The Strategies Of Microbial Substrates Utilization And Relative Microorganisms During Soil Priming Effects

Soil is one of the largest carbon sinks in the ecosystem.Carbon dioxide in the atmosphere can be fixed by plant via photosynthesis and the part of it is stored into soil through a series of biochemical processes.Sink and source capacity of soil depends on the release of greenhouse gases to the atmosphere or sequestration of organic carbon in soil via physicochemical and the biological processes.In addition,the priming effect get more and more attention in recent years,and the response of soil microorganisms to substrate inputs is a decisive factor affecting the priming effect.Elucidating the composition and the role of soil microorganisms in the process of priming help to understand the dynamic changes of soil carbon pool by substrate induced priming under the input of labile organic substrates.In the current incubation study,glucose and glycerol were added to one soil and glucose was added as the labile carbon substrate to two soils with different fertilizer additions.The differences in priming effect were observed.The substrate utilization pattern and functional characteristics of soil microbial communities were analyzed by DNA-SIP(Stable isotope probing)coupled with high-throughput sequencing.The main findings of this study are as follows:(1)Positive priming was triggered by glucose and glycerol addition as the same carbon content and glucose leading to greater intensity of priming than glycerol significantly.The mineralization of glucose was 33.2% higher than glycerol.During the priming,there were significant differences between the taxa utilizing glucose and glycerol in terms of dominant taxa or the community composition,the dominant taxa utilizing glycerol were Firmicutes and Actinobacteria,but the dominant bacteria utilizing glucose were the members of Actinobacteria,Proteobacteria,Gemmatimonadetes and Chloroflexi.At the later stage of priming,the abundance of rstrategists which had the advantage of utilizing labile organic substrates such as Firmicutes decreased.In addition,the abundance of ABC transporter was higher in the bacteria utilizing glycerol than glucose,but the abundance of Bacteria secretion system was opposite trend.(2)Comparing and verifying the glycerol?glucose utilization bacteria inferred by the co-occurrence network statistically with that identified by experiment directly,78.5% ?66.2% of inferred taxa can be found in heavy fraction after DNA-SIP,respectively.(3)After amendment with 90 mg/kg and 60 mg/kg nitrogen,the garden and grassland soil formed different C: N,respectively.All treatments generated positive priming after glucose addition,and greater priming in higher nitrogen treatments than lower.Glucose mineralization was greater in higher nitrogen of garden soil than lower nitrogen,but the reverse trend in grassland soil,this may be related to the abundance of Actinobacteria that has greater advantage of utilizing glucose,and significantly higher abundance of glycoside hydrolases gene in higher nitrogen treatment of grassland soil.In short,microorganisms will take various strategies in response to different substrates addition or soil nutrient status,then influence the priming intensity.