Effect Of Seasonal Grazing On Distribution Of C/N Ratio Of Plants,Soil And Microorganisms In Typical Grassland

Grazing is one of the main disturbance factors of grassland ecosystem,the long-term grazing change the carbon(C)?nitrogen(N)content and C/N of grassland vegetation,soil,soil microorganism,and degrade grassland.The experiment carried out in the semi-arid steppe of Xilinhaote,Inner Mongolia in 2015.It is expected that the effects of different grazing time on the change of C and N in plant-soil-soil microorganism can be studied by controlling stubble height that keep plant growth point according to the seasonal characteristics of plant growth.The results show that:Seasonal grazing can reduce the aboveground plant C and N storage in different degrees.It is aboveground plants store more C and more N,and reduces the impact on root system with the delay of the initial grazing time.June and August grazing has positive on the storage of soil organic matter in the middle and later stages of plant growth,the soil organic matter of July and September grazing gradually shift from the deep layer to the surface with the seasonal change.Seasonal grazing accelerate the fixation of N,which occur in different soil layers in different treatments:10-20 cm in 5-9 month grazing treatment,0-30 cm in June and August grazing and July and September grazing treatments.The delay of the initial grazing time has positive effect on increasing soil microbial biomass in 10-30 cm in the peak period of plant growth in July,while positive effect on soil microbial biomass N mineralizaion in 0-10 cm.5-9 month grazing improve the surface urease activity which is ability of soil provide N,seasonal grazing reduce the urease activity which is ability of soil provide N in 20-30 cm in September.The study found that on semi-arid grasslands,seasonal grazing with limited stubble height accelerate the storage of organic matter from plant to soil and soil microorganism in different degrees.Therefore,it is necessary to take into account the differences of plant,soil and microorganisms in the selection of grazing methods.