Distribution and occupancy of introduced species: a baseline inventory from Phase 3 plots across the country

Abstract

Invasive plant species have significant negative impacts in many ecosystems and are found in many forests around the world. Although not all introduced species become invasive, there are numerous examples of species escaping cultivation and invading natural ecosystems years or even decades after their initial introduction. Regional distributions of invasive species are influenced by climatic and physical conditions; within the landscape, fragmentation, disturbance, and surrounding land use are important factors. Inventory data can help describe the distribution (reported as constancy) and occupancy, (reported as relative richness and cover of introduced species) in forested ecosystems. Vegetation data from 1690 Phase 3 forest inventory plots collected by the U.S. Forest Service's Northern and Pacific Northwest Research Stations' FIA units are used to examine and compare the distribution and occupancy of introduced species. Introduced species were common in forests; 388 species were recorded and 61 percent of all plots had at least one introduced species. Where introduced species occurred, their mean relative richness was 10.7 percent and mean relative cover was 8 percent. However, this varied across regions, level of fragmentation, and distance from roads. Regions with high proportions of forest edge plots had higher overall constancy and occupancy of introduced species. The most commonly recorded introduced species in our analysis was multiflora rose, however, common species varied by ecological region. The most commonly recorded species are highlighted by region, with examples of how these results can inform managers who have limited budgets for invasive plant control.

Parent Publication

• Moving from status to trends: Forest Inventory and Analysis (FIA) symposium 2012

Citation

Schulz, Bethany K.; Moser, W. Keith. 2012. Distribution and occupancy of introduced species: a baseline inventory from Phase 3 plots across the country. In: Morin, Randall S.; Liknes, Greg C., comps. Moving from status to trends: Forest Inventory and Analysis (FIA) symposium 2012; 2012 December 4-6; Baltimore, MD. Gen. Tech. Rep. NRS-P-105. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station. [CD-ROM]: 268-273.