The Biodiversity Of Paddy Soil Microbial Community And Its Correlations With The Chemodiversity Of Dissolved Organic Matter Across Typical Regions In China

Microbes mediate various biogeochemical processes in paddy soils,while their community compositions greatly influence carbon cycle,greenhouse gas production and consumption,metal speciation and behavior,pollutant degradation and crop yield in paddy fields.Therefore,it is necessary to give an insight into the distribution characteristics and driving factors of microbial taxonomic and functional composition across large-scale paddy soils.Dissolved organic matter(DOM)represents a major hotspot for paddy soil biogeochemistry,yet we know little about its chemodiversity let along the ecological correlation between DOM molecules and microbial communities.Therefore,it is necessary to give an insight into the distribution characteristics and driving factors of DOM molecules across large-scale paddy soils.Moreover,It is also necessary to further verify the existence of ecological correlations between microbial biodiversity and DOM chemodiversity.Here,we took soil samples from paddy fields and adjacent lands across four typical rice-growing regions in China:Sanjiang Plain,Lianghu Plain,Taihu Plain and Hani Terrace.Ultrahigh-resolution mass spectrometry,amplicon and metagenomic sequencing were leveraged to explore the spatial distribution characteristics of paddy soil microbial communities and their environmental responses.Network analysis was performed to explore the co-occurrence and mutual exclusion interaction patterns of paddy soil microbes,and the driving mechanism of environmental factors on the changes of microbial community composition.Finally,the geographical distribution pattern of DOM molecules and their environmental responses were investigated,and the ecological correlations between DOM chemodiversity and microbial taxonomic and functional diversity were further verified and characterized.The main findings are as follows:1)Paddy soil harbored unique microbial community composition.Paddy soils have significantly lower microbial a diversity indexes(richness,diversity,and Evenness)than non-paddy soils across different sampling regions.Significant partitions were revealed between paddy soil group and the adjacent soil group for all P diversity matrixes except unweighted PINA.Most taxa in paddy soils and non-paddy soils showed significant differences.The microbiome of paddy soil was also significant from non-paddy soils.Microbial community distribution of paddy soil was significantly influenced by climatic,geographical factors and pH,conductivity,real-time air temperature and real-time soil temperature.The vast majority of individual microbes(OTUs)were affected by some of the other microbes,whereas only a few were directly and strongly influenced by environmental factors.2)Most interrelations in the co-occurrence network of paddy soil microbes are specified.At the same time,most interrelations of rice soil microbes were regional specific.characteristics.For most of the dominant taxa,their subordinate nodes in networks of paddy soils and non-paddy soils have significant different topological indexes.The microbial co-occurrence network of paddy soil is mainly composed of two microbial modules with wide and strong negative correlations between them.Significant differences of taxonomic compositions,topologies and functional potentials were observed between the two modules;the taxonomic compositions of their hubs were also significantly different.The influences of environmental factors on the paddy soil microbial community,were mainly through the driver effects on the changes of network hubs abundances.3)The molecular composition of DOM was demonstrated to exhibit a significant geographical distribution pattern as well as the microbial community;these patterns were proved to be driven by environmental factors(i.e.geographic distance,mean monthly precipitation,pH,mean annual temperature and elevation)and the characteristic of microbial diversity.Among these factors,the variance in DOM composition was best explained by the variance in microbial community,with the converse being true as well.4)The ecological correlation between DOM molecules and microbial communities was proved and characterized at the taxonomic and metabolic aspects of microbial community.An increase in DOM molecules categorized as peptides,carbohydrates,and unsaturated aliphatics,as well as a decrease in those belonging to polyphenolics and polycyclic aromatics,significantly correlated with proportional changes in some of the microbial taxa(e.g.Syntrophobacterales,Thermoleophilia,Geobacter,Spirochaeta,Gaiella,and Defluviicoccus).This DOM compositional variation was also associated with changes in the prevalence of the microbial metabolic pathways(e.g.anaerobic carbon fixation,glycolysis,lignolysis,fermentation and methanogenesis)that either respond to or shape these chemistries.This study investigated the geographic distribution patterns and the driving mechanisms of topsoil microbial community in large-scale paddy fields.The results or conclusions of this study are of scientific significance in revealing the microbial assembly in soil ecological system under long-term human activities,as well as the ecological correlations between microbial community and DOM molecular composition.