Abstract: The regressive succession is certain to take place with long and super-strongly grazing onthe steppe vegetation.With plants population alternating,the biological productivity will decrease,and thesoil as well as the underlying surface will also vary correspondingly.The matter cycle and energy transterwill go down to the lower ecological efficiency level.In different landscape regions of Inner Mongoliasteppe,the processes and locus of the regressive succession is obviously different in different vegetationtypes.In eastern meadow steppe,whore the zonal community is the steppe of Stipa baicalensis,the commu-nity-type of regressive succession is Carex duriuscula community that there is strony resistance to grazing.In the middle typical steppe where the zonal community is the steppe of Leymus chinensis+Stipa grandis,the community-type of regressive succession is the Artemisia frigida community.In western desert steppewhere the dominant plant is Stipa klemenzii the community-type of regressive succession is Ajania achilloides+Cleistogenes sogolica community.The different patterns and series of the regressive successioncan be distinguished by use of the mathematical analysis to plants communities on the basis of the popula-tion alternation of dominant plants and the presence of indicator plant in degenerated communities.This pa-per is the fourth research problem on the correlation between grassland types and grazing pressure in theitem of IMGRASS.

Key words: Inner Mongolia steppe, Grazing pattern, Regressive succession, Succession pattern

摘要： 草原在长期超强度放牧压力下,发生逆行(退化)演替。由于群落中的植物种群更替,使生物生产力衰退,并伴随着土壤与下垫面的变化,导致草原生态系统的物质与能量流程下降到低一级生态效率的系统状态。在内蒙古草原的不同生态区域中,不同草原类型逆行演替的进程与途径差异明显。在东部草甸草原,以贝加尔外茅群系为地带性类型,演替变型是耐牧性很强的寸草苔群落。在中部广大地区的典型草原,以羊草＋大外茅群落为代表,在长期牧压下的演管变型是冷蒿群落。在西部地区的荒漠草原是小针茅群系占优势,退化演替变型是小亚菊＋隐子草群落。对不同逆行演替模式运用植物群落生态学的数量分析方法,按优势植物种群的更替和退化草原群落指标植物的存在度进行演替模式与演替序列的诊断。本文是IMGRASS项目第四课题中的草原生态系统对人类活动(放牧等)的响应研究。

关键词: 内蒙古草原, 放牧压力, 退化演替, 演替模式