A preliminary study on the secondary broad-leaved forest in Nanjing Xianlin
Based on the field investigation,the secondary forest of Xianlin district was discussed by phyto-coenology method.The results show that 60 species,belonging to 49 genera,32 families were identified in this secondary forest,and the dominant family or genus is not significant,suggesting that the composition of the forest distributed unevenly.Among those 15 floristic elements,Pantropic and North Temperate accounted for 45.83%,21.28% at the familial level and 33.33%,19.51% at the generic level respectively;meanwhile,it indicates that the tropic element of community is not heavy,but it is characterized by the infiltration and transition between the tropical and temperate zones.The species distribution frequency show ABCD=E and ABCDE in tree layer and shrub layer respectively,which demonstrate the species distribution in shrub layer is even and on the contrary in tree layer.The community structure seems to be simple,which could be divided into 5 layers,in-cluding upper tree,under tree,shrub,liana and herb.Quercus serrata var.brevipetiolata,Broussonetia papyrifera,Vitex negundo var.cannabifolia and Pinus massoniana are the dominant populations in the tree layer,and their importance values are 16.10%,12.79%,9.31% and 9.20% respectively.Phyllostachys sp.,Q.serrata var.bre-vipetiolata,Rosa multiflora,Symplocos paniculata and B.papyrifera are the dominant populations in the shrub layer.From the view point of main population's size-class structure,Q.serrata var.brevipetiolata and B.papyrif-era are the growing populations,and Pinus massoniana and Platycarya strobilacea are the diminishing popula-tions.Finally,the authors hold that it should be of importance to strengthen the protection and utilization of these secondary forests which will play a significant role in the ecological construction of Xianlin district.