Variability in Hydrology and Ecosystem Properties and Their Role in Regulating Soil Organic Matter Stability in Wetlands of West-Central Florida

Soil organic matter (SOM) provides many ecosystem services that are necessary for continued ecosystem function. The accumulation of SOM in an ecosystem is a function of its persistence time which can range from days to thousands of years. Ecosystem properties including dominant vegetation type, soil texture, and soil moisture in various habitats can regulate the persistence time of SOM. Wetlands, because of their associated ecosystem properties, promote SOM accumulation, but little has been done to determine the ecosystem properties that regulate its persistence over time. In west-central Florida, urbanization and increased water demands have suppressed water tables in isolated wetland ecosystems via hydrological connectivity between ground and surficial waters. In this study, variability in wetland ecosystem properties, in particular dominant vegetation type and hydrological parameters, were tested as mechanisms driving SOM accumulation and stability. Cypress wetlands had significantly more organic matter, carbon (C), and nitrogen (N) than herbaceous marshes. In addition, increased wetland inundation promoted stable SOM accumulation in forested wetlands. By increasing the percent time a forested wetland spent aerobic, decreases occurred in both labile and stable C and N pools. As large storage units of SOM, the decreases in both labile and stable C and N pools in wetland soils have large implications for global C and N cycling. Increased manipulation of wetland water levels, especially in short time scales, can mineralize both short-term and long-term storage units of C and N. Globally, the increase mineralization of large SOC and SON stocks would exacerbate the release of air and water quality pollutants. The sensitivity of both labile and stable SOM pools draws concern when anticipating continued water demands and land use changes of the Tampa Bay region