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Atmospheric nitrate deposition on subalpine meadows of the Lautaret pass

Abstract : Increasing rates of atmospheric nitrate (NO3-atm) deposition in nutrients poor mountainous regions have led to critical changes in nitrogen (N) availability, with consequences on biodiversity (plants, microbes), soils N turnover, and water nutrients status. This will ultimately affect human populations through the loss of critical ecosystem services (e.g., provision of clean freshwater, erosion control, biodiversity). If the impacts of NO3-atm deposition to N-limited basins are now well documented, little is known about the processes driving NO3-atm retention in subalpine ecosystems. In this context, new tools are necessary to better understand the fate of NO3-atm in mountains and to predict the mid and long-term ecological consequences of increasing NO3-atm deposition. This work uses a high-resolution multi-isotopic technique combining 17O, 18O and 15N signatures of NO3- in the different subalpine compartments to understand the temporal and spatial evolution of NO3-atm partitioning in a subalpine watershed of the French Alps. Subalpine streams elevated year-round exports of NO3-atm suggest that the watersheds are kinetically N saturated, especially after snowmelt. The isotopic composition of NO3- in freshwaters also points at the rapid processing of snow ammonium, confirming that snowmelt is “hot moment” for the N cycle in seasonally snow-covered catchments. The monitoring of soils reveals varying NO3-atm proportions depending on the land management treatments and implied biotic and abiotic characteristics. Two dominant subalpine plants showed high proportions of NO3-atm in organs acquired by both root and foliar uptake. These scientific breakthroughs will ultimately lead to a better understanding of how NO3-atm deposition affects the environment.
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Submitted on : Tuesday, February 13, 2018 - 3:28:12 PM
Last modification on : Tuesday, October 6, 2020 - 4:17:02 PM
Long-term archiving on: : Saturday, May 5, 2018 - 3:34:07 PM

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  • HAL Id : tel-01708350, version 1

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Ilann Bourgeois. Atmospheric nitrate deposition on subalpine meadows of the Lautaret pass. Environmental and Society. Université Grenoble Alpes, 2017. English. ⟨NNT : 2017GREAV059⟩. ⟨tel-01708350⟩

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