| The decomposition and transformation of soil organic carbon in the peatland is a key process to regulate carbon cycle in the soil-organism-atmosphere continuum.Furthermore,atmospheric deposition can affect the rate of organic carbon mineralization by participating in soil biogeochemistry processes.To clarify the key mechanism of carbon turnover and interaction of biogenic factors,atmospheric deposition is a crucial parameter to accurately assess greenhouse gas（GHG）emission from peatland.In this study,three peatland located in different climatic zones were selected,namely the Changbai Mountain,Zhejiang and Tibet peatland,simulating dry deposition by the continuous input of lower and higher concentrations of sulfate,ferric and humic acids for laboratory microcosms.Carbon dioxide（CO2）,methane（CH4）emissions and dissolved organic carbon（DOC）from peat soils were monitored,and organic matter（OM）properties were characterized by using mediated electrochemistry and three-dimensional fluorescence spectroscopy.Combined with microbial community analysis in peat soil,the abiotic and biological key factors impacting carbon emission were duly emphasized to understand the key mechanisms controlling GHG emissions.The results show that the input of different atmospheric deposition components mainly affects the CH4 emission and DOC process in peatland,but has little impact on CO2 emission.For the three peat soils:（1）From different input levels of atmospheric deposition components,lower concentration of atmospheric deposition components can promote carbon emissions,while the higher concentration of components will reduce CH4 emissions.Among three peatlands,Tibet peat soil with more abundant and stable carbon had less response with addition of different components.（2）In perspective of abiotic mechanism,sulfate from atmospheric deposition promote the decomposition of relatively stable soil organic matter and humic acid increase DOC and promoted CH4 emission under anaerobic respiration by providing more active substrates for;in addition,ferric iron significantly decreased DOC content,which could protect soil carbon pool.And increased microbial source organic matter suggests that CH4 production may be promoted by microbial interactions with iron oxide.However,the higher concentration of atmospheric deposition components can act as electron acceptors to induce anaerobic methane oxidation（AOM）and lower the CH4 emission from peatlands.（3）From the view of biological mechanism,different atmospheric deposition components generally reduces microbialαdiversity and significantly changed their community composition;promotes non-competitive methanogenic process;The key species of aerobic methane-oxidizing bacteria（Methyloligellaceae,Methylocystis and Methylosinus）probably contribute to AOM and reduce CH4 emission;Moreover,the abundance of ferric reduction bacteria（Bacillus and Bacteroides）in ferric treatment and sulfate-reducing bacteria（Desulfomonilia and Desulfovibrionia）in sulfate treatment is crucial for the atmospheric deposition components reduction-coupled AOM process.In general,findings of this study clarify the biogeochemistry coupling mechanism of OM in regulating GHG with atmospheric deposition components input;The macro-scale atmospheric deposition process can affect the interaction between OM&iron,and OM&sulfur during soil carbon decomposition and the micro-mechanism of its functional microorganisms,thereafter feedback to macroecosystems through regulation of GHG emissions.The results provide important theoretical support for the correct assessment of peatland GHG accounting and carbon emission model calibration. |
