Community Structure Study Of The Midsubtropical Mountain Evergreen And Deciduous Broad-leaved Mixed Forest

In this paper,community structure of 9 different associations in Fujian Wuyishan National Park,Guizhou Fanjingshan National Narure Reserve,Fujian Emeifeng National Narure Reserve are studied.The species composition and community structure,species diversity,floristic composition and geographical elements,ecological niche and interspecific association are analyzed.The main results were as follows:1.In community composition,the mixed evergreen and deciduous broad-leaved forest in a subtropical mountain was mainly composed of deciduous trees and evergreen trees.The tree layers were mainly dominated by the species of Fagus,Cyclobalanopsis and Castanopsis.The shrub layer was mainly composed of Ericaceae,Theaceae and Symplocaceae,with abundant species.Mixed forest had obvious seasonal views and mainly consisted of mesophanerophyte with leathery leaves and papery leaves.2.In species diversity,the species diversity index of mixed forest communities was lower than that of subtropical evergreen broad-leaved forest.The indexs indicated that the diversity of tree layer was higher than that in the shrub and grass layers.The indexes of mixed forest in Wuyishan and Emeifeng were similar and higher than those in Fanjingshan.3.At the family level,the tropical elements took dominant position in communities.Emeifeng,Wuyishan,Fanjingshan accounted for 68.1 8%,56.25%,5 1.72%.The second was the temperate elements.At the generic level,the mixed forest of plots was similar.The temperate elements took dominant position,and they were adjacent to the tropical elements,which revealed transitional characteristics from tropical to temperate.4.On the community similarity,Jaccard index,Ochiai index and Sorensen index showed positive correlation in the mixed forest communities of three reserves at the level of genus and species.The communities of Emeifeng and Wuyishan showed extremely similar results.At the level of family,different sample plots had the higher level of community similarity and the species composition was similar.5.Among the dominant species of trees in mixed forests,Fagus lucida had the largest niche breadth(1.10),which showed the dominant position in communities.Cyclobalanopsis multiervis had the larger niche breadth(1.05),with a wide ecological range.On the whole,the niche overlap of dominant species in mixed forest of Fanjingshan was relatively low,and the preference of dominant species for resources was quite different.6.In interspecific association of dominant species,there was not significantly positive correlation between Wuyishan tree layers and Emeifeng tree layers.In Fanjingshan plots,tree layers were not significantly negative correlation.The independence of species pairs was relatively strong,and the connection between species pairs was loose.In the mixed evergreen and deciduous broad-leaved forests in the subtropical mountains,the species pairs were consistent with their niche overlap.