Research On Elevational Patterns Of Species Diversity For Seed Plants In Tropical And Subtropical China

The distribution patterns of plant diversity on the mountains and the underlying mechanisms have been one of the important issues in ecology and biogeography.Plant communities are the most important primary producers in the terrestrial ecosystem.They provide material and energy for the other biological communities,which are the bases of maintaining the ecosystem productivity.The sharp declines in plant diversity will lead to a series of disastrous consequences,such as ecological environment deterioration,ecological resources loss,and ecosystem imbalance.Previous studies on the distribution patterns of plant diversity have mainly focused on the mechanisms of a single factor or ecological process,ignoring the joint mechanisms of multiple factors and ecological processes.Therefore,a universally accepted understanding of the drivers and mechanisms of plant diversity patterns remains elusive.The mountains in the tropical and subtropical China are one of the regions containing the most abundant plant species in the world.They are the key regions of global biodiversity conservation and also the ideal laboratories of studying plant diversity patterns.The Hainan Mountain,Xishuangbanna Mountain,Honghe Region Mountain,Jade Dragon Snow Mountain and Daba Mountain were selected as the typical study regions.We compiled the plant distribution data from monographs and established the seed plant database containing species name,life-forms and distribution elevations.We extracted environmental data from digital elevation model and WorldClim global database.We studied the elevational patterns of species diversity for all the seed plants and different life-form groups in the tropical and subtropical China.We explored the spatial and climatic influences on those patterns based on the regression and variance partitioning analyses.The results showed that:(1)With the increasing elevation,the species richness of plant groups showed the hump-shaped pattern,but the species density patterns of plant groups were more complex with regional differences.The species density showed an increasing pattern for the plant groups on the Hainan Mountain,while the species density showed the hump-shaped patterns along the elevational gradient on the Xishuangbanna Mountain,Honghe Region Mountain,Jade Dragon Snow Mountain and Daba Mountain.This was related to the area pattern along the elevational gradient.(2)Area explained 21.9-96.2%of the variation in plant species richness.The linear and logarithmic functions were the best species-area models for the plant groups on the Jade Dragon Snow Mountain and Hainan Mountain,respectively.The power functions were the best species-area models for the plant groups on the Xishuangbanna Mountain,Honghe Region Mountain,and Daba Mountain.The mid-domain effect explained 16.5-97.3%of the variation in plant species diversity and its explanatory power decreased with the decreasing species range size.(3)Climatic factors significantly affected the elevational patterns of plant diversity.Mean annual temperature,min temperature of the coldest month,annual precipitation and actual evapotranspiration explained 49.9-97.6%,49.4-97.2%,7.4-92.9%and 26.5-90.9%of the variation in plant species diversity,respectively.The ambient energy hypothesis and the water-energy dynamic hypothesis was supported,while the metabolic theory of ecology,freezing tolerance hypothesis and productivity hypothesis was not supported in this study.(4)Spatial and climatic factors have jointly explained 90.1-99.6%of the variation in plant diversity,while the explanatory power of climatic factors was significantly higher than the spatial factors.There was a strong collinearity between the spatial and climatic factors.Climate factors were the main mechanisms influencing the elevational pattern of plant diversity,and the spatial factors were the supplementary mechanisms.The present study has systematically clarified the mechanisms influencing the elevational patterns of species diversity for the seed plants in the tropical and subtropical China.This study has important guiding significances for the protection of mountain biodiversity and the maintenance of mountain ecosystem stability.