Effect of Fencing on Plant Biomass and Functional Group Structure of Different Types of Degraded Grassland in Qinghai-Tibet Plateau

Based on three types of degraded grassland:alpine meadow,alpine steppe and temperate desertsteppe in Qinghai-Tibet plateau,we analyzed the effect of fencing and grazing on different types of degraded grassland communities.The research results indicate that:(1)The abovegound biomass of three types of grassland increased by 48.1%,10.8%and 34.5%,respectively after five years of fencing.The responsing of underground biomass of three types of grassland were consistent with the aboveground biomass.(2)The propotion of upper-layer(0-10cm)root biomass of alpine steppe and the root-shoot ratio of alpine meadow indicating a‘clear decling trend'while compared with the grazing land.(3)The gramineous plants,which occurred in a higher propotion in the total biomass in feacing grassland than it of grazing on alpine steppe and alpine meadow.Nevertheless,the proportion of troublesome weed in alpine steppe declined significantly and had no significant effects in temperate desert-steppe.