Effects of Exclosure on Typical Steppe Community Properties in Inner Mongolia

The effects of exclosure on plant diversity,community height,coverage,above and under ground biomass in Inner Mongolia typical steppe were investigated by quadrat method.The study was conducted in four treatments,viz.,continuous grazed plot(G),2-year old exclosure(E2),7-year old exclosure(E7) and 26-year old exclosure(E26) plots.The results showed that E26 had the highest richness index and diversity index in the four plots;while E7 had not present increase in diversity index compared with E2 and G(P0.05).Exclosure might maintain or conserve,rather than increase,plant diversity in contrast to grazing.The indicator plant of degradation such as Cleistogenes squarrosa and annual plants such as Salsola collina,Chenopodium aristatum from free grazing plot to exclosure plots showed decrease trend in relative weight and emergence frequency.The above ground biomass of E2 was significantly lower than that of E7;yet E26 had no increase tendency compared with E7.In conclusion,exclosure could significantly improve the grassland productivity in certain period,while there would be no help for grassland productivity if the exclosure lasts too long.