PREDICTING SITE SUITABILITY FOR KUDZU (PUERARIA MONTANA) IN THE GREAT LAKES BASIN AND SURROUNDING REGION
Kudzu (Pueraria montana) is an invasive woody vine widespread throughout the southeastern United States, with recent studies predicting that its habitat will expand northward. New occurrences and recent studies using climatic parameters suggest that the Midwestern region of the United States is at the greatest risk of kudzu invasion. As there have already been 25 reports of kudzu within the Great Lakes basin, and no previous landscape models exist for the basin, I developed probability models from existing spatial data (land cover, hydrology, geology, annual precipitation, elevation, aspect, and known kudzu locations) using generalized additive, bioclimate envelope, and maximum entropy methods. I further expanded each model to include the basin and a 2.25-degree buffer in order to include 193 reported kudzu sites. For each predictive model, I determined the area under the curve (AUC) for a receiver operating characteristic curve (ROC) comparing false positive and false negative rates. I performed field surveys at eight known sites of kudzu presence in Michigan, Indiana, and Ohio. Each presence site was paired with a control (known kudzu absence site). I collected environmental data including canopy cover, volumetric soil moisture, soil pH, litter depth, midstory species diversity and diameter at breast height (DBH), and overstory basal area. Each environmental measure was compared between kudzu presence and control survey sites as well as between in-basin and out?of-basin survey sites using a two-way ANOVA. Maximum entropy models produced the highest AUC in both the basin and buffer models during model development. These models showed that urban and disturbed habitats resulted in the greatest probability of potential habitat for kudzu. I found no statistically significant differences in environmental characteristics between kudzu absent and presence sites or between in- and out-of-basin sites, suggesting kudzu might be dispersal-limited rather than limited by environmental characteristics. Continuing existing management and further monitoring of kudzu spread is likely necessary to limit further introduction and to mitigate spread of kudzu within the Great Lakes region.