The Maintaining Mechanism Study Of Vascular Plants Diversity In Xiaoqinling Nature Reserve

We based on a field investigation of 56 plots(20m×20m)and the census of all Abies chensiensis(living trees and dead tree)in Xiaoqinling,through comparative analysis of distribution pattern and structure of the living trees and dead tree,analysis of the species diversity pattern along the altitudinal gradient,the patterns of species turnover along an elevation and spatial gradient,and discussed the living conditions of the Abies chensiensis and cause of death.The results of the study are as follows:1.(1)The results showed that the forest communities were classified into 5 types by MRT;(2)The results of DCA clearly reflected the distribution range of various community types and better reflect the relationship between species distribution and environmental factors.(3)GAM simulation results show that along environmental gradients,species diversity of different life forms quite different,woody have more clearer distribution pattern than herbs;Richness index,the tree layer showed a significant unimodal distribution pattern,the shrub layer showed a downward trend in mid-elevation and herbceous layer with increasing altitude show a downward trend;Shannon-Wiener index have the same trends with richness index;Pielou index of three layer distribution gentle and variation margin are not great with increasing altitude.2.Results showed that an increase in elevation and spatial distance between plots correlated with an increased compositional dissimilarity coefficient for all species and different habits.Differences in the spatial rate of species turnover were also observed.Spatial distance and elevation together explained 29% of total turnover,and pure spatial distance and pure elevation individually explained 13% and 5% of total turnover,respectively.Our results suggest that distance and elevation are important factors driving spatial turnover of species of vascular plants in alpine ecosystems,and that both dispersal-based and niche-based differences determine observed patterns.The spatial rate of tree species turnover was higher than that of shrubs or herbs,and likewise the effect of dispersal limitation was more significant for tree species' spatial turnover.3.The population dynamics trend of Abies chensiensis is to convert from growth to recession and the curve of mortality and disappear rate show clear rising trend in fluctuation;Abies chensiensis has great relevance with elevation,soil moisture,soil temperature and electrical conductivity;Along with the elevation rising,the mortality of Abies chensiensis has a downward trend.The result shows that the Abies chensiensis population natural propagation abilities is poor and if do not management and protection will eventually go extinct;Soil moisture content is one of the key factors of Abies chensiensis growth and death in Xiaoqnling;On a global scale,the growth and update of Abies chensiensis by inhibition of global warming.