A Process-Based Simulation Model for Canopy Structure and Light Distribution in Wheat.

Quantitative simulation of structure and light distribution within crop canopy is important for prediction of photosynthesis and construction of virtual crops. Based on the earlier wheat (Triticum aestivum L.) morphology model established by the present research group, field experiments with wheat of different plant type cultivars and varied sowing densities were carried out, the time-course changes in canopy structure and light distribution were observed, a process-based model for simulating the growth dynamics of leaf curve was established, an improved simulation model of wheat canopy structure was constructed, and the vertical distribution of photosynthetic photon flux density (PPFD) was simulated. The results indicated that the leaf curvature was increased by raising  the sowing density and that leaf curve could be simulated with a quadratic functions and their varied forms. The maximal value of leaf curvature was considered as the cultivar parameter to reflect the genetic differences, and the plant number per unit area was used to quantify the effects of sowing density. Based on the simulated structure of wheat canopy, leaf angle distribution function (f(θ_L)), extinction coefficient (K(θ)) and leaf area index (F) of the canopy were directly calculated by dividing leaf inclination angle into tiny units and accumulating the corresponding leaf areas, so that the vertical distribution of PPFD could be simulated by using the Beer’s law. The data of the independent field experiment with different wheat cultivars were used to test the model developed here, and the average RRMSE between the estimated and observed values were 17.44% for layer LAI and 19.35% for PPFD, which indicated that the present model could effectively predict the growth dynamics of structure and the light distribution within wheat canopy. Our model could be applied to structure visualization or photosynthesis simulation or some other studies.