Dissertation Evaluating Risk for Current and Future Bromus Tectorum Invasion and Large Wildfires at Multiple Spatial Scales in Colorado and Wyoming, Usa

................................................................................................................................ ii ACKNOWLEDGEMENTS .......................................................................................................... iv CHAPTER 1. BACKGROUND ................................................................................................... 1 History and Ecology of Bromus tectorum in the Western United States .................................. 1 Land Managers’ Concerns Associated with B. tectorum Invasion ........................................... 2 History and Ecology of Large Wildfires in the West................................................................. 2 Land management concerns associated with cheatgrass – wildfire feedback ......................... 3 B. tectorum, large wildfire, and climate change ....................................................................... 4 Species distribution and habitat suitability models as tools for assessing current risk and forecasting potential risk for invasive species and wildfires ..................................................... 6 Caveats in Modeling; model selection, scale, and environmental covariates .......................... 8 Applications ...........................................................................................................................10 CHAPTER 2. USING HIGH RESOLUTION FUTURE CLIMATE SCENARIOS FOR FORECASTING INVASION IN NATIONAL PARKS ..................................................................12 Introduction ...........................................................................................................................12 Methods ................................................................................................................................16 Study Area .........................................................................................................................16 Species Occurrence Data ..................................................................................................16 Environmental Variables ....................................................................................................17 Figure 2.1. Comparison of mean annual temperature (MAT) at three spatial resolutions (4 km, 1 km, and 90 m) for climate normals 1981-2010 in Rocky Mountain National Park, Colorado. Data Sources: PRISM Climate Group (www.prism.oregonstate.edu) WorldClim (www.worldclim.org) and ClimateWNA (http://climatewna.com/). ...............18 Statistical Analysis and Spatial Modeling ...........................................................................19 Model evaluation ................................................................................................................21 Results ..................................................................................................................................22 Variable correlation and parsimony analysis ......................................................................22 Final MaxEnt model with six variables ................................................................................23 Table 2.1. Variables and their relative contribution in the final MaxEnt model. ................23 Figure 2.2. Variable contribution to (a) training gain and (b) AUC (area under curve). Light gray bars indicate how well the model performs with only that variable versus a full model, which are the dark gray bars. Values shown are averaged over 100 replicate MaxEnt model runs. ......................................................................................25 Current and future potential suitable habitat of B. tectorum in the Park ..............................25