Abstract: Alpine Kobresia meadow have a key function in carbon sequestration，water retention and biodiversity conservation on the Qinghai Tibetan Plateau while degraded seriously.The response of plant community to degradation succession was not well understood.Based on the spacetime substitution method，the experiment of degradation gradients （excellent，good，fair，and poor）on alpine meadow was conducted and plant community as well as soil characteristics and water retention was surveyed from mid July to mid August in 2012.The results showed that the minimum of aboveground biomass，topsoil water content and surface rain infiltration and the peak value of topsoil （0-10cm） belowground biomass，topsoil organic matter，topsoil filed water content and mattic epipedon thickness all occurred in fair plots.The results of nonmetric multidimensional scaling (NMDS) on plant community diversity and function groups along degradation gradients showed that the four stages were obviously distinguished Canopy height，aboveground biomass，mattic epipedon thickness and rainfall infiltration rate accounted for the most variations of plant community.The response of plant community to degradation was non equilibrium and the inflexion of plant community variations might occur during the period from fair plots to poor plots.The nonequilibrium degradation processes would play an indicative function in selecting recovery techniques on degraded alpine meadow.

Key words: Alpine Kobresia meadow, Degradation succession, NMDS, Non equilibrium, Plant community