Carbon dioxide fluxes in a southern plains prairie

Atmospheric CO2 concentrations have increased because of changes in land use and burning of fossil fuels. Grasslands are important terrestrial ecosystems that, along with other temperate and arid rangeland resources, comprise more than 50% of the world’s land area. Even though grasslands dominate the world’s landscape, their role in the global C budget has not been adequately documented. The objective of this study was to determine the relationship of vegetation structure and dynamics to CO2 fluxes for a grass and a sagebrush-dominated Southern Plains mixed-grass prairie (latitude 36°36′N, longitude 99°35′W, elevation 630 m) and evaluate their potential for carbon sequestration. The CO2 flux calculated at 20-min intervals was measured from mid-February to early May through mid to late December in 1995–1997 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 per day) than the sagebrush site (0.01 and 0.06 g m−2 per day). Water-use was similar for these two mixed-grass prairie sites. This study indicates that these Southern Plains mixed-grass prairie communities have the potential to sequester C.