Legacy effects of nitrogen deposition on plant nutrient stoichiometry in a temperate grassland

Abstract

Nitrogen (N) deposition has negative consequences for plant communities and ecosystem functioning. Nitrogen deposition is declining or is projected to decline in many regions due to the reduction of N-compound emissions. It remains unknown whether the cessation of N deposition will have legacy effects on plant nutrient stoichiometry. If there are stoichiometric legacy effects at the community-level from prior N enrichment, the contribution of changes in community composition relative to the stoichiometric responses of individual functional groups in driving these changes is unknown. We measured plant N:P ratio at both functional group level and community level in a temperate steppe in three consecutive years following cessation of a 7-year N addition experiment with a wide-range of total amount added N in which the total amount of N added ranged from 0 to 350 g m−2. The total amount of N addition was positively correlated with tall rhizomatous grass productivity and negatively correlated with tall bunchgrass productivity. Plant N:P ratios at both functional group and community levels did not change across N addition gradient. Community composition shifts contributed less than intra-group variation to the total variation of community level nutrient status in response to historic N addition. Our results indicated that biological N:P imbalance in response to N deposition can be rapidly ameliorated after the cessation of N deposition. Such legacy effects of N deposition on plant nutrient status are largely driven by the changes of nutrient status of individual plants instead of N-induced shifts in community composition.