Shifted plant composition predominantly controls nitrogen addition effect on community-level leaf nutrient resorption in a boreal peatland

Background and aims Leaf nutrient resorption process is an indispensable aspect of plant nutrient utilization strategies in boreal peatlands. However, how nitrogen (N) enrichment alters leaf nutrient resorption is unclear at both species and community levels, and the underlying mechanisms remain unknown in these ecosystems. Methods Using a fertilization experiment with four N addition levels, we investigated the influence of increased plant-available N on leaf nutrient resorption efficiency and proficiency at both species and community levels, and disentangled the relative contributions of intraspecific variability and altered plant composition to the shifts in community-level nutrient resorption in a poor fen, Northeast China. Results Leaf nutrient resorption exhibited divergent responses to N addition at species and community levels. For most species, leaf N resorption efficiency remained unchanged, but leaf N resorption proficiency declined after N addition. In contrast, N addition increased leaf phosphorus (P) resorption of most species. At the species level, leaf N resorption declined with increasing green leaf N:P ratio, while leaf P resorption showed an opposite changing trend. Nitrogen addition reduced community-level leaf N resorption efficiency and proficiency, but increased community-level leaf P resorption efficiency and proficiency. Compared with intraspecific variability, altered plant composition contributed much more to N addition-induced shifts in community-level leaf nutrient resorption. Conclusion The plasticity in leaf N:P stoichiometry determines the interspecific responses of leaf nutrient resorption to N addition and shifted plant composition exerts a critical control over N enrichment effect on plant nutrient resorption at the community level in boreal peatlands.