Changes of plant community composition instead of soil nutrient status drive the legacy effects of historical nitrogen deposition on plant community N:P stoichiometry

Aims Uncovering the importance of soil and plant characteristics in driving the legacy effects of nitrogen (N) deposition on plant community nutrient stoichiometry would improve our understanding of plant-soil interaction during restoration of historically N-enriched ecosystems. Methods Based on a field experiment with the cessation of six-year N addition in a temperate steppe of northern China, we measured concentrations and stoichiometry of N and phosphorus (P) in soils and different plant functional groups, under both mown and unmown conditions. Results Historical N addition did not affect soil total and available N and P concentrations and stoichiometry, but significantly altered plant community composition. Plant nutrient concentrations and N:P ratios significantly differed among four plant functional groups. The concentrations and stoichiometric ratios of N and P between soils and plants were generally not correlated. The positive legacy effects of N addition on community N:P stoichiometry were caused by the biomass enhancement of tall bunchgrass, the functional group with the highest N:P ratios. Conclusions Changes in plant community composition instead of soil nutrient status were the main driver for the positive legacy effects of N enrichment on plant community stoichiometry. Given that the recovery of community composition after the cessation of N deposition is generally slow, our findings indicate that the legacy effects of N deposition on soil nutrient cycling would persist in long-term due to the importance of plant-mediated pathway.