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 influencing 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 significantly 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 identified 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.