Gradient Analysis of Vegetation Dominated by Two Subspecies of Big Sagebrush

Stands of vegetation dominated by basin big sagebrush (Artemisia tridentata Nutt. subspecies tridentata) intergrade with stands dominated by Wyoming big sagebrush (Artemisia tridentata Nutt. subspecies wyomingensis) on the Idaho National Engineering Laboratory in southeastern Idaho. Detrended correspondence analysis and correlation were used to elucidate potential relationships between vegetation patterns and soil factors along a gradient from stands having only the subspecies tridentata to stands having only the subspecies wyomingensis. Distributions of the subspecies were consistently associated with gradients in soil texture. Basin big sagebrush was most abundant on sandy soils and Wyoming big sagebrush was dominant on finer textured soils. Mixed stands occurred on central portions of the gradient. Similar results for 3 study areas were observed, despite differences in soil texture between areas. Thus, the distributional patterns are associated with changes in soil texture rather than actual amounts of sand, silt, or clay.