Small-scale spatial heterogeneity of soil properties in undisturbed and reclaimed sagebrush steppe

Abstract

The sagebrush (Artemisia tridentata) steppe is inherently heterogeneous, both above- and belowground disturbances that manipulate vegetation and soil may result in homogenization of soil properties. Our objective was to examine the spatial distributions of soil properties in a sagebrush steppe of south-central Wyoming following disturbance and reclamation. We predicted that soil properties in undisturbed sagebrush steppe would display patchiness, while reclaimed soils would be more uniform. At the experimental scale (<10m2), we examined the spatial correlation structure and patterns of soil properties in a recently disturbed and reclaimed pipeline scar and adjacent undisturbed sagebrush steppe in 2009. In each treatment, we sampled soil (0–0.05m depth, calcareous fine sand Regosol) using a spatially explicit design, and used geostatistics to quantify, interpolate, and visualize spatial patterns of soil chemical and biological properties. Soil nitrogen and organic carbon in the undisturbed plot showed spatial associations with the vegetation, which were not apparent in the reclaimed plot. Our predictions about homogenization were true for soil properties that are known to have strong spatial associations with shrubs. Soil organic carbon concentration, total nitrogen concentration, and microbial abundance experienced homogenization, while soil salinity and alkalinity became patchier after disturbance. In addition to changes in spatial patterns, most soil properties were elevated in the reclaimed soil, compared with the undisturbed soil. This case study illustrates that the degree of soil heterogeneity in this patchy system may change with disturbance. Belowground spatial patterns should be considered when restoring characteristically heterogeneous shrub lands.