Chinese and European privets are among the most aggressive invasive shrubs in forestlands of the southern United States. We analyzed extensive field data collected by the U.S. Forest Service covering 12 states to identify potential determinants of invasion and to predict likelihood of further invasion under a variety of possible management strategies. Results of multiple logistic regression, which classified 75% of the field plots correctly with regard to species presence and absence, indicated probability of invasion is correlated positively with elevation, adjacency (within 300 m) to waterbodies, mean extreme maximum temperature, site productivity, species diversity, natural regeneration, wind disturbance, animal disturbance, and private land ownership and is correlated negatively with slope, stand age, site preparation, artificial regeneration, distance to the nearest road, fire disturbance, and public land ownership. Habitats most at risk to further invasion (likelihood of invasion > 10%) under current conditions occur throughout Mississippi, with a band stretching eastward across south-central Alabama, and in eastern Texas and western Louisiana. Invasion likelihoods could be reduced most by conversion to public land ownership, followed by site preparation, fire disturbance, artificial regeneration, and elimination of animal disturbance. While conversion of land ownership may be neither feasible nor desirable, this result emphasizes the opportunity for reducing the likelihood of invasions on private lands via increased use of selected management practices.
Nomenclature: Chinese privet, Ligustrum sinense Lour, European privet, Ligustrum vulgare L.
Management Implications: Biotic invasions have affected ecosystems worldwide. One of the greatest current challenges facing forest ecosystem management in the southern United States is the control of range expansions by invasive plant species. To move beyond reactive control efforts toward more proactive management requires prediction of potential ranges of invasive species on spatial scales relevant to forest managers. We drew upon extensive geo-referenced datasets on nonnative invasive plants maintained by the U.S. Forest Service to develop an invasion distribution model predicting possible range expansion of Chinese and European privets in forestlands of the southern United States. By identifying determinants of invasion and potential habitat, our analyses should assist land managers and restoration practitioners in planning proactive management strategies and control treatments.