Nutrient resorption and coupling relationships in two plant species with sulfur addition: A two-year study in a meadow

Purpose Sulfur (S) deposition as a global change issue causes worldwide soil acidification, nutrient mobilization and marked changes in plant nutrition. Here, we hypothesize that S deposition would reduce leaf nutrient resorption with this effect varies with yearly fluctuations in precipitation. Methods In a semiarid meadow exposed to S addition, we determined nitrogen (N), phosphorus (P) and S concentrations and nutrient resorption efficiencies (NuRE) of a grass and a sedge across two years with contrasting precipitation difference. Results Concentrations of N, P, and S in green and senescent leaves generally increased with S addition across the two years, with the exception of N and P concentrations in green leaves of the grass that showed no response or even decreased with S addition. The coupling relationships between N and P concentrations were stronger in senescent leaves than in green leaves in the wet year. Leaf NuRE decreased with S addition across the two years as driven by increasing soil N, P and S availability. However, NuRE was higher in the wet year due to lower soil nutrient availability herein as compared with the dry year. Conclusions This study provides new evidence on the role of nutrient resorption in tightening stoichiometric N:P relationships, and that plant nutrient resorption may be favored by higher precipitation to sharpen its tradeoff with soil nutrient availability.