ENVIRONMENTAL FEEDBACK MECHANISMS INFLUENCING SEDIMENT ACCRETION AND VEGETATIVE COMMUNITY DEVELOPMENT IN SHARK RIVER SLOUGH

• Sponsoring Institution: State Agricultural Experiment Station
• Project Status: ACTIVE
• Funding Source: STATE
• Reporting Frequency: Annual
• Accession No.: 0191497
• Project Start Date: Oct 1, 2001
• Project End Date: Sep 30, 2005
• Program Code: [(N/A)]- (N/A)

Recipient Organization
UNIVERSITY OF FLORIDA
G022 MCCARTY HALL
GAINESVILLE,FL 32611

Performing Department
SOIL & WATER SCIENCE

Non Technical Summary
The Effects of water flow on sediment accretion and vegetative community development in the Florida Everglades are not clearly understood. This project will determine the spatial variability in soil accretion rates and evaluate environmental factors influential in soil accretion processes within Shark River Slough

Animal Health Component

50%

Research Effort Categories

Basic

50%

Applied

50%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
102	0330	1000	100%

Knowledge Area
102 - Soil, Plant, Water, Nutrient Relationships;

Subject Of Investigation
0330 - Wetland and riparian systems;

Field Of Science
1000 - Biochemistry and biophysics;

Keywords

sediments

sedimentation

vegetation

nutrient accumulation

carbon

wetlands

plant ecology

communities (ecology)

soil plant nutrient relations

plant biochemistry

environmental factors

environmental stress

spatial variability

soil types

soil characteristics

species composition

rate determination

mechanisms

plant succession

plant ecosystems

quantitative analysis

temporal distribution

soil texture

soil organic matter

nitrogen

phosphorus

hydrology

tissue analysis

Goals / Objectives
Objectives of this project are to evaluate biological and environmental factors regulating sediment accretion rates within Shark River Slough, Florida Everglades, and to determine the extent that biological processes "feedback" to influence environmental stressors. Specific objectives include a) Evaluate spatial variability of organic and marl soils within Shark River Slough, b) Determine if there are correlations between soils characteristics, at various depths, and the present day vegetative community and composition, c) Determine variability of organic and calcite sedimentation rates within Shark River Slough, d) Determine what feedback mechanisms exist between vegetative communities and sediment accretion rates and how these mechanisms might be affected by changes in external forcing functions. These objectives are pertinent components to determine spatial and successional patterns of vegetative community development in wetland ecosystems.

Project Methods
Task 1: Determine spatial variability in soil characteristics, and associated vegetative plant communities in Shark River Slough. This task will evaluate historic soil characteristics at several spatial scales and investigate the relationship between subsoils and present day vegetative communities. Goals of this task are to quantify soil parameters indicative of historic vegetative parent communities, and relate these both spatially (horizontal comparison) and temporally (vertical comparison) with the existing vegetative community. Sampling for this task will include a visual description of the sediment profile and designation of horizons based on texture, color and structural characteristics; horizon bulk density; Loss on Ignition (LOI); and partitioning of organic and inorganic carbon; soil TN, soil TP, and fulvic acid/humic acid ratios. In addition to these parameters, d13C ratio?s and 137Cs peak will be determined on a subset of horizons/cores. Isotope ratio will be used to differentiate between C3 and C4 vegetative species as corroborative evidence in determining parent material of sediment horizons. Task II: Develop two-year deposition/decomposition/dissolution for organic matter and calcite sediment accretion. This task will measure parameters to support model development identified in task III, and evaluate the variability of calcite and organic soil formation factors within Shark River Slough. Along two transect located in Shark Slough, ridge and slough vegetative community types will be selected and carbon budgets as related to soil accretion will be determined. Sampling in these areas will include quantifying liter production from above and belowground biomass, partitioning between inorganic and organic carbon inputs, determining decomposition and dissolution rates of litter and newly deposited calcite, and evaluating spatial variability of surficial soil chemical parameters. To differentiate between environmental vs. substrate quality effects on decomposition rate, two techniques will be used. First, a plant tissue substrate with high C:N:P tissue ratio will be used in all of the community types to evaluate variability in site environmental effects on decomposition rate. Second, plant tissue from each of the community types selected will be tested within their respective community type, and in each of the other community types during the course of the experiment. Task III: Model rates of sediment deposition vs. decomposition/dissolution for sediment accretion. We propose to adapt a mathematical model with simulation, previously developed for research on organic carbon turnover and accumulation in Everglades Water Conservation Area 2A, to (1) summarize and demonstrate the relationships between turnover of organic C pools and previously identified rate-limiting factors, especially hydrology, (2) test the relative significance of controlling factors on model output, and (3) evaluate dynamic and steady-state responses of the state variables to hydrologic conditions as predicted by experimentally-determined relationships.

Progress 10/01/02 to 10/01/03

Outputs
In the Everglades there are two principal sources of soil accretion; one is the result of net organic matter deposition, and the second, calcite formation that is mediated by changes in pH due to photosynthesis within periphyton mat communities. The overall objective of our study is to determine the extent that variability in sedimentation rates is influenced by small-scale autochthonous factors, and to what extent they are related to large-scale allochothonous forcing functions in the Shark River Slough of the Everglades. Over the past year we have focused on feedback mechanisms that exist between vegetative communities and sediment accretion rates, and how these mechanisms might be affected by changes in external forcing functions. Using dominant vegetation to delineate between ridge and slough/wet prairie communities, the difference between average ridge elevation and average slough/wet prairie elevation at the soil and bedrock surfaces were evaluated. No significant differences between bedrock elevations below present day ridge vs. slough/wet prairie communities were identified. However, differences in soil surface elevation between ridge and slough/wet prairie communities were found to decrease to the south and from the center of Shark River Slough toward the edges. This change in soil elevation is similar to changes in the length of hydroperiod and inversely related to flow rate based on our measurements. Differences in plant biomass quality (nutrient content and percent recalcitrant carbon fractions) were determined between species typically found in ridge, slough, and wet prairie communities. Species most commonly found in ridges have significantly greater amounts of residual fiber than species found in wet prairie or slough communities. Therefore, if biomass inputs and decomposition rates are equal, roughly three times as much plant biomass would remain in ridge communities than that of wet prairies. Findings also indicate that the C:N ratio of species occurring in slough/wet prairie communities are typically lower than that of species found in the ridge. This would mean that decomposition rates of slough/wet prairie litter would be less likely hindered by insufficient nitrogen for microbial decomposition than ridge derived litter material. From a soil accretion standpoint, species that colonize higher elevation ridges tend to reinforce the higher elevation sites by having more recalcitrant biomass. Litter parent material was fond to be a greater factor in decomposition rate when compared to differences in environmental conditions. This is substantiated by significant differences found in mass loss between litter types, but no significant difference found between mass losses when comparing decomposition of litter bags with community types. Where environmental condition appears to be a factor is at the larger scale between sites. The southern most site, when compared to that of the other long-term sites, had significantly greater amounts of litter loss regardless of litter type. Distinction between the effects of litter quality and that of the environment will be investigated in more detail in the upcoming field work.

Impacts
Findings of this study will improve scientific knowledge of the processes regulating soil accretion and broader landscape scale vegetative development in the Shark River Slough region of Everglades National Park. This understanding will refine restoration performance measures related to the Comprehensive Everglades Restoration Plan (CERP) and provide guidance where impacts and mitigation management occurs in similar wetland systems.

Publications

• No publications reported this period