Community Structure And Population Dynamics Of Old-growth Pinus Vunnanensis Forest In Mt.Wubao,Yunlong County,Yunnan Province

The Pinus yunnanensis forests are widely distributed in southwestern of China,but most of them are secondary forests or plantations.A large area of old-growth Pinus yunnanensis forest is preserved in the Yunlong Tianchi National Nature Reserve,Yunlong County,Dali Prefecture,western Yunnan Province.In order to understand the community structure and population dynamics of the old-growth forest,we established 24 plots on Mt.Wubao in this Nature Reserve.Then,we classified the forest communities according to the floristic similarity cluster analysis based on our vegetation data.The forest composition,community structure,population structure and growth pattern of each community type were analyzed.The main results are as follows:(1)Six distinctive forest communities were classified as follows:?the coniferous Pinus yunnanensis forest;? the coniferous Pinus yunnanensis and evergreen broad-leaved Lithocarpus variolosus mixed forest;?the coniferous Pinus yunnanensis and deciduous broad-leaved Quercus griffithii mixed forest;?the evergreen broad-leaved and coniferous mixed Castanopsis orthacantha-Pinus yunnanensis-Schima argentea forest;?the coniferous,evergreen and deciduous broad-leaved mixed Pinus yunnanensis-Schima argentea-Quercus griffithii forest;?the coniferous and sclerophylous evergreen broad-leaved mixed Pinus armandii-Quercus rehderiana-Pinus yunnanensis forest.Those six forests in the Tianch area presented as mosaic patterns.(2)Different vertical layered structure has showed among the six forest communities obviously.Pinus yunnanensis and the co-dominant species dominanted the canopy(?20m)and subcanopy(8-20 m)layers as a whole.In the shrub layer,the saplings of the canopy tree species and shrubs of Rhododendron,Eurya,Lyonia,and Viburnum appear.(3)The maximum age of P.yunnanensis was calculated to be 165 years with a maximun breast diameter of 116cm,and a maximum height of 37m.The relationship between DBH and age is:y=1.457x?11.266,where n=71,x is the DBH(cm)and y is age.The overall age-class of P.yunnanensis is characterized by a sporadic growth pattern(multimodal type),which corresponds to its DBH growth trend.It indicates that it depends on gap regeneration.The regeneration of the p.yunnanensis coniferous forest is the most active.(4)The growth rate of its wring width was high within the first 10 years,with a declining trend after the 10th year.P.yunnanensis trees exhibited a basal area increment(BAI)increase within the first 20 years.Then the level was maintained until the 30th year,declining as trees became older.Trees in the older age classes grew more quickly than younger trees at the same age.