Metagenomic Analyses Of Microbial Communities And Their Responses To Anthropogenic Perturbations In Typical Agrotypes

Microbes have been key drivers of biogeochemical cyclesandplay a central role in mediating effluxes of greenhouse gases such as carbon dioxide,methane and nitrous oxide.Environmentalperturbationaffects soil microbial community composition.While microbes iffluenceenvironment in turn by mediating greenhouse gases,carbon and nitrogen sources.Therefore,it forms a circular feedback mechanism between environmental change and microbes.However,it remains elusive how microbial feedback responds to environmental change.In addition,it remains unclear whether soil type affects microbial response to plant cropping or fertilization.To address these questions,we studied microbial community composition in Mollisol in Hailun station,Heilongjiang province,Cambisol in Fengqiu station,Henan province,Acrisol in Yingtan station,Jiangxi province.In 2005,plots were established in each station and reciprocal transplanted to simulate environmental change.Additional treatments of maize cropping and NPK fertilization have been performed in each station since 2006.In 2009,we took Mollisol samples in bare fallow and maize cropping plots at local and transplanted sites.Geo Chip 3.0,DGGE and PLFA were used to determine effect of environmental change and maize cropping on microbial community composition.We found that microbial functional diversity was increased,in addition to concurrent changes in microbial biomass,soil nutrient content and functional processes involved in the nitrogen cycle.However,soil transplant effects on microbial functional community compostion could be overridden by maize cropping.In 2011,we took soil samples in bare fallow,maize cropping and fertilization plots in each station and each type of soil.Bacterial,fungal and functionalcommunities were determined by Illumina Mi Seq sequencingand Geo Chip 4.6,respectively.Different agrotypes were distinct in microbial biomass and community composition.Differences in microbial communities were best explained by soil p H,total phosphorus,total potassium,and annual rainfal.Sencondly,maize cropping changed bacterial composition of Acrisol,fungal composition of Mollisol,but had little effect on bacterial,fungal or functional gene compositions of Cambisol.In addition,soil acidification was observed when fertilization was applied.Microbial compositions of Mollisol and Acrisol were changed,which were significantly correlated to soil p H.In contrast,microbial compositions of Cambisol were unchanged by fertilization,and unrelated to soil p H.Thirdly,fungal community was more sensitive to environmental change simulated by soil transplant than bacterial community.Correlation investigation with samples in 2009 and 2011 revealed strong correlations between carbon cycle genes and CO2 efflux in bare soil but not cropped soil,and between nitrogen cycle genes and nitrification.These findings contributed to a better mechanistic understanding of these soil functional processes and suggesting a potential to incorporate microbial communities in greenhouse gas emission modeling.