Quantifying the Efficacy of Cheatgrass Management

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Bromus tectorum, more commonly known as cheatgrass, is the epitome of an aggressive invader. It has been widely documented to create monocultures in the Great Basin. However, there is a paucity of research on B. tectorum in the north-eastern sagebrush steppe ecosystem – such as southwest Montana. The environmental impacts of dense cheatgrass stands primarily result in the degradation of rangeland, including loss of native species, changes in disturbance regimes, nutrient cycling, and though less documented, shifts in below ground communities. The corresponding changes in ecosystem function associated with loss of biodiversity is often quantified in terms of financial detriment to ranchers, who lose valuable native plant communities that provide nutrient rich forage for livestock, and negative impacts to native fauna such as sage grouse and pronghorn antelope.

Biology technicians on this project are spending the summer conducting vegetation surveys, collecting grass biomass and soil samples and characterizing the environmental variables at each site. There are 16 sites in cheatgrass infested areas near Antelope Peak and the eastern sandhills. Vegetation sampling consists of identifying each species present at each site, and its abundance, and taking some biomass samples to assess forage productivity. Soil is collected and is transported to a lab at Montana State University to analyze the nutrient availability. Four sites will also be seeded with native grass seed.

The goal of this project is to: a) determine the effectiveness of herbicide to decrease cheatgrass, b) identify the impacts cheatgrass and management practices have on the native plant community composition and abundance, and soil nutrients, c) determine at what density the native plant community, especially native grasses successfully competes with cheatgrass, d) evaluate the benefit of seeding based on initial native grass abundance. Answers to all these questions will better inform management decisions, prioritizing the areas of most concern, and identify potentially unknown impacts of cheatgrass besides loss of biodiversity.