Effects Of Warming On Soil Microorganisms In The Permafrost Peatland Of The Great Hing'an Mountains

Boreal mid-high latitude peatland was the important soil carbon pool and stored nearly 1/3 of global soil carbon.These areas were more sensitive to climate warming than the other areas.Climate warming will result in the degradation of permafrost in mid-high latitude peatland.Due to degradation,more CH₄ and CO₂ may released in mid-high latitude peatland leading to positive feedbacks to the global climate change.However,the mechanisms of response and quantities were far unclear.Soil microbial decomposition of SOC results in emitting up to 25%natural CO₂ each year.Regard to methane,it was co-regulated by methanogens and methanotrophs.Studying the response of soil microbes in mid-high latitude peatland can releave the mechanisms of how these areas'feedbacks to climate warming.This can help us to predict the direction of feedbacks.Thus,we chosed a typical permafrost peatland in the Great Hing'an Mountains.We study that both increasing temperature in growing seasons and the changes of freeze-thaw cycles affect soil bacterial,methanogenic and methanotrophic quantities and community structure.The results were showed as follows:?1?Based on OTCs in situ,warming improved 1.66?and 2.86?of soil temperature at 0-10 cm and 10-20 cm depth respectively.Elevated temperatue promote the release of DOC and increase the abundances of methanogens and methanotrophs in 0-10 cm layers.Higher soil temperature increased significantly the copies numbers of mcrA gene.But it did not increased significantly the copies numbers of pmoA gene.Methanobacterium was the predominant community.Increasing temperature did not change the structure of methanogens.However,increasing temperature changed the composition of methanotrophs from Methylobacteriaceae?type I?to Methylocystaceae?type II?.This implies warming promote the release of methane in the surface layers.Both Ace and Chao1 were lower inside of OTC than that in situ of surface layers.However,soil microbial community compostion iiregulately changed under warming.Meanwhile,warming did not affect significantly DOC,the abundances of methangens and methanotrophs and soil microbial community composition in 10-20 cm layers.Together,soil microorganisms in peatland of permafrost were resistant to climate warming.?2?Under the anaerobic background,the soil temperature increasing 10?promote significantly CO₂ and CH₄ emissions in surface and middle peat layers,whereas soil temperature increasing 5?did not promote significantly CO₂ and CH₄emissions.At the deep peat layers,increasing temperature did not promote CO₂emissions and despress CH₄ emissions.This indicates that DOC which were degraded by old carbon can despress CH₄ production.The concentrations of CH₄ in the surface peat layers showed a curve during incubation experiments.This implies that soil microbial community compositons need to more time adjust new environments.?3?At the moss layers,temperature increase of 5?increase the abundances of both methanogens and methanotrophs.However,freeze-thaw regime did not change the composition of soil microbial community.This indicates that increasing temperature lead to more CO₂ release at the moss layers.At the peat laters,freeze-thaw regime hardly change the quantities of total bacteria,methanogens and methanotrophs.However,soil microbial structure changed followed by freeze-thaw regime.The relative abundances of certain Acidobacteria,Chloroflexi,Planctomycetes and Firmicutes which play an important role in cellulose degradetion were increasing.This indicates that soil microbes can degrade more recalcitrant carbon after thaw.CH₄ and CO₂ stored in permafrost released after thaw.Freeze-thaw regime did not change soil microbial abundace in permaforst.The relative abundance of Gp4,Gp6 and Protebacteria were increasing during thaw periods,whereas the relative of methanogens showed oppisite trend.Warming promote soil microbial degradetion and depress CH₄ production.Permafrost can release more CO₂ and degrade recalcitrant carbon during thaw periods.?4?In the seasonal frozen areas,spring freeze-thaw cycles may increase the total abundance of bacterias and methanogens.Whereas autumnal freeze-thaw cycles can promote DOC release and kill soil bacterias and methanogens.Meanwhile,autumnal freeze-thaw cycles can select soil microorganisms related to dormant,psychrotrophs and anaerobic through creating cold and anaerobic environment.During autumnal thaw period,the relative abundance of Acidobacteria and extend Proteobacteria were higher.Whereas the relative abundance of Firmicutes and certain Deltaproteobacteria were higher during frozen period.These bacterias play an important role in anaerobic fermentation and provide substrates for aceticlastic methanogens.During the whole freeze-thaw cycles,Methanosarcinales were the predominant community,and autumnal freeze-thaw cycles can promote CH₄ production.Temperature and substrate were the primary factors regulating the abundance and composition of the microbial communities during autumn FTCs,whereas no factors significantly contributing to spring FTCs were identified.These indicated that the increasing number of FTCs predicted to occur with global climate change could potentially promote CH₄emissions.