Predicting Spotted Knapweed (Centaurea maculosa) Range Expansion Near Missoula Montana Using Localized Climate and Elevation Data

by Cumming, William Frank

Since the 1920s spotted knapweed (Centaurea maculosa) has adapted to a variety of habitats, including pastureland, rangeland, hay land, open forests, road sides, and ditches. In 2003 this plant species dominated more than five million acres in Montana, half of the total infestation of noxious weeds in the state. This project demonstrates the utility of using downscaled Parameter-elevation Regressions on Independent Slopes Model (PRISM) data for predicting vegetation movement within a 2°×2° geographical area surrounding Missoula County, Montana. This localized climate change data was correlated against current knapweed range using validation data from the Volunteer for Wilderness Program at the Wilderness Institute at The University of Montana and the County of Missoula Weed District to examine optimal climatic conditions within the area. Parameters for precipitation and temperature were determined from current locations of spotted knapweed. These relationships were then used, with existing future climate scenarios from the Intergovernmental Panel on Climate Change (IPCC) and the United States Global-change Research Program (USGCRP), to predict the extent of knapweed based on its environmental tolerance ranges. The potential expansion of suitable habitat for spotted knapweed within the study area was significant with minimal increases in temperature and precipitation, but the longterm effects of possible increases of 4.5°C and up to 10 cm of precipitation would cause a contraction of suitable habitat for spotted knapweed. Further studies on tolerance ranges would increase the understanding of potential invasive species movement and climate change.