Hydro-ecological Controls on Soil Carbon Storage in Subtropical Freshwater Depressional Wetlands

Several ecological factors, including hydrology, soil type, and vegetation, influence wetland soil carbon (C) storage, but the relationship among these factors is complex making it difficult to evaluate the potential for increased C storage in natural and restored systems. This study investigated the relationship between hydrologic variables, wetland plant communities, and wetland soil C storage in the upper 50 cm of soil in three wetland community types (bay swamp, cypress swamp, freshwater marsh) in a hydrologically restored subtropical landscape in central Florida, USA. Mean water table depth relative to ground elevation was a better predictor than hydroperiod of surface soil C stock and was positively related to soil C stock in marshes. However, the overall effect of water table depth was small and was often outweighed by other factors including wetland vegetation type and local site conditions. Bay swamps had the highest soil C stock, followed by cypress swamp, marsh, and upland ecotone, respectively. This study highlights the importance of understanding the interplay among multiple factors that drive variation in soil C stock within and among wetland types in these landscapes, and the importance of deeper soil layers to wetland soil C storage at the landscape scale.