PEDOGENESIS ALONG A CLIMOSEQUENCE IN LOESS-DERIVED SOILS OF THE CENTRAL GREAT PLAINS

Little is known of trends in soil properties as influenced by precipitation variables. A transect of seven pioneer cemeteries was identified along an east-west precipitation gradient spanning western Missouri to the western edge of Kansas. Care was taken to select cemeteries that were constructed in soils of loess parent material. In the field, undisturbed portions of the cemeteries were identified prior to sampling. We used hand-probe plastic-lined cores to collect samples in triplicate to 50-cm depths. Cores were divided into 2.5-cm intervals and measured for bulk density, soil organic carbon (SOC), and L* a* b* color. In addition, particle-size distribution (PSD) was measured every 5 cm on a single representative core from each site and used to confirm that the parent material at all sites was loess. Because prior studies have shown a strong relationship between aggregation and SOC, we measured PSD on both untreated samples and samples that were pretreated to remove SOC. The difference in the geometric mean for each pretreated and untreated pair was used as a proxy for aggregation. Soil properties were plotted by depth at each site with standard deviations when applicable. Multivariate techniques including multivariate regression and regression trees were used to evaluate the relative ability of bulk density, depth, precipitation magnitude and timing, and particle-size to explain the variation in SOC. The results of this study are expected to aid in understanding the effects of future precipitation alterations on pedogenesis in loess soils.