Broadband, red-edge information from satellites improves early stress detection in a New Mexico conifer woodland
Three of broadband SVIs were evaluated on the aspect of stress detection. Chlorophyll a/b ratio was used as the indicator of the stress and then compared at plot level. To alleviate BRDF effects and seasonal variation of them, SVIs of each plot were detrended. NDRE based on the red edge position was the best VI as expected. Due to NDVI and GNDVI are based on plant structure, they capture leaf out after physiological changes. Interestingly, GNDVI follows chlorophyll better than NDVI, However, detects the stress more tardily. Though the author mentioned reflectance well tracks chlorophyll a and b, the fact that PROSAIL does not separate chlorophyll a and b could result in ill-posed problem in calculating a/b ratio.
Reference
Eitel, J. U., Vierling, L. A., Litvak, M. E., Long, D. S., Schulthess, U., Ager, A. A., ... & Stoscheck, L. (2011). Broadband, red-edge information from satellites improves early stress detection in a New Mexico conifer woodland. Remote Sensing of Environment, 115(12), 3640-3646.
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