1. Rangeland Resources Research Unit, USDA‐ARS, Crops Research Laboratory, 1701 Centre Ave, Fort Collins, CO 80526, USA
2. Department of Botany and Program in Ecology, University of Wyoming, Laramie, WY 82071, USA
3. Soil, Plant, and Nutrient Research Unit, USDA‐ARS, 2150 Centre Ave, Fort Collins, CO 80526, USA