Spatial Patterns And Competition Relationship Of Dominant Tree Species In Subtropical Forest Community,in Chishui

The spatial distribution pattern and competitive relationship of plant species is a typical problem in community ecology.It is helpful to further understand the potential ecological processes that produce specific spatial patterns and to reveal how the competitive relationships shape the spatial distribution patterns of communities in the process of community succession.Therefore,the every broad-leaved and valley rainforest communities,the bamboo forest community with different expansion stages in the Chishui region as the objects of this research.The fixed sample plot survey and individual tree spatial pattern analysis were used to study the spatial distribution pattern,inter-specific association,diameter at breast height(DBH)and forest vertical structure of dominant forest structures in zonal forest communities,and to explore the spatial expansion strategy of moso bamboo forest community in native forest.In order to provide theoretical basis for in-situ conservation and restoration of biodiversity.The main results as follows:(1)The community structure of dominant tree species of two zonal forest communities in subtropical forest are quite different.In subtropical evergreen broad-leaved forest,2299 individual trees with DBH>1cm were detected and recorded.The result shows that including 105 species with the average DBH and height are 4.79 cm and 7.80 m respectively.In hot and humid valley rainforests,1989 individual trees with DBH>1cm were detected and recorded,The result shows that including 79 species with the average DBH and height are 8.77 cm and 4.98 m respectively.A large number of secondary deciduous broad-leaved forest components appeared in the plot of evergreen broad-leaved forest.Some common species of subtropical evergreen broad-leaved forest,such as Castanopsis carlesii and Schima superba had retreated in dominance.Some deciduous tree species,such as Alniphyllum fortunei,occupied the majority of the individuals in the community at the footpath level,and there were no obvious dominant tree species in the community.The dominant tree species of Musa spp.is dominant in the community,and the important value accounts for 33.6% of the whole plot.(2)Among the two zonal forest communities in subtropical forests,the spatial distribution pattern of dominant tree species is dominated by aggregated at small scale.Its spatial distribution pattern is closely related to its natural regeneration and diffusion pattern.The inter-species association of dominant trees is dominated by no correlation and positive correlation between species,only 3 pairs of weak significant negative correlations were detected among 30 pairs of dominant tree species.This indicates that the evergreen broad-leaved forest and hot valley rainforest communities are in a relatively stable succession process.(3)Among the two zonal forest communities in subtropical forests,the spatial distribution of DBH size of dominant tree species is mainly characterized by the tendency to a random distribution with increasing diameter.However,the relationship between spatial distribution pattern and competition of DBH is different at small scales.In the community of evergreen broadleaved forest,the resource demand for non-uniform distribution of sunlight,water and other resources in Alniphyllum fortunei communities led to the distribution of young regeneration individuals mainly in the forest gap or forest window,forming aggregated distribution of young trees at small scales.The community structure and species in the hot and humid valley has obvious shrub and grass attributes,low height of trees,and the vertical structure is incomplete.The high growth capacity of musa spp.was limited,and the screening of environmental factors such as light factors causes the remaining large tree individuals to gather at a small scale in the gap or forest window.(4)Individual trees among different height classes were in different succession stages in the subtropical evergreen broad-leaved forest.Intra-and interspecies competition had the least influence on the upper height classes,but significantly influenced the intermediate and lower size classes,resulting in an aggregated distribution of lower and intermediate height individuals at small scales.This study helps explain competition strategies and coexistence between different height classes.Additionally,it verified the high sensitivity of the marked correlation function analysis in the competition detection of a plant community.The upper tree species showed random distributions at almost all scales.The middle and lower tree species aggregated on the small scales of 0-6 m,which showed positive associations with each other within a 1 m scale.No intra-class competition of individual trees within the upper height class was detected,nor was there a significant association with other classes.Intra-and interclass competition in the lower and intermediate height classes had some negative influence on the growth and spatial distribution of individuals.(5)Moso bamboo has been expanding in the low-altitude forest community in the Chishui river valley.In some areas,it has become the dominant tree species in the community and significant changes in the community structure and spatial pattern of the native forest.Small bamboo in clustered form colony patches that grow around the larger mature trees,resulting in patch expansion in the native forest community.Mark variogram functions identified significant positive spatial autocorrelation of moso bamboo caused by interactions with similar-sized trees within colony patches.Compared to the native forest species,the strategy of patch expansion and equal tree sizes in colony patches of moso bamboo could prevent regular distribution trend and size-asymmetric competition between nearby bamboo for the asymmetric and limited sources in the forest,enhancing the persistence of moso bamboo in the native forest in our study stand located in a south subtropical rainforest in a river valley.The above results indicate that both zonal forest communities in chishui area are in a relatively stable forest succession stage.Although the evergreen broad-leaved forest communities has been destroyed in history,the in situ conservation work created good conditions for its restoration and succession of polar communities.The subtropical rainforest community in the hot and humid valley in some areas of low altitude is affected by the expansion of moso bamboo seriously the spatial expansion strategy of moso bamboo ensures its competitive advantages.The results can further provide theoretical basis for the study on the coexistence and competition of subtropical forest species,and provide scientific reference for relevant decision makers to formulate sustainable economic development policies and carry out biodiversity conservation and restoration work.