APPLICATION OF A LUE MODEL TO ESTIMATE GPP 8-d USING THE FPAR MODIS PRODUCT IN AN AGRICULTURAL ECOSYSTEM IN THE UPPER SPANISH PLATEAU

摘要

This paper presents the results of the GPP 8-d derived from the FPAR MODIS product, processed with version V005, using a LUE model in an agricultural ecosystem located in the geographical centre of the Spanish plateau over selected periods between 2003 and 2006, especially during the growing season. The LUE model is based on ground PAR measurements, FPAR and a scalar f varying between 0 and 1 to take account of water stress, which was assumed to be equal to the evaporative fraction, EF. The fourth parameter, optimal light use efficiency, (epsilon)_(max), of the dominant land use was fitted through a linear fit between the calculated and observed GPP 8-d values measured at the available eddy covariance tower. The LUE model fitted the observed GPP 8-d (R~(2)velence90.6percent) properly, providing an (epsilon)_(max) of 2.371 g C m~(-2) MJ~(-1), a substantially higher value than typically reported in the literature for crops.