Rhizosphere effects of Parthenium hysterophorus on soil nutrient availability and microbial life-history strategies

Biological invasions impose substantial ecological and economic costs worldwide, yet research on invasive plants has often emphasized changes in aboveground plant communities, with comparatively less attention to belowground microbial communities, particularly those inhabiting the rhizosphere, a biogeochemical hotspot where plant-soil-microbe interactions are most intense. To address this gap, we compared the invasive Parthenium hysterophorus with the co-occurring native grass Cynodon dactylon in a reservoir drawdown zone of the lower Jinsha River, quantifying rhizosphere soil physicochemical properties, extracellular enzyme activities, bacterial and fungal community attributes, and microbial ecological strategies. Compared with C. dactylon , P. hysterophorus was associated with higher soil water content, available phosphorus, microbial biomass carbon and nitrogen, and greater leucine aminopeptidase and alkaline phosphatase activities; although bacterial α-diversity, community-weighted mean rrn copy number, and fungal Shannon diversity remained largely unchanged, the fungal copiotroph/oligotroph increased, while bacterial and fungal taxa exhibited distinct environmental associations, with key bacterial genera primarily related to soil water availability, microbial biomass, β-glucosidase, and leucine aminopeptidase activity, and key fungal genera associated mainly with soil organic carbon, nitrate nitrogen, and N-acetyl-β-glucosaminidase activity. P. hysterophorus is associated with a distinct rhizosphere environment characterized by enhanced nutrient mobilization and selective microbial assembly, particularly of specific fungal taxa such as Septoglomus , Mortierella , and Poaceascoma , suggesting that coordinated shifts in rhizosphere resource acquisition and fungal community composition may represent an important belowground pathway facilitating its establishment and persistence in environmentally dynamic reservoir drawdown zones.