THE EFFECT OF LAI BASED MODIS VEGETATION INDEX IN DIFFERENT SCALE TO ESTIMATE GROSS PRIMARY PRODUCTIVITY

The Moderate Resolution Imaging Spectroradiometer (MODIS) is the primary NASA Earth Observing System instrument monitoring the seasonality of global terrestrial vegetation. MODIS products, such as the MODIS Vegetation Index (VI), Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI), are commonly used in ecological modeling. The difference spatial resolutions (250, 500, 1000 and 5600 m) may cause the error in the output. In this study, the 3-PGS (Physiological Principles Predicting Growth using Satellite data) model was used to examined the errors of gross primary productivity (GPP) based difference spatial resolutions. First, in situ Leaf Area Index (LAI) was compared with NDVI and EVI from Hemispherical Spectroradiometer (HSSR) to find the relationship. Then, these relationships were applied to the model for estimating GPP as the final output. From the results, GPP based on MODIS NDVI at spatial resolution 250 m was performed the less error around 9.12%, whereas GPP based MODIS on EVI at spatial resolution 1000 m was performed the less error around 5.76%. GPP based on MODIS NDVI and EVI at spatial resolution 5600 m were showed the biggest error with 18.47% and 13.02%, respectively. However, the global spatial resolution can be accepted for applying to the model, based on one point, with the error around 20%.