Responses Of Soil Microbial Biomass To Management Methods,Nitrogen Additions,and Precipitation Changes In Horqin Sandy Grassland

Grassland ecosystem is the most widely distributed type of ecosystem in the world,and it is also the largest terrestrial ecosystem in China.It plays an extremely important role in ecological environment and social economy.However,with the increasing material energy demand and industrialization of mankind,the grassland ecosystem has been seriously damaged.It is facing the challenges of global change such as management patterns such as reclamation and grazing,and changes in atmospheric nitrogen deposition and precipitation patterns.Soil is an important place for material circulation and energy conversion in grassland ecosystems.Its quality will directly affect the safety of grassland ecosystems.Soil microbial biomass,as a biological indicator of soil quality assessment,can reflect soil quality development earlier.Degraded state.Therefore,exploring the impact of grassland management patterns and global changes on grassland soil microbial biomass is of great significance for the protection of grassland ecosystems.This study relies on the Naiman Desertification Research Station of the Chinese Academy of Sciences to establish a field test observation field in the semi-arid sandy land of Horqin,northern China,by setting management mode(grazing,enclosure),simulating nitrogen deposition(no nitrogen application,nitrogen addition).And the change of precipitation(CK,60% rain reduction,60% rain increase,60 days of extreme rain reduction,60 days of extreme rain),the control experiment was carried out to test the response of soil microbial biomass carbon and nitrogen in sandy grassland in the past two years.Regularity and explore the reasons for the results.The main findings of the study are as follows:(1)Management pattern,nitrogen addition and precipitation change had significant effects on soil microbial biomass carbon and nitrogen in Horqin sandy grassland,which were as follows:(a)Management mode(p<0.05),nitrogen addition(p<0.01)Changes in precipitation(p<0.05)significantly or significantly altered soil microbial biomass carbon,management patterns and nitrogen addition(p<0.05),management patterns and precipitation changes(p<0.01),management patterns and nitrogen additions And the change of precipitation(p<0.01)had an interaction withthe soil microbial biomass carbon;(b)nitrogen addition(p<0.01),precipitation change(p<0.05)significantly or significantly changed soil microbial organisms There was an interaction between nitrogen,management mode and nitrogen addition(p<0.05),management mode and precipitation change(p<0.05),nitrogen addition and precipitation change(p<0.001)on soil microbial biomass carbon.(2)Soil microbial biomass carbon and nitrogen in Horqin sandy grassland showed significant seasonal variation(p<0.001)in the control experiment,and summer was significantly greater than spring,with no significant interannual variation.There was a significant interaction between soil microbial biomass carbon and interannual variation,management patterns,and nitrogen addition(p<0.01).Seasonal changes and management patterns also had significant interactions with soil microbial biomass carbon(p <0.05).(3)In the detection of soil microbial biomass carbon: grazing treatment increased by 15.23% in the summer,and decreased by 18.93% in spring;the nitrogen treatment decreased by 25.13% compared with the average without nitrogen treatment;The increase or decrease of rain treatment failed to significantly increase the detection value,with an average decrease of 20.19%;the extreme drought 60 days of treatment showed the lowest value in the middle of the test period,and the explosive growth occurred after the recovery of precipitation in January,higher than other precipitation treatment.In the detection of soil microbial biomass nitrogen: the enclosure treatment increased by 11.84% on average;the nitrogen treatment increased by 28.39% on average,and the precipitation changes did not significantly increase the detection value,with an average decrease of 17.64%.(4)No nitrogen application × grazing treatment,grazing × extreme drought 60 days treatment,no nitrogen application × extreme drought 60 days treatment,soil microbial biomass carbon is relatively highest after dry and wet alternation;nitrogen application × enclosure treatment,The soil microbial biomass nitrogen was the highest in the treatment of enclosure × rain reduction 60% treatment,nitrogen application × extreme rain enhancement for 60 days.In summary,this study found that management patterns,nitrogen addition and precipitation changes have significant effects on soil microbial biomass carbon andnitrogen in Horqin sandy grassland through field surveys,but management patterns and global changes in soil microbial biomass carbon The effects of nitrogen are not consistent,and soil microbial biomass carbon is relatively more sensitive.The grassland ecosystem in the study area is relatively fragile,and the changes in external factors are not well adapted.In the short term,the impact of management patterns and global changes has changed.At present,the seasonal rotational grazing policy,nitrogen deposition rate and precipitation pattern in the area are relatively conducive to the improvement of soil microbial biomass in the study area.In the future,soil quality can be protected by reducing the application of nitrogen fertilizer and providing relevant irrigation forecasts by relevant units.The research results can provide a basis for the response of soil microbial biomass to grassland management patterns and global changes in arid and semi-arid sandy grassland ecosystems in northern China.