT and Northwest regions. Previously when comparing concentrations of total C within the soil, the three regions were not significantly different ( < 0.05). The Northeast region was found to have higher detrital percentages associated with N processes and microbial biomass than the other regions (Table 3-5). However, the soil was found to have the highest percentage of microbial activity and N processes on an

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53 areal basis as compared with detritus for all three regions. This may be due to the larger area available for soil N processes to take place as compared to the small quantity of detrital material within the marsh. On the other hand, when using calculations based on concentration values, the detritus layer was associated with higher microbial activity and N processes than the soil. Spatial Sampling Discussion Overall, nutrient concentrations were not observed to be at high levels within the impacted regions as evident by the lack of high PMN and DEA activity extending into the marsh from the two surface water inflow sites. Distinct differences were apparent between the three regions due to nutrient loading (Table 3-5). The Southwest region had lower P concentrations within the detrital layer as well as less PMN activity and NH 4 + concentrations than the Northeast region. This likely was the result of water inflows being discontinued in the Southwest region 10 years before being terminated in the Northeast region. The BCT region had the lowest total P concentrations (Table 3-6) and PMN activity for detritus because of its location within the interior of the marsh. The Southwest and BCT regions have similar N activity rates for detritus, suggesting restoration within the Southwest region over the last 20 years. As for the Northeast region, turnover rates within the system still remained to be functioning at a higher rate than the BCT and Southwest regions. Distribution of PMN activity and NH 4 + concentrations for the detrital layer followed the same spatial distribution of total P concentrations within the marsh, with the highest concentrations in the Northeast region. This implies a relationship between

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54Table 3-4. Select parameters collected during the spatial sampling represented on an areal scale basis for the soil and detrit us layers for all three regions (n = 40). SoilMBNPMN Ext. NH4 + DEATotal PTotal CTotal N mg N m-2 mg N20-N m-2mg N m-2Northeast3234 2885178 11 81237 8560.0042 0.00755350 19342713 1304192 62 BCT3426 1275397 102836 2680.0316 0.04654057 8482811 748173 28 Southwest3820 15403 19 1091016 4420.0 119 0.01735979 796 3269 495169 19.3 mg N m-2g N m-2 DetritusMBNPMN Ext. NH4 + Total PTotal CTotal N mg N m-2mg N m-2Northeast434 57685 101218 274607 509205 19112 10 BCT237 44522.2 26.360.7 128191 175128 1434.3 4.3 Southwest231 21832.2 26.733.1 59278 15771 955 3.2 mg N m-2g N m-2

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55 Table 3-5. Select parameters collected during the spatial sampling (2000) represented as percentages of each parameter within both detritus and soil associated by region (n = 40). The area of detritus and soil were calculated on an mg m -2 basis for MBN, PMN, extractable NH 4 + , and total P. Total C and N were calculated on a g m -2 basis. NortheastDetritus0-10cmMBN1288PMN3268Ext. NH4+1585TP1090TC793TN694BCTDetritus0-10cmMBN694PMN595Ext. NH4+793TP496TC496TN298SouthwestDetritus0-10cmMBN991PMN595Ext. NH4+397TP892TC298TN397%%%

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56 inorganic N availability and total P. The differences in vegetative communities between the regions may have influenced the distribution of DEA within the soil layer. Higher DEA was found within the unimpacted BCT region; therefore implying a stronger relationship between DEA and other environmental properties instead of total P. Table 3-6. Average N/P values within the soil and detritus layers for all three regions, Northeast, Southwest, and BCT. Data are mean values ( + 1 SD) from the respective sampling locations (n=40). NortheastBCTSouthwestDetritus17.6 7.1522.6 3.6116.5 6.34Soil38.5 20.9843.7 5.5928.4 2.64 Temporal Responses of Select Nitrogen Indicators Related to Phosphorus-Loading Impacts Sampling Temporal results from the sampling dates between March 2001 and January 2002 are important in monitoring the effects of seasonal trends in precipitation and temperature. Impacts due to fire in the Southwest and BCT sampling areas occurred around January 31, 2001 (Figure 3-16). The small fire, which occurred in the northeast corner of the marsh, consisted of approximately 178 acres on January 7, 2001. The larger fire extending from the north to the southwest corner of the marsh, including the BCT and Southwest region sampling sites, burned about 6800 acres. Hydrology fluctuations due to rainfall existed throughout the marsh including a drought period, which extended from November 2000 until the beginning of May 2001 (Figure 3-17). Anaerobic conditions (i.e. Eh < 200) were not established until July 2001 for the Northeast and Southwest regions and not until September 2001 for the BCT region (Table 3-7). The

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57 delay in establishing anaerobic conditions within the BCT region may have been due to the hummocky terrain creating topographically higher areas less likely to become flooded. Hydrology data for the marsh as well as Blue Cypress Lake also illustrates the seasonal fluctuations in water level within the system (Figure 3-18). Soil temperature at the 2-3 cm depth ranged from 21C in March to 26C in September and 16C in January across the entire marsh (Table 3-8). Sampling locations were set up within areas consisting of pure stands of vegetation, when possible. However due to the mixture of vegetative species, especially within the Southwest region, the same vegetative groupings as in the spatial analysis were used during the temporal study in order to simplify the analysis. The objective of the temporal study was to examine the seasonal differences in MBN, PMN, Arg-N and DEA between (1) the three regions and (2) the vegetative communities associated with each region. Microbial Biomass Nitrogen Within both the soil and detritus layers, MBN was affected by changes in seasonality ( < 0.05). A significant difference ( < 0.05) in seasonal patterns of MBN between each region was also observed for both the soil and detritus layers (Figure 3-19, 3-20). This significant difference between the three regions for the soil and detritus layers may have been due to the differences in vegetation and/or type of microbial communities present. Different rates of nutrient release and/or uptake may exist between the various vegetative communities over time. This can create different fluxes in nutrient levels available for microbial functions. Furthermore, this result may possibly support previous studies where variations in nutrient release from biomass have been attributed to

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58 Figure 3-16. Map of the burned area within the BCM before the temporal sampling period (March 2001).

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59 Figure 3-17. Average rainfall within the BCM beginning with the spatial sampling (Sept. 2000) and continuing throughout the temporal sampling months (2001). Data are mean values (+ 1 SD) from the respective sampling months (n=30). Table 3-7. Average redox potentials within the soil (5 cm) during the temporal sampling (2001) period combining all three regions, Northeast, Southwest, and BCT. Data are mean values (n=18) with one standard deviation. 0 2 4 6 8 10 12 14Sept N ov Jan M a r M a y July Sept Nov JanAverage Rainfall(in) Drought 0 2 4 6 8 10 12 14Sept N ov Jan M a r M a y July Sept Nov JanAverage Rainfall(in) Drought Drought 0 2 4 6 8 10 12 14Sept N ov Jan M a r M a y July Sept Nov JanAverage Rainfall(in) Drought Drought 0 2 4 6 8 10 12 14Sept N ov Jan M a r M a y July Sept Nov JanAverage Rainfall(in) Drought Drought Drought Drought Month Mar June July Sept Dec Jan Redox (mV) 580 82 213 314 -53 144 Hydrologic Conditions -75 92 -48 -88 599 79Dry Dry Flooded Flooded Flooded Flooded

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60 Figure 3-18. Water level elevations for the BCM and Blue Cypress Lake during the temporal study. Image taken from http://www.saj.usace.army.mil/h2o/plots/BlCyLK.gif . Table 3-8. Average soil temperatures within the soil (2-3 cm) combining all three regions, Northeast, Southwest, and BCT during the temporal study (2001). Data are mean values (n=90) with one standard deviation. MonthSoil Temperature March 21.2 1.45 April 22.4 1.86 May 24.1 1.9 June 25.8 0.71 July 25.8 0.74 August 28 1.63 September 26.5 1.51 October 23.4 2.07 November 19.7 0.85 December 18 2.79 January 15.7 3.53

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61 changes in temperature (Sarathchandra et al., 1988; Verburg et al., 1999; Zak et al., 1999). The gradual decrease in MBN from June to January may be explained by the reduction in energy captured by the microorganisms using alternate electron acceptors as the soils became more reduced due to inundation (Table 3-7). As the microbial biomass activity decreases, the amount of enzyme activity may decrease leading to a reduction in organic N mineralization (McLatchey and Reddy, 1998). Microbial biomass N was significantly higher ( < 0.05) in the Southwest and BCT regions than the Northeast region for the soil and detritus layers (Figure 3-21). Concerning the descriptive temporal analysis of vegetative communities associated with each region, BCT (Panicum) vegetation had higher MBN within the detritus layer than the Northeast (Cladium and Typha sp.) and BCT (Cladium) communities. For the soil, higher MBN was associated with BCT (Panicum) vegetation than the Northeast (Cladium and Typha sp.) communities (Figure 3-22). With respect to the soil layer, MBN was the higher within the BCT than Northeast region, corresponding to the high MBN found regarding Panicum communities in the BCT region. Significantly lower MBN was present for detritus associated with Cladium communities from both the BCT and Northeast regions. The low nutrient status of Cladium may limit the microbial community due to the forms of available C and the small quantity of detritus produced (Davis, 1991). The quantity of microbial biomass may be influenced by the forms of C available due to the type of the substrate (Anderson and Domsch, 1985; Schnurer et al., 1985).

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62 0200400600MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) Northeast Temp MBN (mg N kg-1) 0200400600MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) Northeast Temp Northeast Temp MBN (mg N kg-1) 0200400600MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) Northeast Temp Northeast Temp MBN (mg N kg-1) 0200400600MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) Northeast Temp Northeast Temp MBN (mg N kg-1) Northeast Temp Northeast Temp MBN (mg N kg-1) 0200400600800MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Southwest Temp MBN (mg N kg-1) 0200400600800MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Southwest Temp Southwest Temp MBN (mg N kg-1) 0200400600800MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Southwest Temp Southwest Temp MBN (mg N kg-1) 0200400600800MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Southwest Temp Southwest Temp MBN (mg N kg-1) Southwest Temp Southwest Temp MBN (mg N kg-1) 0200400600800MarchJuneJulySeptDecJanTime (Month)0102030Temperature(*C) BCT Temp MBN (mg N kg-1) 0200400600800MarchJuneJulySeptDecJanTime (Month)0102030Temperature(*C) BCT Temp MBN (mg N kg-1) 0200400600800MarchJuneJulySeptDecJanTime (Month)0102030Temperature(*C) BCT Temp MBN (mg N kg-1) 0200400600800MarchJuneJulySeptDecJanTime (Month)0102030Temperature(*C) BCT Temp MBN (mg N kg-1) Figure 3-19. Seasonal patterns of MBN observed with respect to the Northeast, Southwest, and BCT regions for the soil layer (2001). Temperature is the average taken at 2-3 cm soil depth. Data are mean values ( + 1 SD) from the respective sampling sites (n=18). Three regions were significantly different ( < 0.05) from one another over time by Pillai’s Trace Criterion statistical analysis.

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63 030060090012001500MarchJuneJulySeptDecJanTime (Month)0102030Temperature(*C) Northeast Temp MBN (mg N kg-1) 030060090012001500MarchJuneJulySeptDecJanTime (Month)0102030Temperature(*C) Northeast Temp MBN (mg N kg-1) 030060090012001500MarchJuneJulySeptDecJanTime (Month)0102030Temperature(*C) Northeast Temp MBN (mg N kg-1) 030060090012001500MarchJuneJulySeptDecJanTime (Month)0102030Temperature(*C) Northeast Temp MBN (mg N kg-1) 030060090012001500MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Southwest Temp MBN (mg N kg-1) 030060090012001500MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Southwest Temp MBN (mg N kg-1) 030060090012001500MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Southwest Temp MBN (mg N kg-1) 030060090012001500MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Southwest Temp MBN (mg N kg-1) 030060090012001500MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) BCT Temp MBN (mg N kg-1) 030060090012001500MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) BCT Temp MBN (mg N kg-1) 030060090012001500MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) BCT Temp MBN (mg N kg-1) 030060090012001500MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) BCT Temp MBN (mg N kg-1) Figure 3-20. Seasonal patterns of MBN observed with respect to the Northeast, Southwest, and BCT regions for the detritus layer (2001). Temperature is the average taken at 2-3 cm soil depth. Data are mean values ( + 1 SD) from the respective sampling sites (n=18). Three regions were significantly different ( < 0.05) from one another over time by Pillai’s Trace Criterion statistical analysis.

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64 Potentially Mineralizable Nitrogen The PMN rate was significantly higher ( < 0.05) for the month of March than for the other sampling dates within the detritus and soil layers. This increase of PMN in March was most likely due to the previous fire (January 31, 2001) and the drought (November 2000 – May 2001) (Romanya et al., 2001; Serrasolsas and Khanna, 1995). Combining spatial as well as temporal data, for the BCT region alone, can illustrate this significant increase ( < 0.05) of PMN observed for the month of March (Figure 3-23). During dry periods, release of inorganic N increases because of greater N mineralization rates under aerobic conditions as compared to anaerobic conditions. Under anaerobic conditions, microbial decomposition is less efficient and encompasses a limited microbial population (Patrick, 1982; Tenny and Waksman, 1930). Excluding the month of March from the Pillai’s Trace Criterion statistical analysis, a seasonal effect was observed within both the soil and detrital layers for PMN, however, for the soil, seasonal patterns between the three regions were not statistically different ( < 0.05) (Figure 3-24, 3-25). Temperature changes over time were not shown to be the driving factor behind the seasonality changes of PMN (Figure 3-26). The PMN rates shown in figure 3-26 represent all samples taken throughout the months during the temporal study at their respective temperatures (Table 3-8). An increase in temperature did not produce an increase of PMN within the soil and detritus layers. Other environmental factors, including microbial activity, likely influenced PMN rates besides temperature. Temperature, however, has been shown to influence decomposition rates, where the rate changes with a 10C degree increase in temperature (Q 10 ) (Atlas, 1984; Gale et al., 1992; Reddy and Patrick, 1984; White and Reddy, 2001). An incubation

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65 0200400600NortheastBCTSouthwest Soil MBN(mg N kg-1)baa 0200400600NortheastBCTSouthwest Soil MBN(mg N kg-1)baa 0200400600NortheastBCTSouthwest Soil MBN(mg N kg-1)baa 0200400600NortheastBCTSouthwest Soil MBN(mg N kg-1)baa 02004006008001000NortheastBCTSouthwest Detritus MBN(mg N kg-1)baa 02004006008001000NortheastBCTSouthwest Detritus MBN(mg N kg-1)baa 02004006008001000NortheastBCTSouthwest Detritus MBN(mg N kg-1)baa 02004006008001000NortheastBCTSouthwest Detritus MBN(mg N kg-1)baa Figure 3-21. Microbial biomass N within the soil and detrital layers for all three regions, Northeast, Southwest, and BCT. Bars represent the means ( + 1 SD) of samples (n=36) collected from the respective sampling locations. Contrasting letters above the bars represent differences in significant values ( < 0.05).

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66 0200400600800TCPT/WMOVegetation Soil MBN(mg N kg-1)abb 0200400600800TCPT/WMOVegetation Soil MBN(mg N kg-1) 0200400600800TCPT/WMOVegetation Soil MBN(mg N kg-1)abb 0200400600800TCPT/WMOVegetation Soil MBN(mg N kg-1) 04008001200TCPT/WMOVegetation DetritusMBN(mg N kg-1)bba 04008001200TCPT/WMOVegetation DetritusMBN(mg N kg-1) 04008001200TCPT/WMOVegetation DetritusMBN(mg N kg-1)bba 04008001200TCPT/WMOVegetation DetritusMBN(mg N kg-1) Figure 3-22. Microbial biomass N for the soil and detritus layers with respect to vegetative communities, T = NE, SW Typha sp., C = NE, BCT Cladium, P = BCT Panicum, T/WM = NE, SW Typha sp./Woody Mix, and O = NE, SW Others. Data are mean values (+ 1 SD) from the respective sampling locations (n=18).

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67 study performed at 20, 30 and 40C for determining PMN rates of two soils from both BCT and the Northeast regions did, however, find a slight temperature effect on N mineralization (Figure 3-27). An average Q 10 of 1.0 was found for the PMN rate between 20 and 30C, while an average Q 10 of 1.4 occurred between 30 and 40C. Therefore, greater PMN rates were found to be associated with higher temperatures. The insignificant difference of N mineralization rates between 20 and 30C most likely was the result of the short incubation period (i.e. 10 days). Higher temperatures are necessary for short PMN incubation times to capture the linear increase of N mineralization. This low PMN rate found between 20 and 30C corresponds with the observations from the field. Reported Q 10 values have varied from 1.7 to 3.0. Simple linear interpolation, however, may not provide an accurate estimate of N mineralization at intermediate temperatures (Marion and Black, 1987). 050100150200SeptMarchMayJulySeptNovJanMonthPMN (mg N kg-1d-1) 050100150200SeptMarchMayJulySeptNovJanMonthPMN (mg N kg-1d-1) 050100150200SeptMarchMayJulySeptNovJanMonthPMN (mg N kg-1d-1) 050100150200SeptMarchMayJulySeptNovJanMonthPMN (mg N kg-1d-1) Figure 3-23. Seasonal pattern of PMN rates for the soil within the BCT region, combining both spatial (2000) and temporal (2001) data. Data are meal values ( + 1 SD) from the respective sampling site (n = 40, 18).

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68 050100150200250MarchJuneJulySeptDecJanTime (Month)PMN(mg N kg-1)0102030Temperature(*C) Northeast Temp 050100150200250MarchJuneJulySeptDecJanTime (Month)PMN(mg N kg-1)0102030Temperature(*C) Northeast Temp Northeast Temp 050100150200250MarchJuneJulySeptDecJanTime (Month)PMN(mg N kg-1)0102030Temperature(*C) Northeast Temp Northeast Temp 050100150200250MarchJuneJulySeptDecJanTime (Month)PMN(mg N kg-1)0102030Temperature(*C) Northeast Temp Northeast Temp Northeast Temp Northeast Temp 020406080100120MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) Southwest Temp PMN(mg N kg-1) 020406080100120MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) Southwest Temp PMN(mg N kg-1) 020406080100120MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) Southwest Temp PMN(mg N kg-1) 020406080100120MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) Southwest Temp PMN(mg N kg-1) 050100150200MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) BCT Temp PMN(mg N kg-1) 050100150200MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) BCT Temp BCT Temp PMN(mg N kg-1) 050100150200MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) BCT Temp BCT Temp PMN(mg N kg-1) 050100150200MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) BCT Temp BCT Temp PMN(mg N kg-1) BCT Temp BCT Temp PMN(mg N kg-1) Figure 3-24. Seasonal patterns of PMN observed with respect to the Northeast, Southwest, and BCT regions for the soil layer (2001). Temperature is the average taken at 2-3 cm soil depth. Data are mean values ( + 1 SD) from the respective sampling sites (n=18). Three regions were not significantly different ( < 0.05) from one another over time by Pillai’s Trace Criterion statistical analysis.

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69 0200400600800MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) Northeast Temp PMN(mg N kg-1) 0200400600800MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) Northeast Temp Northeast Temp PMN(mg N kg-1) 0200400600800MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) Northeast Temp Northeast Temp PMN(mg N kg-1) 0200400600800MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) Northeast Temp Northeast Temp PMN(mg N kg-1) Northeast Temp Northeast Temp PMN(mg N kg-1) 0200400600MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) Southwest Temp PMN(mg N kg-1) 0200400600MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) Southwest Temp Southwest Temp PMN(mg N kg-1) 0200400600MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) Southwest Temp Southwest Temp PMN(mg N kg-1) 0200400600MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) Southwest Temp Southwest Temp PMN(mg N kg-1) Southwest Temp Southwest Temp PMN(mg N kg-1) 0200400600800MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) BCT Temp PMN(mg N kg-1) 0200400600800MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) BCT Temp BCT Temp PMN(mg N kg-1) 0200400600800MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) BCT Temp BCT Temp PMN(mg N kg-1) 0200400600800MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) BCT Temp BCT Temp PMN(mg N kg-1) BCT Temp BCT Temp PMN(mg N kg-1) Figure 3-25. Seasonal patterns of PMN observed with respect to the Northeast, Southwest, and BCT regions for the detritus layer (2001). Temperature is the average taken at 2-3 cm soil depth. Data are mean values ( + 1 SD) from the respective sampling sites (n=18). Three regions were significantly different ( < 0.05) from one another over time by Pillai’s Trace Criterion statistical analysis.

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70 Figure 3-26. Potential mineralizable N associated with temperature (C) for unimpacted and impacted regions within the soil and detritus layers, respectively. Data are the actual values from the respective sampling sites collected each month during the temporal study (n=108).

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71 y = 0.7293x + 92.479y = 4.7249x -28.593050100150200203040Temperature (*C)PMN (mg kg-1d-1) y = 0.7293x + 92.479y = 4.7249x -28.593050100150200203040Temperature (*C)PMN (mg kg-1d-1) Figure 3-27. Linear PMN rate at various temperatures (20, 30, and 40C) over 10 days. Points represent the means ( + 1 SD) of samples (n=3) from four different soil samples from the BCT and Northeast regions.

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72 For extractable NH 4 + , a seasonal effect was observed as well as a significant difference ( < 0.05) in seasonal patterns between the three regions within both the soil and detrital layers (Figure 3-28, 3-29). Temperature was observed to partly influence seasonal patterns of extractable NH 4 + concentrations within all three regions for both the soil and detritus layers due to the increase of extractable NH 4 + concentrations with increasing temperatures (Figure 3-30). An increase of N mineralization can lead to an accumulation of ammonium under anaerobic conditions because of the lower metabolic efficiencies of anaerobic microbial populations (Gale and Gilmour, 1988). Nitrification (NH 4 + to NO 3 ) is influenced by dissolved O 2 concentrations, therefore allowing the build up of NH 4 + in the system during the warmer months of July and September after the establishment of anaerobic soil conditions (Table 3-7) (Figure 3-31) (Reddy, 1982; Singh et al., 2000). Dissolved O 2 has also been found to decrease in summer when sediment biological oxygen demand (BOD) was the highest (Howard-Williams and Downes, 1993). For the detritus layer, a significant difference ( < 0.05) in PMN rates was found over time with the Northeast and Southwest regions having higher mineralization rates than the BCT region (Figure 3-32). Extractable NH 4 + concentrations were found to be significantly higher ( < 0.05) in the Northeast and Southwest regions within the detritus layer (Figure 3-32), corresponding to PMN rates. PMN rates and extractable NH 4 + concentrations were not significantly different ( < 0.05) within the soil layer between the impacted and unimpacted regions; therefore, not influenced by total P concentrations. For the detritus layer, total P was found to influence PMN rates and extractable NH 4 + concentrations. Similar correlations have also been found between N mineralization

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73 04080120160MarchJuneJulySeptDecJanTime (Month)Ext. NH4+(mg N kg-1)0102030Temperature (*C) Northeast Temp 04080120160MarchJuneJulySeptDecJanTime (Month)Ext. NH4+(mg N kg-1)0102030Temperature (*C) Northeast Temp 04080120160MarchJuneJulySeptDecJanTime (Month)Ext. NH4+(mg N kg-1)0102030Temperature (*C) Northeast Temp 04080120160MarchJuneJulySeptDecJanTime (Month)Ext. NH4+(mg N kg-1)0102030Temperature (*C) Northeast Temp 020406080100120MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Southwest Temp Ext. NH4+(mg N kg-1) 020406080100120MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Southwest Temp Southwest Temp Ext. NH4+(mg N kg-1) 020406080100120MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Southwest Temp Southwest Temp Ext. NH4+(mg N kg-1) 020406080100120MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Southwest Temp Southwest Temp Ext. NH4+(mg N kg-1) Southwest Temp Southwest Temp Ext. NH4+(mg N kg-1) 020406080100120MarchJuneJulySeptDecJanTime (Month)0102030Temperature(*C) BCT Temp Ext. NH4+(mg N kg-1) 020406080100120MarchJuneJulySeptDecJanTime (Month)0102030Temperature(*C) BCT Temp BCT Temp Ext. NH4+(mg N kg-1) 020406080100120MarchJuneJulySeptDecJanTime (Month)0102030Temperature(*C) BCT Temp BCT Temp Ext. NH4+(mg N kg-1) 020406080100120MarchJuneJulySeptDecJanTime (Month)0102030Temperature(*C) BCT Temp BCT Temp Ext. NH4+(mg N kg-1) BCT Temp BCT Temp Ext. NH4+(mg N kg-1) Figure 3-28. Seasonal patterns of extractable NH 4 + concentrations observed with respect to the Northeast, Southwest, and BCT regions for the soil layer (2001). Temperature is the average taken at 2-3 cm soil depth. Data are mean values ( + 1 SD) from the respective sampling sites (n=18). Three regions were significantly different ( < 0.05) from one another over time by Pillai’s Trace Criterion statistical analysis.

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74 0100200300400MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Northeast Temp Ext. NH4+(mg N kg-1) 0100200300400MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Northeast Temp Northeast Temp Ext. NH4+(mg N kg-1) 0100200300400MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Northeast Temp Northeast Temp Ext. NH4+(mg N kg-1) 0100200300400MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Northeast Temp Northeast Temp Ext. NH4+(mg N kg-1) Northeast Temp Northeast Temp Ext. NH4+(mg N kg-1) 050100150200250300MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Southwest Temp Ext. NH4+(mg N kg-1) 050100150200250300MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Southwest Temp Ext. NH4+(mg N kg-1) 050100150200250300MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Southwest Temp Ext. NH4+(mg N kg-1) 050100150200250300MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Southwest Temp Ext. NH4+(mg N kg-1) 04080120160MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) BCT Temp Ext. NH4+(mg N kg-1) 04080120160MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) BCT Temp BCT Temp Ext. NH4+(mg N kg-1) 04080120160MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) BCT Temp BCT Temp Ext. NH4+(mg N kg-1) 04080120160MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) BCT Temp BCT Temp Ext. NH4+(mg N kg-1) BCT Temp BCT Temp Ext. NH4+(mg N kg-1) Figure 3-29. Seasonal patterns of extractable NH 4 + concentrations observed with respect to the Northeast, Southwest, and BCT regions for the detritus layer (2001). Temperature is the average taken at 2-3 cm soil depth. Data are mean values ( + 1 SD) from the respective sampling sites (n=18). Three regions were significantly different ( < 0.05) from one another over time by Pillai’s Trace Criterion statistical analysis.

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75 Figure 3-30. Extractable NH 4 + associated with temperature (C) for unimpacted and impacted regions within the soil and detritus layers, respectively. Data are the actual values from the respective sampling sites collected each month during the temporal study (n=108).

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76 04080120AerobicAnaerobicAerobicAnaerobicAerobicAnaerobic NEBCTSW Extractable NH4+ (mg N kg-1) N = 12N = 24N = 18N = 18N = 12N = 24 04080120AerobicAnaerobicAerobicAnaerobicAerobicAnaerobic NEBCTSW Extractable NH4+ (mg N kg-1) N = 12N = 24N = 18N = 18N = 12N = 24 Figure 3-31. Extractable NH 4 + concentrations under aerobic vs. anaerobic conditions within the soil for each region, Northeast, Southwest, and BCT. Data are mean values ( + 1 SD) from the respective sampling regions. (NE, SW Aerobic = March and June 2001, NE, SW Anaerobic = July, September, November, December, and January 2001-2002, BCT Aerobic = March, June, and July 2001, BCT Anaerobic = September, November, December, and January 2001-2002.)

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77 0100200300NortheastBCTSouthwest abaPMN(mg N kg-1d-1) 0100200300NortheastBCTSouthwest abaPMN(mg N kg-1d-1) 0100200300NortheastBCTSouthwest abaPMN(mg N kg-1d-1) 0100200300NortheastBCTSouthwest abaPMN(mg N kg-1d-1) 060120180240NortheastBCTSouthwestExt. NH4+(mg N kg-1) aab 060120180240NortheastBCTSouthwestExt. NH4+(mg N kg-1) aab 060120180240NortheastBCTSouthwestExt. NH4+(mg N kg-1) aab 060120180240NortheastBCTSouthwestExt. NH4+(mg N kg-1) aab Figure 3-32. Potentially mineralizable N and extractable NH 4 + within the detrital layer for all three regions, Northeast, Southwest, and BCT. Bars represent the means ( + 1 SD) of samples (n=36) collected from the respective sampling locations. Contrasting letters above the bars represent differences in significant values ( < 0.05).

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78 and total P by other studies (White and Reddy, 2000, 2001). Higher total P values within the Northeast and Southwest regions coincide with higher PMN rates and extractable NH 4 + for detritus (Figure 3-33). Others have also found greater release of inorganic N from detritus than the soil (White and Reddy, 2001). Phosphorus additions have been shown to increase microbial activity (measured by N mineralization rates) for a variety of ecosystems (Biederbeck et al., 1984; Hossain et al., 1995; Munevar and Wollum, 1977; Prescott et al., 1992) while other studies have shown no responses to P additions (Ross et al., 1995; Tate et al., 1991). Concerning the descriptive temporal analysis of vegetative communities associated with each region, PMN rates were significantly lower ( < 0.05) for BCT (Cladium) vegetation than other vegetative communities within the detritus layer (Figure 3-34). This corresponds to the low PMN rates in the BCT region reflecting a higher C/N ratio or lower decomposition rate of the Cladium substrate. No significant difference ( < 0.05) between vegetative communities was found for PMN within the soil. Both Northeast (Typha sp. and Cladium) and Southwest (Typha sp./Woody mix) vegetative communities had higher extractable NH 4 + concentrations ( < 0.05) for the detritus layer than BCT (Panicum) (Figure 3-35). The rapid decomposition rate of Typha sp. likely contributed to the high amount of extractable NH 4 + in both the Southwest and Northeast regions (Davis, 1991). For the soil layer, the only significant difference ( < 0.05) with regards to extractable NH 4 + was between Typha sp. and Cladium communities both from within the Northeast region. For organic soils, nitrogen is mineralized at a steady rate and therefore a constant fraction of total N is always potentially available for mineralization (Reddy, 1982).

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79 Figure 3-33. Potential mineralizable N and extractable NH 4 + associated with total P concentrations for impacted and unimpacted regions within the detritus layer. Ellipse size for illustration purposes only (represents the 0.8 confidence limits).

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80 0100200300400TCPT/WMOVegetationPMN (mg N kg-1d-1) bbbba 0100200300400TCPT/WMOVegetationPMN (mg N kg-1d-1) bbbba 0100200300400TCPT/WMOVegetationPMN (mg N kg-1d-1) bbbba 0100200300400TCPT/WMOVegetationPMN (mg N kg-1d-1) bbbba Figure 3-34. Potential mineralizable N for the detritus layer with respect to vegetative communities, T = NE, SW Typha sp., C = NE, BCT Cladium, P = BCT Panicum, T/WM = NE, SW Typha sp./Woody Mix, and O = NE, SW Others. Data are mean values ( + 1 SD) from the respective sampling sites (n=18). Contrasting letters above the bars represent differences in significant values ( < 0.05). 0100200300TCPT/WMOVegetationExtractable NH4+(mg N kg-1) aaba 0100200300TCPT/WMOVegetationExtractable NH4+(mg N kg-1) 0100200300TCPT/WMOVegetationExtractable NH4+(mg N kg-1) 0100200300TCPT/WMOVegetationExtractable NH4+(mg N kg-1) 0100200300TCPT/WMOVegetationExtractable NH4+(mg N kg-1) aaba 0100200300TCPT/WMOVegetationExtractable NH4+(mg N kg-1) 0100200300TCPT/WMOVegetationExtractable NH4+(mg N kg-1) Figure 3-35. Extractable NH 4 + for the detritus layer with respect to vegetative communities, T = NE, SW Typha sp., C = NE, BCT Cladium, P = BCT Panicum, T/WM = NE, SW Typha sp./Woody Mix, and O = NE, SW Others. Data are mean values ( + 1 SD) from the respective sampling sites (n=18).

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81 Incubation studies have been able to show this linear N mineralization rate at a constant temperature over time (Terry, 1980; Reddy, 1982). This steady rate of N mineralization was also observed in this study (Figure 3-36). Inorganic N availability is mediated by heterotrophic microbial activity; hence soil microbial biomass has been significantly correlated with N mineralization rates in wetland soils (Williams and Sparling, 1988; McLatchey and Reddy, 1998). Microbial biomass N was significantly greater within the unimpacted BCT region than the impacted Northeast region for both the soil and detrital layers. Therefore, the diversity of microbial communities between the three regions may help in maintaining a fairly uniform N mineralization rate regardless of the C/N ratio of the soil (Figure 3-37). y = 5.079x + 57.009R2= 0.89002550751001250246810Time(d)PMN(mg kg-1d-1) y = 5.079x + 57.009R2= 0.89002550751001250246810Time(d)PMN(mg kg-1d-1) Figure 3-36. Linear PMN rate at a constant temperature (40 C) over 10 days. Points represent the means ( + 1 SD) of samples (n=3) from four different soil samples from the BCT and Northeast regions. A significant relationship ( < 0.05) was found between PMN and total N between the impacted and unimpacted regions (Figure 3-38). For BCT, a higher soil total N value was associated with higher PMN rates, while within both the impacted regions,

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82 lower PMN activity corresponded to less total N. This total N range for the soil layer between the regions also corresponds to MBN activity as well (Figure 3-39). This may have been the result of differences in vegetation type between the regions and the amount of available labile total N. Overall among all three regions, PMN rates for the soil were associated with lower C/N ratios as opposed to the detritus layer (Figure 3-40). The soil, therefore, may have more stable forms of total N then detritus, where total N changes with rates of decomposition. Total C was found to significantly differ ( < 0.05) seasonally between regions, likely because of differences in vegetation (Figure 3-41, 3-42). An increase of lignin in the substrate over time decreases the quality or availability of soluble C, which then becomes more resistant to decomposition. Therefore, rates of PMN and microbial activity can be reduced due to the changes in substrate. A greater detrital accumulation in the Northeast and Southwest regions due to productive Typha sp. communities may have stimulated an increase in PMN rates within these regions. Increase in organic matter accumulation in nutrient enriched areas produces younger soils and an increase in net primary productivity (DeBusk and Reddy, 1998). Vegetation type therefore can create differences in soil quality between the impacted and unimpacted sites. Arginine Ammonification The structure of arginine contains three amine groups: HOOCH 2 CHCH 2 CH 2 -CH 2 NHC(NH 2 ) 2 . The release or mineralization of a cleaved amine group can easily be extracted from the soil and measured as NH 4 + (Lin and Brookes, 1999). Arginine ammonification rates can be proportional to the activity of microorganisms present in the soil (Alef et al., 1988; Alef and Kleiner, 1986,1987). Average arginine ammonification

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83 Figure 3-37. Microbial biomass nitrogen and PMN associated with C/N concentrations for impacted and unimpacted regions within the soil layer. Ellipse size for illustration purposes only (represents the 0.8 confidence limits).

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84 Figure 3-38. Potential mineralizable N associated with total N concentrations fimpacted and unimpacted regions within the soil and detritus layers, or respectively. Ellipse size for illustration purposes only (represents the 0.8 confidence lim its).

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85 Figure 3-39. Microbial biomass N associated with total N concentrations for impacted and unimpacted regions within the soil and detritus layers, respectively. Ellipse size for illustration purposes only (represents the 0.8 confidence limits). 050010001500102030405060C/NPMN(mg N kg-1) Soil Detritus 050010001500102030405060C/NPMN(mg N kg-1) Soil Detritus 050010001500102030405060C/NPMN(mg N kg-1) Soil Detritus 050010001500102030405060C/NPMN(mg N kg-1) Soil Detritus Figure 3-40. Distribution of C/N ratios within the soil and detrital layers based on PMN rates. Points represent the samples (n=100) collected from all three regions, Northeast, Southwest, and BCT.

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86 400420440460480500MarchJuneJulySeptDecJanTime (Month)Total C(g kg-1)0102030Temperature(*C) Northeast Temp 400420440460480500MarchJuneJulySeptDecJanTime (Month)Total C(g kg-1)0102030Temperature(*C) Northeast Temp Northeast Temp 400420440460480500MarchJuneJulySeptDecJanTime (Month)Total C(g kg-1)0102030Temperature(*C) Northeast Temp Northeast Temp 400420440460480500MarchJuneJulySeptDecJanTime (Month)Total C(g kg-1)0102030Temperature(*C) Northeast Temp Northeast Temp Northeast Temp Northeast Temp 380400420440460480500MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) Southwest Temp Total C(g kg-1) 380400420440460480500MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) Southwest Temp Southwest Temp Total C(g kg-1) 380400420440460480500MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) Southwest Temp Southwest Temp Total C(g kg-1) 380400420440460480500MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) Southwest Temp Southwest Temp Total C(g kg-1) Southwest Temp Southwest Temp Total C(g kg-1) 420440460480500MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) BCT Temp Total C(g kg-1) 420440460480500MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) BCT Temp Total C(g kg-1) 420440460480500MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) BCT Temp Total C(g kg-1) 420440460480500MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) BCT Temp Total C(g kg-1) Figure 3-41. Seasonal patterns of total C observed with respect to the Northeast, Southwest, and BCT regions for the soil layer (2001). Temperature is the average taken at 2-3 cm soil depth. Data are mean values ( + 1 SD) from the respective sampling sites (n=18). Three regions were significantly different ( < 0.05) from one another over time by Pillai’s Trace Criterion statistical analysis.

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87 400420440460480500MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Northeast Temp Total C(g kg-1) 400420440460480500MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Northeast Temp Northeast Temp Total C(g kg-1) 400420440460480500MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Northeast Temp Northeast Temp Total C(g kg-1) 400420440460480500MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) Northeast Temp Northeast Temp Total C(g kg-1) Northeast Temp Northeast Temp Total C(g kg-1) 350400450500MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) Southwest Temp Total C(g kg-1) 350400450500MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) Southwest Temp Southwest Temp Total C(g kg-1) 350400450500MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) Southwest Temp Southwest Temp Total C(g kg-1) 350400450500MarchJuneJulySeptDecJanTime (Month)0102030Temperature (*C) Southwest Temp Southwest Temp Total C(g kg-1) Southwest Temp Southwest Temp Total C(g kg-1) 400420440460480500MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) BCT Temp Total C(g kg-1) 400420440460480500MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) BCT Temp Total C(g kg-1) 400420440460480500MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) BCT Temp Total C(g kg-1) 400420440460480500MarchJuneJulySeptDecJanTime(Month)0102030Temperature(*C) BCT Temp Total C(g kg-1) Figure 3-42. Seasonal patterns of total C observed with respect to the Northeast, Southwest, and BCT regions for the detrital layer (2001). Temperature is the average taken at 2-3 cm soil depth. Data are mean values ( + 1 SD) from the respective sampling sites (n=18). Three regions were significantly different ( < 0.05) from one another over time by Pillai’s Trace Criterion statistical analysis.

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88 rates were 10.2 + 7.7 mg N kg -1 h -1 and 18.7 + 8.7mg N kg -1 h -1 in September 2001 for all three regions within the soil and detritus layer respectively. Average PMN rates were 1.9 + 0.3 mg N kg -1 h -1 and 4.7 + 2.7 mg N kg -1 h -1 in September 2001 for all three regions for the soil and detritus layers respectively. Similar alanine ammonification rates were found for a Florida wetland soil (0-15 cm) 0.63 to 4.1 mg N kg -1 h -1 (McLatchey and Reddy, 1998). For an Umbrisol in Spain, an arginine ammonification rate of 4.9 to 11.1 mg N kg -1 h -1 was found within 0-15 cm (Leirs et al., 2000). Arginine ammonification and PMN measure a slightly different fraction of soil microbial activity. Potentially mineralizable nitrogen measures the release rate of NH 4 + from the decomposition of large into small and eventually dissolved organic N compounds. The rate-limiting step(s) for this process involves the microbial enzyme activity associated with the break down of the larger organic N compounds. Arginine ammonification measures the microbial activity or more precisely the extracellular enzyme activity involved in the final step of organic N mineralization, deamination (Franzluebbers et al., 1995; McLatchey and Reddy, 1998, White and Reddy, 2001). Therefore, arginine ammonification does not include the rate-limiting step(s) as PMN, which is minimized by providing amino acids that are easily attacked and consumed by microbes (White and Reddy, 2000). Mineralization rates were greater ( < 0.05) for arginine ammonification than PMN because of the simplicity and low C/N ratio of the substrate (Alef and Kleiner, 1986; White and Reddy, 2000, 2001). Within the soil, arginine ammonification rates were 80% higher than PMN as well as 75% higher for detritus.

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89 For both the soil and detritus layers, no significant difference ( < 0.05) was found between the impacted and unimpacted regions by site or vegetation for arginine-N. A seasonal effect did influence ( < 0.05) arginine ammonification within both the soil and detrital layers. A significant difference ( < 0.05) in seasonal patterns for arginine ammonification between all regions, however, was only observed for the soil layer (Figure 3-43, 3-44). The seasonal pattern did not follow temperature changes, even though temperature has been found to significantly effect ammonification rates (Alef and Kleiner, 1986; White and Reddy, 2000). Increased rates of ammonification during December and January may have been due to the enhancement of available nutrients caused by vegetative senescence within the colder months. The quality and quantity of detritus can influence ammonification rates depending upon the C/N ratio of the substrate. Therefore, ammonification within the detritus layer was greater than the soil layer, which contains lower C/N material. This difference within the soil profile has also been observed by others (Alef et al., 1988; Alef and Kleiner, 1986). Arginine ammonification was found to have a distinct relationship to total N within the soil, similar to PMN (Figure 3-45) as also found by other studies (Alef and Kleiner, 1986, 1987; Alef et al., 1988; Kaiser et al., 1992), but contrary to findings by other studies (Lin and Brookes, 1999; White, 1999). Microbial biomass N has been shown to be correlated with organic N mineralization rates (McLatchey and Reddy, 1998; White and Reddy, 2000, 2001), specifically arginine ammonification (Leirs et al., 2000; Bonde et al., 2001; White, 1999). However, a distinct relationship was not found between arginine ammonification and MBN within the detritus layer. Total P was not

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90 0102030JulySeptDecJanTime(Month)Arg–N(mg N kg-1h-1)0102030Temperature(*C) Northeast Temp 0102030JulySeptDecJanTime(Month)Arg–N(mg N kg-1h-1)0102030Temperature(*C) Northeast Temp Northeast Temp 0102030JulySeptDecJanTime(Month)Arg–N(mg N kg-1h-1)0102030Temperature(*C) Northeast Temp Northeast Temp 0102030JulySeptDecJanTime(Month)Arg–N(mg N kg-1h-1)0102030Temperature(*C) Northeast Temp Northeast Temp Northeast Temp Northeast Temp 010203040JulySeptDecJanTime (Month)0102030Temperature(*C) Southwest Temp Arg–N(mg N kg-1h-1) 010203040JulySeptDecJanTime (Month)0102030Temperature(*C) Southwest Temp Southwest Temp Arg–N(mg N kg-1h-1) 010203040JulySeptDecJanTime (Month)0102030Temperature(*C) Southwest Temp Southwest Temp Arg–N(mg N kg-1h-1) 010203040JulySeptDecJanTime (Month)0102030Temperature(*C) Southwest Temp Southwest Temp Arg–N(mg N kg-1h-1) Southwest Temp Southwest Temp Arg–N(mg N kg-1h-1) 0102030JulySeptDecJanTime(Month)0102030Temperature(*C) BCT Temp Arg–N(mg N kg-1h-1) 0102030JulySeptDecJanTime(Month)0102030Temperature(*C) BCT Temp BCT Temp Arg–N(mg N kg-1h-1) 0102030JulySeptDecJanTime(Month)0102030Temperature(*C) BCT Temp BCT Temp Arg–N(mg N kg-1h-1) 0102030JulySeptDecJanTime(Month)0102030Temperature(*C) BCT Temp BCT Temp Arg–N(mg N kg-1h-1) BCT Temp BCT Temp Arg–N(mg N kg-1h-1) Figure 3-43. Seasonal patterns of arginine ammonification observed with respect to the Northeast, Southwest, and BCT regions for the soil layer (2001). Temperature is the average taken at 2-3 cm soil depth. Data are mean values ( + 1 SD) from the respective sampling sites (n=18). Three regions were significantly different ( < 0.05) from one another over time by Pillai’s Trace Criterion statistical analysis.

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91 020406080JulySeptDecJanTime(Month)Arg-N(mg N kg-1h-1)0102030Temperature (*C) Northeast Temp 020406080JulySeptDecJanTime(Month)Arg-N(mg N kg-1h-1)0102030Temperature (*C) Northeast Temp Northeast Temp 020406080JulySeptDecJanTime(Month)Arg-N(mg N kg-1h-1)0102030Temperature (*C) Northeast Temp Northeast Temp 020406080JulySeptDecJanTime(Month)Arg-N(mg N kg-1h-1)0102030Temperature (*C) Northeast Temp Northeast Temp Northeast Temp Northeast Temp 050100150200JulySeptDecJanTime(Month)Arg-N(mg N kg-1h-1)0102030Temperature (*C) Southwest Temp 050100150200JulySeptDecJanTime(Month)Arg-N(mg N kg-1h-1)0102030Temperature (*C) Southwest Temp Southwest Temp 050100150200JulySeptDecJanTime(Month)Arg-N(mg N kg-1h-1)0102030Temperature (*C) Southwest Temp Southwest Temp 050100150200JulySeptDecJanTime(Month)Arg-N(mg N kg-1h-1)0102030Temperature (*C) Southwest Temp Southwest Temp Southwest Temp Southwest Temp 020406080JulySeptDecJanTime(Month)Arg-N(mg N kg-1h-1)0102030Temperature (*C) BCT Temp 020406080JulySeptDecJanTime(Month)Arg-N(mg N kg-1h-1)0102030Temperature (*C) BCT Temp BCT Temp 020406080JulySeptDecJanTime(Month)Arg-N(mg N kg-1h-1)0102030Temperature (*C) BCT Temp BCT Temp 020406080JulySeptDecJanTime(Month)Arg-N(mg N kg-1h-1)0102030Temperature (*C) BCT Temp BCT Temp BCT Temp BCT Temp Figure 3-44. Seasonal patterns of arginine ammonification observed with respect to the Northeast, Southwest, and BCT regions for the detritus layer (2001). Temperature is the average taken at 2-3 cm soil depth. Data are mean values ( + 1 SD) from the respective sampling sites (n=18). Three regions were not significantly different ( < 0.05) from one another over time by Pillai’s Trace Criterion statistical analysis.

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92 Figure 3-45. Total N values associated with arginine ammonification rates within the soil layer for impacted and unimpacted regions. Ellipse size for illustration purposes only (represents the 0.8 confidence limits). found to influence to ammonification rates as supported by other studies (White, 1999; White and Reddy, 2000). Arginine ammonification, therefore, may not be a reliable indicator of changes in microbial activity due to nutrient loading and shifts in vegetation communities (White and Reddy, 2000). Denitrification Enzyme Activity A seasonal effect was not observed for DEA within both the soil and detrital layers. However, DEA did have a significant difference in seasonal patterns ( < 0.05) between the three regions for the detrital layer (Figure 3-46, 3-47). Seasonal patterns of denitrification have been found to be linked to seasonal differences in organic matter production as well as temperature (Howard-Williams and Downes, 1993). The detrital layer had slightly lower DEA rates during the month of March than the other months except July and January. The low DEA rate within the soil and detritus layers for March may have been the result of the drought (low moisture content), low temperatures, and

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93 effects from the fire. The presence of DEA activity in the drier months of March and June possible were due to anaerobic microsites in the soil. An increase in saturated soil conditions after June may increase DEA by redistributing C and NO 3 previously found in the soil to denitrifying microsites (Barton et al., 2000). A temperature effect may have slightly contributed to the seasonal changes of DEA for the soil layer shown by the increase of DEA rates with an increase in temperature within all three regions (Figure 3-48). Other studies have found a weak or negative correlation of denitrification rate with temperature (Groffman et al., 1992; Groffman and Tiedje, 1991; Myrold, 1988; Parsons et al., 1991; Thompson, 1989; Wheatley and Williams, 1989). It has been suggested that other factors than temperature and moisture related to C and N dynamics in the soil have to be considered with denitrification (Griffiths et al., 1998; Groffman and Tiedje, 1991). Denitrifying activity has been shown to vary seasonally independent from the general heterotrophic communities in part because different factors influence denitrifying microorganism activity (Griffith et al., 1998). The DEA increase within the colder months of December and January may have been due to the increase of available nutrients from vegetative senescence. Denitrification has been found to be related with an increase in soil organic matter (Myrold, 1988). In colder months, NO 3 concentrations in soil solution may also increase because of the decrease rate of mobilization and uptake by plants and microbes (Singh et al., 2000). Temporal variability of DEA has also been reported in other studies (Christensen et al., 1990b; Griffiths et al., 1998; Myrold, 1988; Parsons et al., 1991; Sexstone et al., 1985; White and Reddy, 1999).

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94 0.0000.0050.0100.0150.020MarchJuneJulySeptDecJanTime(Month)DEA(mg N2O-N kg-1d-1)0102030Temperature(*C) Northeast Temp 0.0000.0050.0100.0150.020MarchJuneJulySeptDecJanTime(Month)DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1)0102030Temperature(*C) Northeast Temp Northeast Temp 0.0000.0050.0100.0150.020MarchJuneJulySeptDecJanTime(Month)DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1)0102030Temperature(*C) Northeast Temp Northeast Temp 0.0000.0050.0100.0150.020MarchJuneJulySeptDecJanTime(Month)DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1)0102030Temperature(*C) Northeast Temp Northeast Temp DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1)0102030Temperature(*C) Northeast Temp Northeast Temp 0.0000.0010.0020.0030.0040.005MarchJuneJulySeptDecJanTime (Month)0102030Temperature(*C) Southeast TempDEA(mg N2O-N kg-1d-1) 0.0000.0010.0020.0030.0040.005MarchJuneJulySeptDecJanTime (Month)0102030Temperature(*C) Southeast TempDEA(mg N2O-N kg-1d-1) 0.0000.0010.0020.0030.0040.005MarchJuneJulySeptDecJanTime (Month)0102030Temperature(*C) Southeast Temp Southeast TempDEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1) 0.0000.0010.0020.0030.0040.005MarchJuneJulySeptDecJanTime (Month)0102030Temperature(*C) Southeast TempDEA(mg N2O-N kg-1d-1) 0.0000.0010.0020.0030.0040.005MarchJuneJulySeptDecJanTime (Month)0102030Temperature(*C) Southeast Temp Southeast TempDEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1) 0.0000.0010.0020.0030.0040.005MarchJuneJulySeptDecJanTime (Month)0102030Temperature(*C) Southeast Temp Southeast TempDEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1) 0.0000.0010.0020.0030.0040.005MarchJuneJulySeptDecJanTime (Month)0102030Temperature(*C) Southeast Temp Southeast TempDEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1) Southeast Temp Southeast TempDEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1) 0.00000.00050.00100.00150.0020MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) BCT Temp DEA(mg N2O-N kg-1d-1) 0.00000.00050.00100.00150.0020MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) BCT Temp BCT Temp DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1) 0.00000.00050.00100.00150.0020MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) BCT Temp BCT Temp DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1) 0.00000.00050.00100.00150.0020MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) BCT Temp BCT Temp DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1) BCT Temp BCT Temp DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1) Figure 3-46. Seasonal patterns of DEA observed with respect to the Northeast, Southwest, and BCT regions for the detrital layer (2001). Temperature is the average taken at 2-3 cm soil depth. Data are mean values ( + 1 SD) from the respective sampling sites (n=18). Three regions were significantly different ( < 0.05) from one another over time by Pillai’s Trace Criterion statistical analysis.

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95 0.0000.0100.0200.0300.040MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) Northeast Temp DEA(mg N2O-N kg-1d-1) 0.0000.0100.0200.0300.040MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) Northeast Temp Northeast Temp DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1) 0.0000.0100.0200.0300.040MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) Northeast Temp Northeast Temp DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1) 0.0000.0100.0200.0300.040MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) Northeast Temp Northeast Temp DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1) Northeast Temp Northeast Temp DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1) 0.0000.0050.0100.0150.020MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) Southeast Temp DEA(mg N2O-N kg-1d-1) 0.0000.0050.0100.0150.020MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) Southeast Temp Southeast Temp DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1) 0.0000.0050.0100.0150.020MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) Southeast Temp Southeast Temp DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1) 0.0000.0050.0100.0150.020MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) Southeast Temp Southeast Temp DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1) Southeast Temp Southeast Temp DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1) 0.0000.0100.0200.0300.040MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) BCT Temp DEA(mg N2O-N kg-1d-1) 0.0000.0100.0200.0300.040MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) BCT Temp BCT Temp DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1) 0.0000.0100.0200.0300.040MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) BCT Temp BCT Temp DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1) 0.0000.0100.0200.0300.040MarchJuneJulySeptDecJanTime(Month)0102030Temperature (*C) BCT Temp BCT Temp DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1) BCT Temp BCT Temp DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1)DEA(mg N2O-N kg-1d-1) Figure 3-47. Seasonal patterns of DEA observed with respect to the Northeast, Southwest, and BCT regions for the soil layer. Temperature is the average taken at 2-3 cm soil depth. Data are mean values ( + 1 SD) from the respective sampling sites (n=18). Three regions were not significantly different ( < 0.05) from one another over time by Pillai’s Trace Criterion statistical analysis.

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96 Figure 3-48. Denitrification enzyme activity associated with temperature (C) for impacted and unimpacted regions within the soil and detritus layers. Data are the actual values from the respective sampling sites collected each month during the tem poral study (n=108).

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97 Denitrification enzyme activity was significantly higher ( < 0.05) in the Northeast region as compared to the Southwest and BCT regions for the detritus layer. For the soil layer, the BCT region had greater DEA rates than the Southwest region ( < 0.05) (Figure 3-49). Sites within the BCT region were found to have a lower floodwater depth (difference on average > 3.6cm) than the Southwest and Northeast regions, likely allowing more oxygen to come into contact with the soil-water interface for nitrification. Microbial activity was also slightly higher in the soil within the BCT region than the other two regions. The responsiveness of DEA has been attributed to differences in the size of microbial biomass (Myrold and Tiedje, 1985; Griffiths et al., 1998; Tiedje, 1982). Differences in denitrifier species may also affect the onset and rate of enzyme synthesis (Smith and Tiedje, 1979). Variations in soil quality (i.e. availability of soluble C) between the impacted and unimpacted regions may contribute to differences in denitrifier taxa leading to a range of sensitivity to O 2 (Figure 3-50) (Table 3-7) (Cavigelli and Robertson, 2001). Redox conditions did not seem to directly influence DEA rates in any of the three sampling regions (Figure 3-51). Redox conditions are missing for March for the BCT region due to the fire, which destroyed the probe. Moderately reduced soils are however characterized by an Eh between +100 and +400 mV (Kralova et al., 1992). There was a weak negative correlation ( < 0.05) between DEA and total P for the soil layer within the BCT region (Figure 3-52). This supports the finding of higher DEA rates within the unimpacted BCT region of the marsh. Phosphorus loading therefore did not have a direct effect on DEA as shown with the spatial variability from the inflow points (White and Reddy, 1999). The wide range of microbial communities present

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98 0.0000.0020.0040.0060.0080.010NortheastBCTSouthwestDEA(mg N20-N kg-1h-1) Detritus bba 0.0000.0020.0040.0060.0080.010NortheastBCTSouthwestDEA(mg N20-N kg-1h-1) Detritus bba 0.0000.0020.0040.0060.0080.010NortheastBCTSouthwestDEA(mg N20-N kg-1h-1) Detritus bba 0.0000.0020.0040.0060.0080.010NortheastBCTSouthwestDEA(mg N20-N kg-1h-1) Detritus bba 0.0000.0100.0200.030NortheastBCTSouthwestDEA(mg N20-N kg-1h-1) Soil bab 0.0000.0100.0200.030NortheastBCTSouthwestDEA(mg N20-N kg-1h-1) Soil bab 0.0000.0100.0200.030NortheastBCTSouthwestDEA(mg N20-N kg-1h-1) Soil bab 0.0000.0100.0200.030NortheastBCTSouthwestDEA(mg N20-N kg-1h-1) Soil bab Figure 3-49. Denitrification enzyme activity within the detrital and soil layers for all three regions, Northeast, Southwest, and BCT. Bars represent the means ( + 1 SD) of samples (n=36) collected from the respective sampling locations. Contrasting letters above the bars represent differences in significant values ( < 0.05).

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99 0.0000.0080.0160.0240.032AerobicperiodAnaerobicperiodAerobicperiodAnaerobicperiodAerobicperiodAnaerobicperiod NEBCTSW DEA(mg N2O-N kg-1d-1) 0.0000.0080.0160.0240.032AerobicperiodAnaerobicperiodAerobicperiodAnaerobicperiodAerobicperiodAnaerobicperiod NEBCTSW DEA(mg N2O-N kg-1d-1)N=12N=24N=18N=18N=12N=24 0.0000.0080.0160.0240.032AerobicperiodAnaerobicperiodAerobicperiodAnaerobicperiodAerobicperiodAnaerobicperiod NEBCTSW DEA(mg N2O-N kg-1d-1) 0.0000.0080.0160.0240.032AerobicperiodAnaerobicperiodAerobicperiodAnaerobicperiodAerobicperiodAnaerobicperiod NEBCTSW DEA(mg N2O-N kg-1d-1)N=12N=24N=18N=18N=12N=24 0.0000.0080.0160.0240.032AerobicperiodAnaerobicperiodAerobicperiodAnaerobicperiodAerobicperiodAnaerobicperiod NEBCTSW DEA(mg N2O-N kg-1d-1) 0.0000.0080.0160.0240.032AerobicperiodAnaerobicperiodAerobicperiodAnaerobicperiodAerobicperiodAnaerobicperiod NEBCTSW DEA(mg N2O-N kg-1d-1)N=12N=24N=18N=18N=12N=24 0.0000.0080.0160.0240.032AerobicperiodAnaerobicperiodAerobicperiodAnaerobicperiodAerobicperiodAnaerobicperiod NEBCTSW DEA(mg N2O-N kg-1d-1) 0.0000.0080.0160.0240.032AerobicperiodAnaerobicperiodAerobicperiodAnaerobicperiodAerobicperiodAnaerobicperiod NEBCTSW DEA(mg N2O-N kg-1d-1)N=12N=24N=18N=18N=12N=24 Figure 3-50. Denitrification enzyme activity under aerobic vs. anaerobic field soil conditions for each region, Northeast, Southwest, and BCT. Data are mean values ( + 1 SD) from the respective sampling regions. (NE, SW Aerobic = March and June 2001, NE, SW Anaerobic = July, September, November, December, and January 2001-2002, BCT Aerobic = March, June, and July 2001, BCT Anaerobic = September, November, December, and January 2001-2002.)

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100 between these regions may contribute to this variability as well as other environmental factors. Denitrification enzyme activity was not correlated ( < 0.05) with PMN possibly because of the smaller, short-lived microbial pools involved with PMN, which have rapid turnover rates and are influenced by a variety of factors and utilization processes (Griffith et al, 1988). However, DEA was found to be significantly correlated ( < 0.05) with extractable NH 4 + concentrations likely because of the interaction between nitrification and denitrification. The distribution of extractable NH 4 + concentrations and DEA follow similar patterns between sites for detritus, with the Northeast region having the highest values. In the detritus layer, the DEA rates of the Northeast (Typha sp.) vegetative communities were significantly greater ( < 0.05) than BCT (Panicum) communities. For the soil, BCT (Cladium) vegetative communities were significantly higher ( < 0.05) in DEA than the Northeast (Cladium) communities (Figure 3-53). This relationship between vegetation and DEA rates within the detritus layer is also shown between sampling regions. The Northeast region is shown to have the highest detrital DEA activity corresponding to the high DEA activity associated with Typha sp, which has also been observed by Cooper (1994). The accumulation of detrital material may also be less for Cladium, Panicum, Salix, and Myrica than Typha sp. leading to higher detritus activity in the Northeast region. The soil layer is significantly higher ( < 0.05) in DEA activity than the detrital layer. This may be the result of the NO 3 diffusing into the sediment, but may also be influenced by the depth of the water column; by the remaining detrital organic C substrate becoming more resistant; and by the removal of NH 4 + due to plant uptake

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101 -400-2000200400600800MarJuneJulySepDecJanMonthsRedox Northeast AerobicAnaerobic -400-2000200400600800MarJuneJulySepDecJanMonthsRedox Northeast Northeast AerobicAnaerobic -400-2000200400600800MarJuneJulySepDecJanMonthsRedox Northeast Northeast AerobicAnaerobic -400-2000200400600800MarJuneJulySepDecJanMonthsRedox Northeast Northeast AerobicAnaerobic Northeast Northeast AerobicAnaerobic -400-2000200400600800MarJuneJulySepDecJanMonthsRedox Southwest AerobicAnaerobic -400-2000200400600800MarJuneJulySepDecJanMonthsRedox Southwest Southwest AerobicAnaerobic -400-2000200400600800MarJuneJulySepDecJanMonthsRedox Southwest Southwest AerobicAnaerobic -400-2000200400600800MarJuneJulySepDecJanMonthsRedox Southwest Southwest AerobicAnaerobic Southwest Southwest AerobicAnaerobic -2000200400600800MarJuneJulySepDecJanMonthsRedox BCT AerobicAnaerobicFire -2000200400600800MarJuneJulySepDecJanMonthsRedox BCT AerobicAnaerobic -2000200400600800MarJuneJulySepDecJanMonthsRedox BCT BCT AerobicAnaerobicFire -2000200400600800MarJuneJulySepDecJanMonthsRedox BCT AerobicAnaerobic -2000200400600800MarJuneJulySepDecJanMonthsRedox BCT BCT AerobicAnaerobicFire -2000200400600800MarJuneJulySepDecJanMonthsRedox BCT BCT AerobicAnaerobic -2000200400600800MarJuneJulySepDecJanMonthsRedox BCT BCT AerobicAnaerobicFire BCT BCT AerobicAnaerobicFire Figure 3-51. Average redox potential within 5 cm of the soil for the Northeast, Southwest, and BCT regions. Data are mean values ( + 1 SD) from the respective sampling sites (n=36).

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102 Figure 3-52. Total P values associated with DEA within the soil layer for impacted and unimpacted regions. Ellipse size for illustration purposes (represents the 0.8 confidence limits).

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103 0.0000.0050.0100.0150.0200.025TCPT/WMOVegetationDEA (mg N20-N kg-1h-1) Soil a/b 0.0000.0050.0100.0150.0200.025TCPT/WMOVegetationDEA (mg N20-N kg-1h-1) Soil 0.0000.0050.0100.0150.0200.025TCPT/WMOVegetationDEA (mg N20-N kg-1h-1) Soil 0.0000.0050.0100.0150.0200.025TCPT/WMOVegetationDEA (mg N20-N kg-1h-1) Soil 0.0000.0050.0100.0150.0200.025TCPT/WMOVegetationDEA (mg N20-N kg-1h-1) Soil a/b 0.0000.0050.0100.0150.0200.025TCPT/WMOVegetationDEA (mg N20-N kg-1h-1) Soil 0.0000.0050.0100.0150.0200.025TCPT/WMOVegetationDEA (mg N20-N kg-1h-1) Soil 0.0000.0040.0080.012TCPT/WMOVegetationDEA (mg N20-N kg-1h-1) Detritus aa/bba/ba/b 0.0000.0040.0080.012TCPT/WMOVegetationDEA (mg N20-N kg-1h-1) Detritus 0.0000.0040.0080.012TCPT/WMOVegetationDEA (mg N20-N kg-1h-1) Detritus ab 0.0000.0040.0080.012TCPT/WMOVegetationDEA (mg N20-N kg-1h-1) Detritus 0.0000.0040.0080.012TCPT/WMOVegetationDEA (mg N20-N kg-1h-1) Detritus aa/bba/ba/b 0.0000.0040.0080.012TCPT/WMOVegetationDEA (mg N20-N kg-1h-1) Detritus 0.0000.0040.0080.012TCPT/WMOVegetationDEA (mg N20-N kg-1h-1) Detritus 0.0000.0040.0080.012TCPT/WMOVegetationDEA (mg N20-N kg-1h-1) Detritus 0.0000.0040.0080.012TCPT/WMOVegetationDEA (mg N20-N kg-1h-1) Detritus aa/bba/ba/b 0.0000.0040.0080.012TCPT/WMOVegetationDEA (mg N20-N kg-1h-1) Detritus 0.0000.0040.0080.012TCPT/WMOVegetationDEA (mg N20-N kg-1h-1) Detritus ab 0.0000.0040.0080.012TCPT/WMOVegetationDEA (mg N20-N kg-1h-1) Detritus 0.0000.0040.0080.012TCPT/WMOVegetationDEA (mg N20-N kg-1h-1) Detritus aa/bba/ba/b 0.0000.0040.0080.012TCPT/WMOVegetationDEA (mg N20-N kg-1h-1) Detritus 0.0000.0040.0080.012TCPT/WMOVegetationDEA (mg N20-N kg-1h-1) Detritus Figure 3-53. Denitrification enzyme activity with respect to vegetative communities within the soil and detrital layers, T = NE, SW Typha sp., C = NE, BCT Cladium, P = BCT Panicum, T/WM = NE, SW Typha sp./Woody Mix, and O = NE, SW Others. Data are mean values ( + 1 SD) from the respective sampling sites (n=18).

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104 (Reddy and Patrick, 1984). Generally, soil organic C has been found as the most important factor influencing denitrifier populations. Differences in soil characteristics such as total C and total N influence DEA as well (Cavigelli and Robertson, 2001). The BCT region had a lower C/N ratio throughout the temporal sampling period as compared to that of the Northeast and Southwest regions (Table 3-9). An average decrease of C/N ratios was also observed to occur with the transition from the detrital layer into the soil. The higher C/N values associated with the Northeast and Southwest regions may have contributed to the reduction in DEA due to the limited availability of inorganic N to the microbial pool as well as a change in the microbial pool composition (Groffman et al., 1992). The depth of the floodwater layer will affect the thickness of the oxidized layer at the soil-water interface and in turn the rate of N transformations (NH 4 + to NO 3 ) (Hauck, 1979). Ammonia in the aerobic soil layer becomes oxidized to NO 3 , which moves down the soil profile into the anaerobic soil layer and undergoes denitrification. Denitrification may then be reduced if the availability of NO 3 in the soil profile declines (Reddy et al., 1980a; Reddy et al., 1980b). Temporal Sampling Summary Seasonal patterns were found to be significantly different ( < 0.05) between all three regions for MBN and extractable NH 4 + for both the soil and detritus layers. With regards to PMN and DEA rates, seasonal patterns were only significantly different ( < 0.05) between all three regions for the detritus layer. Arginine ammonification rates had significantly different ( < 0.05) seasonal patterns between all three regions for the soil layer only. Vegetative communities as well as the distribution of various microbial populations likely influenced these differences in seasonal patterns between regions. The

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105 forms of available C, C/N ratios of the substrate, and the amount of detrital material produced can affect microbial activity and subsequently impact N processes. Table 3-9. Average C/N values within the soil and detritus layers for all three regions, Northeast, Southwest, and BCT during the temporal sampling. Data are mean values ( + 1 SD) from the respective sampling sites (n=18). NortheastBCTSouthwestMarchSoil 17.3 0.9315.7 0.7518.7 0.73Detritus 40 7.3325.1 3.5326.1 3.62JuneSoil 17.7 0.315.1 1.3717.6 0.48Detritus 30.7 9.7428.4 6.4836.4 3.63JulySoil17.7 0.34 15.2 1.28 17.7 0.57Detritus32.3 5.75 34.1 10.59 34.5 11.03SetemberSoil 17 0.7815.5 1.2118.1 0.74Detritus 29.8 6.6233.4 5.7826.2 4.99DecemberSoil 18.4 1.715.9 1.1918.6 0.48Detritus 30.6 6.5242.2 4.6522.1 0.92JanuarySoil16.7 1.0715.6 1.08 17.8 0.49Detritus28.6 8.4635.4 4.92 26 6.26

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CHAPTER 4 SUMMARY AND CONCLUSIONS Nutrient cycling processes include interactions among plants, soil, hydrology, and microorganisms in ecosystems. These interactions can vary in time and space, complicating the assessment of nutrients in response to changes within the ecosystem. Establishing indicators of soil quality, which represent the capacity of an ecosystem to support nutrient cycling and biodegradation functions, is necessary to preserve and protect our natural resources. Focusing on biochemical properties within the soil can lead to an understanding of the changes that take place because of external harm and/or inputs to the system. This will allow for a faster more efficient method of determining soil quality and therefore the stability of the ecosystem. Because of historic nutrient loading from the surrounding agriculture lands, the vegetative communities within the Blue Cypress Marsh have shifted from dominant Cladium and Panicum communities to more invasive species including Typha sp., Salix, and Myrica. This establishment of different plant communities within the impacted regions can lead to differences between the three regions in soil quality from substrate differences including available C and N. Different growth and nutrient uptake/release rates of vegetation types can modify the detrital quality and accumulation in the marsh, therefore influencing nutrient turnover rates. Soil N transformations (i.e. PMN) then can be indirectly affected by microbial activity through detrital quality and quantity (Figure 4-1). During the spatial sampling in September 2000, flooded conditions existed within the marsh. For the temporal study (March 2001 to January 2002), impacts due to fire in 107

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108 the Southwest and BCT sampling areas occurred around January 31, 2001. Hydrologic fluctuations due to rainfall were also observed in throughout the entire marsh including a drought period, which extended from November 2000 until the beginning of May 2001. P Loadingfrom AgricultureIncreasedProductivity(Vegetation)N Release/Availability Detritus Accumulation P Loadingfrom AgricultureIncreasedProductivity(Vegetation)N Release/Availability Detritus Accumulation P Loadingfrom AgricultureIncreasedProductivity(Vegetation)N Release/Availability (PMN/ Ext. NH4+) Detritus Accumulation P Loadingfrom AgricultureIncreasedProductivity(Vegetation)N Release/Availability Detritus Accumulation P Loadingfrom AgricultureIncreasedProductivity(Vegetation)N Release/Availability Detritus Accumulation P Loadingfrom AgricultureIncreasedProductivity(Vegetation)N Release/Availability (PMN/ Ext. NH4+) Detritus Accumulation Figure 4-1. Increase in N mineralization measured by PMN and extractable NH 4 + as a function of changes in vegetation linked to phosphorus-loading. Soil, vegetation, and hydrology strongly influence microbial processes, therefore allowing them to be used as indicators of ecosystem function. The transformation and storage of nutrients are regulated by soil microbial biomass. Enzymes produced by microbes and plant roots regulate biochemical processes present in the soil. Because of the dynamic characteristics of microbial biomass, the potential exists for it to be a sensitive indicator in the soil reflecting changes from nutrient loading in a system. A significant relationship has been shown between microbial biomass and the amount of mineralizable nutrients in soils. Microbial biomass has also been proven to be a good indicator of changes in the physico-chemical properties of soils such as nutrient availability.

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109 Microbial biomass N was found to be higher within the soil for the unimpacted BCT region than the impacted regions. The different microbial communities present within the soil may influence this diversity of MBN between regions. Nutrient loading of P appeared to have an affect on the microbial communities possibly due to the changes in vegetation type surrounding the inflow regions. Phosphorus loading has been shown to significantly contribute to the spread of cattail and other rapidly growing vegetation into native marshes. The change in vegetative communities will influence the total N and total C available for microbial pools as well as the amount of organic matter and detrital turnover rate. This in turn will alter the soil quality necessary for the function(s) of some microorganisms. The size of the microbial pool of detritus was related to PMN and extractable NH 4 + . Greater MBN within the detrital layer of the impacted regions corresponded to higher PMN rates and extractable NH 4 + concentrations within the Northeast and Southwest regions. In wetland soils, organic N mineralization regulates inorganic N concentrations in the water column and supplies N to microorganisms and plants. The biological transformation of organic nitrogen compounds to NH 4 + is regulated by C/N ratio of the substrate; by extracellular enzyme activity; by the supply of electron acceptors (O 2 ); by temperature; by limiting nutrients; by pH; and by redox conditions. Similar to MBN, higher PMN rates and extractable NH 4 + concentrations were found within the impacted regions versus the unimpacted region for the detritus layer. This was likely due to the changes in vegetation and microbial communities from P-loading. The Southwest region, however, had lower P concentrations within the detrital layer as well as less PMN activity and NH 4 + concentrations than the Northeast region

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110 (Table 3-4). This likely was the result of water inflows being discontinued in the Southwest region 10 years before being terminated in the Northeast region. The impacted Southwest and unimpacted BCT regions have similar N activity rates for detritus, suggesting restoration within the Southwest region over the last 20 years. As for the Northeast region, turnover rates within the system still remained to be functioning at a higher rate than the BCT and Southwest regions. Phosphorus additions have been shown to increase microbial activity (measured by N mineralization rates) for a variety of ecosystems. Total P was significantly correlated with PMN rates and extractable NH 4 + concentrations. Therefore, total P may influence organic N mineralization rates within the system. These results indicate that extractable NH 4 + concentrations may be beneficial as a biogeochemical indicator of P loading. As the end product of PMN, extractable NH 4 + can also be used an excellent indicator of N mineralization rates in flooded soils. The low PMN rates and extractable NH 4 + concentrations in the BCT region corresponds with low activity for Cladium caused by the high C/N ratio of the substrate. An increase in lignin of the substrate over time decreases the quality or availability of soluble C. Therefore, rates of PMN and extractable NH 4 + concentrations are reduced due to the change in substrate. A greater detrital accumulation in the Northeast and Southwest regions due to productive Typha sp. communities may have led to an increase in PMN rates and extractable NH 4 + concentrations within these regions. Increase in organic matter accumulation in nutrient enriched areas produces younger soils and an increase in net primary productivity. Vegetation type therefore can create differences in soil quality between the impacted and unimpacted regions.

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111 Arginine ammonification and PMN measure a slightly different fraction of soil microbial activity. Mineralization of organic N is limited by the breakdown of large, complex compounds, which can be minimized by providing amino acids that are easily attacked and consumed by microbes. Mineralization rates were higher for argininie ammonification than PMN because of the simplicity and low C/N ratio of the substrate. The quality and quantity of detritus can influence ammonification rates depending upon the C/N ration of the substrate. Therefore, ammonification within the detritus layer is greater than the soil layer, which contains material with a lower C/N ratio. Arginine ammonification was not found to be influenced by MBN, vegetative communities, total N and total P. The high variability associated with microbial processes, including extracellular enzyme activity, may have led to the unpredictability of arginine ammonification. These extracellular enzymes may also be short lived in the soil or are too heterogeneous in distribution. Arginine ammonification may therefore not be a reliable indicator of changes in microbial activity due to nutrient loading and shifts in vegetation communities. Soil denitrification potential is measured by DEA and can be related to annual denitrification N loss. The activity of denitrifying bacteria is influenced by the depth of flood water, pH, temperature, energy source, and NO 3 concentrations. However, denitrification rates in the field are often poorly correlated with environmental variables such as soil moisture, temperature, and NO 3 concentrations. Denitrification occurs around the root zone as well because of the transport of O 2 through the stems and roots of the plant into the rhizosphere for nitrification processes.

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112 Denitrification enzyme activity was found to be high for the unimpacted BCT region within the soil layer. This also corresponds to the high MBN found within the BCT region. The responsiveness of DEA has been attributed to the range in the quantity of microbial biomass. Differences in denitrifier species also can affect the onset and rate of enzyme synthesis. Variations in soil quality due to differences in vegetation communities (i.e. availability of soluble C) between the impacted and unimpacted regions may contribute to differences in dinitrifier species. The Northeast had high detrital DEA activity corresponding to high DEA activity and extractable NH 4 + concentrations associated with Typha sp. The accumulation of detrital material may also be less for Cladium, Panicum, Salix, and Myrica than Typha sp. leading to higher detritus activity in the Northeast region. Total P was shown to have a weak negative correlation with DEA within the soil. Reduced turnover within the soil due to an increase in age and poor C quality creates a more stable pool of organic matter less influenced by P-loading. Therefore, DEA does not appear to be reliable as a biogeochemical indicator of historic P-loading within the system for the soil. With respect to the detritus layer, DEA was negatively correlated ( < 0.05) with total P. However, the significant correlation ( < 0.05) between total P and extractable NH 4 + may influence DEA rates under P-loading conditions because of the interaction between nitrification and denitrification. The diversity of microorganisms established between the impacted and unimpacted regions due to P-loading may cause denitrifying activity to vary independent from the general heterotrophic communities. Higher DEA activity found within the soil than detritus may be due to a variety of factors including most importantly the diffusion of NO 3 into the sediment, but also the

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113 composition of organic C substrate. For all three regions, there was an average decrease of C/N ratio observed to occur with transition from the detrital layer into the soil. This may limit DEA because of the restricted availability of inorganic N to the microbial pool as well as a change in the microbial pool composition. Denitrification rates for the entire Blue Cypress Marsh are likely related to nitrification processes in the water column driving NO 3 to diffuse into the anaerobic sediment for denitrifiers rather than an external nutrient input source. The increase of PMN during March can be attributed to the occurrence of fire and drought before sampling. Setting aside the month of March, a seasonal effect was observed within both the soil and detrital layers for PMN, however, within the soil, seasonal patterns between regions were not found to be different. Extractable NH 4 + on the other hand displayed significantly different seasonal patterns between all three regions within both the soil and detrital layers. Microbial biomass N was also observed to follow significantly different seasonal patterns between regions, likely the result of compounding factors including temperature. A significant difference in seasonal patterns between regions was found for DEA with respect to the detrital layer only. Other factors than temperature and moisture related to C and N dynamics in the soil can strongly influence denitrification. Increased microbial activity and availability of inorganic N due to P-loading potentially can lead to serious problems with eutrophication. Nitrogen mineralization has been found to be responsible for maintenance of high rates of primary productivity in estuarine systems. This inorganic N production can affect wetland water and soil quality and, in turn, lead to changes of vegetative species composition. Recent impacts (i.e., 10

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114 years) are still reflected in the Northeast region because of high rates of N cycling and productivity (i.e., detrital production). Potentially mineralizable N rates, extractable NH 4 + and total P concentrations were higher for detrital material within the Northeast region than the impacted Southwest and unimpacted BCT regions (Table 4-1). The impacted Southwest region, where nutrient loading was discontinued 20 years prior, has similar N activity rates for detritus as the unimpacted BCT region. This suggests progress toward restoring the system in the Southwest region to lower nutrient or unimpacted conditions. Use of biogeochemical properties to estimate soil quality is currently limited by the lack of studies that include variations of biogeochemical properties over a wide range of systems. Therefore, further research should include conducting more studies that would provide comparable data of biogeochemical properties in order to establish standards for soil quality evaluation. This compilation of data should also include biogeochemical properties of soils in different areas of the world. Through these additional studies, a greater understanding may be reached regarding wetlands, including their capacity to buffer the effects of human impacts. Wetlands provide numerous and necessary functions for the maintenance of our valuable ecosystems.

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115 APPENDIX SPATIAL AND TEMPORAL SAMPLING DATA Table A-1. Laboratory data for select N pro cesses collected during the spatial (2000) and temporal (2001-2002) study of the BCM. RegionField IDLab ID #SoilMBNPMNDEAExt. NH4 +Arg-NTPTCTN Profile (mg N kg1 )(mg N kg1 d1 ) (mg N20-N kg1 h1 ) (mg N kg1 )(mg N kg1 h1 )mg kg1 g kg1 g kg1 NortheastC11Soil537.3627.960.00226110.00987.44472.4226.25 NortheastC22Soil650.7436.760.00318226.59951.75466.8524.58 NortheastC33Soil512.8524.24136.87953.18463.3627.28 NortheastC44Soil651.1036.680.00182253.59979.31472.926.99 NortheastC55Soil528.0530.18257.32917.07470.2725.19 NortheastC66Soil538.6634.92234.281029.74471.4726.41 NortheastC77Soil417.5634.56216.571073.28469.7227.98 NortheastC88Soil555.4738.31244.031059.82477.8226.84 NortheastC99Soil578.4333.80321.75951.39475.4425.36 NortheastC10B11Soil344.4935.4193.27849.91469.0425.28 NortheastC1112Soil501.2933.73232.47920.93477.2224.6 NortheastC1213Soil347.8827.1678.11935.4748725.57 NortheastC1314Soil310.4417.47136.58719.49480.3436.91 NortheastC1415Soil348.5712.37102.79432.61479.9936.05 NortheastC1516Soil157.0119.480.00048135.51833.53469.8232.64 NortheastC1617Soil216.5925.930.00190176.80929.92458.530.64 NortheastC1718Soil304.6114.910.00045163.64670.83466.5832.34 NortheastC1819Soil325.5528.73251.83980.45462.2438.46 NortheastC1920Soil845.1216.52264.49837.67481.1837.03 NortheastC2021Soil522.1942.23250.95841.63458.7724.22 NortheastC2122Soil394.6330.850.00138133.52613.88463.6225.86 NortheastC2223Soil472.0139.370.00164189.20760.28472.4423.23 NortheastC2324Soil479.7233.640.00088183.90699.20459.9623.3 NortheastC2425Soil380.3845.95258.33719.24459.5434.56 NortheastC2526Soil256.198.43171.73324.81487.9432.7 NortheastC2627Soil1848.8543.63326.611402.30455.7240.01 NortheastC2728Soil186.044.63266.53329.30483.5437.6 NortheastC2829Soil611.939.69302.98483.88478.7937.89 NortheastC29B31Soil166.1613.270.0000032.921001.07487.9937.05 NortheastC3032Soil1011.3620.930.0002773.651123.99448.0937.77 NortheastC3133Soil785.8215.060.0008060.09897.52464.4739.15 NortheastC3234Soil438.1537.39242.55977.78465.130.49 NortheastC3335Soil563.4537.9436.81888.72472.623.26 NortheastC3436Soil329.0130.180.00207139.01893.86468.2132.16 NortheastC3537Soil244.3629.100.00433140.69785.27470.4930.83 NortheastC3638Soil406.1735.070.0039898.52888.95466.6131.54 NortheastC3739Soil227.1630.39169.23881.09440.3423.78 NortheastC3840Soil2045.83149.84575.41796.39432.5523.26 NortheastC3941Soil589.4645.29144.60801.30441.0522.96 NortheastC4042Soil483.8227.46119.79538.69449.9624.34 NortheastC4143Soil305.9131.99138.201054.71442.0131.32 BCTB144Soil301.6866.330.0157323.73584.33470.0528.99 BCTB245Soil519.6871.100.00695119.18716.11466.2328.79 BCTB346Soil344.3771.35138.18791.89461.227.88 BCTB447Soil516.5966.780.01254246.23786.82464.1430.04 BCTB548Soil309.5851.78138.59654.19453.6928.76 BCTB649Soil385.0363.50143.63741.30463.7629.32 BCTB750Soil893.2768.29215.37760.81461.5329.23 BCTB851Soil464.7052.2198.45618.21464.125.39

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116 Table A-1. Continued. Laboratory data for select N processes collected during the spatial (2000) and temporal (2001-2002) study of the BCM. RegionField IDLab ID #SoilMBNPMNDEAExt. NH4+Arg-NTPTCTNProfile(mg N kg1 )(mg N kg1 d1 )(mg N20-N kg1 h1 )(mg N kg1 )(mg N kg1 h1 )mg kg1 g kg1 g kg1 BCTB952Soil301.8353.97138.13634.54467.0423.87BCTB1053Soil207.3252.0984.39708.26450.5524.83BCTB1154Soil559.4057.09124.77691.98470.1730.99BCTB1255Soil716.2474.84125.32801.66466.4329.29BCTB1356Soil474.1049.7588.95613.69475.4228.64BCTB1457Soil433.5445.7995.70506.79469.4824.36BCTB1558Soil275.6231.4672.24528.09469.3728.79BCTB1659Soil227.9048.54122.56494.72462.4524.22BCTB1760Soil443.2654.89118.88594.17476.6327.55BCTB1861Soil440.0969.18133.66657.32461.7624.28BCTB1962Soil648.0874.010.03130174.10682.81452.7128.66BCTB2063Soil670.3485.080.02054186.95668.86457.3627.01BCTB2164Soil708.6768.070.01467150.34694.37459.9228.37BCTB2265Soil643.0078.01142.51666.02466.6928.29BCTB2366Soil446.8465.34155.88650.32463.3726.27BCTB2467Soil932.4884.21190.32742.83458.7433.73BCTB2568Soil391.9165.28123.17584.56463.3529.24BCTB2669Soil548.0760.640.01550148.71563.48469.4129.38BCTB2770Soil566.8670.850.01335155.47622.85459.0329.31BCTB2871Soil679.6167.510.00622122.88616.73460.7728.02BCTB2972Soil523.9563.20116.65548.38464.225.37BCTB3073Soil448.1852.020.0074485.87669.38468.8725.86BCTB3174Soil481.0544.050.0065091.92566.02468.725.6BCTB3275Soil367.0838.7781.00691.89469.0723.64BCTB3376Soil400.7047.560.01785103.13594.74469.9423.7BCTB3477Soil201.3744.20114.21541.84470.0927.58BCTB3578Soil411.8644.58111.91505.35471.4326.93BCTB3679Soil1064.5453.590.00219124.99646.34478.0531.5BCTB3780Soil655.7963.17146.41665.15460.9830.3BCTB3881Soil1272.1279.480.00520251.45725.84454.9729.65BCTB3982Soil672.7259.170.00569152.35550.13466.2129.87SouthwestA183Soil641.5540.270.00364107.37792.25475.8421.8SouthwestA284Soil500.7645.750.00249100.25778.50469.9223.79SouthwestA385Soil794.1946.04192.89892.67462.826.89SouthwestA486Soil456.9542.770.00775106.21814.28469.8121.67SouthwestA587Soil542.1568.02208.31923.40462.3125.69SouthwestA688Soil539.6451.45142.12862.93475.3924.7SouthwestA789Soil509.2452.60122.38935.22468.9528.02SouthwestA890Soil210.3952.9137.34820.12463.0923.97SouthwestA991Soil260.9147.11110.09924.75469.3326.78SouthwestA1092Soil634.2048.4685.961027.99480.726.48SouthwestA1193Soil547.5256.96112.49926.01477.5427.48SouthwestA1294Soil735.0763.86142.98895.21464.8225.31SouthwestA1395Soil691.5848.45124.95882.25462.4622.93SouthwestA1496Soil624.5354.03136.54884.33463.9923.74SouthwestA1597Soil467.2427.3969.64620.81456.1519.75SouthwestA1698Soil635.3941.8177.35672.27466.422.72SouthwestA1799Soil794.8273.31212.46981.28479.9625.47SouthwestA18100Soil742.8767.81178.47993.69460.1126.51

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117 Table A-1. Continued. Laboratory data for select N processes collected during the spatial (2000) and temporal (2001-2002) study of the BCM. RegionField IDLab ID #SoilMBNPMNDEAExt. NH4+Arg-NTPTCTNProfile(mg N kg1 )(mg N kg1 d1 )(mg N20-N kg1 h1 )(mg N kg1 )(mg N kg1 h1 )mg kg1 g kg1 g kg1 SouthwestA19101Soil593.7653.150.00082196.59950.98463.5726.65SouthwestA20102Soil688.3148.050.00315220.34906.34453.2625.41SouthwestA21103Soil20.1836.350.00642245.50925.58454.4225.3SouthwestA22104Soil314.9556.8855.22935.70450.91823.41SouthwestA23105Soil1015.7069.47251.391003.59465.3124.54SouthwestA24106Soil1046.3673.720.00544280.581030.87469.3622.54SouthwestA25107Soil807.5553.600.00415267.97994.09471.1825.18SouthwestA26108Soil745.3350.920.00232242.07936.48474.4625.3SouthwestA27109Soil614.3838.82196.00768.90457.0122.27SouthwestA28110Soil613.4255.700.00657104.13681.56455.0919.94SouthwestA29111Soil442.4926.390.00040212.68677.60466.0722.44SouthwestA30112Soil404.3033.460.00199127.20760.90469.5422.46SouthwestA31113Soil669.1145.08220.59625.15454.4922.49SouthwestA32114Soil530.5840.880.00074124.66870.02467.6825.37SouthwestA33115Soil530.7638.980.00081141.96896.89463.5723.83SouthwestA34116Soil122.1039.36201.49992.04464.3725.77SouthwestA35117Soil179.9436.860.00227111.75876.87470.9223.98SouthwestA36118Soil544.7330.78111.40897.36460.4824.61SouthwestA37119Soil495.3535.510.00366114.74771.40463.6224.25SouthwestA38120Soil468.8222.940.00545102.21792.50460.5123.53SouthwestA39121Soil505.4835.7485.13763.41455.2123.42SouthwestA40122Soil469.3231.890.0012962.92785.39469.0523.46SouthwestA41123Soil401.2642.7384.05796.95466.8224.01NortheastC1124Detritus520.65195.131037.131202.63466.2321.01NortheastC2125Detritus863.43122.49721.891049.39481.1419.61NortheastC3126Detritus1658.63350.591436.891591.81476.8923.89NortheastC4127Detritus196.891197.901135.89470.2520.45NortheastC5128Detritus559.34155.63721.791062.53477.4819.11NortheastC6129Detritus1134.08197.90952.731093.90473.919.33NortheastC7130Detritus880.43182.22602.351117.71472.3718.83NortheastC8131Detritus2832.28606.17462.111.33NortheastC9132Detritus322.6740.4070.641045.08463.5315.76NortheastC10133Detritus489.76202.05761.221078.73484.8824.68NortheastC11134Detritus476.70168.96582.39819.78482.718.03NortheastC12135Detritus768.72170.84726.09934.57485.3318.7NortheastC13136Detritus947.04226.09621.591014.46459.3319.4NortheastC14137Detritus233.22149.39138.89625.77426.4611.2NortheastC15138Detritus899.2766.68512.43993.64469.6217.47NortheastC16139Detritus425.2567.87129.10820.22466.3714.85NortheastC17140Detritus531.8574.04254.611115.79467.6317.48NortheastC18141Detritus168.071066.951254.44454.6320.8NortheastC19142Detritus1082.33207.901130.541268.38466.8936.01NortheastC20143Detritus1034.46164.48643.79981.21470.6323.03NortheastC21144Detritus1470.63116.20878.27656.05472.1614.27NortheastC22145Detritus615.21121.13484.17761.88462.2316.23NortheastC23146Detritus697.38100.06271.60780.63474.1218.36NortheastC24147Detritus582.03235.96907.86838.03432.9916.2NortheastC25148Detritus1432.75206.83557.84958.01468.2833.51NortheastC29149Detritus736.12197.6976.72212.90449.456.95

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118 Table A-1. Continued. Laboratory data for select N processes collected during the spatial (2000) and temporal (2001-2002) study of the BCM. RegionField IDLab ID #SoilMBNPMNDEAExt. NH4+Arg-NTPTCTNProfile(mg N kg1 )(mg N kg1 d1 )(mg N20-N kg1 h1 )(mg N kg1 )(mg N kg1 h1 )mg kg1 g kg1 g kg1 NortheastC31150Detritus805.56454.4935.53NortheastC32151Detritus1012.921362.10447.7721.57NortheastC33152Detritus197.87370.00730.32479.8713.42NortheastC34153Detritus2727.821339.68455.5422.06NortheastC35154Detritus1864.33246.12265.691022.41444.5217.74NortheastC36155Detritus1430.33288.69977.431321.75469.9926.75NortheastC37156Detritus529.1524.9013.55327.08459.847.02NortheastC38157Detritus841.9467.2244.80478.65467.0210.57NortheastC39158Detritus128.8086.1144.09568.17469.4613.27NortheastC40159Detritus398.4621.0394.19374.88459.017.47NortheastC41160Detritus3111.38246.95340.74724.18432.8815.36BCTB1161Detritus478.87451.829.75BCTB2162Detritus596.46450.4110.28BCTB3163Detritus-82.9693.51200.82634.86457.3913.6BCTB4164Detritus969.22101.1183.74643.42443.3512.32BCTB5165Detritus997.14106.6578.40526.14451.3212.16BCTB6166Detritus1062.61688.19469.4514.63BCTB7167Detritus759.5753.24866.91632.12461.5913.48BCTB8168Detritus34.8768.92398.69793.08480.8311.71BCTB9169Detritus378.93659.01491.115.26BCTB10170Detritus3781.6571.63214.48774.59472.8717.18BCTB11171Detritus2487.6674.60393.35644.42453.1410.74BCTB12172Detritus120.9784.6854.75591.66467.5312.97BCTB13173Detritus83.45669.15505.3819.79BCTB14174Detritus1804.9749.93384.44544.92485.0115.84BCTB15175Detritus998.06690.99478.4118.53BCTB16176Detritus694.3059.85286.77629.51469.2617.98BCTB17177Detritus820.9655.8546.54379.26464.1210.65BCTB18178Detritus895.57101.36492.69613.41458.111.49BCTB19179Detritus230.6387.31439.06542.00463.4712.93BCTB20180Detritus1417.72103.1551.90410.70453.168.5BCTB21181Detritus1369.08140.93156.18712.35441.7916.46BCTB22182Detritus408.54159.26138.13546.55458.6711.4BCTB23183Detritus719.6370.1040.59489.05473.3510.56BCTB24184Detritus1198.56138.47256.46641.16454.1618.69BCTB25185Detritus822.8171.1945.83363.74473.758.63BCTB26186Detritus2178.9753.4037.07412.14458.8411.67BCTB27187Detritus667.0155.0214.77316.94465.237.98BCTB28188Detritus274.57359.24476.58.46BCTB29189Detritus38.9616.64314.23476.586.34BCTB30190Detritus48.4361.6425.56417.01398.159.23BCTB31191Detritus327.23460.447.78BCTB32192Detritus262.4040.0338.95470.79480.819.05BCTB33193Detritus420.87462.539.11BCTB35194Detritus1328.22431.51463.919.35BCTB36195Detritus419.10389.097.5BCTB37196Detritus493.92458.8710.77BCTB38197Detritus377.17440.379.51BCTB39198Detritus467.92438.589.95

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119 Table A-1. Continued. Laboratory data for select N processes collected during the spatial (2000) and temporal (2001-2002) study of the BCM. RegionField IDLab ID #SoilMBNPMNDEAExt. NH4+Arg-NTPTCTNProfile(mg N kg1 )(mg N kg1 d1 )(mg N20-N kg1 h1 )(mg N kg1 )(mg N kg1 h1 )mg kg1 g kg1 g kg1 SouthwestA1199Detritus794.7187.2728.27951.28483.6715.02SouthwestA2200Detritus522.0196.27396.58793.26472.1212.06SouthwestA3201Detritus53.08117.01243.95778.37485.1712.1SouthwestA4202Detritus819.0367.95127.21733.33482.6413.3SouthwestA5203Detritus1278.92132.7318.15956.75480.2215.19SouthwestA6204Detritus621.2867.3014.89625.82481.955.84SouthwestA7205Detritus1244.44118.1119.77860.81460.0213.8SouthwestA8206Detritus976.63106.0995.70927.99467.513.3SouthwestA9207Detritus733.05117.4140.07805.24471.2913.4SouthwestA10208Detritus85.1544.97632.64476.0711.76SouthwestA11209Detritus1014.48156.84177.351045.22475.7814.92SouthwestA12210Detritus184.1164.9715.07401.02429.85.78SouthwestA13211Detritus552.38110.3716.74716.26458.1910.87SouthwestA14212Detritus321.8785.57302.47734.70450.7710.86SouthwestA15213Detritus261.4190.459.99637.28463.6713.42SouthwestA16214Detritus608.5876.3016.24531.12463.1514.95SouthwestA17215Detritus1953.55110.15331.281068.58468.5820.36SouthwestA18216Detritus148.22240.221135.22438.4717.99SouthwestA19217Detritus1393.98106.48267.43920.47480.517.14SouthwestA20218Detritus231.33482.881173.15474.4820.85SouthwestA21219Detritus704.6498.32109.21554.26469.5912.21SouthwestA22220Detritus1129.69114.2620.24758.36469.1712.2SouthwestA23221Detritus1234.50128.78170.25941.66476.7315.65SouthwestA24222Detritus77.73133.10343.89986.69472.6416.17SouthwestA25223Detritus116.72528.512506.541841.49460.2624.29SouthwestA26224Detritus2076.36463.741227.251322.47463.9818.91SouthwestA27225Detritus86.017.14671.64480.1316.16SouthwestA28226Detritus400.8678.596.03608.24491.7814.82SouthwestA29227Detritus994.8977.315.72707.93485.3716.36SouthwestA30228Detritus691.9466.535.38670.38494.0115.65SouthwestA31229Detritus660.2617.8834.52418.00472.418.96SouthwestA32230Detritus783.7431.3436.66427.58479.748.86SouthwestA33231Detritus487.78548.99761.04479.1515.14SouthwestA34232Detritus1504.95147.9640.67691.49464.9611.3SouthwestA35233Detritus539.06124.2615.56685.91476.9110.63SouthwestA36234Detritus1570.47152.44130.91766.30486.8914.09SouthwestA37235Detritus206.1379.498.79479.51475.488.04SouthwestA38236Detritus945.900.409.07406.35488.686.91SouthwestA39237Detritus518.2736.196.09413.45494.068.16SouthwestA40238Detritus757.6520.977.37396.84494.727.95SouthwestA41239Detritus568.6269.6721.89487.51480.798.39NortheastC1241Soil66.01255.960.0024512.87990.84472.4727.91Northeast242Soil235.07265.570.0115490.74881.80455.6026.34Northeast243Soil138.65384.620.0083187.46959.38455.6027.76NortheastC22244Soil171.64246.200.0042954.36654.23460.3927.33Northeast245Soil188.23123.140.0012249.27628.81462.4627.20Northeast246Soil101.13196.420.0049047.54665.87464.2624.36BCTB27247Soil228.77172.860.0016287.92573.61464.2727.62BCT248Soil255.3787.790.0097270.31606.74461.7028.49 .

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120 Table A-1. Continued. Laboratory data for select N processes collected during the spatial (2000) and temporal (2001-2002) study of the BCM. RegionField IDLab ID #SoilMBNPMNDEAExt. NH4+Arg-NTPTCTNProfile(mg N kg1 )(mg N kg1 d1 )(mg N20-N kg1 h1 )(mg N kg1 )(mg N kg1 h1 )mg kg1 g kg1 g kg1 BCT249Soil124.49160.430.0027984.72622.37456.2628.60BCTB37250Soil331.9699.1361.54618.36463.4831.41BCT251Soil340.48102.690.0379962.61593.35463.1829.89BCT252Soil316.58294.2051.73686.16470.5831.05SouthwestA25253Soil153.84274.760.0000461.59973.28441.8224.75Southwest254Soil116.6789.380.0005569.61912.88447.8722.93Southwest255Soil288.3795.620.0002166.94939.88452.6924.48SouthwestA34256Soil204.7083.020.0002559.291007.38449.3524.49Southwest257Soil271.3836.320.0034851.701058.87441.7023.89Southwest258Soil227.7140.680.0012537.62900.71452.4122.92NortheastC1259Detritus651.321.650.000156.39911.48452.6114.24Northeast260Detritus356.521.480.000535.14806.07444.4012.45Northeast261Detritus588.653188.730.000058.45620.82458.0311.88NortheastC22262Detritus351.94548.270.000055.63368.94450.128.61Northeast263Detritus439.74436.970.0001165.07425.09454.7210.22Northeast264Detritus541.69369.170.0001214.85462.30448.4712.11BCTB27265Detritus477.58445.7614.21BCT266Detritus844.060.0002636.05431.7017.13BCT267Detritus202.300.0006519.95452.9918.28BCTB37268Detritus779.66839.23409.3319.11BCT269Detritus432.67549.020.001597.23827.81429.5616.62BCT270Detritus700.65330.760.001383.60963.18407.3018.40SouthwestA25271Detritus526.571382.352.8940138.101185.20387.1518.83Southwest272Detritus403.911155.182.699495.61795.85429.7818.57Southwest273Detritus560.50281.610.002452.531144.66390.5913.59SouthwestA34274Detritus167.31199.220.000251.62894.64336.0412.84Southwest275Detritus466.79614.370.000245.79982.62342.9912.39Southwest276Detritus474.631131.140.000388.391009.20363.0012.04NortheastC1305Soil4281.3062.660.017882.73917.11453.9126.13Northeast306Soil1470.8858.860.0108166.35787.15452.7625.25Northeast307Soil484.0778.690.005254.37855.07456.9726.53NortheastC22308Soil408.3351.180.007441.45616.27461.4725.82Northeast309Soil344.7937.650.003930.54653.93461.5325.96Northeast310Soil403.6048.730.001726.25590.16462.0725.82BCTB27311Soil384.0546.660.035656.65517.73462.5129.67BCT312Soil519.5356.510.028934.64509.23466.4028.79BCT313Soil776.4844.370.013134.96488.23460.7427.31BCTB37314Soil635.1446.830.014743.20531.49470.6032.91BCT315Soil541.7146.800.009547.13489.64473.7135.46BCT316Soil544.3845.950.016060.66513.94471.6333.61SouthwestA25317Soil492.2349.940.005540.30910.81448.1825.91Southwest318Soil684.2558.820.004742.17901.43445.1025.39Southwest319Soil610.7058.730.018844.88885.97441.6126.19SouthwestA34320Soil518.9855.350.015536.20837.34435.2623.85Southwest321Soil258.2246.2625.99837.40447.1924.95Southwest322Soil430.6145.760.009135.82849.98450.6625.62NortheastC1323Detritus1756.40142.250.0036129.32848.49444.9319.12Northeast324Detritus1364.56116.340.0243482.46988.22452.6523.38Northeast325Detritus1800.73166.080.0159169.48786.09462.7019.24

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121 Table A-1. Continued. Laboratory data for select N processes collected during the spatial (2000) and temporal (2001-2002) study of the BCM. RegionField IDLab ID #SoilMBNPMNDEAExt. NH4+Arg-NTPTCTNProfile(mg N kg1 )(mg N kg1 d1 )(mg N20-N kg1 h1 )(mg N kg1 )(mg N kg1 h1 )mg kg1 g kg1 g kg1 NortheastC22326Detritus590.7587.830.0005106.72334.44450.1110.32Northeast327Detritus440.4070.220.000195.91414.79453.3111.93Northeast328Detritus756.5475.800.0010106.96426.41446.9812.50BCTB27329Detritus457.8337.310.000358.63325.49446.6911.08BCT330Detritus703.0473.530.0012116.71504.49435.2618.54BCT331Detritus591.0876.75126.40459.71411.9117.79BCTB37332Detritus415.5115.45BCT333Detritus423.9316.54BCT334Detritus432.6713.93SouthwestA25335Detritus562.6367.320.0009128.45886.67420.3310.49Southwest336Detritus56.890.000436.26816.93412.3111.33Southwest337Detritus737.6239.980.001355.17623.39424.2212.93SouthwestA34338Detritus333.0338.310.000151.46402.14Southwest339Detritus396.1846.720.000113.35542.58Southwest340Detritus459.6442.830.000243.55544.17NortheastC1341Soil431.3938.020.014662.9415.32858.82446.7825.42Northeast342Soil322.3639.850.026080.4313.72884.38446.6925.74Northeast343Soil262.4831.580.025061.3112.97896.31443.3324.93NortheastC22344Soil448.0328.340.017494.3810.93662.86447.6824.76Northeast345Soil246.8425.110.025882.74-1.49582.80454.5025.11Northeast346Soil299.4780.110.0145213.1417.72643.75455.0626.25BCTB27347Soil491.4450.060.025668.434.59509.54461.6726.71BCT348Soil414.8032.560.020765.5412.77518.84461.6028.29BCT349Soil412.1227.940.026072.03-0.29536.22457.5630.60BCTB37350Soil483.3529.890.001280.804.96566.35458.4031.48BCT351Soil498.0332.570.002287.943.30530.04457.4032.45BCT352Soil646.0135.740.003275.682.55594.28447.0431.43SouthwestA25353Soil639.3932.630.012987.03-7.281011.34379.4522.01Southwest354Soil529.1435.720.010491.31-2.57941.28429.4624.16Southwest355Soil798.5233.210.0008100.200.18985.28430.5525.07SouthwestA34356Soil500.1231.550.017292.884.43832.00436.6724.55Southwest357Soil523.8728.880.000181.900.33906.04430.7924.51Southwest358Soil642.5029.420.007377.084.73850.59429.4922.91NortheastC1359Detritus150.520.0027363.4349.44907.46435.0115.39Northeast360Detritus366.0080.940.005639.7319.86684.32437.2215.46Northeast361Detritus108.400.0023338.8140.60674.18440.5317.51NortheastC22362Detritus486.1143.670.0013210.84-11.08507.52439.4012.12Northeast363Detritus430.6780.300.0054165.99-2.77521.84441.0211.32Northeast364Detritus481.7879.220.0009150.68-3.62448.82442.6011.95BCTB27365Detritus1141.8255.97151.45353.03435.9910.49BCT366Detritus666.7316.0359.94473.65425.3915.71BCT367Detritus940.8774.9043.89473.61436.7515.91BCTB37368Detritus1427.91441.36428.3013.28BCT369Detritus1226.55612.24426.7817.56BCT370Detritus592.79262.24445.808.61SouthwestA25371Detritus1011.0195.130.0009247.5242.69964.60417.8914.18Southwest372Detritus818.3684.610.0007306.6335.61921.41430.1916.41Southwest373Detritus59.12212.9227.94842.30433.1814.44SouthwestA34374Detritus451.6921.270.0007165.1226.71822.51430.5215.29

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122 Table A-1. Continued. Laboratory data for select N processes collected during the spatial (2000) and temporal (2001-2002) study of the BCM. RegionField IDLab ID #SoilMBNPMNDEAExt. NH4+Arg-NTPTCTNProfile(mg N kg1 )(mg N kg1 d1 )(mg N20-N kg1 h1 )(mg N kg1 )(mg N kg1 h1 )mg kg1 g kg1 g kg1 Southwest375Detritus370.8319.880.000648.6321.99481.83445.418.01Southwest376Detritus529.2261.94120.0619.69555.33432.4411.52NortheastC1377Soil428.1441.010.0102139.0917.38899.08438.9927.66Northeast378Soil142.1940.900.0051118.4111.24857.97442.2925.25Northeast379Soil171.8838.500.0007125.6316.55866.50444.5225.75NortheastC22380Soil275.3233.250.000680.8113.09196.97436.3824.66Northeast381Soil252.3540.350.000799.8515.17590.75442.0027.38Northeast382Soil209.4245.020.0142102.7613.57571.18440.4225.25BCTB27383Soil408.7943.000.014675.3212.36531.37448.7225.48BCT384Soil219.5638.240.017968.774.38506.89453.4128.12BCT385Soil399.3942.180.022284.2612.08486.63451.7728.94BCTB37386Soil489.5553.270.019697.58-2.30516.52455.3030.96BCT387Soil452.7561.990.0228100.1719.33497.61454.9731.06BCT388Soil345.0742.670.011990.4820.72570.21456.8731.67SouthwestA25389Soil235.9050.420.016288.72-3.92913.29431.2923.64Southwest390Soil592.6850.950.010293.08-3.27907.65436.6722.81Southwest391Soil309.1560.680.0145104.101.13890.79436.2124.99SouthwestA34392Soil344.1849.040.016466.8810.49819.57437.7623.25Southwest393Soil421.7449.110.005470.317.21856.55439.7525.43Southwest394Soil232.1239.700.001065.769.56804.33440.6824.65NortheastC1395Detritus418.44138.710.0088202.7411.59793.39472.8922.00Northeast396Detritus420.47187.730.0023242.2710.60634.62471.7017.98Northeast397Detritus344.48163.460.0013194.8011.43770.65470.5117.48NortheastC22398Detritus69.310.0064121.9912.33548.31471.1814.20Northeast399Detritus142.6176.690.0019139.2813.86470.28463.9911.42Northeast400Detritus381.2377.910.0057125.8614.50435.62463.8115.14BCTB27401Detritus135.3145.910.000413.6531.21298.40471.3714.01BCT402Detritus199.3749.830.000316.6429.66445.16463.0113.78BCT403Detritus317.9033.770.00029.3331.16376.56455.6710.36BCTB37404Detritus813.77113.6398.7020.28417.34441.3316.58BCT405Detritus486.37448.4414.26BCT406Detritus992.89205.620.0004438.9833.44257.48443.1214.17SouthwestA25407Detritus403.2298.610.0013170.9216.25914.74447.5621.64Southwest408Detritus495.72133.840.0012213.9411.62904.24453.9423.18Southwest409Detritus1555.22144.860.0009181.7314.74778.63446.5816.84SouthwestA34410Detritus921.71115.250.0001108.3421.79732.51444.3615.60Southwest411Detritus129.780.0004145.046.62402.46447.3515.02Southwest412Detritus588.89118.960.0001114.8927.36532.29443.2813.92NortheastC1413Soil260.9636.780.012640.0914.14737.64436.4726.21Northeast414Soil301.6935.000.014741.4619.23726.18432.0425.22Northeast415Soil204.3833.400.015343.1816.75721.49446.2225.78NortheastC22416Soil254.9829.720.023343.9418.41532.22438.1026.06Northeast417Soil399.7734.880.023442.8916.93506.56439.8424.75Northeast418Soil245.7532.590.017350.1320.60484.76444.5724.17Northeast418-1Soil214.3232.5543.2823.31524.20445.8024.21Northeast418-2Soil318.0036.500.002349.1015.71461.62448.1921.45Northeast418-3Soil219.8520.810.024739.7815.66493.22441.4323.83Northeast418-4Soil253.2842.020.000537.8215.85525.99454.2320.93BCTB27419Soil352.5725.740.018237.1217.27421.85453.6025.54 .

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123 Table A-1. Continued. Laboratory data for select N processes collected during the spatial (2000) and temporal (2001-2002) study of the BCM. RegionField IDLab ID #SoilMBNPMNDEAExt. NH4+Arg-NTPTCTNProfile(mg N kg1 )(mg N kg1 d1 )(mg N20-N kg1 h1 )(mg N kg1 )(mg N kg1 h1 )mg kg1 g kg1 g kg1 BCT420Soil350.4246.520.012637.2618.52443.84452.9327.26BCT421Soil504.2929.710.023639.4117.95458.03451.6927.95BCTB37422Soil421.5334.160.019036.1520.84464.22450.7030.78BCT423Soil318.2230.740.000836.0022.56434.25452.8829.99BCT424Soil352.3438.700.000938.9521.84461.55457.7730.56SouthwestA25425Soil294.3338.280.001443.3023.04748.70428.4323.72Southwest426Soil208.1341.420.000255.2318.16782.53430.6722.53Southwest427Soil428.4748.180.006850.1243.13769.29434.4523.70SouthwestA34428Soil338.3932.8533.3335.56696.56444.0523.26Southwest429Soil340.9931.450.008036.7123.31708.33436.3223.27Southwest430Soil243.9529.270.005331.6524.81648.63442.9224.51NortheastC1431Detritus234.02161.54 0.002094.0825.92653.93452.3213.41Northeast432Detritus488.64174.87 0.000381.3513.23698.44455.0119.05Northeast433Detritus106.49121.49 0.003152.3119.87723.03455.9519.30NortheastC22434Detritus112.74155.28 0.001989.2717.92453.05454.9513.56Northeast435Detritus142.8873.20 0.000139.9411.72363.68456.9711.96Northeast436-1Detritus153.0095.81 0.002450.6213.23362.52Northeast436-2Detritus246.36104.63 0.005858.5319.04373.98Northeast436-3Detritus287.88148.56 0.001141.6822.16391.55Northeast436-4Detritus207.5573.64 0.002756.6220.98367.53BCTB27437Detritus89.9022.48 0.001322.7945.49262.24453.2410.20BCT438Detritus362.7848.92 0.001514.9127.76272.82443.7610.39BCT439Detritus161.0318.25 17.7353.09283.35442.1912.10BCTB37440Detritus477.9758.52 0.000324.66121.49248.51438.8611.54BCT441Detritus396.26113.21 0.000430.4831.94226.00443.288.95BCT442Detritus854.1590.76 0.000329.4373.38253.56437.7210.47SouthwestA25443Detritus745.01105.69 0.0005107.67118.07972.25436.8820.37Southwest444Detritus368.3586.56 0.0009130.2052.57838.15441.8019.42Southwest445Detritus604.20184.40 0.0007154.0124.42955.85SouthwestA34446Detritus303.69244.56 0.0001131.5228.84641.35Southwest447Detritus440.49180.88 0.0005113.4022.97654.97Southwest448Detritus474.22100.84 113.7740.50757.54NortheastC1449Soil182.8431.180.003578.5620.29677.72446.6330.09Northeast450Soil45.0132.240.005680.3727.05734.95445.0425.07Northeast451Soil159.0329.860.007650.7323.67764.68444.2727.20NortheastC22452Soil346.6332.100.007264.1223.98536.77445.9326.91Northeast453Soil581.4139.960.009952.2420.04532.69449.1725.39Northeast454Soil294.8630.210.011269.9122.38520.83450.5426.87Northeast454-1Soil158.2335.140.007983.6524.19532.13Northeast454-2Soil189.8028.600.001082.4721.46463.83Northeast454-3Soil248.2443.870.003950.9629.81484.18Northeast454-4Soil167.0829.820.008653.8020.54548.63BCTB27455Soil322.6827.970.009657.9822.49446.31458.0427.56BCT456Soil248.8831.530.014054.7020.13459.28451.5626.75BCT457Soil290.4431.130.007051.9621.88487.01461.1428.92BCTB37458Soil286.9846.440.001567.6222.66561.94458.9630.34BCT459Soil222.7132.580.008361.6821.78465.39465.8132.33BCT460Soil290.2837.440.011357.4324.42504.15462.2832.02SouthwestA25461Soil246.6633.940.006050.0624.75776.13436.1723.94

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124 Table A-1. Continued. Laboratory data for select N processes collected during the spatial (2000) and temporal (2001-2002) study of the BCM. RegionField IDLab ID #SoilMBNPMNDEAExt. NH4+Arg-NTPTCTNProfile(mg N kg1 )(mg N kg1 d1 )(mg N20-N kg1 h1 )(mg N kg1 )(mg N kg1 h1 )mg kg1 g kg1 g kg1 Southwest462Soil242.0044.550.000078.3724.96790.97438.6524.61Southwest463Soil304.8636.680.001867.8926.63770.94431.7125.33SouthwestA34464Soil188.1833.160.003859.6020.68756.85450.6325.52Southwest465Soil156.0232.610.003955.1319.44731.75444.1525.22Southwest466Soil359.2234.250.006763.3220.99758.14446.9624.25NortheastC1467Detritus361.7285.860.009599.8535.12782.77461.9623.74Northeast468Detritus406.68187.490.0027163.3665.36817.28472.3922.00Northeast469Detritus229.23151.960.001070.3852.13751.40468.0920.86NortheastC22470Detritus38.39111.320.0027176.6256.46375.40461.9413.09Northeast471Detritus108.8095.080.0083114.4449.45402.43468.4011.83Northeast472Detritus166.92105.300.0052137.4444.85433.87468.0014.13Northeast472-1Detritus296.39107.270.0064134.3049.48504.25Northeast472-2Detritus243.3466.140.0057129.5248.57439.30Northeast472-3Detritus189.10100.270.0014221.3361.24512.76Northeast472-4Detritus130.90102.900.0016123.1848.19358.21BCTB27473Detritus215.7865.060.000812.8620.77352.17462.5214.34BCT474Detritus343.9423.390.000710.8830.27256.40443.3010.66BCT475Detritus256.6282.980.000715.4535.11304.96443.1711.94BCTB37476Detritus768.36131.140.001660.0883.41382.34455.0615.86BCT477Detritus834.93123.450.000422.6253.85255.78449.0011.26BCT478Detritus21.986.770.00012.373.96288.90447.0613.48SouthwestA25479Detritus309.1182.500.010081.0871.69917.35436.7222.02Southwest480Detritus378.5172.920.0051132.1178.13842.96441.6122.23Southwest481Detritus696.22174.810.0011109.26208.861143.14451.6618.30SouthwestA34482Detritus372.7895.070.0016104.55131.77455.4912.43Southwest483Detritus534.0285.120.0019110.30107.72871.01433.1115.52Southwest484Detritus613.77120.310.0041120.36119.63848.07452.2516.53

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BIOGRAPHICAL SKETCH Kathryn (Katie) Barch was born in Iowa City, Iowa on July 17, 1977. Shortly thereafter, she moved with her family to the small town of Eureka in Northern California. Growing up, she was surrounded by the vast beauty of the Pacific Coast, rugged mountains and breathtaking redwood forests. Through her childhood outdoor adventures, Katie established her love, appreciation, and concern for the environment. At the age of 13, Katie moved with her family to live in Winchester, Virginia in the beautiful Shenandoah Valley. There she attended high school, leaving after graduation to attend college at Virginia Tech in Blacksburg, Virginia. She earned a B.S. degree in Environmental Science, graduating Magna Cum Laude. Her continued interest and desire to pursue an environmental career to lead to her acceptance of a Hydrologic Science research assistantship with the Wetlands Biogeochemistry Lab at the University of Florida, leading to an M.S. degree in Soil and Water Science. 135