Effects Of Plant Functional Diversity And Phylogenetic Diversity On Community Assembly In Tropical Cloud Forests

Tropical cloud forest is one of the most intact forest types in the tropics.Compared with the low altitude tropical forest,it is rich in plant diversity and the environmental conditions are very special.The community assembly mechanism may be different from the low altitude tropical forest.In this paper,we aimed to investigated plant species composition and measured plant functional traits in Bawangling(BWL),Limushan(LMS)and Jianfengling(JFL)of the tropical cloud forest.In addition,we need to analyze the information of DNA fragments in three cloud forest sites.Finally,we will to construct the phylogenetic tree and species pool gradient,then to explore the effect of plant functional diversity and phylogenetic diversity on the community assembly.More importantly,we will also study the patterns of species pool size and spatial scale on community assembly mechanism in tropical cloud forest.The main results are as follows.1)The results of principal component analysis(PCA)showed that Canopy openness(CO),soil Total phosphorus(TP)and Slope(SP)are the important factors to predict the environment change of tropical cloud forest.And we observed low phylogenetic signals of functional traits expect wood phosphorus content,which suggested that phylogenetic dispersion can not provide a rough approximation of functional dispersion.The observed values of functional diversity(RaoQ)and phylogenetic diversity(MPD)were significantly lower than the expected values of the null model,which indicated that habitat filtering was the driving force for community assembly,soil Total phosphorus(TP)and Slope(SP)have prove to be the key environment filtering for the community structure of BWL and LMS tropical cloud forest,respectively.In the management of high altitude tropical forests,the role of filtering environmental factors should be emphasized.2)There are some differences in five functional traits among three forest sites at intraspecific and interspecific levels.The variation coefficient among-species is higher than that within-species.The variance partition results showed that intraspecific and interspecific variation have different effect on plant function traits.The variation of wood density mainly comes from interspecific level,while the contribution of intraspecific and interspecific variation of the other four leaf functional traits is similar.Comparing RaoQ and CWM observations with expected values based on the functional traits mean values and intraspecific variation coefficient,which shows that intraspecific variation has a significant impact on the community assembly in tropical cloud forest when considering intraspecific variation.In the management of high altitude tropical forests,we should be paid attention to the collocation of different individuals within species in order to improve the intraspecific variation.3)From the comparison of RaoQ observations and expected values,it can be seen that the spatial scale and species pool size have no significant influence on the community assembly mechanism in tropical cloud forest communities.The observed values are significantly lower than the expected values in the four species pool gradients and three spatial scale in the three forest sites.However,based on the comparison result of RaoQ standard effect values,the SES values of three forest sites with different spatial scales and species pool sizes are obviously different.We can detected more significantly habitat filtering effects in larger species pools and small scales,which demonstrated that environmental factors play a more significant role in small scale,and the community assembly mechanism can be more explored accurately based on larger species pools.These results reflect that the protection of high altitude tropical forests should pay attention to the role of environmental factors on small spatial scale and large species pool.