PARENT SESSION
Oral Session #58: Elevated CO2. Presiding: A. Finzi.
Thursday, August 9, 2001. 8:00 AM to 12:00 PM. Madison Ballroom C.
Production of invasive plants in response to elevated CO2 in a closed-canopy, deciduous forest.
Weltzin, Jake1, Norby, Richard2, Thomas, Leigh1, 1 2
ABSTRACT- Increases in the concentration of carbon dioxide (CO2) in the atmosphere, and invasions by non-native organisms, are both predicted to change plant communities and ecosystems in the near future. Because interactions between these two variables may be greater than their individual effects, we are investigating the response of non-native, invasive plants to elevated CO2 in an ongoing, free-air CO2 enrichment (FACE) facility on the Oak Ridge National Environmental Research Park, Tennessee. Five 25-m diameter plots within a stand of sweetgum (Liquidambar styraciflua) have received either ambient (= control) or elevated (537 ppm) CO2 since 1998. In Fall 2000, we clipped subplots within each plot to determine total biomass and biomass of non-native invasive taxa. Total understory biomass and biomass of invasive woody plants did not differ between ambient and elevated treatments (P > 0.25). However, production of Microstegium vimineum, an invasive grass, was greater (P = 0.05) in ambient (82 g/m2) than elevated (58 g/m2) treatments. Total, woody, and M. vimineum biomass were not correlated (P > 0.19) with mean soil temperature (at 10 cm) or mean soil water content (top 20 cm) in 2000. Results suggest that factors other than direct or even indirect effects of CO2 enrichment, such as disturbance or light availability, may dictate at least the proximal response of invasive plants to increasing atmospheric CO2.
KEY WORDS: plant invasions, Microstegium vimineum, biomass production, community composition