Gradients in Lake Effect Snowfall and Fire across Northern Lower Michigan Drive Patterns of Soil Development and Carbon Dynamics

Abstract

Soils and forest ecosystems vary predictably along a 145-km transect in northern Lower Michigan. In the east, Entisols support open jack pine stands. In the central transect, weak Spodosols have formed under oak–pine–aspen forests. In the Lake Michigan snowbelt on the west, strongly developed Spodosols occur beneath mesic northern hardwoods. We hypothesized that increasing amounts of snowfall, coupled with decreasing fire frequencies, promote soil development and enhance soil C dynamics at western sites. We also hypothesized that enhanced soil development facilitated greater proportions of broadleaf tree establishment, which in turn accelerates snowmelt rates and further facilitates soil development by enhancing deeper C translocation. Along the transect, we described, sampled, and characterized twelve soils. Soil development increases east to west along the transect, changing most rapidly at the inner margins of the snowbelt, near the coniferous–broadleaf forest ecotone. Coincident with strong soil development in the snowbelt is an increase in soil C storage and cycling. Depth profiles of C, 13C, and Fe- and Al-humus complexes all suggest that snowmelt percolation drives these patterns. Hardwoods produce and cycle more C than coniferous stands to the east and have thicker snowpacks. In the snowbelt, late-lying snowpacks limit spring fires, and large pulses of snowmelt water drive the fresh, soluble C from O horizons deeper, enhancing soil development and fostering ecosystem productivity. Although the current snowbelt, climate, and fire patterns across the peninsula might date only to ≈7,000 cal yr BP, they have nonetheless affected pedogenesis to the point that a major Entisol-to-Spodosol continuum has formed.