The soil C:N:P stoichiometry is more sensitive than the leaf C:N:P stoichiometry to nitrogen addition: a four-year nitrogen addition experiment in a Pinus koraiensis plantation

The atmospheric deposition of N has rapidly increased in recent years, but whether the C:N:P stoichiometry of older leaves, litter and the mineral layer of soil is more sensitive to N deposition than the C:N:P stoichiometry of new leaves remains unclear. An experiment simulating N deposition (0, 20, 40, and 80 kg·N·ha−1·year−1) was established in a Pinus koraiensis plantation in Northeast China in May 2014. In September 2017, the nutrient concentrations in new and older leaves, litter, and the 0–10 cm and 10–20 cm soil mineral layers were determined. The treatments and leaf stages had no significant interaction effect on the leaf C:N:P stoichiometry. The coefficient of variation among the treatments found for new leaves was significantly lower than that found for the 10–20 cm soil layer, and no significant difference was found among the three leaf stages or among the two soil layers. The C:N:P stoichiometry of older leaves and litter is not more sensitive to N addition than that of new leaves, and the soil C:N:P stoichiometry responds earlier to N addition than the leaf C:N:P stoichiometry. For the forest ecosystem factors associated with stoichiometric traits, the soil C:N:P stoichiometry might be a better indicator of variations under the increased N:P deposition ratio obtained with N deposition.