Evaluation of MODIS Gross Primary Productivity of tropical oil palm in southern Peninsular Malaysia

Evaluation of the MODIS Gross Primary Productivity (GPP) or the MOD17A2 product has not been carried out for croplands, such as oil palm ecosystems in tropical regions. Thus, evaluation of the MOD17A2 is important in order to determine its usefulness for carbon related studies of oil palm. MOD17A2 and its inputs, such as MODIS land cover (MOD12Q1), meteorological data from Global NCEP/DOE II reanalysis dataset, LAI/fPAR (MOD15A2) and light use efficiency (LUE) were evaluated. Of the area of oil palm identified from a land use map, only 40.22% was correctly identified by croplands of MOD12Q1 as oil palm and the remaining 59.78% was misclassified as croplands and forest. From Global NCEP/DOE II reanalysis dataset, photosynthetic active radiation shows the lowest correlation (R²=0.02) whilst daily minimum temperature (T_min) only agreed moderately (R²=0.26) compared to in-situ meteorological data. LAI and fPAR were underestimated by 10.00-16.79% and 9.66-10.80% respectively by MOD15A2. GPP was underestimated 19.10-29.48% by MOD17A2. LUE from site is higher than MODIS LUE of croplands for 0.19 g/m²/MJ/day.