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

Abstract

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.

Virtual Geographic Simulation of Light Distribution within Three-Dimensional Plant Canopy Models

“…The former is used for computing the uncollided propagation of direct solar radiation, and the latter is used for computing the diffuse sky radiation into the canopy. The detail implementation can be found in [36]. Based on the ray tracing algorithm, a discrete number of rays were used to simulate the paths of a nearly continuous distribution of photons.…”

“…Therefore, validations regarding the 3D canopy radiation transfer simulation results are poor or almost non-existent. The PAR captured by the whole canopy based on radiosity was compared to the results estimated using the ray tracing and TURTLE algorithms [35,36]. Figure 9 shows the difference between the simulation results obtained using the two methods.…”

“…Detailed 3D architectural models provide the foundation for canopy radiation transfer and distribution simulation, and the precision of the 3D model has a direct impact on the accuracy of the radiation simulation [36]. As leaves are the major organs that affect light distribution and absorption, they are described explicitly.…”

“…The direct solar light source was described as a reference projection plane located above the canopy that was normalized to the direction of the light [36], and it was discretized into triangles. The normalization of the plane is defined according to the zenith and azimuth angles of the sun, and the reference projection plane is perpendicular to the incident light and must be large enough for rays originating from the plane to illuminate the entire canopy.…”

“…The nested radiosity model [21] was developed to simulate the distribution of light within a canopy at the organ level, and was incorporated into the OpenAlea platform [33] to analyze the light interception of herbaceous canopies [10]. Because light scattering within a canopy accounts for less than 10% of the incident photosynthetically active radiation (PAR) [34], several researchers have directly computed the uncollided propagation of direct solar radiation and diffuse sky radiation into the canopy using ray tracing [35,36], the projection Z-buffer algorithm [37], and a virtual camera based on OpenGL [38]. These simplified methods are useful for connecting to a leaf photosynthetic mode to estimate the canopy photosynthesis rates.…”