Large-Scale/Coarse-Resolution Characterization of Paddy Rice Agriculture in China Using VEGETATION Sensor Data

We have begun to use multi-temporal 10-day composites of the VEGETATION (VGT) sensor in SPOT 4 for mapping and monitoring of paddy rice agriculture in China. VGT has 4 spectral bands: blue (430-470 nm), red (610-680 nm), near-infrared (780-890 nm), and mid-infrared (1580-1750 nm); and it provides daily global coverage at 1-km spatial resolution. We have acquired 10-day composite VGT data of from March 1999 through November 1999 for all of China. Our objectives in the project are twofold: (1) map locations and areas of paddy rice fields as well as rice transplanting periods; (2) estimate rice crop biophysical parameters (leaf area index and aboveground biomass). Our image analysis and field work stretch across the scales of field plots ($\u3c$1-km$^{2}$), landscapes ($\u3c$10,000 km$^{2}$) and regions ($\u3c$1 million km$^{2}$). At intensive field study sites in the Nanjing area, we have collected field data of LAI and aboveground biomass through the rice growing season of 1999, and the results show high correlation between field measured LAI and VGT-derived NDVI (normalized difference vegetation index). Through examination of temporal dynamics of NDVI and NDWI (normalized difference water index) in Nanjing area, we were able to clearly identify the physical system shift from winter wheat cropping system (upland, greening-up in March and harvested in late May/early June) to paddy rice cropping system (flooded land, transplanted in mid June and harvested in late October). We are using these temporal characteristics of NDVI and NDWI to develop a knowledge-based model for mapping rice transplanting period and paddy rice fields at the regional scale. Our preliminary analysis of the VEGETATION 10-day composite data has shown its great potential for mapping and monitoring rice agriculture in China