Community Structure,population Dynamics And Persistence Of Tertiary Relict Dipentodon Sinicus In Southwestern China

Dipentodon sinicus is one of the extant Tertiary relict plants in China.It is a small deciduous tree or shrub.The sizes of various Dipentodon sinicus populations are rather small at the present.It is a second-class protected plant in China.We established 22 and 11 representative plant communities containing this species in Caojian Forest Station of Yunlong County,Yunnan Province and Yushe National Forest Park of Shuicheng County,Guizhou Province to study the community structure,population dynamics and persistence of Dipentodon sinicus.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.Our results were as follows:(1)According to the similarity dendrogram based on vegetation data of 33 plots,6 community types were distinctive:Type 1,Carpinus kweichowensis-Liquidambar formosana-Lithocarpus glaber-Dipentodon sinicus communnity;Type 2,Illicium simonsii-Salix radinostachya-Schima khasiana-Dipentodon sinicus community;Type 3,Dipentodon sinicus community;Type 4,Dipentodon sinicus-Schima khasiana community;Type 5,Dipentodon sinicus-Tetracentron sinense community;Type 6,Pterocarya macroptera-teracentron sinense-Populus yunnanensis-Salix radinostachya community.(2)Among the 6 community types,Dipentodon sinicus community(Type 3)had the lowest values in species richness,Shannon-Wiener and Simpson diversity indices.The maximum age of Dipentodon sinicus was 54 years with 33cm DBH.Dipentodon sinicus reached 16 m in height.Dipentodon sinicus frequency distribution in DBH-class indicated sporadic types according to various community types.The age-class showed that the Dipentodon sinicus populations were in a sporadic type with several peaks in 15-18 years age-classes.(3)In the 6 community types,Dipentodon sinicus' regeneration was more active in Type 1(Carpinus kweichowensis-Liquidambar formosana-Lithocarpus glaber-Dipentodon sinicus community),Type 3(Dipentodon sinicus community)and Type 5(Dipentodon sinicus-Tetracentron sinense community)than that in the other community types(Types 2,4 and 6).This species' regeneration modes were seedlings and sprouts.(4)Dipentodon sinicus was mainly found in unstable habitats with better light conditions,such as landslide sites,steep slopes,along mountain stream sides and roadsides in both study areas of Caojian and Yushe.Its seedling establishment depends on gaps and open microsites.Dipentodon sinicus is a shade-intolerant pioneer species.It is clear that Dipentodon sinicus persistence was maintained by habitats where natural disturbances frequently occurred.