PIOSL-PRO: Construction of the PIOSL Model Considering the Distribution of Multiple Elements

The leaf radiative transfer model can accurately simulate the leaf radiative transfer process by exploring the optical response mechanism of biochemical parameters, reflectance, and transmittance of vegetation leaves. The PROSPECT considering the internal optical structure of leaves (PIOSL) model accurately calculates the radiation transfer process of light inside leaves in the wavelength range of 400–2500 nm by assuming that the leaves comprise two overlapping layers of flat plates with different biochemical parameters and structures. This article used the PIOSL model to distinguish the internal substances in more detail, added the stratification of carotenoids, anthocyanins, proteins, and carbonaceous compounds, and constructed the PIOSL-PRO model. Based on this model, the orientation hemispherical reflectance and transmittance of plant leaves in the LOPEX dataset were simulated, and a beluga optimization algorithm was used to determine the parameters of each layer of leaves and the distribution ratio of absorbed substances. The parameter settings show that the structural parameters of different types of blades are relatively high in the first layer, and the element content tended to be stratified. The PIOSL-PRO model performed better than the PROSPECT-PRO model in simulating reflectance; the mean root-mean-square error (RMSE) of a single monocotyledon sample and a single dicotyledon sample were 1.4 and 0.8 lower than those of the PROSPECT-PRO model, respectively. The PIOSL-PRO model provides a more detailed division of the material inside the leaves, providing a more accurate explanation of the optical response principle of vegetative leaves.