Abstract: By setting up sample transects and using α and β diversity indices,this paper studied the woody plant diversity and its responses to cutting in the stream riparian primeval and secondary forests along an altitudinal gradient in Changbai Mountains. The results showed that all of the primeval forest communities distributed at different altitudes were composed of 11-13 tree species, but the importance of these tree species varied with altitude. Conifer species gradually took the place of broad-leaved tree species along the altitudinal gradient. Cutting not only made the tree species richness and importance changed, but also further strengthened the trend of tree species replacement. The Shannon-Wiener diversity index of the woody plants in primeval forests varied from 2.454 to 2.544 at the altitudes of 750-800 m, 800-850 m and 850-900 m, which was higher than that (2.250) at the altitude of 900-950 m . Cutting changed this distribution pattern, and enlarged the fluctuation (2.174-2.692) among the communities at different altitudes. The Cody index of primeval forest communities along the altitudinal gradient varied from 1.5 to 3.5, and the community similarity coefficient varied from 0.85 to 0.94. As for the secondary forest communities, their Cody index and community similarity coefficient changed from 0.5 to 6.0 and from 0.68 to 0.91, respectively, indicating that cutting increased the tree species replacement rate, and reduced the community similarity. However, a higher continuity still existed in the secondary forest communities.

Key words: Crop residue, Soil respiration, Soil microbial biomass