关键词: 三江源自然保护区, 森林-草甸交错带, 濒危植物, 定量评价, 濒危等级, 优先保护序列

Abstract: This paper studied the vegetation characteristics and smallscale spatial heterogeneity of Caragana mirophylla community in Horqin Sandy Land in northeast Inner Mongolia of China under grazing and under 6 and 12 years enclosure, aimed to assess the effects of grazing and enclosure on vegetation restora tion. In the sampling plots of grazing and different years enclosure, the species composition of  C. mirophylla community all dominated by annual herbaceous plants. The species richness in grazed plot and in the plots enclosed for 6 and 12 years was 22, 19, and 20, respectively, with no significant difference. In the plots enclosed for 6 and 12 years, the plant density was (124.46±5.22) plants·m^-2  and (203.05±10.38) plants·m^-2,  respectively, being significantly higher than that in grazed plot, which suggested that enclosure was an effective method to accelerate the vegetation restoration in Sandy Land. The Shannon-Wiener  index, Simpson species diversity, and Pielou evenness in enclosed plots were lower than those in grazed plot, and decreased with increasing enclosure duration.  The small scale spatial heterogeneity of vegetation in enclosed plots was smaller than that in grazed plot. The longer the enclosure duration, the smaller the spatial heterogeneity was.

Key words: Sanjiangyuan Nature Reserve, Forest-meadow ecotone, Rare and endangered plant species, Quantitative evaluating, Endangered grading, Conservation priorities sequence