Temporal Changes And Influencing Factors Of The Plant Diversity In Typical Forest Ecosystems In China

Species diversity is the dependence of human life and the guarantee of survival,and is the core and cornerstone of ecosystem services.The spatial and temporal distribution of species diversity and its influencing factors are the core research issues of biogeography and ecology.However,the long-term trends in species diversity are not consistent locally and globally.Long-term monitoring data sets indicate that significant changes are taking place in the species composition of many communities,while the dynamic changes in forest species diversity and plant composition in China are not yet clear.All these related scientific problems need to be further studied.Here,based on long-term observation data from CERN's nine typical forest ecosystem field stations,we found that the changes of species richness and plant composition of typical forest ecosystem in China from 1999 to 2015.The main conclusions were as follows:(1)During 1999-2015,the number of large and medium-sized plants in the tropical rain forest in south China has been on the rise,with a net growth of 728 plants/ha and an average annual growth of 57 plants/ha.However,the composition change of forest plants from the presence of few large individual plants to a majority of small plants has only occurred in China's southern subtropical broadleaf forests and broadleaf and coniferous mixed forests.In China's northern deciduous broad-leaved forest and coniferous forest,the number of large and small individuals tends to decrease.(2)The main reason for the change of forest species composition in China's natural forests in the past 15 years is the occurrence of extreme events.The extreme snow and ice disaster in China's southern subtropical region,led to the deaths of more than 200 large plant individual of subtropical broad-leaved forest,followed by a large number of forest gaps,which promoted the growth of undergrowth,caused the forest plant restructuring-the equilibrium state dominated by from a few large individuals to a maj ority of small individuals.The total number of plant individuals was still in a stable state.However,the total number of plant individuals in the boreal temperate forest declined,which was mainly affected by high winds.While large individuals were blown down and broken,small individuals died due to lack of shelter for large individuals.This paper studies the temporal change of forest species diversity and analyzes the impact of climate change on forest plants,providing theoretical basis for implementing biodiversity protection and coping with climate change.(3)During 1999-2015,the species richness,shannon-wiener index,Pielou index and Simpson index of typical forest ecosystem in China all showed a stable trend,while the diversity index of subtropical coniferous forest showed a significant trend of increasing,and the increased species were mainly broad-leaved tree species,which was attributed to the succession of coniferous tree species to broad-leaved tree species.Through correlation analysis,it was found that only the species richness,shannon-wiener index,Pielou index and Simpson index of tropical monsoon rain forest were correlated with the extreme drought factors,which was mainly due to the large reduction of tropical monsoon rain forest plants and the death of about 600 plants/ha during the period of extreme climate.The correlation between the diversity index of other vegetation types and the extreme climate factors is low,mainly because the number of plant individuals as a whole does not change significantly.(4)In a typical forest ecosystem,the order of species diversity index of different functional types was analyzed.We found in tropical monsoon forest the order of species richness,Shannon Wiener index and Pielou index of different function type are arbor,small arbor,shrub,and the order of Simpson index is arbor,shrub,small trees.It indicated that the ecological dominance of dominant species in the tropical monsoon rainforest tree layer was relatively high,and the species diversity and uniformity of this layer were relatively rich.In the subtropical broad-leaved forest and coniferous and broad-leaved mixed forest,the species richness of the tree layer was the highest,the order of Shannon-wiener index and Simpson index are all the small tree,shrub,tree.However,the Pielou index of shrub layer was the highest,and the tree was the second.The species diversity of small tree layer in subtropical broad-leaved forest and coniferous and broad-leaved mixed forest was higher,while the uniformity of shrub layer was higher.The species richness and Pielou index were higher in the shrub layer of the subtropical coniferous forest,while the Shannon-wiener index and Simpson index were higher in the tree layer.It showed that the uniformity of shrub layer in subtropical coniferous forest is higher than other layers,while the dominance of tree layer is higher,and the species diversity is richer.The species richness,Shannon-wiener index,Pielou index and Simpson index of shrub layer were higher in the temperate broad-leaved forest and coniferous forest than in the tree layer.The species richness of shrub layer in temperate broad-leaved forest and coniferous forest was higher than other layers.