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.

Net ecosystem–atmosphere exchange of CO2 (NEE) was measured in two boreal bogs during the snow‐free periods of 1998, 1999 and 2000. The two sites were located in European Russia (Fyodorovskoye), and in central Siberia (Zotino). Climate at both sites was generally continental but with more extreme summer–winter gradients in temperature at the more eastern site Zotino. The snow‐free period in Fyodorovskoye exceeded the snow‐free period at Zotino by several weeks. Marked seasonal and interannual differences in NEE were observed at both locations, with contrasting rates and patterns. Amongst the most important contrasts were: (1) Ecosystem respiration at a reference soil temperature was higher at Fyodorovskoye than at Zotino. (2) The diurnal amplitude of summer NEE was larger at Fyodorovskoye than at Zotino. (3) There was a modest tendency for maximum 24 h NEE during average rainfall years to be more negative at Zotino (−0.17 versus −0.15 mol m−2 d−1), suggesting a higher productivity during the summer months. (4) Cumulative net uptake of CO2 during the snow‐free period was strongly related to climatic differences between years. In Zotino the interannual variability in climate, and also in the CO2 balance during the snow‐free period, was small. However, at Fyodorovskoye the bog was a significant carbon sink in one season and a substantial source for CO2‐C in the next, which was below‐average dry. Total snow‐free uptake and annual estimates of net CO2‐C uptake are discussed, including associated uncertainties.

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Energy and latent heat fluxes lambdaE were measured over ombrotrophic bogs in European Russia (Fyodorovskoye) and in central Siberia (Zotino) using the eddy covariance technique, as part of the EuroSiberian Carbonflux Project. The study covered most of the snowfree periods in 1998, 1999 and 2000; in addition some data were also collected under snow in early spring and late autumn 1999 and 2000. The snowfree period in Europian Russia exceeds the snowfree period in central Siberia by nearly 10 weeks. Marked seasonal and interannual differences in temperatures and precipitation, and hence energy partitioning, were observed at both sites. At both bogs latent heat fluxes (lambdaE) exceeded sensible heat fluxes (H) during most of the snowfree period: maximum lambdaE were between 10 and 12 MJ m(-2) d(-1) while maximum H were between 3 and 5 MJ m(-2) d(-1). There was a tendency towards higher Bowen ratios at Fyodorovskoye. Net radiation was the most influential variable that regulated daily evaporation rates, with no obvious effects due to surface dryness during years with exceptionally dry summers. Total snowfree evaporation at Fyodorovskoye (320 mm) exceeded totals at Zotino (280 mm) by 15%. At the former site, evaporation was equal to or less than precipitation, contrasting the Zotino observations, where summer evaporation was distinctly higher than precipitation. During the entire observation period evaporation rates were less than 50% of their potential rate. These data suggest a strong 'mulching' effect of a rapidly drying peat surface on total evaporation, despite the substantial area of free water surfaces during parts of the year. This effect of surface dryness was also observed as close atmospheric coupling