Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: September 8, 2004
Publication Date: February 2, 2005
Citation: Polley, H.W. 2005. Influence of CO2 enrichment on plant community and soils systems in mesic rangelands. In: Society for Range Management 58th Annual Meeting and Trade Show, February 5-11, 2005, Fort Worth, Texas. 2005 CDROM. Technical Abstract: The concentration of atmospheric carbon dioxide (CO2) has increased by about 35% since Industrialization and may rise to twice the pre-Industrial level within the century. Effects of CO2 enrichment on several aspects of plant physiology are well-established, but the manifestation of physiological changes in grassland structure and functioning remains uncertain. We exposed a grassland in central Texas to a continuous gradient in CO2 spanning pre-Industrial to elevated concentrations to determine effects of past and predicted increases in CO2 on plant composition and grassland carbon (C), water, and nitrogen (N) dynamics. Increasing CO2 accelerated a successional shift in vegetation from the dominant grass to perennial forbs during the 4 years of this study. Biomass production rose dramatically from subambient to elevated CO2, despite the shift in plant composition and despite temporal changes in the responses of biomass and tissue N to CO2 among species and species groups. Increasing CO2 lessened soil water depletion, improved plant water status, and increased leaf water use efficiency over both subambient and elevated concentrations. By contrast, soil C storage and N cycling were most responsive to CO2 at subambient concentrations. Soil C was lost at subambient CO2, but was unchanged at elevated concentrations, implying that the capacity of these grassland soils to continue as a C sink is limited. As indicated by the large responses of biomass production and grass-forb relative abundances to CO2, however, many aspects of grassland structure and functioning may remain sensitive to CO2 as concentration rises to twice the pre-Industrial level during coming decades.