THE EFFECT OF LONG-TERM LAND USE CHANGES ON SOIL ORGANIC CARBON IN SOUTHERN WISCONSIN

Transformation of undisturbed Wisconsin prairies to agricultural soils has resulted in a loss of soil carbon. Tillage of agricultural soils exposes soil organic matter (SOM) to oxygen, and the carbon in SOM will oxidize to the atmosphere. Soil carbon greatly improves the physical, chemical, and biological properties of the soil. Equally as important, carbon locked in the soil does not impact carbon concentrations in the atmosphere, which contributes to global climate change. The objective of the study was to quantify the amount of organic carbon in undisturbed versus agricultural soils. A total of six paired sites were selected for this research. Undisturbed soils were classified as areas that have not been disturbed for 50+ years. In all cases disturbed and undisturbed areas were less than 100 meters apart and sampled at three depth intervals: 0-10 cm, 10-40 cm, 40-100 cm. Total organic carbon was on average 44.3% lower in agricultural versus undisturbed soils. Data from the depth intervals also shows that differences in carbon concentrations between undisturbed and agricultural soils were most significant in the 40-100 cm interval (57% higher in undisturbed) compared to the 0-10 cm interval (22% higher in undisturbed). This data supports that a tremendous amount of carbon has been lost to the atmosphere due to land use conversion.