Identifying Structural Thresholds in Annual Grass–Invaded Rangelands

Invasive plants have an increasing impact on the ecological and economic functions of natural systems. Cheatgrass ( Bromus tectorum L.) is invasive annual grass that widely impactful throughout most western United States. Describing management thresholds in cheatgrass-invaded rangelands may help managers conserve native plant communities. The objective this research was to determine if direct, predictable relationships exist between pretreatment vegetation conditions post-treatment changes perennial biomass following cheatgrass control. We sampled locations representing a gradient cheatgrass-to–perennial ratios before application two imazapic formulations—liquid with water carrier dry sand/granular carrier—at field sites near Saratoga Pinedale, Wyoming. monitored responses 1 yr treatment 2 treatment. observed general pattern posttreatment increases were greater where relative canopy cover higher, magnitudes increase varied according site conditions. tentatively suggest at 4:1, increased herbicide > 10:1, beyond which grasses no longer observed. Such provide starting point for threshold identification be transferrable across communities but need explored broader scale adequately make recommendations.