Nitrogen deposition influences the response of Potentilla tanacetifolia to phosphorus addition

Phosphorus is an essential macronutrient for all living plants and plant production. Simultaneously, atmospheric nitrogen deposition also affects plant productivity at a global scale. However, few studies have investigated how plants respond to P addition while simultaneously considering N deposition. We investigated plant biomass, nutrient status and stoichiometric ratios on Potentilla tanacetifolia in response to P fertilization under contrasting N addition rates in a typical meadow steppe in Inner Mongolia, China. Aboveground biomass of P. tanacetifolia increased under increasing levels of P fertilization under conditions of N addition. However, there was no significant change in biomass when only phosphorus was added. Plant leaf and stem P concentrations increased linearly with P addition when there was no N addition. Our results suggest that increased plant P nutrition under P addition will not turn into plant growth enhancement unless N demands are also satisfied. Nitrogen addition significantly increased leaf N concentrations, and leaf and seed N: P ratios, when there was no P fertilization. Nevertheless, the effects of N addition were weakened, and eventually disappeared when P fertilization rates increased. This indicates that N-induced alterations of the plant nutrition status and stoichiometric ratios were P availability-dependent. Overall, our results suggest that multiple-nutrient constraints and their interactions must be considered when assessing plant nutrient and growth responses to nutrient enrichment