Estimating and Validating Wheat Leaf Water Content wi th Three MODIS Spectral Indexes: A Case Study in Ningx ia Plain, China

Abstract

Water content plays an important role in the process of plant photosynthesis and biomass accumulation. Many methods have been develo ped to retrieve canopy leaf water content from remote sensing data. However, the vali dity of these methods has not been verified, which limits their applications. This stu dy estimates the Leaf Water Content (LWC) of winter wheat with three most widely used i ndexes: Normalized Difference Water Index (NDWI), Simple Ratio (SR), and Shortwave Infrared Perpendicular Water Stress Index (SPSI), as well as MODIS short wave an d near infrared data, and then compares remote sensing estimates of vegetation wat er content with field-measured values measured in concurrent dates. The results in dicate that the three indexes are significantly correlated with the LWC of winter whe at at the 0.01 significance level. They all have good accuracy with higher than 90%. The in dexes derived from MODIS bands 6 and 2 were better than those from bands 7 and 2 for measuring wheat leaf water content, and the correlations of the former two (NDWI and SR ) were stronger than that of SPSI . Keywords : Near infrared band, Remote sensing, Short wave in frared band. Spectral characteristic index, Validation.