Research on canopy reflectance modeling of Phyllostachys pubescens forest based on the PROSAIL canopy radiative transfer model

Canopy spectral reflectance is directly related to inversion of Phyllostachys pubescens Mazel canopy parameters, which is of great significance in the indirect estimation of P. pubescens forest soil fertility. The effects of model parameters on leaf and canopy reflectance at the leaf and canopy scales were analyzed based on PROSPECT and PROSAIL models. PROSAIL canopy radiative transfer was used to establish the leaf area index (LAI) and a canopy reflectance lookup table for P. pubescens forest, with optimum canopy reflectance then determined by the cost function to achieve accurate simulation of P. pubescens forest canopy reflectance. Results showed that at the leaf scale, the sensitivity of the input parameters in the PROSPECT model decreased in the order of leaf structure parameters (N) > chlorophyll content (C_ab) > equivalent water thickness (EWT) > dry matter content (C_m) > carotenoid content (C_ar). At the canopy scale, the sensitivity of the input parameters in the PROSAIL model decreased in the order of LAI > C_ab > EWT > C_m > N > C_ar > ALA (average leaf angle). Leaf reflectance was greater than canopy reflectance. In the 400 to 900 wavelength range, canopy spectral reflectance of the PROSAIL model exhibited better fitting than the measured reflectance, with a relative error of 6.71%.