The sparse crown along both riversides of the Tarim River plays an important role in firming the sand and restraining the
desertification. It is very difficult to obtain the spectrum information from the remotely sensed data because of the low
percentage of coverage of the sparse vegetation, which affects the classification accuracy of the identification of ground
objects and the extraction of vegetation biophysics. It is a key obstruction in developing the quantification of the RS
technology. Taking the sparse vegetation at the Tarim River Basin as the research object, this paper predicts the surface
bidirectional reflectance of the discontinuous plant canopies in the extremely arid based on the observed ground
spectrum. Two different approaches are presented for the tree and the shrub. The first is to simulate the spectrum of the
tree with the Geometric Optical-Radiative Transfer model based on ground observation. In the second approach,the
spectral responses of sparse shrub and bare soil have been simulated using the linear Geometric Optical (GO) model.
Comparing the simulated bidirectional reflectance with actual remote sensing data (EO-1), the spectral differences of
these data are analyzed.