Beef cattle pasture to wetland reconversion: Impact on soil organic carbon and phosphorus dynamics

摘要

There is a major need to understand the historical condition and chemical/biological functions of the ecosystems following a conversion of wetlands to agricultural functions. To better understand the dynamics of soil total organic carbon (TOC) and phosphorus (P) during beef cattle pastures to wetland reconversion, soil core samples were collected from the beef cattle pasture and from the natural wetland at Plant City, FL, during five summer seasons (2002-2007). The levels of TOC and soil P were significantly affected by changing land use and hydrology. Draining natural wetlands to grazed pastures resulted in very pronounced reduction of TOC from 180.1 to 5.4 gg~(-1). Cumulative concentrations of total phosphorus (TP) in soils (1134 mg kg~(-1)) under drained condition are two to three times lower than those in soils (2752 mg kg~(-1)) under flooded condition over the periods of land use reconversion. There was a declining trend (r=0.82**; p ≤ 0.01) in total soil P from natural wetland (763 mg kg~(-1)) to altered pastures (340 mg kg~(-1)), largely as organic-bound P (natural wetland, 48%; grazed pastures, 44%; altered pastures, 29%). These results are important in establishing baseline information on soil properties in pasture and wetland prior to restoring and reconverting pasture back to wetland conditions. The results further suggest that changes in soil properties due to changing land use and hydrologic conditions (drying and re-wetting) could be long lasting.