Towards long-term standardised carbon and greenhouse gas observations for monitoring Europe's terrestrial ecosystems : a review

Research infrastructures play a key role in launching a new generation of integrated long-term, geographically distributed observation programmes designed to monitor climate change, better understand its impacts on global ecosystems, and evaluate possible mitigation and adaptation strategies. The pan-European Integrated Carbon Observation System combines carbon and greenhouse gas (GHG; CO2, CH4, N2O, H2O) observations within the atmosphere, terrestrial ecosystems and oceans. High-precision measurements are obtained using standardised methodologies, are centrally processed and openly available in a traceable and verifiable fashion in combination with detailed metadata. The Integrated Carbon Observation System ecosystem station network aims to sample climate and land-cover variability across Europe. In addition to GHG flux measurements, a large set of complementary data (including management practices, vegetation and soil characteristics) is collected to support the interpretation, spatial upscaling and modelling of observed ecosystem carbon and GHG dynamics. The applied sampling design was developed and formulated in protocols by the scientific community, representing a trade-off between an ideal dataset and practical feasibility. The use of open-access, high-quality and multi-level data products by different user communities is crucial for the Integrated Carbon Observation System in order to achieve its scientific potential and societal value.Peer reviewe

The FLUXNET2015 dataset and the ONEFlux processing pipeline for eddy covariance data

The FLUXNET2015 dataset provides ecosystem-scale data on CO2, 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.Peer reviewe

Dynamics and mechanisms of volatile organic compound exchanges in a winter wheat field

The understanding of biogenic volatile organic compound (BVOC) exchanges has become a key scientific issue because of their high reactivity and their impact in the atmosphere. However, so far, few studies have focused on BVOCs exchanged by agricultural species, and in particular by winter wheat, despite this species being the leading worldwide crop in terms of harvested area. This study for the first time investigated BVOC exchanges from winter wheat during most developmental stages of the plant. Fluxes were measured in Belgium at the ecosystem-scale using the disjunct eddy covariance by mass scanning technique, and a proton-transfer-reaction mass spectrometer for BVOC ambient mixing ratio measurements. As is usually observed for crops and grasses, the winter wheat field emitted mainly methanol, although bi-directional exchanges were observed. The second most exchanged compound was acetic acid which was captured during the entire growing season. Bi-directional exchanges of acetaldehyde and acetone were also reported. Terpene exchanges were 22 times smaller than oxygenated VOC (OVOC) exchanges. For all compounds, the exchanges were the most pronounced at the end of the growing season, i.e., under warm, dry and sunny conditions. Senescence-induced emissions were furthermore observed for methanol and acetaldehyde. For all investigated OVOCs, the exchanges very likely originated from both the soil and the plants. Despite their mixed origin, the MEGAN (Model of Emissions of Gases and Aerosols from Nature) v2.1 up-scaling model could adequately reproduce the methanol, acetaldehyde and acetone exchanges measured at this site during the mature and senescence phases of the plant, when the standard emission factor and the leaf age factor were adapted based on the measurements. In contrast, the model failed to reproduce the measured acetic acid exchanges. When the standard emission factor values currently assigned in MEGAN were applied, however, the exchanges were largely over-estimated for all compounds. © 2019 Elsevier Lt

The FLUXNET2015 dataset and the ONEFlux processing pipeline for eddy covariance data

Abstract The FLUXNET2015 dataset provides ecosystem-scale data on CO2, 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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