The fate of nitrogen inputs in a warmer alpine treeline ecosystem: a 15 N labelling study

Summary Global warming may accelerate nitrogen (N) transformations in the soil, with potentially large effects in N-poor high-elevation ecosystems. To gain insight into the partitioning of inorganic and organic N inputs within the plant–soil system and how warming influences these patterns, we applied a 15N label (15NH4Cl or 15N-glycine) shortly after snowmelt during the sixth year of experimental soil warming (+4 °C) at treeline in the Swiss Alps. Seven weeks after labelling, approximately 60% of the applied label remained in the soil organic layer to 10 cm depth, whereas label recovery summed over all measured plant pools was