Assimilation Of Carbon Substrates With Different Availability Within Microorganisms Regulated By Long-term Fertilization

The flow of plant-derived carbon in soil is a key component of global carbon cycling,and soil microorganisms catalyze Earth's biogeochemical reactions,including the degradation and accumulation of soil organic matters.Soil-microorganisms-substrates is the unity of material cycle and energy flow in ecosystem,which affect and restrict each other and the process of them have influence on the function of soil as the biggest carbon pool on the earth.Our study sampled the soils received long-term of organic and mineral fertilizer application which formed a gradients of soil pH and SOC for incubation,aiming to figure out the mineralization pattern of carbon substrates with different availability,and how microorganisms assimilating substrates and SOC.The main findings of our study are as follows:(1)Long-term fertilization would change the properties of soil(e.g.pH,DOC),thus changed microbial community composition and structure indirectly.Under different fertilizer managements,soil bacterial and fungal community structure had a shift.(2)Glucose was mineralized more rapidly in soil than straw.In 30 days incubation,21.0-52.1%of glucose was mineralized,while 10.8-20.5%of straw was mineralized.Both glucose and straw would lead to positive priming effects in soil,PE intensity was significantly higher in M treatment than in CK.Cumulative mineralization and priming intensity had a relation with fertilization,and manure treatments enhanced both mineralization and priming.(3)After the addition of 13C-glucose,heavy fraction after DNA-SIP was dominated by Actinobacteria,Proteobacteria and Firmicutes,and the bacterial community structures between different fertilization treatments were diversed in heavy fractions.Microorganisms in light fractions as the "background" bacterial community remained relatively constant throughout the SIP incubation,including oligotrophic species like A.cidobacteria,which made use of complex carbon sources.(4)Copiotrophs like Fimicutes had a competitive edge in the early stage of micromolecule carbon mineralization,but would be replaced by other microorganisms like Chloroflexi,Actinobacteria in the late stage.From stage 1 to stage 2 of straw mineralization,the abundance of cellobiohydrolase genes decreased while the abundance of laccase genes increased.