INTERPRETATION OF ENVIRONMENTAL GRADIENTS WHICH INFLUENCE SAGEBRUSH COMMUNITY DISTRIBUTION IN NORTHEASTERN NEVADA

Regression of soil attributes with sample ordination scores suggested that the plant communities respond to a complex gradient involving soil depth, water holding capacity, mollic epipedon thickness, clay content, and effective rooting depth. Soil chemical properties which displayed significant correlations with sample ordinations included pH, base saturation, calcium, total nitrogen, organic matter, and phosphorus. These soil properties are considered to either directly influence or indirectly reflect the available soil moisture of a site. The transition from black sagebrush Artemisia nova to low sagebrush A. arbuscula, basin big sagebrush A. tridentata spp. tridentata and mountain big sagebrush A. tridentata ssp. vaseyana stands along DECORANA Axis 1 appeared to represented a gradient of increasing available soil moisture. Elevation and aspect were not correlated with sample ordination scores, presumably due to various soil properties which modify the direct effects of elevation and aspect on available soil moisture. -from Author