No abstract

No abstract

This study investigated phosphorus (P) concentrations in Dofiana seasonal wetlands in southwestern Spain as the wetlands started to fill following storm events after a drought. Both soluble and particulate P flowed into the Dofiana wetlands through runoff. A gradient in the soluble reactive phosphorus (SRP) concentrations was found from the littoral to the pond center following a 108.5-mm storm. The SRP concentration was 100 times higher 2 m from the shoreline than it was at the pond center. Neither the incoming SRP nor the total P concentrations were related to the magnitude of storm events. They were always highest during the initial filling periods (first two weeks) and lower after subsequent, even heavier storms (>100 mm) a month later. Deposited sediments were a net P sink during the initial filling period of ponds. Samples of fresh vegetation, soil, and manure from a wetland watershed were washed in distilled water for 19 h, and the SRP in the leachates was measured in the laboratory. The highest SRP concentration (1.5 mg gDW -j) was leached from the fine (<0.1 mm), organic-matter-rich (25% OM) soil fraction from uplands. The SRP concentration found in pasture soil was 1.3 nag gDW-', followed by fresh scrub (1.25 mg gDW l), and manure (0.9 mg gDW-'). Only during periods of heavy rainfall does runoff drain from the uplands to the basin of the wetland watersheds. Therefore, we conclude that incoming P concentrations to Dofiana wetlands vary greatly from year to year according to changes in hydro-meteorological conditions,