$EPA NRMRL \ NATIONAL RISK MANAGEMENT RESEARCH LABORATORY www.epa.gov/nrmrl GROUND WATER AND ECOSYSTEMS RESTORATION RESEARCH Quantifying and Modeling the Risk of Disturbance to Ecosystems Caused by Invasive Species Introduction to the Problem Invasive species are biological pollutants that threaten ecosystem health. Identifying the mechanisms of invasion and developing predictive models of invasion will be critical to developing risk management strategies for limiting the economic and environmental damage caused by invaders. Background Eastern redcedar (Juniperus virginianct), a prolific evergreen tree and its associated vertebrate seed dispersers, will be used as a model invader- disperser system. Limiting factors of invasion (growth and seed dispersal; see Figure 1) will be studied through manipulative field experiments conducted at Oklahoma State University's (OS Us) Cross Timbers Experimental Range Research Site. Researchers from OSU will collaborate to complete research tasks. Objectives • Investigate the mechanisms of invasion by Juniperus virginianct • Quantify the susceptibility of ecosystems to invasion • Develop predictive models of invasion probability based on empirical data Approach The effects of local plant diversity and soil characteristics on J. virginianct survival and growth (which are measures of invasion ability) will be examined in a field experiment. J. virginianct seedlings will be planted in three distinct ecosystem types: old field, deciduous forest, juniper forest (see Figure 2). Seedling growth and survival will be analyzed in relation to adjacent plant species and soil type and chemistry. J. virginianct dispersal limits will be studied by monitoring seed consumers (see Figure 3) and their rates of consumption at J. virginianct trees, fenced to exclude small mammals and deer. A greenhouse experiment will be conducted to determine the effects of both nitrate nitrogen and ammonium nitrogen on seedling growth. Models of ecosystem susceptibility to J. virginianct invasion will be developed using empirical data collected in this study and projecting onto existing geographical data bases on vegetation type, soil type, animal distributions, and nitrogen deposition in the United Sates. The Circle of Invasion Juniper Invasion Seedling Growth Seed Dispersal Figure 1: The Circle of Invasion Figure 2: Plant diversity and soil effects on growth Figure 3: Seed Dispersers: Cedar Waxwing The National Risk Management Research Laboratory's mission is to advance scientific and engineering solutions that enable EPA and others to effectively manage current and future environmental risks. NRMRL possesses unique strengths and capabilities and is dedicated to providing credible technological information and scientific solutions that support national priorities and protect human health and the environment. ------- Accomplishments to Date (February 2003) • Completed all field work on plant diversity, soil characteristics, and seed consumption • Completed lab analysis of soils • Presented papers and posters at three national meetings • Greenhouse study is under way Near-Future Tasks • Continue greenhouse experiment on nitrogen effects on growth • Complete reports for field and lab work portions of study • Develop predictive models of invasion Goals • Arrive at a better understanding of the mechanisms of ecosystem invisibility • Develop unique field techniques • Identify vulnerable stages of invader life history • Develop predictive models of invisibility applicable to other species and useful to land managers responsible for addressing invasive species problems Investigators Collaborators Paul Mayer Oklahoma State University Ground Water and Ecosystem Restoration Division U.S. Geological Survey Ada, Oklahoma 74820 580-436-8647 The National Risk Management Research Laboratory's mission is to advance scientific and engineering solutions that enable EPA and others to effectively manage current and future environmental risks. NRMRL possesses unique strengths and capabilities and is dedicated to providing credible technological information and scientific solutions that support national priorities and protect human health and the environment. ------- |