Relationship of 2 100-2 300 nm Spectral Characteristics of Wheat Canopy to Leaf Area Index and Leaf N as Affected by Leaf Water Content

摘要

The effects of leaf water status in a wheat canopy on the accuracy of estimating leaf area index (LAI) and N were determined in this study using extracted spectral characteristics in the 2 000-2 300 nm region of the short wave infrared (SWI) band. A newly defined spectral index, relative adsorptive index in the 2 000-2 300 nm region (RAI_(2000-2300)), which can be calculated by RAI_(2000-2300) = (R_(2224) - R_(2054)) (R_(2224) + R_(2054))~(-1) with R being the reflectance at 2 224 or 2 054 nm, was utilized. This spectral index, RAI_(2000-2300), was significantly correlated (P < 0.01) with green LAI and leaf N concentration and proved to be potentially valuable for monitoring plant green LAI and leaf N at the field canopy scale. Moreover, plant LAI could be monitored more easily and more successfully than plant leaf N. The study also showed that leaf water had a strong masking effect on the 2 000-2 300 nm spectral characteristics and both the coefficient between RAI_(2000-2300) and green LAI and that between RAI_(2000-2300) and leaf N content decreased as leaf water content increased.