The invasion of Euphorbia jolkinii is mediated through the regulation of nitrogen transformation by functional microbial abundance in rhizosphere soils

Introduction: Euphorbia jolkinii Boiss. is a native invasive weed. Its invasion altered microbial composition, total nitrogen (TN) and available nitrogen (AN). However, the mechanisms inffuencing N transformation remain unclear. Particularly, the roles of the microbiome and genes in mediating N transformations to facilitate E. jolkinii invasion remain poorly understood. Therefore, the primary objectives of this study were to evaluate how E. jolkinii invasion affects N transformation, microbial interactions, and key genes associated with AN accumulation. Methods: We compared three patches (non-invaded, lightly, and heavily invaded patches of E. jolkinii) by analyzing rhizosphere soils of E. jolkinii and Poa crymophila Keng. Integrating soil physicochemical indices with metagenomic sequencing, we investigated the relationships among microbial communities, gene abundance, and N transformation. Results: With E. jolkinii increasing invasion intensity, N accumulation and transformation rates were signiffcantly reduced in the rhizosphere of P. crymophila but enhanced in that of E. jolkinii, particularly for AN. Metagenomic analysis revealed that the invasion and expansion of E. jolkinii promoted functional adaptation of the microbial community, particularly by enriching the N cycling-related genes and increasing their relative abundance in the rhizosphere soil of E. jolkinii. Moreover, it inhibited the accumulation of N transformation functional genes in the rhizosphere soil of the companion plant, P. crymophila. Structural equation modeling identiffed Nitrospirota, Edaphobacter, Anaeromyxobacter, and soil N transformation rates as key drivers of AN accumulation. Discussion: E. jolkinii facilitated N accumulation in its rhizosphere by modulating N-transforming microbes and key functional genes, underscoring one of its invasive advantages.