Study On Non-Spatial Structure Characteristics And Comprehensive Competition Index Of Natural Secondary Phoebe Bournei Forest

Phoebe bournei was the national secondary protective plant.in China.Based on typical sample investigation of its natural secondary forest,five probability density functions,including Weibull distribution,normal distribution,lognormal distribution,gamma distribution and beta distribution,were used to screen the optimal distribution function of the diameter at breast height(DBH),tree height and crown width of Phoebe bournei population and community,and to set up its parameter prediction models.Aiming at Phoebe bournei population and community,the eight neighbourhood translation method was used to determine the objective trees and the competitive trees were selected by the methods of four neighbourhoods,Voronoi map and crown overlap,respectively.Based on the Hegyi simple competition index,the comprehensive competition index of the factors such as DBH,tree height,crown width and tree spacing was reconstructed.A comparative analysis was made between the simple competitive index and comprehensive competitive index of different selection methods of the competitive trees.The results would provide a reference for protecting and managing the natural secondary forest.The main results and conclusions were as follows:(1)The DBH distributions of Phoebe bournei population and community were all conforming to the weibull distribution law,and the acceptance rates were 94% and 81%,respectively.The tree height distributions of Phoebe bournei population and community were all conforming to the Weibull distribution law,and the acceptance rates were 88% and 56%,respectively.The crown width distributions of Phoebe bournei population and community were all conforming to the lognormal distribution law,and the acceptance rates were 81% and 63%,respectively.(2)The passing rates of the Weibull distribution parameter prediction models of DBH and height distribution of the Phoebe bournei population were all 86%.The passing rates of the Weibull distribution parameter prediction models of DBH and height distribution of the Phoebe bournei community were all 100%.It showed that Weibull distribution function could better reflect the distribution characteristics of the DBH and tree height of the natural secondary Phoebe bournei forest.(3)The pearson correlation analysis of the simple competition index,comprehensive competition index with various factors(DBH,tree height and crown width)of Phoebe bournei population and community were all showed that there was a significant negative correlation between the simple competition index and comprehensive competition index with the DBH,tree height and crown width(P<0.01).The correlations between the comprehensive competition index with the DBH,tree height and crown width were all higher than that of Hegyi simple competition index.The correlations between the simple competition index and comprehensive competition index based on the Voronoi map were all higher than the simple competition index and comprehensive competition index constructed by the other two methods.(4)According to the fitting curves of the simple competition index and comprehensive competitive index of Phoebe bournei population and community with all factors(DBH,tree height and crown width)were concluded: the DBH,tree height and crown width were bigger,the simple competition index and comprehensive competition index were smaller.The simple competition index and comprehensive competition index had power function relation with DBH,tree height and crown width.The fitting degrees between the comprehensive competition index with DBH,tree height and crown width were all higher than that of Hegyi simple competition index.The fitting degrees between the simple competition index and comprehensive competition index with the diameter,tree height and crown based on the Voronoi map were all higher than the simple competition index and the comprehensive competition index constructed by the other two methods.