Greenhouse gas flux measurements from agricultural sites within the Swiss FluxNet network

The Swiss FluxNet provides ecosystem scale flux data for the major land use types in Switzerland. While the current station network includes long-term eddy covariance flux measurements from two forest sites (mixed deciduous forest Lägeren and evergreen spruce forest Davos), three permanent grassland sites (Chamau, Früebüel and Alp Weissenstein) as well as three cropland sites (Oensingen, Tänikon and Forel) complement the network. In addition, the measurements cover an altitude gradient ranging from 393 to 1978 m.a.s.l. Carbon dioxide (CO 2 ) and water vapor (H 2 O) fluxes are measured continuously at all sites, while nitrous oxide (N 2 O) and methane (CH 4 ) fluxes are also quantified at some sites. Currently, 123 site-years of data are openly shared with FLUXNET. Ancillary meteorological and soil microclimate data are collected continuously as well; plant growth is routinely monitored at all agricultural sites, i.e., grasslands and croplands. Together with the management data, such continuous measurements allow integrated multi-year (Feigenwinter et al. 2023b) and multi-site (Zeeman et al. 2010) comparisons, identification of drivers for greenhouse gas (GHG) fluxes (Maier et al. 2022, Feigenwinter et al. 2023a), quantification of C sequestration (Emmel et al. 2018), as well as assessments of management practices towards sustainable agriculture (Fuchs et al. 2018). Here, we will present long-term CO 2 fluxes (since 2004) as well as CH 4 and N 2 O fluxes measured at the six agricultural Swiss FluxNet sites, i.e., three permanent grasslands and three croplands with their typical Swiss crop rotation. Moreover, the contribution of abiotic and biotic drivers to intra- and interseasonal variations in GHG fluxes will be discussed, potential trade-offs among climate mitigation goals identified, and the importance of management information emphasized. We encourage other research teams to use the open-access dataset, growing annually, and seek collaboration in integrated flux measurements worldwide.