Quantitative relationships between field-measured leaf area index and vegetation index derived from VEGETATION images for paddy rice fields

In an effort to develop the quantitative relationships between fieldmeasured leaf area index (LAI ) and VEGETATION-derived vegetation indices for paddy rice fields, we have measured LAI of paddy rice fields at 10-day intervals at five sampling sites in Jiangning County, Jiangsu Province of China during the rice growing season (July to October) of 1999, using a LI-COR LAI-2000 plant canopy analyser. Twenty-seven 10-day VEGETATION (VGT) synthesis products (VGT-S10) from 1-10 March to 21-30 November 1999 were acquired. Normalized difference vegetation index (NDVI) values were calculated for the VGT-S10 products, using ground surface reflectance values of VGT spectral bands (B3-near-infrared; B2-red). After rice transplanting in mid to late June, LAI increased rapidly and reached its plateau by early to mid August. There were similar temporal dynamics of NDVI and LAI among the five sampling sites over the growing season of paddy rice in 1999. Simple linear regression analyses indicate that there are statistically significant linear relationships between NDVI and LAI data over the growing season of paddy rice in 1999.