Unravelling community assemblages through multi-element stoichiometry in plant leaves and roots across primary successional stages in a glacier retreat area

Our understandings on the patterns and mechanisms of plant community assembly during succession, especially the primary succession in glacier retreat areas, remain limited. The Hailuogou Glacier Chronosequence provides a distinctive place to disentangle the biotic interactions and abiotic filtering effects on community successional trajectories. Through community-weighted approaches, we quantified elements allocation and regulation in leaves and roots, N:P stoichiometry, and the biotic and abiotic controls guiding community dynamics along the 120-year chronosequence. Across seven primary successional stages, plant leaves featured higher concentrations of macro-elements with lower coefficients of variation (CV) with increasing succession; whereas, fine roots contained more micro-elements with higher CV. From the early to late stages, foliar N:P increased linearly from 8.2 to 20.1. These findings highlighted that the limiting factor for plant growth shifted from N to P over one century of deglaciation. Edaphic factors (pH, bulk density, N and P concentrations) acted as deterministic filtering for trait convergence in the early stages, while biotic factors (species richness and plant litter biomass) for competitive exclusion dominated the late stages hosting species with stronger homoeostatic regulation and more conservative nutrient use.