چکیده (انگلیسی):

An explicit analytical model for calculating vegetation canopy reflectance, the multiple-layer canopy radiative transfer model (MRTM), has been developed in this paper. The model is based on radiative transfer theory by separating the roles of incident direct and diffuse radiation and radiation singly and multiply scattered by foliage. Specifically, the vertical heterogeneity of biophysical and biochemical parameters within the canopy was carefully treated in the model. This model was validated with field measurements from a deciduous forest canopy. The results proved that the model could reproduce the measured reflectance quite well. In addition, the performance of MRTM was found to be superior in comparison to other canopy models such as PROSAIL, ACRM and FRT. The significant effect of vertical heterogeneity on the canopy reflectance was clearly identified by different scenarios, which indicates that the influence of vertical variation in leaf area density and leaf chlorophyll, water, and dry matter contents cannot be neglected, especially when the total LAI is large. If such influences are ignored, significant biases in the estimated canopy reflectance can be expected. Since this multiple-layer model is a hybrid one that offers efficient calculation, it could serve as a primary model to develop more accurate reflectance models for inhomogeneous forests at plot and regional scales in future studies.