REMOTE-SENSING OF VEGETATION CANOPY PHOTOSYNTHETIC AND STOMATAL CONDUCTANCE EFFICIENCIES

The problem of remote sensing the canopy photosynthetic and stomatal conductance efficiencies is investigated with the aid of one- and three-dimensional radiative transfer methods coupled to a semiempirical mechanistic model of leaf photosynthesis and stomatal conductance. Desertlike vegetation is modeled as clumps of leaves randomly distributed on a bright dry soil with partial ground cover. Normalized difference vegetation index (NDVI), canopy photosynthetic (E(p)), and stomatal efficiencies (E(s)) are calculated for various geometrical, optical, and illumination conditions. A base case is defined to investigate the dynamics of E(p) and E(s) with respect to ground cover, clump leaf area index, soil reflectance, and atmospheric conditions. The contribution of various radiative fluxes to estimates of E(p) is evaluated and the magnitude of errors in bulk canopy formulation of problem parameters are quantifieid. The nature and sensitivity of the relationship between E(p) and E(s) to NDVI is investigated and an algorithm is proposed for use in operational remote sensing.