As part of a multi-scale project to predict invasive plant spread in response to climate and land-use change, we are evaluating the environmental conditions that facilitate the establishment of three invasive alien species (IAS) in New England. Previously developed predictive models have highlighted areas of northern New England currently lacking IAS as places where these species may potentially thrive. As these IAS move northward, they will encounter novel conditions affecting establishment and growth. How these species respond will influence their further spread and impact across the region.

We established a regional transplant experiment to test predictive model results and to estimate the colonization potential for three common IAS in New England: Berberis thunbergii, Celastrus orbiculatus, and Alliaria petiolata. Native analogs to each of these species were selected to quantify response differences; Lindera benzoin, Vitis labrusca, and Arabis glabra. Regional site locations represent a broad climate gradient across New England from Connecticut to northern Maine. Individual transplant plots were selected to capture the local environmental heterogeneity in light, soil moisture, and soil type. We investigated each species’ growth and mortality response to the gradient of environmental variables: light, soil moisture, soil nitrification rate, and local climates using individually-based Bayesian models.

Results/Conclusions

Current results indicate that some of the invasive species are tolerant to a broad climate gradient across New England. B. thunbergii and C. orbiculatus show no significant difference in growth between regions. Native analogs to these species, L. benzoin and V. labrusca, chosen for their similar growth forms and co-occurrence, show different patterns of regional response. The herbaceous A. petiolata and the native A. glabra experienced greater mortality in the northern latitude plots, pointing to a limit to range expansion. Across all plots, soil moisture was the primary environmental driver of growth for most species. The observed species tolerance limits and responses to environmental variables, together with regional climate model projections for New England, will help us predict and understand how IAS, in comparison with their native ecological analogs, may respond to climate change in the future.