Bromus tectorum L. (common names downy brome or cheatgrass) is a winter annual grass that was introduced into the United States from Eurasia in the late 19th century, and has since altered the structure and function of native and agro- ecosystems throughout the western United States. In Rocky Mountain National Park (RMNP), B. tectorum has been implicated in threats to ecological preservation such as interspecific competition with native flora and increased fire intensity. Given predicted climate change scenarios, we expect B. tectorum to habit areas where it is not currently present in RMNP, including areas of great importance to the preservation of native habitats. Our objectives in this study were to better understand the species-environment relationships of B. tectorum in RMNP, and to model current and future distributions of B. tectorum in RMNP. Using field collected B. tectorum occurrence data in RMNP (n=211), maximum entropy distribution modeling (Maxent), climate data (Climate WNA), and geographic information systems (GIS) we created maps of current and predicted B. tectorum distribution based on its climatic niche. Model performance was assessed using area under the ROC (receiver operating characteristic) curve or AUC.
Results/Conclusions
The Maxent modeling algorithm performed exceptionally well in predicting the climatic niche of B. tectorum, with an AUC value of 0.96. Mean annual temperature was the climatic variable with the strongest effect on B. tectorum distribution. The future climate scenario showed an increase from approximately 5% to 23% of the total area of the Park being habitable by B. tectorum based on its climatic niche. The B. tectorum distribution maps we created from the models may be useful to land managers in selecting areas where B. tectorum removal and management efforts should be focused. They will also assist managers and the general public in understanding the impacts of climate change on B. tectorum distribution in RMNP.