干旱区生态环境知识资源中心

The present study provides the first detailed phytosociological description of the plant communities of Hulunbeier grassland, the easternmost part of the Eurasian steppe. Using phytosociological methods, vegetation data were collected from 109 plots in six areas spanning 300 km and covering a large proportion of the east-west axis of Hulunbeier steppe. Five main phytosociological plant communities were identified: meadow steppe of Veronico incanae-Stipetum baicalensis, ruderal vegetation of Cannabi-Sphallerocarpetum gracilis, steppe of Poo attenuatae-Stipetum grandis, heavily grazed steppe of Allium polyrhizum community, and Glycyrrhizo uralensis-Achnatherum splendens. The Poo attenuatae-Stipetum grandis was divided into two subunits: a Potentilla acaulis subassociation and a Caragana microphylla subassociation. The ordination of the communities showed a strong gradient from the drier western steppe to the wetter eastern steppe. Compared with 20 years ago, the zonal floristic composition had drastically changed from S. krylovii being dominant to the salt-tolerant A. polyrhizum and A. splendens becoming dominant. Species richness was lower in the communities nearby water sources suggesting intensive grazing and tramping than in the typical community of the steppe zone. Species richness was lower in the abandoned fields than in adjacent uncultivated sites. These results suggest that both grazing pressure and cultivation had changed the floristic composition and decreased the species richness in the area.