The Research Of The Species Diversity And Niche Characteristics Of Davidia Involucrata Community On The Edge Of Sichuan Basin

Davidia ircvolucrata is a unique relic species to China originating from the the Tertiary ancient tropical flora,and is included in the national class I protected plant category.Its distribution area is mainly located in the marginal of the Sichuan Basin which is concentrated in Qionglai mountain,Emeishan,Erlangshan,Daliangshan,Xiaoliangshan and Wolong Nature Reserves.In this paper,through the typical sampilng method and using the flora,species diversity and niche theory to conduct survey and laboratory analysis of the D.involucrata community in order to understand the current status of D.involucrata community and provide theoretical basis for further strengthening the protection of D.involucrata community.The main conclusions as followed:(1)The dicotyledon in the angiosperms occupied the absolute advantage of 318 species belonging to186 genera and 82 families.The reason why Rosaceae and Liliaceae have a wide distribution range and appear most are that they have rich species and are well tolerated by the environment;flora of seed plants reflects two major properties of tropical and temperate nature.(2)The community structure is deciduous broad-leaved mixed forest which the dominant species are deciduous broadleaved trees like D.involucrata.The population of D.involucrata in the tree layer which is an important dominant species in the community are regenerated by the sprouting branches.The dominant species in the shrub layer is the Chimonobambusa szechuanensis.Elatostema stipulosum is used as the dominant species of herb layer.There is that the communities have certain similarities in their habitats.(3)Human disturbance is the main cause of changes on the species diversity index in all layers.At the same time,there were also differences in species diversity indices.The richness index of shrub layer was positively correlated with that of tree layer.The species richness index of herb layer showed a significant negative correlation with the Pielou evenness index of tree layer.(4)The populations with high important value at different layers in different communities occupied a dominant position in the community with a wide distribution range,high resource utilization and a large niche breadth;species with large niche breadths are prone extrmely to niche overlap,but it is determined not only by the niche breadth,but also by other factors,and there is no absolute correlation between niche overlap and interspecific competition.(5)There is a positive correlation between the niche breadth and the important value.Some levels of partial communities can reach significant levels.