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Title: EFFECTS OF ELEVATED ATMOSPHERIC CO2 ON INVASIVE WEED SPECIES IN MANAGED TERRESTRIAL ECOSYSTEMS OF THE SOUTHEASTERN U.S.

Author
item Rogers Jr, Hugo
item GJERSTAD, DEAN - AUBURN UNIVERSITY
item Runion, George
item Prior, Stephen - Steve
item Price, Andrew
item VAN SANTEN, EDGAR - AUBURN UNIVERSITY
item Torbert, Henry - Allen

Submitted to: Technical Report
Publication Type: Other
Publication Acceptance Date: 9/15/2005
Publication Date: 9/15/2005
Citation: Rogers Jr, H.H., Gjerstad, D.H., Runion, G.B., Prior, S.A., Price, A.J., Van Santen, E., Torbert III, H.A. 2005. Effects of elevated atmospheric co2 on invasive weed species in managed terrestrial ecosystems of the southeastern U.S. Southeastern Regional Center, National Institute for Global Environmental Change, Annual Report for Fiscal year 2004. University of Alabama, Tuscaloosa, AL. 4pp.

Interpretive Summary: One neglected aspect of global environmental change is how invasive plants might react to the rise in atmospheric CO2 level. Invasive plant pests can disrupt farm and forest systems and this threat is great for the southeastern U.S., with its numerous ports of entry and mild climate. We have started studies to monitor the response of several invasive plants by growing them under two levels of atmospheric CO2 (ambient or elevated). Preliminary information for two of these (Johnson grass and sicklepod), indicate greater growth under high CO2, especially for sicklepod. For both, we also found a reduction in the number and weights of reproductive parts. Our findings suggest that although these invasive plants may grow bigger in a high CO2 world, their ability to spread might be reduced.

Technical Abstract: Invasive plants are considered to be a major threat to the Earth's biodiversity and are estimated to cost U.S. agricultural and forest producers 34 billion dollars each year from decreased productivity and increased costs of production for weed control. While considerable effort is being spent studying these exotic plant pests, little consideration of how invasive plants might react to the increasing carbon dioxide (CO2) concentration in the atmosphere has been given. We have been growing a variety of invasive plants under ambient and elevated levels of CO2. To date, study has concluded for two species (Johnson grass [Sorghum halepense] a C4 grass and sicklepod [Cassia obtusifolia] a C3 N2-fixing legume). Results show that, while both plants grew larger under the high level of CO2, the response of sicklepod was much greater (average increase in aboveground dry weight = 37%) than did Johnson grass (20%). In addition, both species showed a delay or decrease in reproduction when exposed to elevated CO2 as evidenced by reduction in both numbers and dry weights of reproductive structures. These results suggest that, while invasive weeds may grow larger under a future, high CO2 environment, their ability to spread might be reduced.