BELOTE, R. TRAVIS1, JAKE F. WELTZIN1, and RICHARD J. NORBY2. Department of Ecology and Evolutionary Biology University of Tennessee Knoxville, TN 37996 and Oak Ridge National Laboratory Oak Ridge, TN 37831-What are the effects of elevated CO2 on a plant community dominated by two invasive plants?


Rising levels of atmospheric carbon dioxide (CO2) and invasions by non-native organisms are predicted to change patterns and processes of native ecosystems in the near future. Likewise, rising CO2 levels may increase the success of some plant invaders.  We are examining species composition, aboveground production and biomass, and cover of the understory plant community in ambient and elevated CO2 treatments in an ongoing, free-air CO2 enrichment (FACE) facility on the Oak Ridge National Environmental Research Park, Tennessee. Five 25-m diameter plots have received either ambient (= control) or elevated (537 ppm) CO2 since 1998. The understory plant community in these plots is dominated by several non-native plant species including Lonicera japonica and Microstegium vimineum, two highly invasive plants in the Southeastern U.S.  Results from the 2000 and 2001 growing season indicate that M. vimineum (C4) cover and production was about 50% greater in ambient CO2 plots than in elevated CO2 plots (P£0.01). In contrast, L. japonica (C3) cover was about 22% greater in elevated plots than ambient plots (P£0.09).  This pattern suggests competitive interactions between the two invasive species.  In summer 2001, we conducted a field ‘press’ competition experiment wherein we grew M. vimineum and L. japonica alone and in competition and added a watering treatment to half the plots.  We will discus the relationships between the two invasive plants and the effect of elevated CO2 on invasive species.