Understanding the Effects of Annual Invasive Grasses on Rangelands and Wildfire
The Challenge
Annual invasive grasses are one of the greatest challenges in today’s rangelands. These fast-growing species outcompete native plant life, diminishing biodiversity and creating large areas that are dominated by a single species. As they continue to colonize new areas, they are reshaping the range in a multitude of ways. Invasive grasses reduce wildlife and livestock food resources and are a major contributing factor to the increasing frequency and spread of wildfires. As these fast-growing species spread to across the landscape and die off during the hot, dry summer months, leaving behind a tapestry of fine fuels that feed wildfires.
Despite the rapid increase in invasives throughout Idaho and the western range, we lack a deeper understanding of how these annual invasive grasses interact with the landscape. The degree to which annual invasives contribute to wildfires, to what degree they are affecting plant biodiversity, how to effectively control them with herbicides and grazing, as well as how annual grass herbicides interact with other aspects of range ecology are all factors that lack scientific study.
Our Response
To understand the vast ways that invasive annual grasses affect the rangelands, research that involves multiple disciplines and research areas, as well as a ‘place-based’ approach, meaning that research can occur for multiple years in specific places, are needed. The Rangeland Center has the unique capacity of facilitating cross-cutting, place-based research to answer key questions about the role invasive annual grasses in western range.
Reducing Fire Risk and Stimulating Native Plant Diversity Through Annual Grass Management
Annual grasses are a threat to sagebrush steppe plant communities and increase the risk of wildfires. Managing annual grasses in ecosystems like the University of Idaho’s Rinker Rock Creek Ranch can reduce risk of wildfire, resulting in healthier plant communities to avoid disruption to working landscapes and for Idahoans to.
Research Highlights in Invasive Annual Grasses
Changes in the sagebrush steppe from Cheatgrass
Georgia Harrison, a Ph.D. student in Plant Sciences, is researching how invasive annual grasses, such as cheatgrass, change sagebrush steppe plant communities and fire risk and behavior. She has been conducting surveys to observe changes due to invasive species and experiments to better understand invasive species can influence how fire moves across the landscape.
Georgia is researching at Rinker Rock Creek Ranch, working with a team of botanists to survey plant cover and gaps between plants. Recent work involved resurveying areas which were previously assessed to gather data on how invasive plants are changing the range. The team has also been assessing brush biomass with drones in to collect data on how invasives change biomass in rangelands.
Fire behavior and invasive grasses
While it is known that invasive annual grasses contribute to wildfire spread and shorten the fire return interval, the mechanisms behind this observation have not been widely studied. Georgia Harrison (Ph.D. Candidate in Plant Sciences) has been studying the flammability of various annual invasive grasses to better understand how different species influence fire behavior. Through using a mobile combustion chamber at Rinker Rock Creek Ranch, she is gathering data on how quickly invasive annual grasses catch fire along, as well as the rate and intensity at which they burn. Rangeland Center members Dr. Tim Prather and Dr. Ava Strand have been working closely with Georgia on this study, which will help answer key questions on how invasive grasses fuel wildfire intensity, frequency, and spread.