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. [ABSTRACT FROM AUTHOR]