Altitudinal and Latitudinal Variations of Snowpack N Concentration over the French Alps
The aim of the study was to get a picture of the geographical variations of N deposition in the snowpack over the French Alps. Using a collaborative research approach, we sampled 139 snow cores along 27 altitudinal gradients between 1100 and 3300 m a.s.l. in the end of February 2013, at maximum snowpack accumulation. Comparing the snowpack composition at a fixed elevation (2000 m), we observed a clear gradient of increasing nitrate concentrations from the south to the north of the massif. This gradient was less marked for NH4. Mineral N loads were 100–500 g ha−1 in the south and 100–1000 g ha−1 in the north. For several massifs of the Northern Alps, nitrate and ammonium concentrations decreased as elevation increased. This altitudinal variation was not observed (or less) in the south. The weighted average inorganic N concentrations measured in bulk precipitation during the same winter at three monitoring sites at medium altitude (1000–1300 m) were about twice higher than the measured concentrations in the snowpack at 2000 m. We suggest that these altitudinal and latitudinal gradients should be taken into account to model the deposition of N at high altitude and to analyze the relative effects of N deposition on remote alpine ecosystems.
KeywordsN deposition Snowpack Elevation French Alps Collaborative research
We are very grateful to the group of students (Jim Felix Faure, Gabin Piton, Josepha Bleu), scientists (Jean Marcel Dorioz, Pascal Pernet, Pierre Faivre, Christian Crouzet, Sylvie Guittonneau), ecologists, and park rangers (Anne Delestrade, Julien Heuret, Patrick Perret, Fabrice Anthoine and Geoffrey Garcel) who, in addition to the authors, sampled the snowpack cautiously according to the protocol. We thank Jean Christophe Clement (USMB) for useful comments on the manuscript.
This work was financed by a grant of the Université Savoie-Mont Blanc.
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