Submitted to: Wildland Shrub Symposium Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: April 12, 2004
Publication Date: August 1, 2004
Citation: Sims, P.L., Bradford, J.A. 2004. Carbon dioxide and evapotranspiration fluxes across grassland and sand sagebrush dominated mixed prairie [abstract]. Wildland Shrub Symposium. p. 60. Technical Abstract: Rangelands comprise about 50 percent of the world's land area. Their role in the global C budget is only now being adequately documented even though rangelands dominate the earth's landscape. Our objective was to determine the relationship of vegetation structure and dynamics to CO2 and ET fluxes for a grass and a sagebrush-dominated Southern Plains mixed-grass prairie. CO2 and ET fluxes, calculated at 20-minute intervals, were measured from mid-February to early May through mid to late December for 3 years on both sites using Bowen ratio/energy balance instrumentation. Plant measurements included aboveground and belowground biomass, leaf area, and canopy height. Estimated annual net CO2 fluxes into these systems were 257 and 23 g m-2 yr-1, respectively, for the grass and sagebrush-dominated sites. Average daily flux during the sampling period and estimated annual rate of daily CO2 flux for the grass-dominated prairie site were greater (1.54 and 0.70 g m-2 d-1) than the sagebrush site (0.01 and 0.06 g m-2 d-1). Seasonal ET measured over the 1995, 1996, and 1997 sampling periods averaged 564 and 515 mm for the grassland and sagebrush dominated mixed-grass prairie sites. Daily ET, averaged over the approximately 230 d measurement period, was 2.28 mm d-1 for the grassland and 2.30 mm d-1 for the sagebrush site. When extrapolated to an annual basis, ET on both sites was about 660 mm and averaged 1.8 mm d-1. Even though water-use was similar for the two sites, differences in vegetation structure resulted in marked differences in CO2 flux.