Effects of land-use history on soil spatial heterogeneity of macro- and trace elements in the Southern Piedmont USA

To quantify effects of land-use history on soil spatial heterogeneity, we sampled surficial mineral soils (0-7.5 cm depth) using a spatially-explicit design within three 0.09-ha plots in each of three ecosystems in the Southern Piedmont area of USA. The three ecosystems were old hardwood forests, cultivated agricultural fields, and old-field pine forests, three common ecosystems in the region that represent the common trajectory of nearly two centuries of land-use history. In total, 243 soil samples were collected and 12 soil properties were measured on each sample. Results indicated that: (i) land-use history altered soil properties' central tendencies and their spatial heterogeneities; (ii) within-plot variations indexed by coefficients of variation and Cochran's C tests of within-plot variances were generally much higher in hardwood and pine-forest soils than in cultivated soils; (iii) for soil C, and major and trace elements spatial patterns as indicated by trend-surface analysis, correlograms, and interpolation maps were evident under hardwood and pine forests and much less so under cultivation. We document cases in which land use alters both the soil property's central tendencies and their heterogeneity (C, N, C:N ratio, Ca, and K), and cases in which changes are apparent in central tendency but not in heterogeneity (bulk density, Db). Relative to soils that have never been cultivated, spatial heterogeneity is greatly reduced in many soil properties by plowing, fertilization, and other practices associated with agricultural crop production, but that successional forest growth on previously cultivated soils re-establishes heterogeneity of soil properties within a few decades. Overall, within-plot variances were very high for most properties especially of the forested soils and indicate that researchers should better match sample sizes and sample designs with the variability of the soil properties they are studying. © 2010 Elsevier B.V. All rights reserved.

Duke Scholars

Author Daniel D. Richter Earth and Climate Sciences