Abstract: Alpine tundra are sensitive and vulnerable to global climate change. With open-top chambers (OTCs) in alpine tundra of the Changbai Mountains, we compared the responses of community compositions of tundra invaded by various degrees of Deyeuxia angustifolia to warming, aiming to understand the possible changes of plant community compositions under global warming. Our results showed that the average air temperature of the OTCs increased by 2.1 ℃ during the growing season, which can simulate the amplitude of temperature increase in the next century. Soils of different plant communities differed in their response to experimental warming. During the growing season, surface soil temperature of the mixed Rhododendron chrysanthum-Vaccinium uliginosum community, R. chrysanthum-D. angustifolia community and D. angustifolia-R. chrysanthum community increased by 2.13, 1.00 and 1.06 ℃, respectively. Those results indicated that soil temperature of the native plant community increased significantly and the changes of plant community compositions could effectively inhibit soil warming, resulting in reducing ecological response to warming. After 3-year continuous warming, the composition of the three plant communities changed. The importance values of D. angustifolia significantly increased in the R. chrysanthum-D. angustifolia community and D. angustifolia-R. chrysanthum community. In contrast, the importance value of R. chrysanthum decreased, especially in R. chrysanthum-D. angustifolia community and R. chrysanthum-V. uliginosum communitiy. Experimental warming inhibited native species, but promoted D. angustifolia encroachment. Warming had minimal effects on the colonization of D. angustifolia, whereas had important influence on its growth and expansion. Along with the invasion of D. angustifolia, vegetation changes were more notable in response to warming. The Simpson index, Shannon index and Pielou index under warming treatment were lower than under control treatment in the three plant communities. Similarly, species diversity decreased in plant communities, with the obvious decline in the D. angustifolia-R. chrysanthum community. Therefore, climate warming led to biodiversity decline of alpine tundra communities.

Key words: simulated warming, alpine tundra of the Changbai Mountains, plant community composition, biodiversity