Submitted to: Society for Range Management Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: August 26, 2004
Publication Date: February 7, 2005
Citation: Morgan, J.A. 2005. Influence of CO2 enrichment on plant community and soils systems in semi-arid rangelands. Society for Range Management Meeting Proceedings. Abstract #283. Technical Abstract: It is now widely accepted that rising atmospheric CO2 concentration enhances photosynthesis and stimulates productivity in many agro-ecosystems, which in turn results in a cascade of ecosystem responses to the increased plant production and C gains. However, it is the indirect effect that CO2 has on plant water relations that may be particularly important in driving semi-arid rangeland responses to CO2. Research conducted in mostly native and semi-natural grasslands shows that stomata of most herbaceous plant species close in response to rising CO2 concentration, a reaction that results in increased leaf and plant water use efficiency, higher plant and soil water status, and altered seasonal evapotranspirational dynamics. These water relations responses can result in substantial increases in net primary production, and suggest that semi-arid systems may be among the world's more responsive ecosystems to rising atmospheric CO2. However, CO2-enhanced productivity is accompanied by lower forage N, due in large part to the inability of soil N release to keep pace with increased plant productivity. Further, different sensitivities among plant species to elevated CO2 can cause significant shifts in plant community species composition with important ecological and management consequences. Such changes in leaf N and species composition can lower forage quality and significantly alter nutrient cycling, and thus have important ecological and management consequences. These affects of increasing atmospheric CO2 on ecosystem processes are already underway and are certain to influence the structure and functioning of semi-arid rangelands as atmospheric CO2 concentrations continue to rise.