Spatiotemporal variations in growing season exchanges of CO2, H2O,and sensible heat in agricultural fields of the Southern GreatPlains
Climate, vegetation cover, and management create fine-scaleheterogeneity in unirrigated agricultural regions, with important but notwell-quantified consequences for spatial and temporal variations insurface CO2, water, and heat fluxes. We measured eddy covariance fluxesin seven agricultural fields--comprising winter wheat, pasture, andsorghum--in the U.S. Southern Great Plains (SGP) during the 2001-2003growing seasons. Land-cover was the dominant source of variation insurface fluxes, with 50-100 percent differences between fields planted inwinter-spring versus fields planted in summer. Interannual variation wasdriven mainly by precipitation, which varied more than two-fold betweenyears. Peak aboveground biomass and growing-season net ecosystem exchange(NEE) of CO2 increased in rough proportion to precipitation. Based on apartitioning of gross fluxes with a regression model, ecosystemrespiration increased linearly with gross primary production, but with anoffset that increased near the time of seed production. Because theregression model was designed for well-watered periods, it successfullyretrieved NEE and ecosystem parameters during the peak growing season,and identified periods of moisture limitation during the summer. Insummary, the effects of crop type, land management, and water limitationon carbon, water, and energy fluxes were large. Capturing the controllingfactors in landscape scale models will be necessary to estimate theecological feedbacks to climate and other environmental impactsassociated with changing human needs for agricultural production of food,fiber, and energy.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Director. Office of Science. Biological andEnvironmental Research
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 926902
- Report Number(s):
- LBNL-63014; R&D Project: G23801; BnR: KP1205010
- Journal Information:
- Earth Interactions, Vol. 11, Issue 17; Related Information: Journal Publication Date: Oct. 2007
- Country of Publication:
- United States
- Language:
- English
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