Light interception efficiency analysis based on three-dimensional peach canopy models

Light interception capability is a critical factor affecting the growth, development, fruit yield and quality of fruit trees; thus, it is beneficial to cultivate optimal canopy types with high light interception efficiency. In this study, we present a quantitative method of analyzing light interception by tree canopies based on a virtual plant model. A detailed three-dimensional (3D) peach model with a natural growth shape was reconstructed and then the branches in the model were pruned to generate canopies with an open center form. These models were used to calculate the light interception and corresponding net photosynthesis. A solar radiation transfer model was used to determine the radiation intensity at the top of the canopy, and a ray tracing algorithm and turtle algorithm were utilized to simulate the spatial distribution of direct and diffuse radiation, respectively, in the tree canopy and obtain the photosynthetically active radiation (PAR) for each leaf. In the final step, we applied the photosynthesis model to calculate the canopy net photosynthetic rate. To compare the light interception efficiency among various plant canopy shapes, the net production rate at the whole-canopy scale and the average net photosynthetic rate per unit leaf area were calculated. The simulation results showed that peach canopies with an open center form provided better results compared with canopies with a natural form in terms of light penetration and air ventilation. Our method supports quantitative analysis of light interception and use efficiency for different types of canopy architectures at each time step and for individual leaf units. The approach was implemented in the interactive parametric individual 3D tree modeling software ParaTree. The extended ParaTree software is useful for fruit tree management applications because it provides an intuitive tool that can assist in tree pruning and design for ideal canopy architecture types.