Quantifying soil profile change caused by land use in central missouri loess hillslopes

Three major challenges are present when studying anthropogenic impacts on soil profile properties: (i) site selection; (ii) sampling and modeling native and cultivated soil-landscape relationships; and (iii) graphically and statistically comparing native and cultivated sites to model soil profile changes. This study addressed those challenges by measuring and modeling selected soil profile properties of paired (native) forest and analogous nonnative (cultivated) loess hillslopes in central Missouri. The paired hillslopes in Saline County were mapped as Mollic Hapludalfs and the paired hillslopes in Boone County were mapped as Typic Hapludalfs. Horizonation and depth distribution of Hapludalf soil properties provide markers when measuring land use impacts on soil profile properties. Summit pedons on the four sites verified the mapping and classification. Transect data revealed soil profile variation by slope position and by site. Regression analysis identified relationships at the p < 0.007 level between depth to clay maximum (adjusted R² = 0.74), thickness of the A horizon (adjusted R² = 0.32), thickness of the subsurface horizon (adjusted R² = 0.69), depth to the top of the B horizon (adjusted R² = 0.69), clay content of the surface horizon (R² = 0.76), organic C content of the surface horizon (adjusted R² = 0.56), and depth to ≤7.5 g kg^-1 organic C (adjusted R² = 0.59) and slope position and site characteristics. A different response surface for each site for each soil characteristic supported the hypothesis that vegetative history and land use significantly affected the distribution of these soil properties.