Study On Species Composition And Community Classification Of Castanopsis Forest In Hubei Province

Evergreen broad-leaved forest is the zonal climax forest community in subtropical region,which contains rich species diversity,complex community structure and high productivity.However,due to the long history of human activities and the rapid economic development in the central and eastern regions of China,the zonal evergreen broad-leaved forest vegetation has been disturbed and destroyed seriously for a long time.Castanopsis(Fagaceae)is the main constructive species of evergreen broad-leaved forest in China,and also an important timber material.Hubei province locates in "China subtropical evergreen broad-leaved forest area-Eastern(humid)evergreen broad-leaved forest sub-area",and Castanopsis forest is one of the main types of evergreen broad-leaved forest in this area.It is of great significance for the protection and sustainable use of zonal forest vegetation to carry out a systematic study on the forest community in Hubei province.Therefore,in this study we investigated 29 plots of Castanopsis forests to analyze the species composition,floristic composition,community structure and species diversity patterns.The results are as follows.(1)376 species of plants belonging to 210 genera,88 families were recorded in Castanopsis forests in Hubei,including 12 species of ferns in 10 families and 11 genera,8 species of gymnosperms in 4 families and 7 genera,and 356 species of angiosperms in 74 families and 192 genera.In the tree layer,there were 121 species in 35 families,70 genera,while 273 species in 58 families and 135 genera in the shrub layer,45 species in 26 families and 41 genera in the herb layer and 30 species,25 genera,19 families of inter stratum plant were recorded,respectively.(2)For the floristic areal-type,the tropical types had much more families(40,67.80%)than those of temperate types(19,32.20%).However,the number of genus in the tropical types(97,51.87%)roughly equaled to those of temperate types(85,45.45%).The Pantropic type,which had 28 families,was dominant in tropical types,while the North Temperate type had the most families(15)in the temperate types.At the level of genus,genera from Pantropic type also was the largest component of tropical types.However,genera from the North temperate type(28),the E.Asia type(27)and the type of E.Asia & N.Amer.Disjuncted(23)constituted the temperate types together.(3)Longitude significantly affected the species diversity of Castanopsis forest,which showed decreasing trend towards east.The species number and Shannon index of tree layer increased significantly with increasing altitude,but the altitude patterns of shrub layer and herb layer were not significant.There were no distinct patterns of species number and diversity index along latitude gradient.By comparing the species diversity among different community types,no significant differences in the species richness at all levels of tree,shrub and herb layers,or in the biodiversity index at all levels of tree layer were found.(4)The community classification results suggested that there were five main community types: Castanopsis tibetana community,Castanopsis sclerophylla community,Castanopsis fargesii community,Castanopsis faberi community and Castanopsis eyrei community.CCA analysis showed that among the environmental factors,altitude,longitude,slope and soil total phosphorus had the greatest influence on species composition.The results of variance decomposition indicated that the topography and soil parameters had significant influences on the species composition of Castanopsis forest,with an interpretation rate of 68.94%.(5)In 29 plots,the tree layer contained 1,955 woody individulas with an average DBH of 14.43 cm.Among them,5～10cm(474 individuals,24.25%)and 10～15cm(404 individuals,20.66%)contained the largest number of individuals,and the sum of them was nearly half of the number of individuals in the tree layer(44.91%).The individual DBH distribution of trees in all the Castanopsis forests showed a single peak to the left.The species-abundance distribution is a typical inverted "J" curve with a few common species and many rare species.In summary,Castanopsis forests in Hubei province had high species diversity,complex community structure,and diverse floristic types.The topography and soil factors explained most of the variations of species composition in Castanopsis forests.This study provided theoretical basis and data support for the protection and management of evergreen broadleaved forest in Hubei province.