关键词: 演替恢复阶段, 次生林, 群落结构, 地理成分, 中亚热带, 马尾松+柯+檵木针阔混交林, 柯+红淡比+青冈常绿阔叶林

Abstract: [Objective] The objectives of this study were to compare the composition,structure,floristic characteristics of two forest communities at adjacent successional stages in the central-subtropical China,in order to enrich information on forest dynamics in subtropical regions,and provide scientific basis for accelerating forest ecological restoration and biodiversity conservation.[Method] By adopting the space-for-time substitution method,and combining Phytocommunity Studies method,two different forest communities,comprising of 45-50 years old Pinus massoniana+Lithocarpus glaber+Loropetalum chinensis conifer-broadleaved mixed forest (PLL) and 80-90 years old L.glaber+Cleyera japonica+Cyclobalanopsis glauca evergreen broadleaved forest (LAG) were selected to represent middle succession stage and successional climax stage in the study region,respectively.Three permanent plots in size of 30 m×30 m were established along the slope in two types of forest communities.All woody plants with diameter at breast height (DBH) larger than 1 cm were mapped,tagged,and identified to species.Community diversity indices,eigenvalue and similarity coefficient were calculated.[Result] In both PLL and LAG communities,the tree species were abundant,a few species appeared to be in absolute dominant,and spatial distribution in the community were uniform.The species richness and species diversity index were obviously higher in LAG than those in PLL.The dicotyledonous plants increased substantially in LAG compared with PLL.The differences of community structure between PLL and LAG reflected in the species composition of trees,especially evergreen broad-leaved species.The canopy of PLL mainly consisted of trees of Pinaceae and Fagaceae,exhibiting the characteristics of conifer-broadleaved mixed forest.However the upper layers of LAG forest were more diverse and mainly composed of various evergreen broad-leaved trees,such as Fagaceae,Lauraceae,Anacardiaceae,Hamamelidaceae,and Alangiaceae,and exhibiting the characteristics of evergreen broad-leaved forest.The vertical stratification on the number of tree species and the number of individual trees was structured into two layers.The species of each layer were more diverse in LAG than in PLL,especially in the (1-5 m) layer and the canopy (higher than 15 m) layer.The DBH structure displayed an inverse"J "pattern,and the individuals were mainly concentrated in range from 1 to 8 cm of DBH in both PLL and LAG forests.The number of species and the number of individual trees of middle and large diameter classes were more in LAG than in PLL.In the PLL,P.massoniana was degrading due to the poor regeneration under forest,meanwhile,L.glaber and L.chinensis became dominating,reflecting succession direction from PLL to LAG.I the LAG degradation of P.massoniana was obvious,L.glaber and C.glauca became dominating,and C.lanceolata was relatively stable.The flora of the PLL and the LAG were mainly Pan tropical distribution of tropical elements,with clear transition from tropics to temperate.There were more tropical families,genera and species in the LAG than in the PLL.[Conclusion] There were significant differences in the species composition and community structure between the PLL and the LAG.The study indicated that vegetation restoration in subtropical region should follow the succession dynamics of the community.For the P.massoniana conifer-broad leaved mixed forest at the middle succession stage,we should close hillsides for reforestation to allow its natural succession or use artificial intervention such as replanting of evergreen broad-leaved tree species,in order to shorten the duration of restoration,establish reasonable tree species composition and improve stand quality.By using the LAG as a basis,it was necessary to strengthen the utilization of the Pan-tropical distributed plants,and select broad-leaved tree species with similar origins and successions as the dominant species in the improvement of secondary forest or" conversion conifer forest to broadleaved forest".

Key words: successional restoration stage, secondary forest, community structure, phytogeographical floristic composition, central-subtropical, Pinus massoniana + Lithocarpus glaber + Loropetalum chinensis conifer-broadleaved mixed forest, Lithocarpus glaber + Cleyera japonica + Cyclobalanopsis glauca evergreen broadleaved forest