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Biosphere-atmosphere exchange of reactive nitrogen and greenhouse gases at the NitroEurope core flux measurement sites: Measurement strategy and first data sets

Skiba, U., Drewer, J., Tang, Y.S., van Dijk, N., Helfter, C., Nemitz, E., Famulari, D., Cape, J.N., Jones, S.K., Twigg, M., Pihlatie, M., Vesala, T., Larsen, K.S., Carter, M.S., Ambus, P., Ibrom, A., Beier, C., Hensen, A., Frumau, A., Erisman, J.W., Brüggemann, N., Gasche, R., Butterbach-Bahl, K., Neftel, A., Spirig, C., Horvath, L., Freibauer, A., Cellier, P., Laville, P., Loubet, B., Magliulo, E., Bertolini, T., Seufert, G., Andersson, M., Manca, G., Laurila, T., Aurela, M., Lohila, A., Zechmeister-Boltenstern, S., Kitzler, B., Schaufler, G., Siemens, J., Kindler, R., Flechard, C., Sutton, M.A.
Agriculture, ecosystems & environment 2009 v.133 no.3-4 pp. 139-149
nitrogen, greenhouse gases, biogeochemical cycles, soil-plant-atmosphere interactions, temperate forests, grasslands, agricultural land, wetlands, spatial variation, temporal variation, nitrous oxide, methane, carbon dioxide, measurement, atmospheric deposition, leaching, vegetation, plant litter, soil biology, land use, land management
The NitroEurope project aims to improve understanding of the nitrogen (N) cycle at the continental scale and quantify the major fluxes of reactive N by a combination of reactive N measurements and modelling activities. As part of the overall measurement strategy, a network of 13 flux 'super sites' (Level-3) has been established, covering European forest, arable, grassland and wetland sites, with the objective of quantifying the N budget at a high spatial resolution and temporal frequency for 4.5 years, and to estimate greenhouse gas budgets (N₂O, CH₄ and CO₂). These sites are supported by a network of low-cost flux measurements (Level-2, 9 sites) and a network to infer reactive N fluxes at 58 sites (Level-1), for comparison with carbon (C) flux measurements. Measurements at the Level-3 sites include high resolution N₂O, NO (also CH₄, CO₂) fluxes, wet and dry N deposition, leaching of N and C and N transformations in plant, litter and soil. Results for the first 11 months (1.8.2006 to 30.6.2007) suggest that the grasslands are the largest source of N₂O, that forests are the largest source of NO and sink of CH₄ and that N deposition rates influence NO and N₂O fluxes in non-agricultural ecosystems. The NO and N₂O emission ratio is influenced by soil type and precipitation. First budgets of reactive N entering and leaving the ecosystem and of net greenhouse gas exchange are outlined. Further information on rates of denitrification to N₂ and biological N₂ fixation is required to complete the N budgets for some sites. The quantitative roles played by CO₂, N₂O and CH₄ in defining net greenhouse gas exchange differ widely between ecosystems depending on the interactions of climate, soil type, land use and management.