| 1. |
- Franz, D, et al.
(författare)
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Towards long-term standardised carbon and greenhouse gas observations for monitoring Europe´s terrestrial ecosystems: a review
- 2018
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Ingår i: International Agrophysics. - : Walter de Gruyter GmbH. - 0236-8722 .- 2300-8725. ; 32, s. 439-455
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Luyssaert, S., et al.
(författare)
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CO2 balance of boreal, temperate, and tropical forests derived from a global database
- 2007
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 13:12, s. 2509-2537
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Forskningsöversikt (refereegranskat)abstract
- Terrestrial ecosystems sequester 2.1 Pg of atmospheric carbon annually. A large amount of the terrestrial sink is realized by forests. However, considerable uncertainties remain regarding the fate of this carbon over both short and long timescales. Relevant data to address these uncertainties are being collected at many sites around the world, but syntheses of these data are still sparse. To facilitate future synthesis activities, we have assembled a comprehensive global database for forest ecosystems, which includes carbon budget variables (fluxes and stocks), ecosystem traits (e.g. leaf area index, age), as well as ancillary site information such as management regime, climate, and soil characteristics. This publicly available database can be used to quantify global, regional or biome-specific carbon budgets; to re-examine established relationships; to test emerging hypotheses about ecosystem functioning [e.g. a constant net ecosystem production (NEP) to gross primary production (GPP) ratio]; and as benchmarks for model evaluations. In this paper, we present the first analysis of this database. We discuss the climatic influences on GPP, net primary production (NPP) and NEP and present the CO2 balances for boreal, temperate, and tropical forest biomes based on micrometeorological, ecophysiological, and biometric flux and inventory estimates. Globally, GPP of forests benefited from higher temperatures and precipitation whereas NPP saturated above either a threshold of 1500 mm precipitation or a mean annual temperature of 10 degrees C. The global pattern in NEP was insensitive to climate and is hypothesized to be mainly determined by nonclimatic conditions such as successional stage, management, site history, and site disturbance. In all biomes, closing the CO2 balance required the introduction of substantial biome-specific closure terms. Nonclosure was taken as an indication that respiratory processes, advection, and non-CO2 carbon fluxes are not presently being adequately accounted for.
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| 3. |
- Poyatos, R., et al.
(författare)
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Global transpiration data from sap flow measurements: the SAPFLUXNET database
- 2021
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Ingår i: Earth System Science Data. - : Copernicus GmbH. - 1866-3508 .- 1866-3516. ; 13:6, s. 2607-2649
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Tidskriftsartikel (refereegranskat)abstract
- Plant transpiration links physiological responses of vegetation to water supply and demand with hydrological, energy, and carbon budgets at the land-atmosphere interface. However, despite being the main land evaporative flux at the global scale, transpiration and its response to environmental drivers are currently not well constrained by observations. Here we introduce the first global compilation of whole-plant transpiration data from sap flow measurements (SAPFLUXNET, https://sapfluxnet.creaf.cat/, last access: 8 June 2021). We harmonized and quality-controlled individual datasets supplied by contributors worldwide in a semi-automatic data workflow implemented in the R programming language. Datasets include sub-daily time series of sap flow and hydrometeorological drivers for one or more growing seasons, as well as metadata on the stand characteristics, plant attributes, and technical details of the measurements. SAPFLUXNET contains 202 globally distributed datasets with sap flow time series for 2714 plants, mostly trees, of 174 species. SAPFLUXNET has a broad bioclimatic coverage, with woodland/shrubland and temperate forest biomes especially well represented (80 % of the datasets). The measurements cover a wide variety of stand structural characteristics and plant sizes. The datasets encompass the period between 1995 and 2018, with 50 % of the datasets being at least 3 years long. Accompanying radiation and vapour pressure deficit data are available for most of the datasets, while on-site soil water content is available for 56 % of the datasets. Many datasets contain data for species that make up 90 % or more of the total stand basal area, allowing the estimation of stand transpiration in diverse ecological settings. SAPFLUXNET adds to existing plant trait datasets, ecosystem flux networks, and remote sensing products to help increase our understanding of plant water use, plant responses to drought, and ecohydrological processes. SAPFLUXNET version 0.1.5 is freely available from the Zenodo repository (https://doi.org/10.5281/zenodo.3971689; Poyatos et al., 2020a). The "sapfluxnetr" R package - designed to access, visualize, and process SAPFLUXNET data - is available from CRAN.
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| 4. |
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| 5. |
- Wingate, L., et al.
(författare)
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Interpreting canopy development and physiology using a European phenology camera network at flux sites
- 2015
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4189. ; 12:20, s. 5995-6015
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Tidskriftsartikel (refereegranskat)abstract
- Plant phenological development is orchestrated through subtle changes in photoperiod, temperature, soil moisture and nutrient availability. Presently, the exact timing of plant development stages and their response to climate and management practices are crudely represented in land surface models. As visual observations of phenology are laborious, there is a need to supplement long-term observations with automated techniques such as those provided by digital repeat photography at high temporal and spatial resolution. We present the first synthesis from a growing observational network of digital cameras installed on towers across Europe above deciduous and evergreen forests, grasslands and croplands, where vegetation and atmosphere CO2 fluxes are measured continuously. Using colour indices from digital images and using piecewise regression analysis of time series, we explored whether key changes in canopy phenology could be detected automatically across different land use types in the network. The piecewise regression approach could capture the start and end of the growing season, in addition to identifying striking changes in colour signals caused by flowering and management practices such as mowing. Exploring the dates of green-up and senescence of deciduous forests extracted by the piecewise regression approach against dates estimated from visual observations, we found that these phenological events could be detected adequately (RMSE < 8 and 11 days for leaf out and leaf fall, respectively). We also investigated whether the seasonal patterns of red, green and blue colour fractions derived from digital images could be modelled mechanistically using the PROSAIL model parameterised with information of seasonal changes in canopy leaf area and leaf chlorophyll and carotenoid concentrations. From a model sensitivity analysis we found that variations in colour fractions, and in particular the late spring 'green hump' observed repeatedly in deciduous broadleaf canopies across the network, are essentially dominated by changes in the respective pigment concentrations. Using the model we were able to explain why this spring maximum in green signal is often observed out of phase with the maximum period of canopy photosynthesis in ecosystems across Europe. Coupling such quasi-continuous digital records of canopy colours with co-located CO2 flux measurements will improve our understanding of how changes in growing season length are likely to shape the capacity of European ecosystems to sequester CO2 in the future.
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| 6. |
- Jourdan, F., et al.
(författare)
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High-precision dating of the Kalkarindji large igneous province, Australia, and synchrony with the Early-Middle Cambrian (Stage 4-5) extinction
- 2014
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Ingår i: Geology. - 0091-7613. ; 42:6, s. 543-546
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Tidskriftsartikel (refereegranskat)abstract
- The voluminous Kalkarindji flood basalts erupted in Australia during the Cambrian and covered >2 x 10(6) km(2). New U-Pb and Ar-40/Ar-39 age data from intrusive rocks and lava flows yielded statistically indistinguishable ages at ca. 511 Ma, suggesting a relatively brief emplacement for this province. A zircon age of 510.7 +/- 0.6 Ma shows that this province is temporally indistinguishable at the few-hundred-thousand-year level from the Early-Middle Cambrian (Stage 4-5) boundary age of 510 +/- 1 Ma, which marks the first severe extinction of the Phanerozoic and an extended marine anoxia period. Sulfur concentration measurements ranging from < 50 to 1900 mu g/g, and fractal analysis of extensive explosive volcanic breccias, suggest that blasts and phreatomagmatic explosions have contributed to injection of large amounts of sulfur into the stratosphere. In addition, magma intrusions in oil, gas, and sulfate deposits may have generated significant emission of CH4 and SO2 which, along with volcanic gases, would have combined to cause an oscillation of the climate and led to the Cambrian extinction.
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| 7. |
- Ong, Ken K., et al.
(författare)
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Pregnancy Insulin, Glucose, and BMI Contribute to Birth Outcomes in Nondiabetic Mothers
- 2008
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Ingår i: Diabetes Care. - : American Diabetes Association. - 0149-5992 .- 1935-5548. ; 31:11, s. 2193-2197
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE - We investigated the effects of normal variations in maternal glycemia on birth size and other birth outcomes. RESEARCH DESIGN AND METHODS - Women in two unselected birth cohorts, one retrospective (n = 3,158) and one prospective (n = 668), underwent an oral glucose challenge at 28 weeks of gestation. In the retrospective study, glycemia was linked to routine birth records. In the prospective study, offspring adiposity was assessed by skinfold thickness from birth to age 24 months. RESULTS - In the retrospective study, within the nondiabetic range (2.1-7.8 mmol/l), each 1 mmol/l rise in the mother's 60-min glucose level was associated with a (mean +/- SEM) 2.1 +/- 0.8% (P = 0.006) rise in absolute risk of assisted vaginal delivery, a 3.4 +/- 0.8% (P < 0.0001) rise in emergency cesarean delivery, a 3.1 +/- 0.7% (P < 0.0001) rise in elective cesarean delivery, and a 46 +/- 8 g (P < 0.0001) increase in offspring birth weight. in the prospective study, fetal macrosomia (birth weight >90th centile) was independently related to the mother's fasting glucose (odds ratio 2.61 per + 1 mmol/l [95% CI 1.15-5.93]) and prepregnancy BMI (1.10 per +1 kg/m(2) [1.04-1.18]). The mother's higher fasting glycemia (P = 0.004), lower insulin sensitivity (P = 0.01), and lower insulin secretion (P = 0.02) were independently related to greater offspring adiposity at birth. During postnatal follow-up, the correlation between the mother's glycemia and offspring adiposity disappeared by 3 months, whereas prepregnancy BMI was associated with offspring adiposity that was only apparent at 12 and 24 months (both P < 0.05). CONCLUSIONS - Prepregnancy BMI, pregnancy glycemia, insulin sensitivity, and insulin secretion all contribute to offspring adiposity and macrosomia and may be separate targets for intervention to optimize birth outcomes and later offspring health.
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