| The typical riparian primeval and secondary forest communities of Changbai Mountain were taken as research objects in this paper. The structure characteristics (constructive species replacement, diameter class structure, age class structure, volume and productivity), laws of succession and the distribution patterns and responses to the felling disturbance of woody plant diversity (species richness, α diversity and β diversity) were studied in the riparian primeval and secondary forest communities by systematically sampling along an altitudinal gradient and using research methods of sample transects and contrastive analysis methods of divided-stratum frequency and stem numbers, diversity indices (species richness, Shannon-Weiner diversity index, Pielou species evenness, Whittaker index, Cody index and community similarity coefficient). This paper revealled the change laws of the structure, dynamic and woody plant diversity of the riparian forest communities, evaluated the effects of felling disturbance by constrastive analyzing and supplied a theoretical basis for conserving and managing the biological resources in the riparian forest communities of Changbai Mountain. The research results as follows:(1) The structure characteristics of the riparian forest communities were that: ①The riparian forest communities were all composed of 11 to 13 tree species whichever distributed at different altitudes. But their positions changed in the communities. The coniferous tree species gradually took the place of the dominant position of broad-leaved tree species. Felling disturbance not only changed the positions of each tree species in the communities, but also further strengthened the trends of tree species replacement. ?The diameter class structures of the constructive species all took on reversed "J" shape in the riparian forest communities along an altitudinal gradient. With the increase of the diameter class, the gradual decrease of the numbers of stumpage. Felling disturbance had greater influences on the diameter class distribution patterns, distribution amplitude, proportion of stem numbers, continuity and discontinuity of distribution and the dynamic trends of the riparian forest communities along an altitudinal gradient. ?The relationship between the individual age and DBH of the constructive species took on markedly positive linear correlation trend, and the age class structures all took on reversed "J" shape in the riparian forest communities along an altitudinal gradient, too. Felling disturbance had greater influences on the age class distribution patterns, distribution amplitude, proportion of stem numbers, continuity and discontinuity of distribution, functions of the coniferous and the broad-leaved tree species in the age class structure evolving process, and the dynamic trends of the riparian forest communities along an altitudinal gradient. (4)The volume of the riparian primeval forestcommunities took on gradually increasing trend along an altitudinal gradient, yet the riparian secondary forest communities' took on single peak distribution pattern along the same altitudinal gradient, and felling disturbance had greater influences on the volume, productivity, composition structure of volume, constructive species volume and the dynamic trends of the riparian forest communities along an altitudinal gradient.(2) There were differences in the succession trends between the riparian primeval and secondary forest communities along an altitudinal gradient: ?The riparian primeval forest communities would be developing to the stage of Korea Spruce broad-leaved mixed forest at the low altitudinal region from 750m to 800m, however, they would be developing to the climax communities composed of Korea Spruce and Korean Pine upon the low-middle altitudinal regions from 800m to 950m. ?The riparian secondary forest communities would be developing to the stage of broad-leaved mixed forest dominated by broad-leaved species below the low-middle altitudinal regions from 750m to 850m, however, they would be developing to.the stage of needle broad-leaved mixed forest dominated by Olga Bay Larch and Korea Spruce needle-leaved species upon the high-middle altitudinal regions from 850m to 950m.(3) The characteristics of the woody plant diversity in the riparian forest communities were that: ?The distribution pattern of species diversity in the riparian primeval forests along an altitudinal gradient was that a diversity index (Shannon-Weiner) varied from 2.454 to 2.544, which distributed at the altitudinal regions of 750m~800m, 800m~~850m, 850m ~ 900m. But the altitudinal region of 900m ~ 950m (2.250) was the decreased distribution pattern. And felling disturbance not only changed the distribution pattern (fluctuation pattern), but also enlarged the variation amplitude (2.174~2.692) of the riparian forest communities along an altitudinal gradient. ?Along the same altitudinal gradient, Cody index of the riparian primeval forest communities varied from 1.5 to 3.5, and the community similarity coefficient varied from 0.851 to 0.939. Nevertheless, Cody index or community similarity coefficient of the riparian secondary forest communities changed from 0.5 to 6.0 or from 0.684 to 0.913. Therefore felling disturbance not only increased the rate of tree species replacement, but also reduced the community similarity of the riparian forest communities along an altitudinal gradient. Yet there was still higher continuity of the distribution of the riparian secondary forest communities along an altitudinal gradient.
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