The influence of land management on concentrations of dissolved organic carbon and its effects on the mobilization of aluminium and iron in podzol soils in Mid‐Wales

Abstract

Abstract. The aluminium (Al), iron (Fe) and Dissolved Organic Carbon (DOC) contents of the soil solution were monitored in two upland grassland and afforested podzol soils in Mid‐Wales. Al organo‐metallic complexes predominated in the O horizon leachates of the grassland soil, whereas inorganic monomeric Al forms dominated in the lower mineral horizons. Dissolved organic matter determines the chemistry, solubility, and transport of Al and Fe in the O horizon, and these are under strong biological control. The distributions of organic‐Al, Fe and DOC within the soil profile were consistent with traditional podzolization theory. Observed increases in the molar ratios of Al:DOC in solution in the lower soil horizons may be responsible for the small solubility of Al organo‐metallic complexes in those horizons. Afforestation increased the concentrations of organic‐Al and Fe in the soil solution as compared with the concentrations observed for the grassland soil. Clearcutting further significantly mobilized Al and Fe from the upper soil horizon, primarily by increasing the DOC concentration in the soil water.