The FLUXNET2015 dataset provides ecosystem-scale data on CO 2 , water, and energy exchange between the biosphere and the atmosphere, and other meteorological and biological measurements, from 212 sites around the globe (over 1500 site-years, up to and including year 2014). These sites, independently managed and operated, voluntarily contributed their data to create global datasets. Data were quality controlled and processed using uniform methods, to improve consistency and intercomparability across sites. The dataset is already being used in a number of applications, including ecophysiology studies, remote sensing studies, and development of ecosystem and Earth system models. FLUXNET2015 includes derived-data products, such as gap-filled time series, ecosystem respiration and photosynthetic uptake estimates, estimation of uncertainties, and metadata about the measurements, presented for the first time in this paper. In addition, 206 of these sites are for the first time distributed under a Creative Commons (CC-BY 4.0) license. This paper details this enhanced dataset and the processing methods, now made available as open-source codes, making the dataset more accessible, transparent, and reproducible.

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Abstract. Globally, peat lands are considered to be a sink of CO 2 , but a source when drained. Additionally, wet peat lands are thought to emit considerable amounts of CH 4 and N 2 O. Hitherto, reliable and integrated estimates of emissions and emission factors for this type of land cover have been lacking and the effects of wetland restoration on methane emissions have been poorly quantified. In this paper we estimate the full greenhouse gas (GHG) balance of a restored natural peat land by determining the fluxes of CO 2 , CH 4 and N 2 O through atmosphere and water, while accounting for the different Global Warming Potentials (GWP's).The site is an abandoned agricultural peat meadow, which has been converted into a wetland nature reserve ten years ago, after which the water level was raised. GHG fluxes were measured continuously with an eddy covariance system (CO 2 ) and flux chamber measurements (CH 4 land and water. CO 2 emission has decreased significantly as result of the raised water table, while CH 4 fluxes have increased. In GWP's the area was a small net GHG sink given as CO 2 -equiv. of −86 g m −2 yr −1 (over a 100-year period).

Abstract. Carbon dioxide and methane fluxes were measured at a tundra site near Chokurdakh, in the lowlands of the Indigirka river in north-east Siberia. This site is one of the few stations on Russian tundra and it is different from most other tundra flux stations in its continentality. A suite of methods was applied to determine the fluxes of NEE, GPP, R eco and methane, including eddy covariance, chambers and leaf cuvettes. Net carbon dioxide fluxes were high compared with other tundra sites, with NEE=−92 g C m −2 yr −1 , which is composed of an R eco =+141 g C m −2 yr −1 and GPP=−232 g C m −2 yr −1 . This large carbon dioxide sink may be explained by the continental climate, that is reflected in low winter soil temperatures (−14 • C), reducing the respiration rates, and short, relatively warm summers, stimulating high photosynthesis rates. Interannual variability in GPP was dominated by the frequency of light limitation (R g <200 W m −2 ), whereas R eco depends most directly on soil temperature and time in the growing season, which serves as a proxy of the combined effects of active layer depth, leaf area index, soil moisture and substrate availability. The methane flux, in units of global warming potential, was +28 g C-CO 2 e m −2 yr −1 , so that the greenhouse gas balance was −64 g C-CO 2 e m −2 yr −1 . Methane fluxes depended only slightly on soil temperature and were highly sensitive to hydrological conditions and vegetation composition.

, an average for wet sites of 23.4 mg m À2 hr À1 , and an average for dry sites of 1.6 mg m À2 hr À1. Multilinear regression demonstrates that the methane flux depends on both water table and active layer thickness. However, these factors alone cannot explain the large floodplain methane fluxes. We hypothesize that the large fluxes from floodplain sites are caused by (1) higher primary productivity of the floodplain vegetation and a high plant-mediated transport of methane, and (2) enhanced supply of substrate for methanogens by sedimentation of particulate organic matter from flood water. Our results indicate that changes in discharge and organic matter transport of arctic rivers may have a considerable effect on arctic methane fluxes.