Response Of Vegetation And Soil Properties,Carbon And Nitrogen Pools To Different Grazing Patterns In Alpine Meadow In Qilian Mountains

Qilian Mountains,the important component of the ecological barrier of western China,play an irreplaceable role in maintaining sustainable development and preventing desertification in Hexi Corridor.Alpine meadow,the main vegetation type in Qilian Mountains,is the important production base of animal husbandry.Alpine meadow also plays important ecological roles in maintaining the carbon storage,soil and water conservation and maintenance of biodiversity.However,the adverse natural conditions and human activities result in alpine meadow degradation in recent years.Grass-land degradation not only affects economic sustainability and development but also threatens social stability and ecological security.Grazing is the most important use of grassland worldwide.Scien-tific grazing patterns can not only effectively improve grassland productivity,maintain high biodi-versity,but also promote the grassland ecological services.However,the overgrazing in Qilian Mountains is serious,and this kind of unscientific grazing seriously restricts the sustainable devel-opment of local animal husbandry.So,it is necessary to explore a scientific and reasonable grazing regime for sustainable development of grassland and the restoration of degraded grassland ecosystem.Grazing management strategy has significant effects on grassland vegetation characters,soil charac-ters,grassland ecosystem carbon and nitrogen pools,but the effects of different grazing patterns on grassland plant community composition and structure,soil characters,grassland ecosystem carbon and nitrogen storage remain unclear.Therefore,we evaluated the height,density,coverage,above-and below-ground biomass,litter biomass and biodiversity,soil physical properties,soil chemical properties,soil biological property,organic carbon and total nitrogen storage in plant,litter,root and soil in alpine meadow under different grazing patterns(continuous grazing,CG;heavy grazing in cold season,HG;lightly grazing in cold season,LG;rotational grazing,RG;Non-grazing,NG)in Qilian Mountains.The main research results are as follows:(1)The HG,LG,RG and NG sites all significantly increased the vegetation coverage,density,above-and below-ground biomass,Shannon-wiener diversity index,Pielou evenness index,richness index and Simpson index,when compared to the CG site.And the highest values were found in the RG site.NG site significantly increased the density of gramineae plants,while significantly de-creased the density of cyperaceae,leguminosae,forbs,total density,the total species and biodiversity.There was 20 species plant lost from the community in NG site,when compared to RG site.Five years of grazing exclusion in the alpine meadow leads to lower plant biodiversity and density and results in the vegetation being dominated by a few species with strong colonization abilities.Consid-ering the productivity and biodiversity,use and update of grassland resources,the rotational grazing could be the best grazing strategy for the alpine meadow in the Qilian Mountains.(2)Different grazing patterns only had significant effect on soil characteristics in 0-10,10-20and 20-30 cm soil layers.The HG,LG,RG and NG sites all significantly increased the soil moisture,soil organic carbon,total nitrogen,total phosphorus,soil avaible nutrient,soil microbial biomass carbon,soil microbial biomass nitrogen and soil enzyme activity in the 0-10,10-20 and 20-30 cm soil layer when compared to the CG site.And the highest values were found in the RG and NG site.The HG,LG,RG and NG sites all significantly decreased the soil bulk density and soil compaction in the 0-10,10-20 and 20-30 cm soil layer when compared to the CG site.And the lowest values were found in the NG site.Different grazing patterns had no significant effect on soil potassium.Furthermore,the structural equation model analysis showed that soil physical properties were the most important determining factors determine the vegetation characters.Considering the soil nutrient,use and update of grassland resources,the rotational grazing could be the best grazing strategy for the alpine meadow in the Qilian Mountains.(3)The HG,LG,RG and NG sites all significantly increased the organic carbon and total nitro-gen storage in plant,litter,root and soil,when compared to the CG site.The highest values of eco-system organic carbon and nitrogen storage were found in the RG site,and the lowest were found in the CG site.The results indicated that the RG was the most beneficial strategy to accumulation of organic carbon and nitrogen storage in alpine meadow ecosystem.The organic carbon and nitrogen storage in RG site increased by 8748 and 785 g/m~2,respectively,compared to the CG site.Therefore,the change of grazing pattern can effectively promote the organic carbon and nitrogen storage in al-pine meadow ecosystem.Considering the carbon and nitrogen pools,use and update of grassland re-sources,the rotational grazing could be the best grazing strategy for the alpine meadow in the Qilian Mountains.Although grazing exclusion and rotational grazing all could effectively improved the grassland productivity,soil nutrients and the organic carbon and nitrogen pools in alpine meadow,the enclo-sure leads to lower plant biodiversity and density and results in the vegetation being dominated by a few species with strong colonization abilities.Furthermore,considering the use of alpine meadow and the economic development of the pastoral area,the rotational grazing is the optimum grazing pattern in Qilian Mountains.