Abstract: Aims By investigating aboveground and belowground nutrient allocation strategies of dominant tree species, Juniperus saltuaria and Rhododendron nivale, under different interaction intensities at the alpine treeline of the Sygera Mountains, this study aims to provide theoretical basis and support for ecological protection and restoration for alpine zone. Methods This study focuses on the J. saltuaria community(Cover:60%), the J. saltuaria dominated community(Cover:20%), the R. nivale dominated community(Cover:56%), and the R. nivale community(Cover:75%) at the alpine treeline of the Sygera Mountains. In August 2022, leaves, roots, and soil within the canopy range of dominant species in these four plant communities were collected. The nutrient element content of the samples was measured, and the aboveground and belowground nutrient and stoichiometric characteristics of J. saltuaria and R. nivale under different interaction intensities were analyzed using ecological stoichiometry and Partial Least Squares Path Model (PLS-PM). It aims to clarify the differences in nutrient strategies of the two dominant tree and shrub species under varying interaction intensities at the alpine treeline of the Sygera Mountains. Important findings The results showed that (1) leaf C content in the J. saltuaria community was higher than that in the J. saltuaria dominated community, while N, P, and K contents were the opposite; root C content in the J. saltuaria community was lower than that in the J. saltuaria dominated community, while N, P, and K contents were higher. In the R. nivale dominated community, leaf C and K contents were higher than those in the R. nivale community, whereas N and P contents were lower; root C and N contents were higher in the R. nivale dominated community, while P and K contents were lower. In all four plant communities, leaf C, N, P, and K contents were significantly higher than in roots, as nutrients are transported to leaves from other plant organs to sustain normal physiological activities. (2) Compared to the J. saltuaria community, the J. saltuaria dominated community preferred to allocate more nutrients to leaves, representing an aggressive nutrient strategy. In contrast, the R. nivale dominated community transported more nutrients to roots compared to the R. nivale community, reflecting a more conservative nutrient strategy. Additionally, a positive feedback mechanism exists between plant communities and soil nutrients in the study area.

Key words: Key words Alpine treeline, Tree-shrub interaction, Nutrient allocation strategy, Ecological stoichiometry, Plant community, Nutrient restriction