Florida Coastal Everglades Long Term Ecological Research
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PAST WORKING GROUPS

Soils and Sediments Working Group
(Phase I, 2000-2006)


Abstract:
The Organic Matter in Soils/Sediments Working Group is mandated to 1) provide baseline data on OM quantity and quality for other FCE-LTER researchers, 2) investigate the coupling between physical, chemical and biotic aspects of OM accumulation, preservation and cycling in the soil/sediments.

Soil core Edward Castaneda retrieving a soils core to assess sedimentation and nutrient accumulation rates in a dwarf mangrove forest

Soil Elevation and Carbon Balance: Net change in soil elevation is being monitored using the soil elevation table (SET) technique. SET stations are currently in place at all estuarine wetland sites (SRS-4, 5, & 6 and TS/Ph-6, 7, & 8). Some additional SETs may be installed at freshwater wetland sites. Soil OM turnover rates are being estimated with respiration measurements of CO2 and methane fluxes performed several times a year. These in combination with the SET, %OM, %C and bulk density measurements will allow us to estimate long-term carbon fluxes in both peaty and marly soils. We are also quantifying belowground primary productivity at all estuarine wetland sites, and will soon be quantifying this parameter at all freshwater wetland sites. Root productivity and turnover rates in mangrove plots along the Shark River and Taylor Slough under different hydrologic and soil conditions are currently determined using a sequential coring technique as well as ingrowth cores. The cores were obtained inside plots where mangrove forest structural changes have been monitored during the last 5 (Shark River) and 2 years (Taylor Slough) . Total carbon, nitrogen and phosphorous concentrations will be determined along with measures of bulk density. Pore water samples for nutrient analyses (NH4, N+N, PO4, H2S) were sampled in the same places where sedimentation cores were obtained. Accretion rates will be estimated using Cesium-137 and Lead 210 activity.


Organic Matter Characterization: In order to provide a soil/sediment OM characterization for the FCE-LTER, surface grab samples are collected once a year from all LTER sites and subjected to a variety of chemical analyses. These consist of bulk OM characterizations such as %OM, C/N, total P and total N, d13C and d15N stable isotope composition and 13C-NMR. At stations where a flocculent layer of OM overlaying the soils/sediments is available (mainly the freshwater marshes) this 'Floc' is also collected and characterized. Locations for floc analyses are sampled biannually starting in Fall 2001. In addition to the bulk-parameter characterizations, detailed molecular-level analyses are performed at all sites (including the floc samples) annually. These consist of detailed GC/MS characterizations of the solvent extractable lipids or 'biomarkers'. In addition to the characterization of surface soil/sediment/k 'grab' samples, biannual sampling events of the Shark River and Taylor River estuary in the Everglades are performed beginning in Spring 2001, where OM in suspended particulate matter (SPM) is conducted at slack low and high tide along the salinity gradient and correlated with other water quality parameters (see Nutrient Work Group summary). In addition SPM samples are collected at a central station in the river over a 48-hour period. These SPM samples are characterized using GC/MS of biomarkers as well as through bulk OM characterizations such as %OM, C/N and both d13C and d15N stable isotope measurements.


Biogeochemistry of OM-Iron-Sulfur coupling: Soils/sediment analysis of FCE-LTER sampling locations of the freshwater marsh and estuarine mangrove systems along the Shark River Slough (SRS-six locations) and Taylor Slough/Panhandle (TS/Ph-eight locations) transects, and sediment analysis of the Florida Bay transect (TS/Ph-three locations) are being studied for organic matter-Fe-S interactions. For surface soils and for deeper sediment samples, complete annual measurements of porosity, dry bulk density and organic density using standard methods are performed annually. Analyses of acid-volatile sulfide, chromium reducible sulfide and reactive and non-reactive forms of iron and phosphorus are completed using sequential extraction methods. The results of these analyses provide important baseline information on the characteristics of the soils from each of the SRS and TS/Ph transects where different partitioning of potential limiting nutrients is expected based on soil type (e.g., peaty versus marly soils), seasonal flooding characteristics (e.g., permanently flooded versus seasonal drawdowns), and/or proximity to the shallow subtidal estuary (e.g. adjacent to coastal shelf versus Florida Bay). The effects of restoration initiatives and/or long-term changes in climate and disturbance can also be tracked by observed changes in soil nutrients over the course of the study.
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National Science Foundation logo This material is based upon work supported by the National Science Foundation through the Florida Coastal Everglades Long-Term Ecological Research program under Cooperative Agreements #DEB-1237517, #DBI-0620409, and #DEB-9910514. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
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