|Mayeux Jr, Herman|
Submitted to: American Meteorological Society
Publication Type: Proceedings
Publication Acceptance Date: July 1, 2002
Publication Date: July 1, 2002
Technical Abstract: This research effort involved numerous ARS rangeland and pasture scientists from ten western states (ND, OK, TX, AZ, CO, WY, MT, UT, ID, OR) in cooperation with the Texas A&M University Blackland Research Center. The project focused on assessment of CO2 flux over native rangeland at each of the locations. The Bowen ratio/energy balance (BREB) method was used to measure CO2 flux, and supporting data included annual precipitation, peak lea area index (LAI), standing biomass, litter, root biomass, and soil carbon. There were four years of data for most sites (generally 1996 to 1999) and all sites had at least three years of CO2 flux data. Where estimates of net annual CO2 fluxes have been completed it appears that rangelands are a sink for atmospheric CO2. The average annual sequestration ranges from slightly less than 200 g Co2 m-2 yr-1 at an arid sagebrush site to about 1100g CO2 m-2 yr-1 at a mesic tallgrass prairie site. There is large variation in yearly estimates, with most sites functioning as CO 2 sources during dry years and sinks during normal or wet years. Peak LAI and average annual precipitation accounted for 89% of the variation in average maximum monthly CO2 flux across the measurement sites. Our results suggest that U.S. rangelands are likely a sink for atmospheric CO2, although yearly weather patterns control sink/source relations within a site. Relatively easily obtained measurements (precipitation and LAI) hold promise for estimating CO2 fluxes across rangeland ecosystems.