Linking microbial biogeochemical cycling genes to the rhizosphere of pioneering plants in a glacier foreland

Glacier retreat raises global concerns but brings about the moment to study soil and ecosystem development. In nutrient-limited glacier forelands, the adaptability of pioneering plant and microbial species is facilitated by their in-teractions, including rhizosphere effects, but the details of this adaptability are not yet understood. In the rhizosphere of five pioneering plants, we comprehensively deciphered the microbial taxonomic and functional compositions. Two nitrogen -fixing microbial genera, Bradyrhizobium and Mesorhizobium, were among the most abundant taxa in the rhizomicrobiome. Moreover, several rhizobial genera, including Rhizobium, Pararhizobium, Allohrizobium, and Sinorhizobium, head the list of major modules in microbial co-occurrence networks, highlighting the vital roles of nitrogen-cycling taxa in the rhizomicrobiome of pioneering plants. Microbial genes involved in nitrogen, sulfur, phos-phorus, and methane cycles were simultaneously correlated with microbial community dissimilarity, and 12 func-tional pathways were detected with distinct relative abundances among soils. Zooming in on the nitrogen-cycling genes, nifW, narC, nasA, nasB, and nirA were mainly responsible for the significant differences between soils. Further-more, soil pH and the carbon/nitrogen ratio were among the topsoil properties interacting with nitrogen and sulfur cycling gene dissimilarity. These results explicitly linked biogeochemical cycling genes to the rhizomicrobiome and soil properties, revealing the roles of these genes as microbial drivers in mediating rhizosphere soil-plant-microbiome interactions.

Automated summary

Glacier retreat attracts global concerns and provides an opportunity to study soil and ecosystem development. This study deciphered the microbial taxonomic and functional compositions in the rhizosphere of pioneering plants, revealing the significant roles of nitrogen-cycling taxa and biogeochemical cycling genes in mediating rhizosphere soil-plant-microbiome interactions.