Study On The Plant Community Structure And Community Phylogenetic Assembly Of The Xiao Qin Island In The Miaodao Islands

The island habitat is an ideal place for the study of community structure and community assembly.In October 2016 and May 2017,a detailed vegetation investigation on the forest community of the Xiao Qin Island was carried out by using the survey method that the sample line combined with sample quadrat.Taking the tree layer,shrub layer and herb layer as the main research objects to analyze the species composition,species importance value,species diversity and community structure of plant communities concretely,based on 20 sample lines and 149 sample quadrats.And the build process of the community is inferred based on the method of phylogenetic structure.It can provide a reference for the community assembly of the Miaodao Is Iands and other island,and has a great value in both theory and application.(1)There are 100 species of plants recorded in the Xiao Qin Island,belonging to 38 families and 86 genera.Among them,there are 1 species of gymnosperm and 99 species of angiosperms.Pinus thunbergii is the only gymnosperm.There are 16 species of tree plants,26 species of shrub plants,49 species of herb plants and 9 vine plants.The species of shrub layer and herb layer are the most abundant.There are not the largest family and the larger family in the Xiao Qin Island,the medium familise are Leguminosae and Compositae.There are not the genus containing more than five species,the genus containing 4 species are Lespedeza and Artemisia.The species of the Xiao Qin Island are almost all single family and single species.(2)Dominant species of tree layer is more obvious.Pinus thunbergii is the constructive species,and occupy the dominant position in the community.Robinia pseudoacacia is the sub dominant species.And there are fewer companion species in the tree layer.The species of shrub layer and herb layer are abundant,with many companion species and occasional species.The dominant species of shrub layer are sun plants mainly,such as Flueggea suffruticosa,Grewia biloba and Caragana rosea,etc.The dominant species of herb layer are mainly Carex lanceolata,Artemisia sacrorum and Artemisia argyi,etc.(3)There was a positive correlation between Patrick richness index,Shannon-Winner diversity index,Simpson dominance index and Pielou evenness index of forest community in the Xiao Qin Island.The species diversity is the highest on the south slope of the Dashanding Mountain,followed by the Shachi Hill in the Xiao Qin Island.The species diversity is the lowest on the northwest and northeast slope of the Dashanding Mountain and the north and northwest slope of the Dongbeiding Mountain.(4)The index of Patrick richness,Shannon-Winner diversity and Simpson dominance of forest community in the Xiao Qin Island changes is in the order herb layer,shrub layer and tree layer from high to low,and the index of Pielou evenness is shrub layer,herb layer and tree layer from high to low.On the tree layer,the species diversity of the south slope is higher than that of the north slope,the west slope is higher than that of the east slope.On the shrub layer,the species diversity of the south slope is higher than that of the north slope,the east slope is higher than that of the west slope.On the herb layer,the species diversity of the southeast slope of the Dashanding Mountain is the highest.The species diversity of tree layer,shrub layer and herb layer of the Shachi Hill both is higher.(5)Through the Spearman rank correlation analysis,it is found that the factors affecting the species diversity of the Xiao Qin Island are mainly slope,organic matter,available potassium and available phosphorus.The species diversity of the tree layer has no obvious effect on the species diversity of the understory shrub layer,but it has a significant inhibitory effect on the species diversity of the understory herb layer.The species diversity of shrub layer had no obvious effect on the herb layer.(6)The similarity coefficient between the 20 sample lines of the Xiao Qin Island is bigger,the vegetation types of all kinds of sample lines are similar,and the difference of spatial distribution of vegetation types is small.The community of the tree layer of the Xiao Qin Island is divided into pure Pinus thunbergii forest and mixed Pinus thunbergii and Robinia pseudoacacia forest according to the dominant species.The mixed Pinus thunbergii and Robinia pseudoacacia forest is divided into four types of A,B,C and D.A type mixed forest has only Pinus thunbergii and Robinia pseudoacacia,and the dominant species is Pinus thunbergii;the constructive species of B type mixed forest is Pinus thunbergii;the constructive species of C type mixed forest is Robinia pseudoacaci;the constructive species of D type mixed forest is Pinus thunbergii and Robinia pseudoacacia.Based on the important value of shrub layer,the community of is divided into 7 types that are Flueggea suffruticosa association,Flueggea suffruticosa and Caragana rosea association,Flueggea suffruticosa and Lespedeza bicolor association,Flueggea suffruticosa and Grewia biloba ociation,Flueggea suffruticosa,Grewia biloba and Caragana rosea association,Flueggea suffruticosa,Grewia biloba and Celtis bungeana association,Flueggea suffruticosa,Grewia biloba and Rhamnus parvifolia association respectively by using the classification method of TWINSPAN.Based on the important value of herb layer,the community is divided into 6 types that are Artemisia sacrorum association,Carex lanceolata,Artemisia sacrorum and Roegneria kamoji association,Carex lanceolata,Artemisia sacrorum and Miscanthus sinensis association,Artemisia sacrorum and Miscanthus sinensis association,Artemisia sacrorum and Carex lanceolata association,Artemisia argyi,Carex lanceolata and Roegneria kamoji association respectively.(7)The plant species name are determined with the help of mature DNA bar code technology,and the species pedigree tree of the Xiao Qin Island is established with the help of Phylomatic online software and Figtree software.NRI and NTI are calculated with the help of the Picante and Ape software packages of R,and are used to analyze the phylogenetic structure of the plant species of the Xiao Qin Island.The species phylogenetic structure of 20 communities of the Xiao Qin Island is all divergent,indicating that the relationship between plant species on the Xiao Qin Island is far away from each other.That is,the effect of isolation of island habitat on the distribution of plant species in the Xiao Qin Island is not significant.In the 20 communities,45% of the communities that the phylogenetic structure of the species that have near relative is agminated,and 55% of the communities that the phylogenetic structure of the species that have near relative is divergent.