Abstract
BackgroundPaddy soil dissolved organic matter (DOM) represents a major hotspot for soil biogeochemistry, yet we know little about its chemodiversity let alone the microbial community that shapes it. Here, we leveraged ultrahigh-resolution mass spectrometry, amplicon, and metagenomic sequencing to characterize the molecular distribution of DOM and the taxonomic and functional microbial diversity in paddy soils across China. We hypothesized that variances in microbial community significantly associate with changes in soil DOM molecular composition.ResultsWe report that both microbial and DOM profiles revealed geographic patterns that were associated with variation in mean monthly precipitation, mean annual temperature, and pH. DOM molecular diversity was significantly correlated with microbial taxonomic diversity. An increase in DOM molecules categorized as peptides, carbohydrates, and unsaturated aliphatics, and a decrease in those belonging to polyphenolics and polycyclic aromatics, significantly correlated with proportional changes in some of the microbial taxa, such as Syntrophobacterales, Thermoleophilia, Geobacter, Spirochaeta, Gaiella, and Defluviicoccus. DOM composition was also associated with the relative abundances of the microbial metabolic pathways, such as anaerobic carbon fixation, glycolysis, lignolysis, fermentation, and methanogenesis.ConclusionsOur study demonstrates the continental-scale distribution of DOM is significantly correlated with the taxonomic profile and metabolic potential of the rice paddy microbiome. Abiotic factors that have a distinct effect on community structure can also influence the chemodiversity of DOM and vice versa. Deciphering these associations and the underlying mechanisms can precipitate understanding of the complex ecology of paddy soils, as well as help assess the effects of human activities on biogeochemistry and greenhouse gas emissions in paddy soils.
Highlights
Paddy soil dissolved organic matter (DOM) represents a major hotspot for soil biogeochemistry, yet we know little about its chemodiversity let alone the microbial community that shapes it
Microbial and DOM biogeography in paddy soils Across four rice-growing regions in China, we collected soil samples from 88 flooded paddy fields, wherein most rice plants were at the tillering phase (Fig. 1 and Table 1)
In this study, we demonstrated that DOM molecular distribution correlates with microbial community structure, taxonomy, and functional potential in paddy soils from sites representing gradients of temperature, precipitation, pH, and human activity
Summary
Paddy soil dissolved organic matter (DOM) represents a major hotspot for soil biogeochemistry, yet we know little about its chemodiversity let alone the microbial community that shapes it. The continuous flooding in bunded fields of cultivated rice (Oryza sativa) utilizes 24–30% of the world’s developed freshwater resources and represents one of the major sources of Recently, the evidence-based soil continuum model questioned the secondary synthesis of “humic substances,” or the “humification,” and interpreted organic debris as a unique source of soil organic matter (SOM) and DOM [5]. This approach has been applied to marine [18, 19] and inland water [4, 20, 21], and a handful of comparative experiments have examined soil DOM at the molecular level [3, 14, 15, 22]; the microbial taxonomic and metabolic structures that influence the molecular distribution of soil DOM remain unknown
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