Evaluating different management treatments for reducing Bromus tectorum cover and reestablishing native grass species.
Many regions of the western United States have experienced major land use changes and degradation over the past 150-200 years. One of the main drivers of this was the invasion of non-native species including Bromus tectorum. Also known as cheatgrass, B. tectorum is a non-native winter annual grass native to Eurasia. It was introduced to the United States through contaminated grain and quickly spread from agricultural lands to rangelands and sagebrush steppe. In cases where B. tectorum has become the dominant species on a landscape it can greatly reduce the biodiversity and functioning of that system. The unique life history pattern of B. tectorum allows it to preempt resources from native species, specifically perennial bunchgrass seedlings, reducing the establishment of new native individuals. However, it has also been shown that mature perennial bunchgrasses are strong competitors with B. tectorum and high levels of bunchgrasses are often associated with low levels of B. tectorum. Much of the research surrounding B. tectorum focuses on control methods, and less on how it is interacting with and potentially impacting the communities it invades.
My research focuses on understanding the relationships between B. tectorum and native perennial bunchgrasses to help inform ecologically based management to develop diverse, resilient rangelands. To do this I am executing a neighborhood competition study on unmanipulated neighborhoods to piece apart what individual plant-plant interactions are occurring between B. tectorum and other species in the community. I am also assessing how the amount of native perennial grasses present impact B. tectorum cover and the success of restoration seeding projects. Restoration seeding in semi-arid regions is very difficult due to limitations like high temperatures, low precipitation, and seed predation. In attempt to ameliorate these barriers, I am evaluating the impact of using seed pellets instead of broadcast seed. Seed pellets are a novel tactic where seeds are combined with organic material and a binding agent. The aim of the pellets is to protect the seeds from extreme temperatures and predation until enough precipitation has fallen to disintegrate the pellet and stimulate germination. In addition to plant-plant interaction and restoration tactics, I am also evaluating several novel management tactics. Bromus tectorum and other rangeland weeds are often managed with herbicide application or targeted grazing, but it is important to have a wide range of management options available to reduce reliance on any one method. The novel methods I am testing are a biofumigant (mustard seed meal) and a soil amendment. The mustard seed meal contains plant defense compounds that can also reduce seed germination. The soil amendment contains micronutrients and is designed to improve soil health, but it has also been shown to reduce germination of B. tectorum. In combination these studies will hopefully provide valuable information to ranchers and land managers as to how they can manage B. tectorum infestations while promoting native diversity and resilient ecosystems.