Soil Bacterial Diversity During Wetland Vegetation Succession In Gannan Area

Soil bacteria is one of the important components of soil microbes,plays an important role in promoting soil carbon and nitrogen cycling,and it is also a key biological indicator for monitoring changes of composition and structure in ecosystem.Gannan is a permafrost region that is sensitive to climate change located in the eastern part of the Qinghai-Tibet Plateau.In recent years,due to the impact of global warming,the succession process of aboveground vegetation has changed,while the response of soil microbial communities,especially the composition and structure of bacterial communities to environmental factors under freezing and thawing conditions has received little attention.In the thesis,we firstly determined the aboveground vegetation succession sequence along the water gradient and typical dominant vegetation based on the multi-year water accumulation area,they were wetland(A1),swampy meadow 1(A2),swampy meadow 2(A3),mature meadow(A4).Secondly,used Illumina MiSeq technology to sequence the 16S rRNA partial fragments of 0-20cm soil bacteria under freeze-thaw condition,the composition and structure of the bacterial community were analyzed on the basis of it.Thirdly,explored its relationship to soil temperature,pH,soil water content,and aboveground biomass.Finally,the bacterial species correlation network and functional features were analyzed.The results showed that:(1)Soil bacterial diversity changed with succession stage and showed the highest diversity in A4;soil bacterial composition at each stage was similar at the phylum level,main dominant groups included Actinobacteria,Proteobacteria,Acidobacteria,and Chloroflexi etc,while the genus level showed significant difference.Multi-level species discriminant analysis(LEfSe)found that some populations with significant abundance differences play an important role in shaping community characteristics.For example,the Blastocatellaceae with the highest LDA score(4.74)could be well adapted the environment of A4,therefore it had the highest abundance in A4;(2)Soil moisture has the greatest influence on the composition and structure of bacterial communities,followed by ground temperature and soil pH,while aboveground biomass has the least impact on it;(3)The species correlation network analysis found that four stages showed different patterns,some key bacterial communities(such as Proteobacteria and Acidobacteria)could adapt to the environment of four succession stages and form close relationships with other related species,which indicated these bacterial communities play an irreplaceable role in ecological processes;(4)Bacterial functional feature analysis indicated that the soil bacterial community in this area was rich in metabolic functions and the functional structures between the stages were similar.This study revealed the composition and structure of bacterial diversity in freeze-thaw soil,provided a basis for an in-depth understanding of the above-and belowground interactions and response to climate change on Tibetan Plateau for the first time.