[1] Colorado State Univ, Dept Hort & Landscape Architecture, Ft Collins, CO 80523 USA
[2] Colorado State Univ, Ctr Rhizosphere Biol, Ft Collins, CO 80523 USA
[3] Colorado State Univ, Grad Program Cell & Mol Biol, Ft Collins, CO 80523 USA
[4] Univ Chicago, Dept Ecol & Evolut, Chicago, IL 60637 USA
[5] USDA ARS, Soil Plant Nutrient Res Unit, Ft Collins, CO 80526 USA