INVESTIGATING THE EFFECTS OF WATERSHED DEVELOPMENT ON WETLAND GREENHOUSE GAS CONCENRATION DURING PLANT DORMANCY

Wetlands are critical in global carbon and nitrogen cycles, serving as both sources and sinks of greenhouse gases (GHGs) such as methane (CH₄) and carbon dioxide (CO₂). While much research focuses on GHG dynamics during the growing season, when plants have a strong influence on GHG dynamics, less is known about these processes during plant dormancy. This study investigates the influence of watershed development on wetland GHG concentrations during the dormant season by comparing two Maryland wetlands: one in an urban watershed (Pike Branch) and one in a rural watershed (Goshen Branch). Monthly porewater samples were collected from upstream and downstream locations at each site from October through April. CH₄ and CO₂ concentrations were analyzed using gas chromatography. Results indicated that CH₄ concentrations were generally higher in downstream areas and more variable than CO₂, with a significant effect of watershed development observed at the urban site. In contrast, CO₂ concentrations showed a modest increase over time at the rural site but without consistent spatial trends. These findings suggest that watershed development and site-specific environmental conditions significantly influence winter GHG dynamics in wetlands. By focusing on the dormant season, this study enhances our understanding of microbially mediated GHG production in the absence of active plant processes and highlights the role of urbanization in shaping wetland biogeochemistry.