Visual Simulation Research On Growth Polymorphism Of Chinese Fir Plantation Based On Different Comprehensive Grade Models Of Spatial Structure

Since tree morphological structure is strongly influenced by internal genetic and external environmental factors,accurate simulation of individual morphological structural changes in trees is important for the effective implementation of forest management planning,and is the premise of forest management and 3D simulation.However,the existing studies are one-sided and unitary in considering the relationship between trees internal and external environment and changes in tree morphological structure growth,and the research on the impact of growth environments and stand spatial structures on tree morphological structure and growth is still limited.Based on this,this study aims to construct a method that can accurately simulate the growth difference of forest morphological structure in different growth dominance degrees and spatial structure states within the stand,and combine with three-dimensional dynamic visualization technology to realize the visual simulation of growth polymorphism of Chinese fir stand.Based on the data of 6 plots collected by Huangfengqiao State-owned Forest Farm from 2012 to 2017,this study comprehensively analyzes the spatial structure and non-spatial structure of stands from the three dimensions of individual tree-spatial structure unit-stand.In this paper,relevant parameters representing the degree of tree growth dominance and the competitive of spatial structure were selected to quantitatively describe the tree growth status,and the Comprehensive Grade Model of Spatial Structure(CGMSS)was constructed by these parameters to comprehensively evaluate tree growth states in the stand and grade them from 0 to 10 correspondingly.At the same time,the morphological structural growth models of Chinese fir DBH,H,CW and UBH were developed based on CGMSS using nonlinear regression methods,and the visualization simulation of Chinese fir stand growth polymorphism was realized based on 3D model segmentation and dynamic organization methods and timeline animation techniques.The main results and conclusions are as follows:The CGMSS-based growth models of Chinese fir DBH,H,CW and UBH proposed in this study had an estimation accuracy of more than94% for the stand scale.When tree growth space is limited(CGSS>4),the competitive relationship between trees usually has a greater impact on the morphological structure growth of trees.Therefore,this study analyzed the prediction accuracy of the CGMSS-based growth models of Chinese fir at CGSS=5-10,the lowest was 71% and the highest reached 97%,and the prediction accuracy of all models except the UBH growth model were greater than 80% at CGSS=5-10.By analyzing the SSU-based growth model proposed by other scholars,the minimum value of tree prediction accuracy at CGSS=5-10 is lower than 55%,and the maximum is not more than 85%.Among them,DBH growth models at 5-10 levels,H growth models at 8-10 levels,UBH growth models at 5,7-10 levels,and CW growth models at 0,5-10 levels have prediction accuracy lower than75%.Comparing the prediction accuracy of the SSU-based UBH growth model in each grade,the results obtained are also lower than the CGMSS-based UBH growth model.The results of the visualization simulation in this paper show that the CGMSS-based Chinese fir morphological structure growth model is effective in visualizing the growth polymorphism of Chinese fir stands,and the simulation effect is closer to the real growth state of trees,which effectively achieves the accurate simulation of the differentiated growth of stands with different growth dominance and spatial structure states,and the effect is better than the SSU growth model.In addition,the Chinese fir stand growth polymorphism visualization system developed in this paper based on the UE4 3D engine runs well on a common computer platform,showing more realistically the simulation effects of the basic morphological structures of Chinese fir tree height,diameter at breast height,crown width and under-living branch height in different growth states,realizing the 3D visualization of Chinese fir plantation management,and providing a scientific basis for the verification and formulation of forest management.