Boreal forests have been evidenced to be highly sensitive to enhanced nitrogen (N) deposition due to prevailing N limitations. External N inputs from atmospheric deposition are expected to alter plant nutrient stoichiometry and consequently induce nutrient imbalances, the magnitude of which may vary across plant functional groups. Although the effects of N addition on foliar nutrients of dominant trees have been extensively studied, it is not clear how this might vary between different functional groups at the whole community level. By conducting a six-year N-addition experiment with four treatments (0, 20, 50 and 100 kg N ha-1 yr-1) in a boreal forest in Northeast China, we assessed the responses of leaf stoichiometry of multiple nutrients (N, phosphorus [P], potassium [K], calcium [Ca] and magnesium [Mg]) across tree, shrub and herbaceous layers.
Results/Conclusions
Our results indicate varied responses of leaf nutrient stoichiometry across species and plant functional groups. Although species varied in their response to N addition, six-year N addition generally increased the leaf N concentration and decreased the leaf P and Ca concentrations at the community scale. The leaf N concentration increased with soil inorganic N while leaf K, Ca and P concentrations decreased with increasing soil inorganic N. Furthermore, the leaf N:P, N:K, N:Ca and N:Mg ratios increased significantly in response to high N addition (100 kg N ha-1 yr-1) and tree appeared to be more sensitive. This significant alteration in plant leaf stoichiometry suggests an N-induced imbalance in leaf N, P, K, Ca and Mg at the community level, which might constrain plant growth and carbon sequestration in boreal forests under N deposition.