Effects of nitrogen addition on leaf nutrient stoichiometry in an old‐growth boreal forest

Boreal forests have been evidenced to be highly sensitive enhanced nitrogen (N) deposition due prevailing N limitations, and external inputs from atmospheric are expected alter plant nutrient stoichiometry. Previous studies mostly focused on the dominant tree species while neglecting understory plants that often play important role in cycles forest ecosystems. By conducting a six-year N-addition experiment with four treatments of 0 (control), 20 (low N), 50 (medium 100 (high N) kg N·ha−1·yr−1 boreal Northeast China, we assessed responses leaf stoichiometry (N, phosphorus [P], potassium [K], calcium [Ca], magnesium [Mg]) for tree, shrubs, grass. Although different addition varied, addition, especially medium high treatments, generally increased concentration decreased P Ca concentrations. As result, foliar N:P, N:K, N:Ca, N:Mg ratios consistently across functional groups under compared control, grass Deyeuxia angustifolia showed larger increase its than shrubs. The soil inorganic nonlinear saturating form, other nutrients either (P, Ca) or were not affected (Mg, K) by availability. Consequently, linearly increasing In spite this alteration availability, their less low treatment both trees plants, suggesting minor effects current rates balance forests.