title: Subalpine Pyrenees received higher nitrogen deposition than predicted by EMEP and CHIMERE chemistry-transport models.
abstract: Deposition of reactive nitrogen (N) from the atmosphere is expected to be the third greatest driver of biodiversity loss by the year 2100. Chemistry-transport models are essential tools to estimate spatially explicit N deposition but the reliability of their predictions remained to be validated in mountains. We measured N deposition and air concentration over the subalpine Pyrenees. N deposition was found to range from 797 to 1,463 mg N m(-2) year(-1). These values were higher than expected from model predictions, especially for nitrate, which exceeded the estimations of EMEP by a factor of 2.6 and CHIMERE by 3.6. Our observations also displayed a reversed reduced-to-oxidized ratio in N deposition compared with model predictions. The results highlight that the subalpine Pyrenees are exposed to higher levels of N deposition than expected according to standard predictions and that these levels exceed currently recognized critical loads for most high-elevation habitats. Our study reveals a need to improve the evaluation of N deposition in mountains which are home to a substantial and original part of the world's biodiversity.
authors.affiliation: 1] Université Toulouse 3 Paul Sabatier, CNRS, ENFA, UMR5174 Laboratoire Evolution &Diversité Biologique, 118 route de Narbonne 31062 Toulouse Cedex 9, France. [2] Centre d'Etudes Spatiales de la BIOsphère, 31401 Toulouse Cedex 9, France.
authors.forename: Marion
authors.initials: M
authors.lastname: Boutin
authors.affiliation: Centre d'Etudes Spatiales de la BIOsphère, 31401 Toulouse Cedex 9, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Lamaze
authors.affiliation: INERIS, Institut National de l'Environnement Industriel et des Risques, 60550 Verneuil-en-Halatte, France.
authors.forename: Florian
authors.initials: F
authors.lastname: Couvidat
authors.affiliation: Université Toulouse 3 Paul Sabatier, CNRS, ENFA, UMR5174 Laboratoire Evolution &Diversité Biologique, 118 route de Narbonne 31062 Toulouse Cedex 9, France.
authors.forename: André
authors.initials: A
authors.lastname: Pornon