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United States Department of Agriculture

Agricultural Research Service

Research Project: HYDROLOGIC PROCESSES, SCALE, CLIMATE VARIABILITY, AND WATER RESOURCES FOR SEMIARID WATERSHED MANAGEMENT Title: Assessing net ecosystem carbon exchange of U.S. terrestrial ecosystems by integrating eddy covariance flux measurements and satellite observations

Authors
item Xiao, J. - PURDUE UNIVERSITY
item Zhuang, Q. - PURDUE UNIVERSITY
item Law, B. - OREGON STATE UNIVERSITY
item Baldocchi, D. - UNIV. CALIFORNIA BERKELEY
item Chen, J. - UNIVERSITY OF TOLEDO
item Richardson, A. - UNIV. OF NEW HAMPSHIRE
item Melillo, J. - MARINE BIOLOGICL LAB
item Davis, K. -
item Hollinger, D. -
item Wharton, S. -
item Oren, R. -
item Normets, A. -
item Fischer M., L -
item Verma, S. -
item Cook, D. -
item Sun, G. -
item Mcnulty, S. -
item Wofsy, S. -
item Bolstad, P. -
item Burns, S. -
item Curtis, P. -
item Drake, B. -
item Falk, M. -
item Foster, D. -
item Gu, L. -
item Hadley, J. -
item Katul, G. -
item Litvak, M. -
item Ma, S. -
item Martin, T. -
item Matamula, R. -
item Meyers, T. -
item Monson, R. -
item Munger, J. -
item Oechel, W. -
item Tha Paw, U. -
item Schmid, H. -
item Scott, Russell
item Starr, G. -
item Suyker, A. -
item Torn, M. -

Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 2009
Publication Date: November 1, 2010
Citation: Xiao, J., Zhuang, Q., Law, B.E., Baldocchi, D.D., Chen, J., Richardson, A.D., Melillo, J.M., Davis, K.J., Hollinger, D.Y., Wharton, S., Oren, R., Noormets, `., Fischer M., L., Verma, S.B., Cook, D.R., Sun, G., Mcnulty, S., Wofsy, S.C., Bolstad, P.V., Burns, S.P., Curtis, P.S., Drake, B.G., Falk, M., Foster, D.R., Gu, L., Hadley, J.L., Katul, G.G., Litvak, M., Ma, S., Martin, T.A., Matamula, R., Meyers, T.P., Monson, R.K., Munger, J.W., Oechel, W.C., Tha Paw, U.K., Schmid, H.P., Scott, R.L., Starr, G., Suyker, A.E., Torn, M.S. 2010. Assessing net ecosystem carbon exchange of U.S. terrestrial ecosystems by integrating eddy covariance flux measurements and satellite observations. Agricultural and Forest Meteorology. 151: 60-69.

Interpretive Summary: More accurate projections of future carbon dioxide concentrations in the atmosphere and associated climate change as well as carbon accounting and climate policy-making depend on improved scientific understanding of the terrestrial carbon cycle. Despite the consensus that U.S. terrestrial ecosystems act as a carbon sink, the size, distribution, and interannual variability of the sink remain uncertain. Here we report total terrestrial carbon uptake in the conterminous U.S. at -0.68 Pg C yr-1 with the majority of the sink in regions dominated by evergreen and deciduous forests and savannas based on novel estimates of net ecosystem carbon exchange with high spatial (1km) and temporal (8-day) resolution derived from flux tower measurements and wall-to-wall satellite observations. We find that the U.S. terrestrial ecosystems could offset 40% of the fossil-fuel carbon emissions. The dominant sources of interannual variation of the carbon sink include extreme climate events and disturbances, with droughts in 2002 and 2006 reducing U.S. net ecosystem carbon uptake by ~20% relative to a normal year, and disturbances including wildfires and hurricanes resulting in reduced carbon uptake or carbon release into the atmosphere.

Technical Abstract: More accurate projections of future carbon dioxide concentrations in the atmosphere and associated climate change as well as carbon accounting and climate policy-making depend on improved scientific understanding of the terrestrial carbon cycle. Despite the consensus that U.S. terrestrial ecosystems act as a carbon sink, the size, distribution, and interannual variability of the sink remain uncertain. Here we report total terrestrial carbon uptake in the conterminous U.S. at -0.68 Pg C yr-1 with the majority of the sink in regions dominated by evergreen and deciduous forests and savannas based on novel estimates of net ecosystem carbon exchange with high spatial (1km) and temporal (8-day) resolution derived from eddy covariance flux tower measurements and wall-to-wall satellite observations. We find that the U.S. terrestrial ecosystems could offset 40% of the fossil-fuel carbon emissions. Our results show that the U.S. terrestrial carbon uptake varied between -0.51 and -0.70 Pg C yr-1 over the period 2001-2006. The dominant sources of interannual variation of the carbon sink include extreme climate events and disturbances, with droughts in 2002 and 2006 reducing U.S. net ecosystem carbon uptake by ~20% relative to a normal year, and disturbances including wildfires and hurricanes resulting in reduced carbon uptake or carbon release into the atmosphere. Our novel approach can be applied to other regions of the globe to refine the global terrestrial carbon budget.

Last Modified: 12/25/2014
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