Experimental Changes in Snow Cover on Freeze-Thaw Cycling, Soil Aggregate Properties, and Organic Carbon Pools in an Agricultural Field and a Restored Prairie in Southwestern Wisconsin

• Main Author: Boswell, Edward P
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2018
• Subjects: Soil sciences
• ISBN: 9781392779835; 1392779839

Seasonal snow cover is an important component of the over-winter climate as it affects the cyclical freezing and thawing of soils over approximately 55% of the northern hemisphere. However, snow cover is variable both temporally and spatially. In addition, climate models predict that the timing, magnitude and duration of snow cover will change. This research investigated the effects of variable snow cover on soil aggregation, freeze-thaw cycles as a central mechanism for aggregate disruption, and soil carbon dynamics within and between an agricultural field and a post-agricultural 13-year-old prairie.The results of a three winter (November-April, 2014–2016) experimental snow manipulation field study showed that soil aggregation was lower (i.e. aggregates were disrupted) after winters with conditions of no snow cover but higher after conditions simulating a thick, sustained snow cover. In both cases and in both vegetation types, aggregates returned to a threshold by the end of the growing season (as measured in the fall) suggesting that future investigations into the implications of aggregate disruption resulting from variable snow cover should be focused on the early growing season. These soil aggregate changes did not result in significant changes to soil critical shear stress as a proxy for spring time soil detachment potential. Freeze-thaw (FT) cycles are proposed mechanisms for the disruption of soil aggregates however, an agreed-upon method for quantifying and characterizing freeze-thaw cycles, which potentially holds the key to understanding their differential effects, is lacking. In this research, I propose a set of parameters to quantify and characterize FT cycles and also present a set of R language functions that automate their quantification and characterization. These tools will valuably inform FT investigations in the context of a changing climate.Root biomass, root length density, microbial biomass, and soil respiration were all significantly greater in the prairie restoration than in the agricultural field but there was no significant increase in soil organic carbon with 13 years of prairie restoration. There was no significant effect of snow manipulation treatment on carbon pools other than reduced soil respiration in the no-snow plots. It appears that the carbon pools most likely to increase soil aggregation and subsequent SOC carbon accrual are increasing in the prairie restoration, but have not yet resulted in significant SOC changes.Lastly, part of this work focused on developing an outdoor educational program themed around soil development and conservation efforts that address the continued loss of soil from agricultural landscapes and the steady decline in soil science education in the U.S. The outdoor education program entitled “Soil on the Move” along with an elementary school curriculum will take advantage of the landscape, infrastructure, and proximity to Madison, WI offered by Pope Farm Conservancy, the same setting used for the research components of this dissertation.