Process-Based Simulation Model for Growth Dynamics of Plant Type Index in Wheat

【Objective】This study was designed to explore the dynamic changing characteristics of wheat(Triticum aestivum L.) plant type index and the effects of planting density on plant type index.【Method】Based on the field experiments with three cultivars(Aikang 58 with erect leaf,Yangmai 12 and Yangmai 16 with flat leaf) and three planting densities in wheat,the time-course measurements were carried out on the indices of leaf type and stem type at main growing stages of wheat,and then the dynamic changing patterns of plant type indices and the effects of planting density on the dynamics of plant type indices in wheat were analyzed and simulated.【Result】The results indicated that the layer LAI of different plant-type cultivars had a trend of "middle layer upper layer lower layer",and the layer LAI was gradually concentrated in the middle or upper layer with the growing progress.In addition,the larger LAI of the middle or upper layer was observed on high population density.The significant differences of plant height component index(the ratio of the length of rachis and penultimate internodes to plant height,IL) between high and low population densities were observed.The plant height component index(the ratio of the length of n internode to the length of n internode adding(n-1) internode,In) of different plant-type cultivars were all decreased first and increased later from lower to higher leaf positions.In addition,the remarkable effect of planting density was observed on In of upper internode.As for Aikang 58,a relatively constant LOV with a slight "up-down-easing down" trend was observed.As for Yangmai 12,the change pattern of LOV was in "gentle-decrease-gentle" trend.As for Yangmai 16,a trend of "gentle-decrease-increased slightly" was showed.Based on the analysis of plant type index dynamics and the existing morphological model,the dynamics of layer LAI was simulated by using the methods of canopy cutting and leaf area integration,and the dynamics of the plant height component index and LOV were simulated by using combined morphological parameters.In addition,the comprehensive plant type component index was constructed by integrating different morphological indices,and reflected the dynamic changes of the leaf type and stem type synthetically.Testing of the dynamic models of layer LAI,plant height component index and LOV with independent dataset showed that the average RRMSE values of layer LAI and LOV were 17.44%,7.64%,and 10.66%,respectively.【Conclusion】The results indicated a good performance and reliability of models for predicting plant type index in wheat.The model can not only provide technical supports for the simulation of canopy structure in wheat,but also lay a foundation for the simulation of light distribution and photosynthesis within wheat canopy.