RUI: Dynamics of European Buckthorn (Rhamnus cathartica L.) Invasion in the Northeastern United States

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Invasive non-native plants threaten the ecological integrity and economic value of natural areas throughout the world. Despite the severity of this growing problem, our understanding of how exotic plants become established in new areas and move across the landscape is weak. The objective of this research is to describe the process by which European buckthorn (Rhamnus cathartica), a shrub native to Eurasia, colonizes new areas in North America and how that process varies with ecological context. Field observations and experiments will be used to examine each stage of the colonization process in second-growth deciduous forests, conifer plantations, and abandoned agricultural fields. Differences in microclimate, soils, and resident fauna will be considered as potential sources of variation in colonization. Spatial configuration of the environment also will be considered as a factor affecting colonization. Detailed stand-level maps relating species composition, canopy gaps, edges, and streams to European buckthorn distribution will reveal factors facilitating colonization and spread. Aerial photographs and geographic information systems will allow measurement of size, shape and spatial context of areas occupied by this plant. This research will demonstrate whether fragmentation of North American forests serves to promote or inhibit the spread of European buckthorn.European buckthorn competes with native plants and is a host of oat crown rust fungus, a disease that attacks oat crops. Native birds nesting in this shrub experience high rates of predation, and leaves of European buckthorn may be toxic to native mammals. This research will lead to a greater knowledge of the physiology and ecology of this relatively unstudied species of conservation concern. In addition, this research will contribute to understanding of how invasion success is affected by the properties of invaded ecosystems. This study also will quantify how forest fragmentation due to timber harvest and abandonment of agricultural lands affects the movement of an exotic species across the landscape. Although many invasive species are found in human-modified environments, there is growing concern about the presence of invasive species within pristine natural areas. Understanding the effect of environmental context, within particular settings and among settings in the landscape, will guide land managers and scientists to identify potential threats to natural environments.