Fire and nitrogen effects on a purple threeawn-dominated plant community in the northern Great Plains

Purple threeawn (Aristida purpurea Nutt. varieties) is a native grass capable of rapidly increasing on rangelands, forming near monocultures, creating a stable state. Rangelands throughout the Great Plains and Intermountain West have experienced increases in purple threeawn abundance, leading to reductions in overall forage quality and community diversity. Our objectives were to: 1) examine prescribed fire and nitrogen as tools to shift species composition in a purple threeawn invaded community, 2) reveal vegetation management strategies appropriate for reducing purple threeawn abundance 3) quantify fire effects on purple threeawn plant characteristics and 4) determine the relationship between purple threeawn survival and fire behavior. Fire reduced purple threeawn abundance one-growing season post-fire, with sustained reductions two-growing seasons post-fire. Nitrogen had no effect on purple threeawn abundance. Heat duration and dosage were good predictors of purple threeawn mortality. Summer prescribed fire appears to be the best management tool to reduce purple threeawn abundance.