Two Kinds of Modified Spectral Indices for Retrieval of Crop Canopy Chlorophyll Content
Based on the thorough analysis of the spectral response mechanism of vegetation indices, which are used widely to retrieve chlorophyll content at present, taking advantage of sample reflectance data of crop canopy, simulated by models PROSPECT + SAIL, the sensitivity differences of these vegetation indices for chlorophyll content are compared and discussed, including Pigment-Specific Simple Ratio a ( PSSRa) , Pigment-Specific Simple Ratio b (PSSRb) , Pigment-Specific Normalized Difference a (PSNDa) , Pigment-Specific Normalized Difference b (PSNDb) , Normalized Pigments Chlorophyll ratio Index (NPCI) , Pigment Ratio Index (PRI) , Modified Chlorophyll Absorption Ratio Index ( MCARI) and Triangular Vegetation Index (TVI). The analysis results indicated that the above vegetation indices were either sensitive to changes of soil background or affected by saturation at high LAI levels. Therefore, it is not an ideal way to retrieve chlorophyll content by these vegetation indices. Then, four new kinds of modified spectral indices based on TVI and MCARI are proposed, including Modified Triangular Vegetation Index 1 ( MTVI1 ) , Modified Triangular Vegetation Index 2( MTVI2) , Modified Chlorophyll Absorption Ratio Index 1 (MCARI1) and Modified Chlorophyll Absorption Ratio Index 2( MCARI2). The spectral response mechanism of four modified spectral indices was disclosed that they are both less sensitive to soil background and green LAI and more sensitive to the variation of chlorophyll content, and their performances of chlorophyll content retrieval were validated with the experimental data. The experiment demonstrated that two modified spectral indices, MTVI2 and MCARI2, are proved to be the better predictors for chlorophyll content, and the retrieval model of chlorophyll content of crop canopy can be established based on them.
NETL
NSTL
万方数据
维普
