The Influence Of Large Trees On Spatial Distribution Of Adjacent Trees In Broadleaved Korean Pine Forests In Xiaoxing'an Mountains

The spatial pattern of forests depends on their internal characteristics,interspecific relationships,external environmental characteristics,and interactions with different individuals of the same species plant.At the same time,it also determines the spatial situation of growth competition among trees and provides habitats of animals,plants,and microorganisms.The spatial distribution of individuals in forest stands is closely related to the ecological process of their formation.The study of the spatial distribution pattern is helpful to further understand the ecological process of its formation,therefore forest spatial structure has always been an important topic of ecology research.In this study,we used the data of two 10.4 hm2 and five 1.0 hm2 original broadleaved Korean pine forests sample plots in Xiaoxing'an Mountains in Heilongjiang province,China.According to the data for the sample plots and referring to relevant methods for tree diameter classification,the trees in the sample plots were divided into five size classes as follows:size class 1(1 cm?DBH<5 cm);size class 2(5 cm?DBH<10 cm);size class 3(10 cm?DBH<30 cm);size class 4(30 cm?DBH<50 cm);and size class 5(DBH?50 cm),and the size class 5 trees are regarded as large-diameter individuals.This paper conducted the following three aspects of the research:(1)The number of tree species and shrub species in seven sample plots in Xiao Xing'an Mountains was counted,and the diameter class of all trees in the sample plot was divided.The species composition of different diameter class trees in the sample plot was compared,and the differences among different plots were analyzed.(2)We borrowed the calculation idea of O-ring statistic in this study,but made the individual plant as the object of exploration,calculated the density of adjacent trees in the ring of different distances of each object tree,and obtained the areas that are common to all the object trees or most object trees are easily clustered by adjacent trees.And the comparative analysis was carried out among the sample plots.(3)The degree of mingling of large-diameter individuals with adjacent trees of different distances and diameters was calculated by the method of mingling degree calculation.The influence of large-diameter individuals on the spatial pattern of adjacent trees was explored,and the reasons for the influence and how large-diameter individuals played their roles in it were analyzed.The results are as follows.There is a ring structure of small trees surrounding a large tree.And the ring structure changes with the difference of sample plot and the change of the adjacent trees diameter class.In the two northern sample plots,diameter class 2 of adjacent trees(5.0?DBH<10.0 cm)and diameter class 3 of adjacent trees(10.0?DBH<30.0 cm)all formed ring structures with radii of 4?7 m from the large-diameter trees,analogously,in the two central sample plots,diameter class 2 and class 3 of adjacent trees formed ring structures with radii of 5?9 m and 5?8 m,respectively,and in the three southern sample plots,diameter class 2 and class 3 of adjacent trees formed ring structures with radii of 7?11m and 6?10 m,respectively.But the diameter class 1 of adjacent trees and diameter class 4 of adjacent trees didn't form ring structures.There is an internal relationship between the ring structure formed and the gap dynamics theory by the analysis.The ring structure is a form of forest dynamic change,which will appear or disappear with the growth of trees.In addition,the phenomenon that the ring structure shifted back with the decrease of latitude may be related to temperature or other conditions,which needs further exploration.Due to the requirement of large number of large-diameter individuals when exploring the degree of mingling between large-diameter individuals and adjacent trees,5 small samples of 1 hm2 could not meet the requirement,so only two large samples of 10.4 hm2 were used in the study of this problem.The results showed that in the two plots,the mingling degree between the large-diameter individuals and the adjacent trees was the lowest at 5?6 m and 6?7 m.As adjacent tree diameter increased,the mingling degree between it and the large-diameter individuals declined.This revealed that around the large-diameter individuals there was a ring of small trees congeneric with the large-diameter individuals.In addition,the mingling degree of small and medium diameter trees(size class 1,2,3 adjacent tree)with large-diameter individuals maintained high mingling degree,while the mingling degree of size class 4,size class 5 with large-diameter individuals decreased significantly,with size class 5 adjacent tree being the lowest.The formation of this ring structure is closely related to density dependence.By analyzing the distribution pattern and its causes of adjacent trees around large-diameter individuals in broad-leaved Korean pine forests in Liangshui and Shengshan,the important role of large-diameter individuals in controlling the surrounding stand structure,maintaining species diversity and promoting forest succession was demonstrated,which provided data support for the management and management of broad-leaved Korean pine forests.