Podzolization under forest and stump prairie vegetation in northern Michigan

The contrast in vegetation between the second-growth forests of northern Michigan and the nearby 'stump prairies' is striking. Prior to the logging and fires of the late nineteenth century both areas supported dense forest. Neither geomorphological surface boundaries nor soil drainage patterns appear to explain the origin and maintenance of the contrasting vegetation types. Representative pedons of forest and stump prairie vegetation stands were sampled. Soil texture was not different between the forest and stump prairie sites, but spodic horizon development, as shown by illuvial accumulations of Fe, Al, and OC, was slightly stronger where forest regeneration has occurred than in the stump prairie. Ortstein content represents the primary difference between the soils in forested and stump prairie areas. The relative lack of ortstein in the nutrient-poor and droughty soils may therefore have been a factor in the origin of the stump prairie. Other factors, such as pre-logging forest vegetation and logging-era wildfires, were probably also involved. The soils were examined for evidence of podzolization processes. The distribution of extractable Fe and Al in the soils indicates that organically bound sesquioxides are most common in the Bhs and ortstein portions of Bs horizons, while inorganic forms of Fe and Al become more abundant in the lower B horizon. These data are best explained as a result of two sets of processes: (1) the translocation of organically bound sesquioxides into the B horizon, and (2) the further translocation of Al (and perhaps Fe) as amorphous aluminosilicate complexes. Both sets of processes appear to be active in the soils simultaneously.