title: Evaluation of modelled net primary production using MODIS and landsat satellite data fusion.
abstract: BACKGROUND
  To improve estimates of net primary production for terrestrial ecosystems of the continental United States, we evaluated a new image fusion technique to incorporate high resolution Landsat land cover data into a modified version of the CASA ecosystem model. The proportion of each Landsat land cover type within each 0.004 degree resolution CASA pixel was used to influence the ecosystem model result by a pure-pixel interpolation method.
  
  
  RESULTS
  Seventeen Ameriflux tower flux records spread across the country were combined to evaluate monthly NPP estimates from the modified CASA model. Monthly measured NPP data values plotted against the revised CASA model outputs resulted in an overall R2of 0.72, mainly due to cropland locations where irrigation and crop rotation were not accounted for by the CASA model. When managed and disturbed locations are removed from the validation, the R2increases to 0.82.
  
  
  CONCLUSIONS
  The revised CASA model with pure-pixel interpolated vegetation index performed well at tower sites where vegetation was not manipulated or managed and had not been recently disturbed. Tower locations that showed relatively low correlations with CASA-estimated NPP were regularly disturbed by either human or natural forces.
authors.affiliation: Yellowstone Ecological Research Center, 2048 Analysis Dr. Ste. B, Bozeman, MT 59718 USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Jay
authors.affiliation: CASA Systems 2100, LLC, PO Box 1631, Los Gatos, CA 95030 USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Potter
authors.affiliation: Yellowstone Ecological Research Center, 2048 Analysis Dr. Ste. B, Bozeman, MT 59718 USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Crabtree
authors.affiliation: Science and Environmental Policy, California State University, Monterey Bay, 100 Campus Center, Seaside, CA 93955 USA.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Genovese
authors.affiliation: Yellowstone Ecological Research Center, 2048 Analysis Dr. Ste. B, Bozeman, MT 59718 USA ; Department of Zoology, University of Oxford, The Tinbergen Building, S Parks Rd, Oxford, OX1 3PS UK.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Weiss
authors.affiliation: Yellowstone Ecological Research Center, 2048 Analysis Dr. Ste. B, Bozeman, MT 59718 USA.
authors.forename: Maggi
authors.initials: M
authors.lastname: Kraft
keywords: Ameriflux; EVI; Landsat; MODIS; Net primary production