Response of leaf, sheath and stem nutrient resorption to 7 years of N addition in freshwater wetland of Northeast China.

Background and Aims: Increased N availability induced by agricultural fertilization applications and atmospheric N deposition may affect plant nutrient resorption in temperate wetlands. However, the relationship between nutrient resorption and N availability is still unclear, and most studies have focused on leaf nutrient resorption only. The aim of our study was to examine the response of leaf and non-leaf organ nutrient resorption to N enrichment in a temperate freshwater wetland. Methods: We conducted a 7-year N addition experiment to investigate the effects of increased N loading on leaf, sheath and stem nutrient (N and P) resorption of two dominant species ( Deyeuxia angustifolia and Glyceria spiculosa) in a freshwater marsh in the Sanjiang Plain, Northeast China. Results: Our results showed that, for both leaf and non-leaf organs (sheath and stem), N addition decreased N resorption proficiency and hence increased litter N concentration. Moreover, the magnitude of N addition effect on N resorption proficiency varied with fertilization rates for D. angustifolia sheaths and stems, and G. spiculosa leaves. However, increased N loading produced inconsistent impacts on N and P resorption efficiencies and P resorption proficiency, and the effects only varied with species and plant organs. In addition, N enrichment increased litter mass and altered litter allocation among leaf, sheath and stem. Conclusions: Our results highlight that leaf and non-leaf organs respond differentially to N addition regarding N and P resorption efficiencies and P resorption proficiency, and also suggest that N enrichment in temperate freshwater wetlands would alter plant internal nutrient cycles and increase litter quality and quantity, and thus substantially influence ecosystem carbon and nutrient cycles. [ABSTRACT FROM AUTHOR]