Using MODIS image data to estimate the terrestrial net primary productivity (NPP) of ecological zone in Taiwan.

Net primary productivity (NPP) estimation was one of the most important issues in studies of global climate change and terrestrial ecosystems. Remote sensing data, among others, is currently the most popular method used to estimate NPP. MODIS primary productivity products (MOD17) were the first regular, near-real-time data sets for repeated monitoring of vegetation primary productivity on vegetated land at 1 km resolution in an 8-day interval. It was advantageous for monitoring ecological conditions, natural resources and environmental changes. In this research, we studied the suitability of MODIS NPP in Taiwan. We explored the differences in the time-variant NPP and compared the results with previous studies. Six years of MODIS image data (2001 to 2006) were used to construct the NPP map, and the results of time-variant NPP data analyzed statistically. The results showed that during the years 2001-2006, the NPP data concentrated mainly in the 1 000-1 500 g/(cm2•year) with an average of 1 035.64 g/(cm2•year), accounting for 24.2%-54.5% of that of the total area. A comparison of NPP data of ecological zone indicated that NPP data was within the range of results of previous studies, which proved that the application of MODIS NPP in Taiwan was reliable.