USGS Water Resources Discipline Grant: Biogeochemical Impacts of Sea-Level Rise on Tidal Wetlands

The recipient institution will be responsible for collecting, processing, and analyzing samples for the uptake of carbon, nitrogen, and phosphorus by vegetation (aboveground and root biomass) and soil microbes. The recipient must have extensive experience measuring biogeochemical properties in floodplain wetland ecosystems, as well as sufficient laboratory instrumentation, field equipment, and personnel to conduct the work. While this research should have applications for watersheds throughout the southeastern U.S., emphasis should be placed on the Savannah (Georgia) and Waccamaw (South Carolina) Rivers. The specific objectives of this funding opportunity include:

1. Uptake and Assimilation: Estimate annual uptake of N and P as well as C assimilation by vegetation using the total annual NPP of trees and marsh vegetation, sampling tree and marsh grass components for determination of nutrient concentrations, and calculating uptake (or assimilation) by multiplying dry weights and concentrations. Estimate fine root NPP by utilizing sequential coring techniques, modified to include phenological information from minirhizotron studies conducted along the Savannah River.
2. Coarse root production: Two sets of cores (7.5 cm diameter) should be collected at 1.5 month intervals from subplots in close proximity to locations of aboveground NPP data collection. Productivity of coarse roots can be estimated by excavating root systems, measuring root dry weights, and developing allometric equations that relate coarse root biomass to DBH. Root samples will be collected for determination of elemental concentrations. Marsh productivity will be based on the difference between winter vs. late growing season standing crops of aboveground and belowground biomass. Peak biomass in high marshes often occurs in the late growing season. Samples of aboveground components and root tissues will be collected, and all plant tissue samples will be analyzed for C, N, and P similarly to how sediment samples will be analyzed above.
3. Estimate microbial biomass C and N: A chloroform – fumigation technique will be used to estimate C and N immobilization in soil microbial biomass. Soil samples will be analyzed from the soil cores collected by the NRP. These subsamples will be fumigated within 24 hours. Samples will be extracted and the resulting solutions will be analyzed for C and N using a Dohrman DC 80 TOC Analyzer and Kjeldahl analysis, respectively. Immobilization will be calculated as the difference between element contents of fumigated vs. nonfumigated samples.