Relationships Between Soils and Presettlement Forests in Baraga County, Michigan

Soils data and data on the presettlement forests of Baraga County, taken from the General Land Office (GLO) Survey, were stored and analyzed in a geographic information system (GIS). The purpose of the research was to determine county-wide witness tree distributions and autecological relationships among 14 major tree species and soil wetness and texture, in this geologically and edaphically diverse region of northern Michigan. In all, 12,760 trees were coded by species, location and diameter from the GLO data, which were recorded between 1846 and 1853. Tree data were overlain on soil mapping units which were coded by natural drainage class and particle-size family. All trees located in mapping unit complexes (two or more soil types) or within 25 m of certain soil boundaries were eliminated from further consideration through a selection/buffering procedure leaving 6210 trees of 14 species for use in the analysis. Contingency tables were calculated to assess the strength and direction of the relationships between each tree species and soil texture, soil wetness and texture/wetness combinations. County-wide distributions of species were strongly related to soil patterns, with a prominent forest ecotone occurring near the boundary between two distinct till provinces. Most upland forests were dominated by sugar maple and yellow birch; prevalent lowland species included balsam fir, black spruce and white cedar. Hemlock was common only near Lake Superior on sandy fills that lacked a silt cap. Especially notable was the association between a nearly pure stand of jack pine and the dry sandy soils of the Baraga (glacial outwash) Plains. Evidence for widespread disturbance by wildfires on the level plains contrasts with the relatively long period of only small gap-scale disturbances that existed on more rolling, mesic and wet sites.