Abstract, Ecological Society of America Annual Meeting, Madison, WI, August, 2001.

What are the combined effects of global climate change and biological invasions on insect community structure?

Nathan J. Sanders1,*, Jake F. Weltzin1, R. Travis Belote1, and Richard J. Norby2

1Department of Ecology and Evolutionary Biology University of Tennessee Knoxville, TN 37996 2Oak Ridge National Laboratory Oak Ridge, TN 37831 *email: nsanders@utk.edu phone: (865) 974-8648

Rising levels of atmospheric carbon dioxide (CO2) and invasions by non-native organisms are predicted to change plant communities in the near future. Rising CO2 levels may affect particular herbivorous insects because C:N ratios are altered under elevated CO2 levels. Likewise, if native host plants are displaced by non-native plants, the structure of insect communities may change. To date, no studies have examined the effects of elevated CO2 on entire insect communities, and only a few have examined the impact of invasions by non-native plants. We are examining species composition of the undestory plant and insect 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 species. Results from the May sampling period indicated that insect morphospecies richness in ambient CO2 plots (23 species) was approximately 25% greater than in elevated CO2 plots (18 species) (P=0.059). We will continue to sample the insect communities in each plot. We will also determine plant species percent cover and C:N ratios of the understory plant community. We will discus the relationships among these variables, global climate change, and the impact of non-native species on insect community structure.