Structure And Spatial Distribution Pattern Of Pinus Densata Populations In Milin,Southeastern Tibet

The structure of tree populations can characterize the status of forest regeneration,while the spatial pattern of tree populations reflects the interrelationship between individual trees in horizontal and vertical space,which is an important tool to study the characteristics of tree populations,ecological processes and their relationship with the environment.The typical coniferous forests in Milin,southeast Tibet,are less disturbed by human activities and are ideal objects for exploring the structure and spatial distribution patterns of tree populations.To this end,this paper investigated three sample plots(size: 5500-6400 m2)of Pinus densata coniferous pure forests in Milin,southeastern Tibet,in the altitude range of 2946-2977 m.Information on tree diameter at breast height,height,crown width,and stand spatial location were recorded.Based on environmental data for the sample plots,structural analysis of Pinus densata forests,population life table analysis,and spatial point pattern analysis of Pinus densata populations were conducted,and the following results were obtained:(1)The diameter structure distribution of the three Pinus densata sample plots all showed a growth pattern,with significant positive correlations among tree crown width,diameter at breast height,and tree height;the survival curves of the Pinus densata sample plots showed Deevey-I curves and Deevey-II curves.(2)Within the three Pinus densata sample plots,small and medium trees were clustered at the 0-8 m and 0-4 m scales,respectively,which may be due to seed dispersal and surface habitat heterogeneity,while large trees were randomly distributed at all scales,which may be due to adult trees competing for survival resources.(3)Within the three Pinus densata sample plots,there were significant positive correlations between small and large trees at the 1-4 m and 6-12 m scales,and positive correlations between small and medium trees at the 0-2 m scale,but no significant correlations between medium and large trees.Based on the density constraint analysis,small trees in ML1 and ML3 samples showed a certain degree of additional aggregation relative to large trees,while there was always no density constraint in ML2 sample plots.In summary,all Pinus densata populations in Milin,southeastern Tibet,have good regeneration ability;within the alpine pine sample sites,small and medium trees are clustered within small scales,while large trees show random distribution;small trees have significant positive correlation with medium and large trees within small scales,while no spatial correlation exists between medium and large trees.The spatial distribution patterns and intraspecific relationships of Pinus densata populations are the result of a combination of environmental conditions,surface habitat and self-thinning.This study provides a basis for understanding the population structure,spatial distribution characteristics and intraspecific relationships of Pinus densata forests in Southeast Tibet,and provides a reference for local forest conservation and management.