The Dynamic Of OM Chemistry And Microbial Community And Their Interactions Regulate Carbon Turnover

Organic carbon(OC)mineralization is mainly affected by environmental factors,substrate types and microbial community composition.Since the preferences of microorganisms to substrates,the relationship between substrates and microbial community as well as their contribution to mineralization needs to be further studied.By carrying out incubation and pot experiment,combining with high throughput sequencing,metagenomics,Fourier transform ion cyclotron resonance mass spectrometry(FT-ICR MS)and stable isotope technology,we investigated the dynamic change of microbial community and the C chemical composition of substrates(biochar,straw,roots exudates)as well as their co-effect on C mineralization.(1)The interactions between OM chemistry and microbial community and its regulation of carbon turnover during biochar degradation processRecalcitrant biochars pyrolyzed at 500?and 600?were amended into C3 soil(BC₅₀₀and BC₆₀₀).Mineralization,microbial community,DOM components were analyzed after 28-days incubation.Results indicated that proportions of the recalcitrant components of DOM(condensed aromatics,tannin and lignin)were depleted,while the relative abundance of DOM labile components(lipids,carbohydrates)were increased in biochar amended soils,indicating that CO₂loss was mainly from recalcitrant C.Bacterial community shift towards dominance of A-strategists(e.g.,Alphaproteobacteria,Actinobacteria)because of stress ambient(e.g.,neutralization of soil acidity)and resources absence in biochar amended soil.Also,A-strategists were negatively correlated with DOM recalcitrant components,suggesting that they might be SOC miner in biochar enriched soil and contribute to SOC loss.(2)The interactions between OM chemistry and microbial community and its regulation of carbon turnover during straw degradation processA 210-days microcosm incubation of labeled straw amended into Acrisol and Phaeozem was undertaken to investigated the dynamic changes and relationship between microbial community and straw chemical composition,and their co-effects on OC mineralization.Results indicated that the relative priming effect mechanism of Acrisol and Phaeozem was different.In Acrisol,the relative priming effect was mainly affected by r-strategists and labile C.With the consumption of r-strategists and accumulation of recalcitrant C,K-strategists would also contributed to relative priming effect in the later period.While in Phaeozem,the relative priming effect was mainly caused by the utilization of recalcitrant carbon by K-strategists,but the few of labile C would also affect the relative priming effect in the early stage.(3)The interactions between root exudates chemistry and microbial community and its regulation of carbon turnoverHigh,medium and low photosynthetic efficiency rice were planted in greenhouse.Pulse labeling was carried out after 28 and 77 days,then destructive sampling to investigated root exudates,rhizosphere microbiome and root respiration.The results are as follows:i)In the vegetative stage,the root exudates were mainly unsaturated aliphatic,lipids and protein/amino sugar and enriched copiotrophic bacteria(Gammaproteobacteria,Bacteroidetes and Firmicutes),which possessed high functional genes for decomposing labile compounds,root respiration were higher.The amount of root respiration,the relative abundance of bacteria(Myxococcota,Acidobacteriota and Cyanobacteria)as well as function genes of GH120 and PL10were decreased with the increasing of plant photosynthetic efficiency.ii)In the reproductive stage,root exudates were mainly tannin and lignin,gathering oligotrophic bacteria(Cyanobacteria,Acidobacteriota,Myxococcota),which have the high abundance genes of decomposing cellulose and pectin.Root respiration was low and there were few differences between plants.In conclusion,when under environment stress,S-strategists use labile C to change their characteristics(structure and composition of cell membrane)to resist stress.When under suitable environment and sufficient resources,Y-and r-strategists utilize labile C to reproduce.When existing suitable environment but scarce resources,A-and K-strategists contribute to mineralization by utilizing recalcitrant carbon through co-metabolism.Meanwhile,microorganisms change the C chemical composition by using it,conversely,the affinity of microorganisms to C chemical components regulates themselves.The interaction between chemical components and microorganisms further affects OM decomposition,which can provide management theories for carbon mineralization and sequestration in various ecosystems.