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Impact of atmospheric nitrogen deposition on the microbial
nitrogen cycle in an Arctic tundra soil

Human activities are a major source of atmospheric pollution and especially for nitrogen (N). N atmospheric pollution, by the way of the rain and the snow mainly, downfall on the ecosystems, increasing the input of N in whole ecosystems. This N input has many consequences, from the climate change, marine and freshwater eutrophication, lost of plant biodiversity, to human health threats. In some area in the north hemisphere the deposition rate is more than an order of magnitude greater than in pre-industrial times. Thus, effects on ecosystem N cycle are high and could be greater in ecosystems with a low-N availability, like temperate forest or tundra ecosystems. Our research fit into a European project, NSINK, which study the impact of the nitrogen downfall on the nitrogen cycle in the high Arctic (Svalbard islands) at different scale: aquatic ecosystems (lake, ocean), terrestrial ecosystems (plant, soil, snow) and atmosphere. The overall aim is to know more about the nitrogen dynamic in the high Arctic. My research focus on the impact of the nitrogen deposition on the microorganisms (bacteria and fungi) within the soil. Microorganisms within the soil play a key role in the nitrogen cycle, regulating many processes and determine ecosystem N availability. The biodiversity, the biological functions (atmospheric N fixation, denitrification, nitrification, annamox), density of the microorganisms and soil chemical and physical characteristics (e.g. pH, dissolved in/organic N) will be measure over three years in field works in an Arctic tundra soil after simulated N deposition.