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Published September 1997 | Published
Journal Article Open

Interannual variation in global-scale net primary production: Testing model estimates


Testing estimates of year‐to‐year variation in global net primary production (NPP) poses some challenges. Large‐scale, multiyear records of production are not readily available for natural systems but are for agricultural systems. We use records of agricultural yields at selected sites to test NPP estimates produced by CASA, a global‐scale production model driven by both meteorological data and the satellite‐derived normalized difference vegetation index (NDVI). We also test estimates produced by the Miami model, which has underlain several analyses of biosphere response to interannual changes in climate. In addition, we test estimates against tree ring data for one boreal site for which data from both coniferous and deciduous species were available. The agricultural tests demonstrate that CASA can reasonably estimate interannual variation in production. The Miami model estimates variation more poorly. However, differences in NDVI‐processing algorithms substantially affect CASA's estimates of interannual variation. Of the four versions tested, the FASIR NDVI most closely reproduced yield data and showed the least correlation with changes in equatorial crossing time of the National Oceanic and Atmospheric Administration satellites. One issue raised is the source of the positive trends evident in CASA's NDVI‐based estimates of global NPP. The existence of these trends is consistent with potential stimulation of terrestrial production by factors such as CO2 enrichment, N fertilization, or temperature warming, but the magnitude of the global trends seen is significantly greater than suggested by constraints imposed by atmospheric fluxes.

Additional Information

© 1997 American Geophysical Union. (Received November 27, 1996; revised May 5, 1997; accepted May 12, 1997.) Paper number 97GB01419. We thank Anne Ruimy for the CESBIO NDVI version, Dan Baldwin (Colorado State University) for the original equatorial crossing time program, F.-W. Badeck for the global FBM estimates, and Jasmin John for help with the meteorological data. we also thank the Distributed Active Archive Center (Code 902.2) at the Goddard Space Flight Center, Greenbelt, Maryland, for producing the Pathfinder data and distributing them. The original Pathfinder data products were produced under the NOAA/NASA Pathfinder program; by a processing team headed by Mary James of the Goddard Global Change Data Center; and the science algorithms were established by the AVHRR Land Sciences Working Group, chaired by John Townshend of the University of Maryland. Goddard's contributions to these activities were sponsored by NASA's Mission to Planet Earth Program. We also wish to thank the helpful staffs at the Canadian Wheat Board, Statistics Canada, the USDA-NASS and Departments of Agriculture in Kansas and Oklahoma, the USDA Foreign Agricultural Service, and the Grains Research and Development Corporation in Australia, and N.M. Holbrook. Burt Bartlett at the Oklahoma Department of Agriculture, Katherine Chambers, reference librarian at the University of California, Davis, Emily Binnian, USGS, and Andrew Weiss, Center for Conservation Biology, were particularly helpful. We appreciate the critical comments of Franz-W. Badeck, Deborah Gordon, Anne Ruimy, Peter Vitousek, and three anonymous reviewers and the support of the WESTGEC component of the DOE NIGEC program and the NASA EOS-IDS program. C. Malmström was supported by a U.S. Department of Energy Graduate Fellowship for Global Change (administered by the Oak Ridge Institute for Science and Education), G. Juday was supported by NSF grant DEB 9211769 for the Bonanza Creek Long-Term Ecological Research Site and by the USDA Maclntire-Stennis Cooperative Forestry Research Program, J. Randerson was supported by a NASA Global Change Fellowship, and S. Los was supported by a NASA EOS-IDS grant (Sellers-Randall-Mooney), contract NAS5-31732. This is Carnegie Institution of Washington publication number 1330.

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August 19, 2023
October 19, 2023