Effect Of Grazing And Mowing On Soil Respiration And Soil Microbialin Communities In Leymus Chinensis Steppe Of Inner Mongolia

Soil respiration is an important part of the global carbon cycle,which directly regulates the atmospheric CO₂concentration and influencesclimate.China has a large area of grassland,and the carbon storage in China's grassland plays a key role in global carbon cycle.We studied the variation in soil respiration and its compoments(i.e.,plant root and soil microbial respiration)as well as soil microbial acvitivies in a typical steppe grassland dominated by Leymus chinensis under three experiment land use types,i.e.,grazing,mowing and enclosing(no grazing nor mowing).We aimed to understand the effects of three dominant land use types in the grassland region on the components of soil respiration and associated soil microbial mechanisms,as well as the cascading effects at ecosystem level.Our results showed that1.Soil respiration was lower under grazing than under mowing and enclosing;the CO₂ emission flux was the highest under mowing(11301.9 Kg·C·hm^-2·a^-1),lowest under grazing(7526.247 Kg·C·hm^-2·a^-1),and in between under enclosing(10055.3Kg·C·hm^-2·a^-1).2.Plant root respiration account for 38-42%,and soil microbial respiration account for 57-61%,in total soil respiration.3.The temperature sensitivity of total soil respiration was relatively high under enclosing,the temperature sensitivity of soil microbial respiration was realtively high under grazing,and the temperature sensitivity of plant root respiration was realtively high under mowing.4.Soil respiration rate could be explained by a set factors,and the strength of the effects of these factors were in an order of soil,climate,microbial and vegetation factors.Soil bulk density,pH and moisture had significant effects on soil respiration(P<0.05)?5.Soil microbial communities diverged under long-term(15 years)grazing,mowing and enclosing;the bacterial and fungal genera richness was the highest under enclosing.Grazing significantly reduced the biomass and diversity of fungal community.6.The belowground biomass carbon was the major source of soil carbon.Soil organic carbon density showed no difference across land use types.Grazing grassland reduced CO₂ emission,compared with the grassland mowing and enclosing grassland,thus reduction of stocking rate had the positive effects for grassland biodiversity and production,but also for carbon.Our results deepened the understanding of the soil respiration processes and its regulating factors,and is useful in the development of sustainable grassland management regimes adaptive to climate changes.