Imbalanced stoichiometric patterns in foliar nutrient resorption response to N and P addition in grazing alpine grassland

Although the effect of nutrient availability on plant nutrient resorption has been extensively studied, the influence of nutrient addition on the coupled biogeochemical cycling of N and phosphorus (P) remains unclear. Studies on how increased nutrient addition affects the imbalance between N and P resorption are limited. We investigated the influence of a wide nutrient addition gradient on the foliar nutrient resorption of dominant grass, Stipa capillata, in grazing alpine grassland. We applied seven addition levels for N (0.5-24 g N.m(-)(2) yr(-1)) and P (0.05-3.2 g P.m(-2)yr(-1)), collected plant and soil samples, and calculated plant foliar nutrient resorption. Results showed that N and P resorption efficiencies decreased with increasing N addition and N:P resorption ratios. However, N and P resorption efficiencies significantly decreased but N:P resorption ratios increased with the P addition gradient. Moreover, the N:P resorption ratios were negatively correlated with senesced foliar N:P ratios. Our findings suggest that N and P responses to nutrient fertilization are tightly coupled at the intraspecific level. Hence, plants show different tendencies of resorbing nutrient with N and P addition, leading to imbalance between N and P. Plant stoichiometric patterns were regulated by the nutrient status of senesced foliar. This study reveals that nutrient additions accelerate ecosystem N and P cycling, N and P cycles are coupled, but their resorptions are imbalanced. The imbalanced stoichiometric patterns in foliar nutrient resorption response to nutrient enrichment provide insights into N and P cycling under human-driven nutrient imbalance scenarios.