内蒙古草原植被在持续牧压下退化演替的模式与诊断

草原在长期超强度放牧压力下，发生逆行演替。由于群落中的植种群更替，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。

The Regressive Succession Pattern and Its Diagnostic of Inner Mongolia Steppe in Sustained and Superstrong Grazing

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 Ajaniaachilloides+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.