PODZOLIZATION UNDER FOREST AND STUMP PRAIRIE VEGETATION IN NORTHERN MICHIGAN

The contrast in vegetation between the second-growth forests of northe rn 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 dra inage patterns appear to explain the origin and maintenance of the con trasting vegetation types. Representative pedons of forest and stump p rairie vegetation stands were sampled. Soil texture was not different between the forest and stump prairie sites, but spodic horizon develop ment, as shown by illuvial accumulations of Fe, Al, and OC, was slight ly stronger where forest regeneration has occurred than in the stump p rairie. Ortstein content represents the primary difference between the soils in forested and stump prairie areas. The relative lack of ortst ein 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 als o involved. The soils were examined for evidence of podzolization proc esses. The distribution of extractable Fe and Al in the soils indicate s that organically bound sesquioxides are most common in the Bhs and o rtstein portions of Bs horizons, while inorganic forms of Fe and Al be come more abundant in the lower B horizon. These data are best explain ed as a result of two sets of processes: (1) the translocation of orga nically bound sesquioxides into the B horizon, and (2) the further tra nslocation of Al (and perhaps Fe) as amorphous aluminosilicate complex es. Both sets of processes appear to be active in the soils simultaneo usly.