Community structure and species diversity of Pinus-Quercus forests in Jiufeng area of Beijing

Based on the date collected from 8 sample plots of Mt.Jiufeng,community structure and species diversity of Pinus-Quercus forests were studied in that area.The results showed that soil appears a little acidic and low-fertility.There are 36 families,56 genera and 58 spicies in the community.Arbor is the dominant species,with a maxmum density of 1 975 plant/hm~2.Phanerophytes are the largest in all species and therophytes are in the middle,which reflects the moisture condition is midding in community.The stratification of the vertical structure of this community is obvious,with three main layers-tree stratum,shrub layer and herbs layer.Quercus variabilis is absolutely dominant in the tree stratum,its importance value is the heighest and the superiority is obvious.The tree stratum's species diversity index is low,community's species richness and species diversity index are mostly influenced on shrub layer and herbs layer and the community is at prophase of recover.The community's species richness,species diversity index and equality index reflect accordant trend.Among the three layers,the Shannon-Wiener index,Simpson index,species encounter rate and Pielou index in the herbs layer are the heighest,and the tree stratum are the lowest.