HR: 0800h
AN: B51C-0216    [Abstracts]
TI: Evaluation of the Empirical Piecewise Regression Model in Simulating GPP in the Northern Great Plains
AU: * Zhang, L
EM: lizhang@usgs.gov
AF: SAIC, USGS National Center for Earth Resources Observation and Science, 47914 252nd Street, Sioux Falls, SD 57198 United States
AU: * Zhang, L
EM: lizhang@usgs.gov
AF: Geography Department, South Dakota State University, Box 504, Brookings, SD 57007 United States
AU: Wylie, B K
EM: wylie@usgs.gov
AF: SAIC, USGS National Center for Earth Resources Observation and Science, 47914 252nd Street, Sioux Falls, SD 57198 United States
AU: Fosnight, E A
EM: fosnight@usgs.gov
AF: SAIC, USGS National Center for Earth Resources Observation and Science, 47914 252nd Street, Sioux Falls, SD 57198 United States
AB: For better understanding the carbon fluxes in the grassland ecosystems, an empirical piecewise regression (PWR) model was developed to estimate gross primary production (GPP) for the grassland ecosystems in the Northern Great Plains and Northern Kazakhstan. The PWR model spatially scales up the localized flux tower measurements across an ecoregion at 1-km resolution. In this study, we compared the PWR GPP and the MODIS GPP with five grassland flux tower measurements. Then we employed cross-validation to evaluate the PWR GPP values. We also compared PWR GPP and MODIS GPP for grasslands for the entire study area. Factors that may explain the spatial pattern of the GPP differences between the two models were explored using decision tree technique. The results indicated that the PWR modeling approach was robust with a good agreement (agreement coefficient d=0.71-0.97) between PWR model and tower measurements. Cross-validation showed a relatively low agreement (d=0.71-0.78) at two influential flux tower sites. We also observed that the PWR GPP was lower than or similar to the MODIS GPP in the east and higher in the west and south. Further analysis suggested that percentage of C4 grasses, soil water holding capacity, percentage of clay, and percentage of crop mixed in the grassland contributed to the GPP difference of the PWR and MODIS models.
DE: 0428 Carbon cycling (4806)
DE: 0466 Modeling
DE: 0480 Remote sensing
SC: Biogeosciences [B]
MN: Fall Meeting 2005