Spatio-temporal trends of nitrogen deposition and climate effects on Sphagnum productivity in European peatlands

To quantify potential nitrogen (N) deposition impacts on peatland carbon (C) uptake, we explored temporal and spatial trends in N deposition and climate impacts on the production of the key peat forming functional group (Sphagnum mosses) across European peatlands for the period 1900–2050. Using a modelling approach we estimated that between 1900 and 1950 N deposition impacts remained limited irrespective of geographical position. Between 1950 and 2000 N deposition depressed production between 0 and 25% relative to 1900, particularly in temperate regions. Future scenarios indicate this trend will continue and become more pronounced with climate warming. At the European scale, the consequences for Sphagnum net C-uptake remained small relative to 1900 due to the low peatland cover in high-N areas. The predicted impacts of likely changes in N deposition on Sphagnum productivity appeared to be less than those of climate. Nevertheless, current critical loads for peatlands are likely to hold under a future climate. •We model the effect of N deposition combined with climate on production of Sphagnum between 1900 and 2050.•Spatially explicit projections are indicated on an updated European peatland distribution map.•Results stress the vulnerability of temperate Sphagnum peatlands to current and future N deposition.•Future impacts of N deposition on Sphagnum productivity likely depend more on climate change than on N deposition rate. Temperate Sphagnum peatlands are vulnerable to current and future N deposition and current critical loads for peatlands are likely to hold under a future climate.