Effects of nitrogen addition on plant manganese nutrition in a temperate steppe

Background Manganese (Mn) is an essential nutrient for plant growth and a key factor driving litter decomposition. Nitrogen (N) deposition is expected to enhance soil Mn availability via soil acidification, and subsequently to increase plant Mn concentrations. Aims We aimed to quantify the responses of Mn concentrations in green and senesced shoots at both species and community levels to N addition, and determine whether N addition would decrease Mn retranslocation efficiency during plant senescence. Methods We examined the changes of Mn concentrations in soil and in green and senesced shoots of all plant species across multiple N addition rates ranging from 0 to 50 g N m(-2) y(-1) in a temperate steppe after six years treatments. Plant Mn retranslocation efficiency were quantified at species, life form, and community levels. The relationship between plant Mn nutritional parameters and soil Mn availability across the N addition gradient was analyzed. Results There were positive correlations between plant Mn concentrations and N addition rates for most species. Relative to the control plots, community-level mean Mn concentration in green and senesced shoots in the plots received the highest level of N addition increased by 137.50% (from 0.19 mg kg(-1) to 0.08 mg kg(-1)) and 187.50% (from 0.23 mg kg(-1) to 0.08 mg kg(-1)), respectively. There was no correlation between Mn retranslocation efficiency and N addition rates at species, life form and community levels. Plant Mn status was weakly correlated with soil Mn concentrations for most species. Conclusions Plant Mn retranslocation showed conserved responses to increasing N addition rates, which would be an adaptive strategy for plants in face of N-induced higher soil Mn availability.