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United States Department of Agriculture

Agricultural Research Service

Title: Carbon Dioxide Fluxes over Three Great Plains Grasslands.

Authors
item Frank, Albert
item Sims, Phillip
item Bradford, James
item Mielnick, P - TEXAS AGR EXP STA-TEMPLE
item Dugas, W - TEXAS AGR EXP STA-TEMPLE
item Mayeux Jr, Herman

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: February 10, 2000
Publication Date: N/A

Interpretive Summary: Atmospheric CO2 levels are increasing rapidly due to burning of fossil fuels and land use changes. Grassland ecosystems occupy large areas in the US. The role of these grasslands in the capture of atmospheric CO2 has not been determined. We used the Bowen ratio/energy balance technique to measure CO2 fluxes over a mid-grass prairie at Mandan, ND; a mixed-grass prairie at Woodward, OK; and a tallgrass prairie at Temple, TX representin three diverse grassland ecosystems along a latitudinal gradient of 31N to 46N in the Great Plains of the USA. Annual net CO2 uptake averaged 348, 336, and 1822 g m2/y or the equivalent of 946, 914, and 4956 kg C/ha/y being stored annually at Mandan, Woodward, and Temple, respectively. Carbon dioxide fluxes at each site were frequently reduced by periods of below normal precipitation, but all sites sequestered C. Carbon uptake tracked biomass production, which was greatest at Temple followed by Woodward and Mandan. These results suggest that these grasslands, which are typical of grassland ecosystems that cover millions of hectares in the Great Plains, are potential sinks for CO2 if managed properly.

Technical Abstract: Terrestrial grassland ecosystems are an important component of the global carbon (C) cycle. We used the Bowen ratio/energy balance technique to measure CO2 fluxes and evapotranspiration (ET) over a mid-grass prairie at Mandan, ND; a mixed-grass prairie at Woodward, OK; and a tallgrass prairie at Temple, TX representing three diverse grassland ecosystems along a latitudinal gradient of 31N to 46N in the Great Plains of the USA. Measurements from early spring through late autumn 1995 through 1997 were used to estimate daily, seasonal, and annual net CO2 uptake. Annual net CO2 uptake, calculated using estimates of CO2 efflux during winter, averaged 348, 336, and 1822 g/m2/y at Mandan, Woodward, and Temple, respectively. These fluxes are equivalent to 946, 914, and 4956 kg C/ha/y being stored annually at Mandan, Woodward, and Temple, respectively. The greater net CO2 fixation at Temple resulted from effects of burning the esite in February 1995, a longer season of active CO2 fixation, and greater precipitation. Carbon dioxide fluxes were frequently reduced by periods of below normal precipitation, but all sites sequestered C. Peak above ground and root biomass were 1028 and 15630 kg/ha for Mandan, 3234 and 16463 kg/ ha for Woodward, and 3834 and 19352 kg/ha for Temple. Average peak LAI was 0.5, 1.2, and 2.7 for Mandan, Woodward, and Temple, respectively. Daily ET rates during the period of measurement averaged 2.6, 2.3, and 3.1 mm/d at Mandan, Woodward, and Temple, respectively. These results suggest that these grasslands, which are typical of grassland ecosystems that cover millions of hectares in the Great Plains, are potential sinks for CO2.

Last Modified: 10/22/2014
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