Mature mountain big sagebrush plants near the bottom and midway up a hillside had maximum rooting depths between 183 and 213 cm, @?60 cm deeper than roots of Wyoming big sagebrush plants just below the ridge. Maximum lateral root spread was between 122 and 152 cm. Approximately 60% of total root system weight was located in the surface 30 cm of soil. Total nonstructural carbohydrate concentrations in root decreased from 6.8% in plants at the bottom site to 3.8% in plants at the ridge site. This response could have resulted from an environmental gradient, by a release from competition, or from subspecies differences. Total carbohydrate reserves of individual plant root systems were =7.7 g. Published in Ecology, volume 59, issue 6, on [...]