Characteristics of plant community and its functional groups in desert grassland under effects of seasonal regulation of grazing intensity

Taking the Stipa breviflora desert grassland in Inner Mongolia as test object,a randomized block experiment was conducted to reveal the changes in the aboveground biomass of plant community,its diversity,the biomass of functional groups,importance value,and variation coefficient under the effects of the seasonal regulation of six grazing intensities.In the treatment of zero-grazing in spring,severe grazing in summer and moderate grazing in autumn,the aboveground biomass and Shannon diversity index were significantly higher than those of the other treatments.In the treatments of zero-grazing in spring,light grazing in summer and moderate grazing in autumn and of severe grazing in spring,severe grazing in summer and light grazing in autumn,the biomass of perennial grasses was significantly lower than that in other treatments and CK.The biomass of the annual and biennial forbs showed negative correlations with those of the perennial grasses,shrubs,semi-shrubs,and perennial forbs;while the biomass of perennial forbs was significantly positively correlated with those of perennial grasses,shrubs,and semishrubs.The importance value of the shrubs and semi-shrubs in the treatment of severe grazing in spring,severe grazing in summer and light grazing in autumn was significantly higher than that in other treatments and CK.The variation coefficient of the community biomass was the lowest(averagely 29%),that of the perennial forbs and perennial grasses was lower(averagely 49% and 56%,respectively),and the variation coefficient of the shrubs and semi-shrubs and of the annuals and biennials was higher(averagely 79% and 105%,respectively).It was suggested that the treatment of zero-grazing in spring,light grazing in summer and moderate grazing in autumn would be the more reasonable seasonal regulation mode of grazing intensity.