Forest Associations and Soil Drainage Classes in Presettlement

Baraga County, Michigan

 

Randall J. Schaetzl and Daniel G. Brown

 

            General Land Office (GLO) Survey notes for Baraga County, Michigan were analysed to determine the composition of forest associations present circa 1850, sorted out by natural soil drainage classes.  Our study illustrates the significant effect that soil drainage and wetness have on forest composition, and provides data on various tree species’ importance on different classes of soil drainage. 

            Our tree data came from witness trees identified by GLO surveyors.  Tree locations were plotted and overlain onto a modern soil map using a geographic information system.  Each soil mapping unit was placed into one of seven natural soil drainage classes, and tree data tallied by drainage class.  Additionally, we identified spatially-contiguous species groupings from the GLO tree ‘map’ by developing lists of trees (relative density only) for randomly placed circular plots within the county.  The random plot data were examined using ordination and classification methods. 

            Pines, especially jack pine, dominated the very driest sites in the county which had experienced widespread fire.  Sugar maple and other shade-tolerant species (primarily hemlock and yellow birch) forested the mesic and slightly wetter sites.  Hemlock dominated sites that were either slightly drier or slightly wetter than mesic; these sites still retained sugar maple and yellow birch as common associates.  On the wettest sites black spruce was the dominant species; white cedar and tamarack were subdominants.  On no soil was white pine the principal species, but it was present on most soil drainage classes.  Because many soils were dominated by shade-tolerant climax species, evidence for widespread, nonfire-related disturbance in Baraga County in the early 1800s is lacking.  The cluster analysis of random plot data illustrated that this method can produce classes or groupings that are comparable to the natural soil drainage-based classes.