The Study Of Chinese Fir Stand Visual Simulation Basedon Crown Competition Index

In forest ecosystems, tree growth is influenced by genetic characteristics and environment. Crown, where photosynthesis takes place and energy exchange between trees and environment occurs, plays an important role in tree growth. In addition, neighborhood competition among trees also has great influence on tree growth. Tree size, number of trees and spatial distribution of adjacent trees were decisive factors for resource allocation in forest. It’s generally considered that there came tree competition when crowns or roots overlapped. Therefore, tree competition could be elucidated more accurately when number of competitive trees was counted on the basis of crown factor. Competition was widely used in stand growth simulation, besides competition of individual tree growth, competition of overall growth allocation should also be counted in simulation, in order to build growth prediction models for individual trees. Competition among plants was divided into symmetrical competition and asymmetrical competition, according to whether plant competitiveness was taken into account in resources allocation. Allocation in symmetrical way was simple and practicable, however, results of allocation could be inaccurate due to regardless of effect of individual plant competition, in consequence, prediction accuracy of growth model could be inaccurate. Therefore, plant competitiveness should be taken into consideration in stand overall growth allocation.In the research, Chinese fir(Cunninghamia Lanceolata) was used as research object. Plots were set in Huangfengqiao National Forest Farm, Hunan Province. Based on form of Hegyi competition index, crown factor which had great influence on tree growth was taken into consideration, then crown competition index was built. Relation between crown competition index and individual tree competitiveness was studied. According to individual tree competitiveness, overall growth of Chinese fir stand was allocated to individual trees. Thus, with known overall growth, the goal of individual tree growth quantitative modeling was accomplished. Stand growth simulation module based on crown competitive index was programmed to analog Chinese fir growth under different stand conditions. Distribution, growth condition and growth prediction of Chinese fir were visually displayed by visualization techniques, which could be used as a convenient platform to observe Chinese fir and provided effective reference for Chinese fir plantation management.The main research contents and conclusions were as follows:(1) Crown competition index was built, with an additional factor that represented overlap of competitive tree crown and objective tree crown. Correlation analysis was taken between actual tree growth and crown competition index, also between actual tree growth and Hegyi competition index. Results showed that crown competition index was on the same competition tendency as Hegyi competition index. In addition, crown competition index and tree growth had a more substantial correlation. Therefore, relationship between tree competition and tree growth in stand could be better indicated by crown competition index. Consequently, crown competition index could be used for stand growth prediction and simulation.(2) Based on crown competition index, stand overall growth allocation model was built. Correlation between crown competition index and tree growth was ascertained. Tree competitiveness was defined as the reciprocal of crown competition index, so that tree competitiveness and tree growth was positively correlated. According to tree competitiveness, stand overall growth in plot was allocated. T-test and residual analysis were taken between measured values and predicted values. Results showed that there’s no significant difference between predicted values and measured values. Therefore, tree growth could be better predicted by the growth allocation model based on competition index(3) According to theoretical methods and models above, stand growth simulation software module based on competition index was developed. Graphs and images were used to display survey data of trees as well as to illustrate tree distribution and tree growth in a multidimensional way, which provided a convenient and visual platform for scientific research, education and forest management.