Positive effects of leguminous shrub encroachment on multiple ecosystem functions of alpine meadows and steppes greatly depended on increasing soil nutrient.

• Leguminous shrub encroachment enhanced ecosystem multifunctionality in alpine grasslands. • Facilitative effects of leguminous shrub on EMF-diversity and productivity in alpine grasslands. • Leguminous shrub encroachment significantly increased soil nutrient contents in alpine grasslands. • Increasing of ecosystem multifunctionality resulted from higher soil nutrients by shrub encroachment. Shrub encroachment in grassland ecosystems is projected to intensify worldwide because of rapid climate change and anthropogenic activity, amplifying the encroachment of woody shrubs and strongly altering the ecosystem function. The effects of leguminous shrub encroachment on multiple dimensions of ecosystem functioning, however, remains poorly understood. This study experimentally quantified the effects of leguminous shrub encroachment (primarily Caragana spinifera Kom.) on various ecosystem functionality relevant to plant diversity, productivity, and storage of soil carbon (C) and nitrogen (N) in alpine meadows and steppes. Further, the study assessed the potential influences of shrub encroachment on ecosystem multifunctionality (EMF, EMF-diversity, EMF-productivity, EMF-C, and EMF-N). Our findings suggest that leguminous shrub encroachment enhanced ecosystem multifunctionality in alpine meadows and steppes. Plant diversity and aboveground biomass of herbaceous species increased after leguminous shrub encroachment. Additionally, the impacts of leguminous shrub encroachment on belowground biomass differed with grassland types, increasing in alpine steppes but decreasing in alpine meadows. The shrub encroachment resulted in significant increases in soil nitrogen and overall nutrient contents in both forms of alpine grasslands. Our findings highlight that shrub encroachment's increasing of ecosystem multifunctionality was closely related to the promotion of plant diversity, biomass of herbaceous plants, and soil nutrients. Overall, our study demonstrates that the encroachment of leguminous shrubs can promote ecosystem multifunctionality in both alpine meadows and alpine steppes. These findings expand our understanding of the ecosystem functioning in leguminous shrub‐encroached alpine meadows and steppes. [ABSTRACT FROM AUTHOR]