ARS | Publication request: MEASURING CARBON FLUXES OVER NORTHERN GREAT PLAINS RANGELANDS

Submitted to: Research Update for Fort Keogh Livestock and Range Research Laboratory
Publication Type: Other
Publication Acceptance Date: September 1, 1997
Publication Date: N/A

Technical Abstract: The role of various ecosystems in regulating atmospheric carbon dioxide levels is a critical issue in global climate change research. Although rangelands cover a vast area, more than 40% of the land area in the world and 150 million acres in the Northern Great Plains, few have estimated their potential role as a source or sink for atmospheric carbon. Missing too are measures of how environment and management affect this role. Goals of the proposed studies are to: 1) quantify rangeland ecosystem contributions to regulating atmospheric gases; and 2) better estimate impacts of livestock grazing rangelands. Two studies will be conducted at Fort Keogh. Carbon dioxide flux at a landscape level is being monitored in the first study. The Bowen-Ratio unit was installed on an ungrazed silty range site. Soil properties, vegetation characteristics, and other data needed to study cause and effect in flux variation are being sampled periodically. Effects of seasonal grazing on carbon dioxide flux will be estimated in the second experiment. Treatments imposed on replicated plots are: no grazing, grazed in mid-May, and grazed in mid- July. From mid-April to mid-November (weather permitting) at about 30 days intervals, data will be collected for standing crop, leaf area on clipped and nonclipped plots, soil organic matter, root mass to a 11.8 inch soil depth, within-day variation in carbon dioxide concentration above 10.8 square feet of rangeland, and carbon dioxide evolved from bare soil. Measurements begun in 1996 and will be continued through 1998. Information from these studies should provide improved estimates of the contribution of Northern Great Plains ranges and associated grazing practices to carbon dioxide flux and ultimately to global warming.