Novel evidence from Taxus fuana forests for niche-neutral process assembling community

Background:Understanding the mechanisms underlying community assembly is helpful for conservation and restoration of communities,particularly those that contain rare and endangered species like Taxus fuana,which are endemic to the Western Himalayas.The niche(limiting similarity)vs.neutral(randomness)assembly of the T.fuana forest community in Gyirong County,Tibet,China,was investigated.The net relatedness index(NRI)was calculated using a phylogenetic tree.The phylogenetic characteristics of the community and its relationships with environment were analyzed.Results:The value of the mean NRI at the community level was less than-1.96,indicating that the phylogenetic structure was overdispersed;whereas majority of the NRIs at the tree,shrub,and herb layers were within-1.96 to 1.96,indicating random dispersion.Environmental factors accounted for 44.38％,46.52％,24.04％,and 14.07％of the variation at the community level,tree,shrub,and herb layer,respectively.The phylogenetic structure at the community level and tree layer were significantly influenced by both topographic and soil factors,while shrub and herb layers tended to be affected by a single environmental factor.Conclusions:Community assembly of the T.fuana forest was simultaneously affected by niche and neutral pro-cesses,and their variations were closely related to the environment.Neutral process dominated community as-sembly in the shrub and herb layers.However,the interaction of limiting similarity and randomness played a dominant role at the community level and tree layer;and contributed to maintenance of biodiversity stability.The synergy of multiple environmental factors had a more obvious influence on community assembly than individual environmental factors,especially at the community level.These findings would help to understand the conser-vation of rare and endangered tree species,such as T.fuana,in the native community;and highlight the importance of random and non-random processes in assembly and biodiversity maintenance of alpine plant communities.