Vegetation and cropping effects on pedogenic processes in a sandy prairie soil

The presence of native prairies in the Lower Wisconsin River valley that have not been cropped affords a mean of comparison across undisturbed and managed ecosystems. A native prairie soil and a prairie converted to corn (Zea mays L.) and red pine (Pinus resinosa Aiton) plantations were studied to determine the influence of vegetation on soil-forming processes in the sandy landscape of the Lower Wisconsin River valley. Effects of afforestation and cultivation were determined by separating organic matter among particle-size and chemical fractions, differentiating among forms of extractable Fe and Al, and measuring dissolved organic carbon (DOC), Fe and Al in bulk precipitation, throughfall, and soil solutions at three depths. The soil under native prairie vegetation showed distinctive horizonation, including an umbric epipedon formed by melanization. Thickness of the A horizon was significantly less in the forested and cultivated soils than in the prairie soil. Greater amounts of the floatable fraction of organic C, fulvic acids, and Fe-organic complexes were present in the forested soils than in the prairie soil. Carbon concentration in the A horizon of the cultivated soil was significantly lower than in the prairie and forested soils, due to losses by erosion, decomposition, and DOC leaching. In the cultivated soil, the floatable and humin fractions showed the greatest decrease in C concentration compared with the prairie soil. Analysis of the solution data indicated leaching of soluble Pe-organic complexes under coniferous and corn vegetation, suggesting that afforestation and cultivation initiated incipient podzolization.