ARS | Publication request: EFFECTS OF ELEVATED ATMOSPHERIC CO2 ON INVASIVE WEED SPECIES IN MANAGED TERRESTRIAL ECOSYSTEMS OF THE SOUTHEASTERN U.S.

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 16, 2005
Publication Date: May 16, 2005
Citation: Runion, G.B., Rogers Jr, H.H., Gjerstad, D.H., 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. [abstract]. In: Joint Southeast Regional Center-Midwest Regional Center (SERC-MWRC) National Institute for Global Environmental Change (NIGEC) Regional Conference, Program and Abstracts, May 16-17, 2005, Oak Ridge, Tennessee. p. 17.

Technical Abstract: Invasive weeds are estimated to cost U.S. agricultural and forest producers 34 billion dollars each year from decreased productivity and weed control efforts. Invasive plant pests, via their competitive aggression and absence of natural controls, have the ability to disrupt terrestrial ecosystems and impact biodiversity; nowhere is this threat greater than in the southeastern U.S. with its numerous ports of entry and mild climate. Elevated atmospheric CO2 is known to stimulate photosynthesis, resource use efficiency, and carbon allocation to belowground plant structures and, therefore, may impact the competitiveness of invasive plants; however, little is known about this aspect of global change. We will investigate the effects of elevated CO2 on growth, physiology, water relations, competitive ability, and control of invasive weed species detrimental to the Southeast economy. This research addresses three hypotheses and will take place in three associated phases. The first phase will address Hypothesis 1 - elevated atmospheric CO2 will increase growth of all invasive plants, but the magnitude of response will vary among plant functional guilds which will impact system carbon dynamics. The response of individual invasive plant species (from differing functional guilds) to elevated CO2 will be assessed. We will examine: C4 grasses (cogongrass, Johnson grass); a C4 sedge (purple nutsedge); a C3 N2-fixing legume (sicklepod); a herbaceous C4 biennial (musk thistle); a C3 broadleaf evergreen shrub (Chinese privet); and possibily a C3 perennial (tropical soda apple). The second phase will address Hypothesis 2 - herbicide tolerance of invasive weeds will increase with CO2 enrichment. Plants (particularly cogongrass ecotypes collected from across the Southeast) will be treated with recommended herbicides at the highest labeled rate as well as one-half and one-quarter of the highest labeled rate. Herbicide efficacy will be visually rated on a zero (no effect) to 100 (complete effect) scale, and re-growth will be measured; efficacy will be compared to a non-treated check for each CO2 level. The final phase will address Hypothesis 3 - competition from invasive species will reduce growth and yield of crops, which will also impact carbon dynamics by altering allocation among species. Based on findings from the first two phases, a series of competition studies under ambient and elevated CO2 will be conducted. Some possible pairing include: cogongrass with loblolly pine; sicklepod and/or purple nutsedge with soybean and/or grain sorghum; and musk thistle and/or tropical soda apple with pasture bahiagrass. These combinations represent problems commonly encountered by Southeastern producers and represent species which differ in lifeform, growth habit, and physiology. Data from this research will fill key gaps in our current knowledge of ecosystem level responses to rising CO2 and will generate information that helps combat invasive plants in a future CO2-enriched world.