|Mayeux Jr, Herman|
|Bradford, James - Jim|
Submitted to: International Rangeland Congress
Publication Type: Abstract Only
Publication Acceptance Date: 9/30/2002
Publication Date: 7/3/2003
Citation: Mayeux, H.S., Dugas, B., Svejcar, A.J., Angell, R.F., Johnson, D.A., Frank, A.B., Emmerich, W.E., Morgan, J.A., Sims, P.L., Bradford, J.A. 2003. The ARS rangelands CO2 flux network: Do rangelands sequester carbon? Proceedings of the 7th International Rangeland Congress. p. 1083-1084. Interpretive Summary: abstract only
Technical Abstract: Long-term measurements of CO2 fluxes in major terrestrial ecosystems are required to determine which ecosystems account for the C sink thought to exist in North America. Considerable information has accumulated regarding C storage on crop lands, and other networks are measuring net C accumulation in forests and other ecosystems. Less information is available regarding C sequestration by rangelands, despite their extensive distribution. The objective here is assess C storage in light of the findings of a coordinated effort to measure CO2 fluxes and net ecosystem productivity (NEP) over major grassland ecosystems of the western and central U.S., using the Bowen ratio/energy balance approach. Measurements of CO2 fluxes at the 10 ARS CO2 Flux Network locations indicate that all but the most arid are functioning as sinks. NEP is positive in most years in the absence of any herbivory, fire, or other influence which might alter productivity and thus C assimilation. Net annual fluxes at these sites vary widely with precipitation and other variables, but rates averaged over years range from 200 g CO2 m-2 yr-1 at an arid sagebrush site to over 700 g CO2 m-2 yr-1 at a mesic tallgrass prairie site. Annual fluxes are consistently negative in respect to the terrestrial surface on arid grasslands in Arizona, where respirational losses of CO2 may be over-estimated due to evolution from calcareous soil surfaces. An average NEP on U.S. rangelands of 200 g CO2 m-2 yr-1, or 0.54 metric tons of C ha-1 yr-1, represents about 168 million metric tons of C sequestered annually over the 312 million ha of U.S. rangelands.