Quantifying the Effects of Wintertime Processes on Soil Detachment.

Although freeze-thaw cycles and changes in snowpack are intuitively known to disrupt soil aggregates, little quantitative understanding exists regarding the effect of these wintertime processes on soil characteristics leading to erosion. Because the number of freeze-thaw cycles and intensity of precipitation events (including snowfall) are predicted to increase in the Midwestern US, quantifying the effect of these changes on soil detachment is timely and critical to our understanding of springtime soil erosion. In this presentation, I will briefly summarize the current understanding of these interactions, largely from laboratory studies, and detail a field study in which we are testing hypotheses related to the manipulation of wintertime processes on soil aggregate stability and resistance to detachment. The study design includes replicated treatments of natural snow accumulation, insulated plots to simulate a thick, sustained snow pack, and snow exclusion in an agricultural field and an adjacent restored prairie. Changes in soil temperature, moisture, and freeze depth were achieved between treatments allowing us to compare the response variables. We will report on wet soil aggregate stability and fractionation, as well as soil detachment using a cohesive strength meter (CSM), a novel approach to estimate in situ critical shear stress.