Responses of nutrient concentrations and stoichiometry of senesced leaves in dominant plants to nitrogen addition and prescribed burning in a temperate steppe

The quality of senesced leaves is a strong driver for litter decomposition and nutrient cycling in terrestrial ecosystems. The effects of global change factors and ecosystem management strategies on nutrients and stoichiometry of mature leaves have been well established. In contrast, we still know little about their effects on the quality of senesced leaves, which would be different from that of mature leaves due to the occurrence of nutrient resorption during leaf senescence. We examined the effects of nitrogen (N) addition (5.25 g N m−2 yr−1), prescribed fire (with four frequencies, including no burning and burning every 1, 2, 4 years), and their interactions on N and phosphorus (P) concentrations and N:P ratios in senesced leaves of five dominant species in a temperate steppe of northern China. Nutrient concentrations and N:P ratios of senesced leaves varied substantially among the five species. Nitrogen addition increased N concentrations and N:P ratios but had no significant effect on P concentrations. Fire significantly increased N and P concentrations and N:P ratios in senesced leaves across all species. The effects of fire depended on its frequency. There was no interaction between N addition and fire in affecting nutrient concentrations and stoichiometry of senesced leaves. Our results suggested that N addition and fire can potentially alter litter quality by changing senesced leaves nutrient status and stoichiometric ratios, with an indirect effect on litter decomposition and ecosystem nutrient cycling in the grassland ecosystems.