Global remote sensing of water–chlorophyll ratio in terrestrial plant leaves

I evaluated the use of global remote sensing techniques for estimating plant leaf chlorophyll a  +  b ( C ab ; μg cm −2 ) and water ( C w ; mg cm −2 ) concentrations as well as the ratio of C w / C ab with the PROSAIL model under possible distributions for leaf and soil spectra, leaf area index ( LAI ), canopy geometric structure, and leaf size. First, I estimated LAI from the normalized difference vegetation index. I found that, at LAI values <2, C ab , C w , and C w / C ab could not be reliably estimated. At LAI values >2, C ab and C w could be estimated for only restricted ranges of the canopy structure; however, the ratio of C w / C ab could be reliably estimated for a variety of possible canopy structures with coefficients of determination ( R 2 ) ranging from 0.56 to 0.90. The remote estimation of the C w / C ab ratio from satellites offers information on plant condition at a global scale.