A Spodosol-Entisol Transition in Northern Michigan

Randall J. Schaetzl

Soils in northern lower Michigan, all formed in sandy glacial outwash, were examined to determine the effects of vegetation and fire frequency vs. climate on their development. To accomplish this, soil development was quantified for 13 pedons that span a region known as the Grayling Fingers. Next, a GIS was used to examine spatial interrelationships among the following data sets for the Fingers area: soils, climate, and presettlement vegetation. The 13 sampled pedons span a major pedologic ecotone between an area of strongly expressed spodic morphology (with hardwood forests, low fire frequencies, and deep snowpacks) and one where soils are Psamments. The Psamment area is dominated by jack pine and oak barrens, which frequently burned in presettlement time, and have much less snow cover in winter. The texture and mineralogy of all pedons are generally similar, thereby ruling out parent material as a controlling factor in their development. The relationships among vegetation patterns and soil development remain unclear in this area. Spatial relationships among snowfall amounts and snowpack thicknesses, however, correlate extremely well to soil development patterns. Thus, I conclude that in this region, patterns of soil development are related primarily to the influence of snowmelt infiltration and its previously documented impact on podzolization. Overstory vegetation may provide a strong, reinforcing influence or may be reacting in turn as a dependent variable to soil development and soil moisture during spring, as impacted directly by snowmelt infiltration.