Canopy Reflectance, Photosynthesis, and Transpiration. III. A Reanalysis Using Improved Leaf Models and a New Canopy Integration Scheme

1 h e theoretwal analyses of Sellers (1985, 1987), which hnked canopy spectral reflectance properties to (unstressed) photosynthetw rates and conductances, are cmtwally remewed and significant shortcomings are ~dent~fied These are addressed m thin article principally through the incorporation of a more sophmtwated and reahstw treatment of leaf phystological processes within a new canopy integration scheme It m assumed, based on ecophysiological observations and arguments, that leaf physiologwal properttes vary throughout the plant canopy m response to the radmtion-we~ghted timemean profile of photosynthetwally actwe radmtion (PAR) These modificatzons yield a s~mpler and more robust theoretical relationship between canopy b~ophysical rates (photosynthesm, conductance) and spectral vegetation radices (SVI) The results indicate that area-averaged SVI, as obtained from coarse resolution satelhte sensors, may gwe good estimates of the area-integrals of photosynthesm and conductance even for spatially heterogenous (though phys~ologwally umform) vegetation c o v e r s