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Sökning: WFRF:(van Geel J.)

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1.
  • Charman, D. J., et al. (författare)
  • Climate-related changes in peatland carbon accumulation during the last millennium
  • 2013
  • Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4189. ; 10:2, s. 929-944
  • Tidskriftsartikel (refereegranskat)abstract
    • Peatlands are a major terrestrial carbon store and a persistent natural carbon sink during the Holocene, but there is considerable uncertainty over the fate of peatland carbon in a changing climate. It is generally assumed that higher temperatures will increase peat decay, causing a positive feedback to climate warming and contributing to the global positive carbon cycle feedback. Here we use a new extensive database of peat profiles across northern high latitudes to examine spatial and temporal patterns of carbon accumulation over the past millennium. Opposite to expectations, our results indicate a small negative carbon cycle feedback from past changes in the long-term accumulation rates of northern peatlands. Total carbon accumulated over the last 1000 yr is linearly related to contemporary growing season length and photosynthetically active radiation, suggesting that variability in net primary productivity is more important than decomposition in determining long-term carbon accumulation. Furthermore, northern peatland carbon sequestration rate declined over the climate transition from the Medieval Climate Anomaly (MCA) to the Little Ice Age (LIA), probably because of lower LIA temperatures combined with increased cloudiness suppressing net primary productivity. Other factors including changing moisture status, peatland distribution, fire, nitrogen deposition, permafrost thaw and methane emissions will also influence future peatland carbon cycle feedbacks, but our data suggest that the carbon sequestration rate could increase over many areas of northern peatlands in a warmer future.
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2.
  • Gallego-Sala, Angela V., et al. (författare)
  • Latitudinal limits to the predicted increase of the peatland carbon sink with warming
  • 2018
  • Ingår i: Nature Climate Change. - : Springer Science and Business Media LLC. - 1758-678X .- 1758-6798. ; 8:10, s. 907-
  • Tidskriftsartikel (refereegranskat)abstract
    • The carbon sink potential of peatlands depends on the balance of carbon uptake by plants and microbial decomposition. The rates of both these processes will increase with warming but it remains unclear which will dominate the global peatland response. Here we examine the global relationship between peatland carbon accumulation rates during the last millennium and planetary-scale climate space. A positive relationship is found between carbon accumulation and cumulative photosynthetically active radiation during the growing season for mid- to high-latitude peatlands in both hemispheres. However, this relationship reverses at lower latitudes, suggesting that carbon accumulation is lower under the warmest climate regimes. Projections under Representative Concentration Pathway (RCP)2.6 and RCP8.5 scenarios indicate that the present-day global sink will increase slightly until around AD 2100 but decline thereafter. Peatlands will remain a carbon sink in the future, but their response to warming switches from a negative to a positive climate feedback (decreased carbon sink with warming) at the end of the twenty-first century.
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3.
  • Loisel, Julie, et al. (författare)
  • A database and synthesis of northern peatland soil properties and Holocene carbon and nitrogen accumulation
  • 2014
  • Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 24:9, s. 1028-1042
  • Tidskriftsartikel (refereegranskat)abstract
    • Here, we present results from the most comprehensive compilation of Holocene peat soil properties with associated carbon and nitrogen accumulation rates for northern peatlands. Our database consists of 268 peat cores from 215 sites located north of 45 degrees N. It encompasses regions within which peat carbon data have only recently become available, such as the West Siberia Lowlands, the Hudson Bay Lowlands, Kamchatka in Far East Russia, and the Tibetan Plateau. For all northern peatlands, carbon content in organic matter was estimated at 42 +/- 3% (standard deviation) for Sphagnum peat, 51 +/- 2% for non-Sphagnum peat, and at 49 +/- 2% overall. Dry bulk density averaged 0.12 +/- 0.07 g/cm(3), organic matter bulk density averaged 0.11 +/- 0.05 g/cm(3), and total carbon content in peat averaged 47 +/- 6%. In general, large differences were found between Sphagnum and non-Sphagnum peat types in terms of peat properties. Time-weighted peat carbon accumulation rates averaged 23 +/- 2 (standard error of mean) g C/m(2)/yr during the Holocene on the basis of 151 peat cores from 127 sites, with the highest rates of carbon accumulation (25-28 g C/m(2)/yr) recorded during the early Holocene when the climate was warmer than the present. Furthermore, we estimate the northern peatland carbon and nitrogen pools at 436 and 10 gigatons, respectively. The database is publicly available at https://peatlands.lehigh.edu.
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  • Trondman, Anna-Kari, et al. (författare)
  • Pollen-based quantitative reconstructions of Holocene regional vegetation cover (plant-functional types and land-cover types) in Europe suitable for climate modelling
  • 2015
  • Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 21:2, s. 676-697
  • Tidskriftsartikel (refereegranskat)abstract
    • We present quantitative reconstructions of regional vegetation cover in north-western Europe, western Europe north of the Alps, and eastern Europe for five time windows in the Holocene [around 6k, 3k, 0.5k, 0.2k, and 0.05k calendar years before present (bp)] at a 1 degrees x1 degrees spatial scale with the objective of producing vegetation descriptions suitable for climate modelling. The REVEALS model was applied on 636 pollen records from lakes and bogs to reconstruct the past cover of 25 plant taxa grouped into 10 plant-functional types and three land-cover types [evergreen trees, summer-green (deciduous) trees, and open land]. The model corrects for some of the biases in pollen percentages by using pollen productivity estimates and fall speeds of pollen, and by applying simple but robust models of pollen dispersal and deposition. The emerging patterns of tree migration and deforestation between 6k bp and modern time in the REVEALS estimates agree with our general understanding of the vegetation history of Europe based on pollen percentages. However, the degree of anthropogenic deforestation (i.e. cover of cultivated and grazing land) at 3k, 0.5k, and 0.2k bp is significantly higher than deduced from pollen percentages. This is also the case at 6k in some parts of Europe, in particular Britain and Ireland. Furthermore, the relationship between summer-green and evergreen trees, and between individual tree taxa, differs significantly when expressed as pollen percentages or as REVEALS estimates of tree cover. For instance, when Pinus is dominant over Picea as pollen percentages, Picea is dominant over Pinus as REVEALS estimates. These differences play a major role in the reconstruction of European landscapes and for the study of land cover-climate interactions, biodiversity and human resources.
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5.
  • Goni, Maria Fernanda Sanchez, et al. (författare)
  • The ACER pollen and charcoal database : a global resource to document vegetation and fire response to abrupt climate changes during the last glacial period
  • 2017
  • Ingår i: Earth System Science Data. - : Copernicus GmbH. - 1866-3508 .- 1866-3516. ; 9:2, s. 679-695
  • Tidskriftsartikel (refereegranskat)abstract
    • Quaternary records provide an opportunity to examine the nature of the vegetation and fire responses to rapid past climate changes comparable in velocity and magnitude to those expected in the 21st-century. The best documented examples of rapid climate change in the past are the warming events associated with the Dansgaard-Oeschger (D-O) cycles during the last glacial period, which were sufficiently large to have had a potential feedback through changes in albedo and greenhouse gas emissions on climate. Previous reconstructions of vegetation and fire changes during the D-O cycles used independently constructed age models, making it difficult to compare the changes between different sites and regions. Here, we present the ACER (Abrupt Climate Changes and Environmental Responses) global database, which includes 93 pollen records from the last glacial period (73-15 ka) with a temporal resolution better than 1000 years, 32 of which also provide charcoal records. A harmonized and consistent chronology based on radiometric dating (C-14, U-234/Th-230, optically stimulated luminescence (OSL), Ar-40/Ar-39-dated tephra layers) has been constructed for 86 of these records, although in some cases additional information was derived using common control points based on event stratigraphy. The ACER database compiles metadata including geospatial and dating information, pollen and charcoal counts, and pollen percentages of the characteristic biomes and is archived in Microsoft Access (TM) at https://doi. org/10.1594/PANGAEA. 870867.
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6.
  • Luttik, Marie Louise A., et al. (författare)
  • Long-term follow-up in optimally treated and stable heart failure patients: primary care vs. heart failure clinic. Results of the COACH-2 study
  • 2014
  • Ingår i: European Journal of Heart Failure. - : Oxford University Press (OUP): Policy B / Wiley: 12 months. - 1388-9842 .- 1879-0844. ; 16:11, s. 1241-1248
  • Tidskriftsartikel (refereegranskat)abstract
    • AimsIt has been suggested that home-based heart failure (HF) management in primary care may be an alternative to clinic-based management in HF patients. However, little is known about adherence to HF guidelines and adherence to the medication regimen in these home-based programmes. The aim of the current study was to determine whether long-term follow-up and treatment in primary care is equally effective as follow-up at a specialized HF clinic in terms of guideline adherence and patient adherence, in HF patients initially managed and up-titrated to optimal treatment at a specialized HF clinic. Methods and resultsWe conducted a multicentre, randomized, controlled study in 189 HF patients (62% male, age 72 11 years), who were assigned to follow-up either in primary care (n = 97) or in a HF clinic (n = 92). After 12 months, no differences between guideline adherence, as estimated by the Guideline Adherence Indicator (GAI-3), and patient adherence, in terms of the medication possession ratio (MPR), were found between treatment groups. There was no difference in the number of deaths (n = 12 in primary care and n = 8 in the HF clinic; P = 0.48), and hospital readmissions for cardiovascular (CV) reasons were also similar. The total number of unplanned non-CV hospital readmissions, however, tended to be higher in the primary care group (n = 22) than in the HF clinic group (n = 10; P = 0.05). Conclusionsless thanp id="ejhf173-para-0003"greater thanPatients discharged after initial management in a specialized HF clinic can be discharged to primary care for long-term follow-up with regard to maintaining guideline adherence and patient adherence. However, the complexity of the HF syndrome and its associated co-morbidities requires continuous monitoring. Close collaboration between healthcare providers will be crucial in order to provide HF patients with optimal, integrated care.
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7.
  • Taieb, A., et al. (författare)
  • Guidelines for the management of vitiligo : the European Dermatology Forum consensus
  • 2013
  • Ingår i: British Journal of Dermatology. - : Oxford University Press (OUP). - 0007-0963 .- 1365-2133. ; 168:1, s. 5-19
  • Forskningsöversikt (refereegranskat)abstract
    • The aetiopathogenic mechanisms of vitiligo are still poorly understood, and this has held back progress in diagnosis and treatment. Up until now, treatment guidelines have existed at national levels, but no common European viewpoint has emerged. This guideline for the treatment of segmental and nonsegmental vitiligo has been developed by the members of the Vitiligo European Task Force and other colleagues. It summarizes evidence-based and expert-based recommendations (S1 level).
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  • Van der Plicht, J, et al. (författare)
  • The Preboreal climate reversal and a subsequent solar-forced climate shift
  • 2004
  • Ingår i: Journal of Quaternary Science. - : Wiley. - 1099-1417 .- 0267-8179. ; 19:3, s. 263-269
  • Tidskriftsartikel (refereegranskat)abstract
    • Accurate chronologies are essential for linking palaeoclimate archives. Carbon-14 wiggle-match dating was used to produce an accurate chronology for part of an early Holocene peat sequence from the Borchert (The Netherlands). Following the Younger Dryas-Preboreal transition, two climatic shifts could be inferred. Around 11 400 cal. yr BP the expansion of birch (Betula) forest was interrupted by a dry continental phase with dominantly open grassland vegetation, coeval with the PBO (Preboreal Oscillation), as observed in the GRIP ice core. At 11 250 cal. yr BP a sudden shift to a humid climate occurred. This second change appears to be contemporaneous with: (i) a sharp increase of atmospheric C-14; (ii) a temporary decline of atmospheric CO2; and (iii) an increase in the GRIP Be-10 flux. The close correspondence with excursions of cosmogenic nuclides points to a decline in solar activity, which may have forced the changes in climate and vegetation at around 11 250 cal. yr BP. Copyright (C) 2004 John Wiley Sons, Ltd.
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17.
  • Yeloff, D, et al. (författare)
  • High precision C-14 dating of Holocene peat deposits : a comparison of Bayesian calibration and wiggle-matching approaches
  • 2006
  • Ingår i: Quaternary Geochronology. - : Elsevier BV. - 1871-1014. ; 1:3, s. 222-235
  • Tidskriftsartikel (refereegranskat)abstract
    • The chronologies of five northern European ombrotrophic peat bogs subjected to a large ANIS C-14 dating effort (32-44 dates/site) are presented here. The results of Bayesian calibration (BCal) of dates with a prior assumption of chronological ordering were compared with a Bayesian wiggle-match approach (Bpeat) which assumes constant linear accumulation over sections of the peat profile. Interpolation of BCal age estimates of dense sequences of C-14 dates showed variable patterns of peat accumulation with time, with changes in accumulation occurring at intervals ranging from 20 to 50 cm. Within these intervals, peat accumulation appeared to be relatively linear. Close analysis suggests that some of the inferred variations in accumulation rate were related to the plant macrofossil composition of the peat. The wiggle-matched age-depth models had relatively high chronological uncertainty within intervals of closely spaced 14 C dates, suggesting that the premise of constant linear accumulation over large sections of the peat profile is unrealistic. Age models based on the assumption of linear accumulation over large parts of a peat core (and therefore only effective over millennial timescales), are not compatible with studies examining environmental change during the Holocene, where variability often occurs at decadal to centennial time-scales. Ideally, future wiggle-match age models should be constrained, with boundaries between sections based on the plant macrofossil composition of the peat and physical-chemical parameters such as the degree of decomposition. Strategies for the selection of material for dating should be designed so that there should be enough C-14 dates to accurately reconstruct the peat accumulation rate of each homogeneous stratigraphic unit.
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18.
  • de Jong, R, et al. (författare)
  • Climate and Peatlands
  • 2010
  • Ingår i: Changing Climates, Earth Systems, and Society. - 9789048187157 - 9789048187164 ; , s. 85-122
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)
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19.
  • Högström, R., et al. (författare)
  • DEVELOPMENT OF MEASUREMENT AND CALIBRATION TECHNIQUES FOR DYNAMIC PRESSURES AND TEMPERATURES : RESULTS AND ACHIEVEMENTS
  • 2022
  • Ingår i: 6th TC16 Conference on Pressure and Vacuum Measurement 2022, Together with the 24th TC3 Conference on the Measurement of Force, Mass and Torque, the 14th TC5 Conference on the Measurement of Hardness, and the 5th TC22 Conference on Vibration Measurement. - : International Measurement Confederation (IMEKO).
  • Konferensbidrag (refereegranskat)abstract
    • This paper presents the main results and achievements of the EMPIR DynPT project [1]. Dynamic measurement of pressure and temperature are a key requirement for process control in several demanding applications, such as automotive, marine and turbine engines, manufacturing processes, and ammunition and product safety. The quality of these measurement has been significantly improved in this project through development of dynamic measurement standards and methods and characterized sensor technologies and means of estimating measurement uncertainties in real process conditions.
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