Study On Soil Nitrogen Removal Function Of Different Land Use Types In Xiong'an New Area

In the context of rapid economic and social development,people used multifarious land use patterns in soil to meet the needs of material and spiritual life.It caused obvious differences in soil natural structure,physical properties,chemical properties,and so on.The differences between soils seriously affected the community structure and diversity of soil denitrifying microorganisms and anaerobic ammonia oxidizing microorganisms,as well as their gene abundance and potential rate.In this paper,the soil of woodland,farmland,and wetland was taken as the objects,the denitrification and anaerobic ammonium oxidation of different land-use types in Xiong'an New area were studied from horizontal and vertical dimensions.Soil potential denitrification rate and potential anammox rate were measured by isotope tracer technique,gene abundance was determined by fluorescence quantitative PCR technique,High-throughput sequencing technique was used to analyze the community structure and diversity of microorganisms.The main results of this paper were as follows:(1)It was found that there were some differences in the physical and chemical properties of different types of soils,and some regularity was found in the physical and chemical properties of soils with different depths.The differences were mainly reflected in the following two aspects: the soil moisture of wetland was about OTU50% higher than that of woodland and farmland soil;the nitrate concentration of woodland and farmland soil was about OTU 20 times higher than that of wetland soil.The regularity of soil physical and chemical properties at different depths was mainly shown in the following three aspects: with the increase of soil depth,the soil temperature decreased gradually,the soil humidity increased at first and then decreased,and the electrical conductivity increased at first and then tended to be stable.Soil nitrate-nitrogen mainly existed in shallow soil.(2)Denitrification was the main way of soil nitrogen removal in woodland,farmland and wetland.The denitrification ability of wetland soil was the strongest,farmland was the second,and woodland was the lowest.In terms of denitrification rate and gene abundance,the three types of soil from high to low were wetland >farmland > woodland.It indicated that there was a positive correlation between denitrification microbial biomass and denitrification.The abundance of soil denitrifying microorganisms had significant vertical distribution characteristics.With the increase of soil depth,the gene abundance of soil nirS denitrifying microorganisms decreased gradually,indicating that the process of soil denitrification mainly occurred in the shallow surface of the soil.(3)There were significant differences in the community structure of soil nirS denitrifying microorganisms among the three land-use types.The community structure of woodland soil was the most complex and there were many kinds of microorganisms,while the structure of farmland soil community was the simplest.OTU1 and OTU2 were the main microorganisms involved in denitrification in farmland soil.Denitrifying microorganisms in wetland soil were mainly concentrated in Cluster5 and Cluster4,and the abundance of other types of denitrifying microorganisms was low.Also,the Alpha diversity of nirS denitrifying microorganisms decreased with the increase of soil depth.50 cm deep soil could be divided into three different types of community structure,which were surface type(0-5 cm),middle type(5-15 cm),and deep type(15-50 cm).There were significant differences in community composition and relative abundance.(4)In the three types of soil,there were mainly three genera of microorganisms involved in the process of anaerobic ammonia oxidation,which were Brocadia,Kuenenia,and Jettenia,respectively.And the community structure of anaerobic ammonia oxidation microorganisms in woodland and farmland soil was single and similar,including only Brocadia,while the community structure of anaerobic ammonia oxidation microorganisms in wetland soil was much more complex,including Brocadia,Kuenenia,and Jettenia.However,the anaerobic ammonia oxidation rate of wetland soil was low,which was less than 10% of woodland and farmland soil.The species of anaerobic ammonia oxidation microorganisms in farmland soil were very different at 15 cm.Brocadia was dominant above 15 cm,while Kuenenia and Brocadia existed at the same time below 15 cm depth,indicating that there were differences in microbial species involved in the anammox process at different depths.To sum up,the nitrogen removal function of wetland soil was the strongest,followed by farmland soil,and woodland soil was the lowest.In the three types of soil,denitrification was the main way of nitrogen removal,the anaerobic ammoxidation process plays a small role,and nitrogen removal mainly occurs in shallow soil.The community structure and abundance of denitrifying microorganisms and anammox microorganisms in wetland soil were different from those in woodland and farmland soil.