DISSERTATION RESEARCH: Effects of Nutrient Enrichment and Salinization on the Fate and Persistence of Soil Organic Matter in Tidal Freshwater Wetlands

点击翻译按钮获取中文摘要

Coastal wetlands are a globally significant sink for carbon due to high rates of plant growth and low rates of microbial organic matter breakdown. These ecosystems, however, are increasingly threatened by salinization, nutrient enrichment and other human disturbances. Salinization and nutrient enrichment are known to alter plant growth and microbial breakdown, however there is uncertainty regarding their effect on the carbon balance of coastal wetlands. Changes in plant and microbial communities brought on by human disturbances may lead to either increased net carbon release from wetland soils or to increased storage of carbon as soil organic matter. The soil organic matter pool, therefore, reflects feedbacks between plants and microbes and integrates them over long time-scales, providing a useful tool for assessing the cumulative impacts of salinization and nutrient enrichment on the wetland carbon cycle. In order to assess the impacts of salinization and nutrient enrichment on wetland carbon cycling, soil will be collected from tidal freshwater wetlands in coastal Georgia where either salinity or nutrients have been experimentally increased above natural levels. In addition, the interactive effects of salinization and nutrient enrichment will be explored by transplanting vegetated soil cores between nutrient-enriched and salinized wetland sites. Soils will be incubated for one year and analyzed for changes in 1) quantity and composition of soil organic matter 2) microbial demand for different types of soil organic matter and 3) rates of microbial organic matter breakdown. Results from this study will be integrated with previously collected data on plant and microbial processes at each site. This research contributes to a fundamental understanding of ecosystem scale carbon cycling by examining two of the most common human activities affecting wetlands on a global scale: salinization resulting from rising sea level and freshwater management, and nutrient runoff from agricultural activities. Understanding the impacts of these disturbances is important for protecting wetland ecosystems and maintaining their ability to provide key ecosystem services, such as carbon sequestration and wildlife habitat. Environmental science and policy students from the School of Public and Environmental Affairs at Indiana University and k-12 educators from the Georgia Coastal Ecosystems LTER Schoolyard Program will be involved in all aspects of this study. The implications of this research will be discussed as part of the School?s Wetlands Biology and Regulation course. Results will be communicated in scientific meetings, peer-reviewed publications and directly to coastal Georgia residents and resource managers through ongoing collaborations with the Sapelo Island National Estuarine Research Reserve, The Nature Conservancy and the Georgia Department of Natural Resources.