Introduced Plant Species Found on Two-thirds of Forest Inventory Plots in the Northeast and Midwest United States
Introduced plant species have significant negative impacts in many ecosystems and are found in many forests around the world. However, there are few data sources that enable the assessment of introduced species occupancy in native plant communities over broad regions. Vegetation data from 1,302 forest inventory plots across 24 states in northeastern and mid-western United States were used to examine and compare the distribution of introduced species in relation to forest fragmentation across ecological provinces and forest types, and to examine correlations between native and introduced species richness. Scientists found 305 introduced species recorded, with multiflora rose (Rosa multiflora) being the most common species. Sixty-six percent of all forested plots had at least one introduced species, where they made up 7 percent of the plant flora in intact stands, but 14 percent of the flora on forest edges. The study is the first to document the abundance of nonnative plant species over a broad region-specifically, 24 states and 14 ecological provinces. Because it compares the distribution of introduced species to native species in relation to forest fragmentation across ecological provinces and forest types, the study can help managers to target forest stands where management actions will be most effective. Identifying seemingly benign introduced species that are more prevalent than realized will also help focus attention on newly emerging invasive plants.