| 1. |
- Thomas, H. J. D., et al.
(författare)
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Global plant trait relationships extend to the climatic extremes of the tundra biome
- 2020
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Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- The majority of variation in six traits critical to the growth, survival and reproduction of plant species is thought to be organised along just two dimensions, corresponding to strategies of plant size and resource acquisition. However, it is unknown whether global plant trait relationships extend to climatic extremes, and if these interspecific relationships are confounded by trait variation within species. We test whether trait relationships extend to the cold extremes of life on Earth using the largest database of tundra plant traits yet compiled. We show that tundra plants demonstrate remarkably similar resource economic traits, but not size traits, compared to global distributions, and exhibit the same two dimensions of trait variation. Three quarters of trait variation occurs among species, mirroring global estimates of interspecific trait variation. Plant trait relationships are thus generalizable to the edge of global trait-space, informing prediction of plant community change in a warming world.
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| 2. |
- Maes, S.L., et al.
(författare)
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Environmental drivers of increased ecosystem respiration in a warming tundra
- 2024
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Ingår i: Nature. - : Springer Nature. - 0028-0836 .- 1476-4687. ; 629:8010, s. 105-113
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Tidskriftsartikel (refereegranskat)abstract
- Arctic and alpine tundra ecosystems are large reservoirs of organic carbon. Climate warming may stimulate ecosystem respiration and release carbon into the atmosphere. The magnitude and persistency of this stimulation and the environmental mechanisms that drive its variation remain uncertain. This hampers the accuracy of global land carbon–climate feedback projections. Here we synthesize 136 datasets from 56 open-top chamber in situ warming experiments located at 28 arctic and alpine tundra sites which have been running for less than 1 year up to 25 years. We show that a mean rise of 1.4 °C [confidence interval (CI) 0.9–2.0 °C] in air and 0.4 °C [CI 0.2–0.7 °C] in soil temperature results in an increase in growing season ecosystem respiration by 30% [CI 22–38%] (n = 136). Our findings indicate that the stimulation of ecosystem respiration was due to increases in both plant-related and microbial respiration (n = 9) and continued for at least 25 years (n = 136). The magnitude of the warming effects on respiration was driven by variation in warming-induced changes in local soil conditions, that is, changes in total nitrogen concentration and pH and by context-dependent spatial variation in these conditions, in particular total nitrogen concentration and the carbon:nitrogen ratio. Tundra sites with stronger nitrogen limitations and sites in which warming had stimulated plant and microbial nutrient turnover seemed particularly sensitive in their respiration response to warming. The results highlight the importance of local soil conditions and warming-induced changes therein for future climatic impacts on respiration.
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| 3. |
- Rixen, C., et al.
(författare)
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Winters are changing: snow effects on Arctic and alpine tundra ecosystems
- 2022
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Ingår i: Arctic Science. - : Canadian Science Publishing. - 2368-7460. ; 8:3, s. 572-608
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Tidskriftsartikel (refereegranskat)abstract
- Snow is an important driver of ecosystem processes in cold biomes. Snow accumulation determines ground temperature, light conditions, and moisture availability during winter. It also affects the growing season's start and end, and plant access to moisture and nutrients. Here, we review the current knowledge of the snow cover's role for vegetation, plant-animal interactions, permafrost conditions, microbial processes, and biogeochemical cycling. We also compare studies of natural snow gradients with snow experimental manipulation studies to assess time scale difference of these approaches. The number of tundra snow studies has increased considerably in recent years, yet we still lack a comprehensive overview of how altered snow conditions will affect these ecosystems. Specifically, we found a mismatch in the timing of snowmelt when comparing studies of natural snow gradients with snow manipulations. We found that snowmelt timing achieved by snow addition and snow removal manipulations (average 7.9 days advance and 5.5 days delay, respectively) were substantially lower than the temporal variation over natural spatial gradients within a given year (mean range 56 days) or among years (mean range 32 days). Differences between snow study approaches need to be accounted for when projecting snow dynamics and their impact on ecosystems in future climates.
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| 4. |
- Natali, S. M., et al.
(författare)
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Large loss of CO2 in winter observed across the northern permafrost region
- 2019
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Ingår i: Nature Climate Change. - : Springer Science and Business Media LLC. - 1758-678X .- 1758-6798. ; 9:11, s. 852-857
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Tidskriftsartikel (refereegranskat)abstract
- Recent warming in the Arctic, which has been amplified during the winter(1-3), greatly enhances microbial decomposition of soil organic matter and subsequent release of carbon dioxide (CO2)(4). However, the amount of CO2 released in winter is not known and has not been well represented by ecosystem models or empirically based estimates(5,6). Here we synthesize regional in situ observations of CO2 flux from Arctic and boreal soils to assess current and future winter carbon losses from the northern permafrost domain. We estimate a contemporary loss of 1,662 TgC per year from the permafrost region during the winter season (October-April). This loss is greater than the average growing season carbon uptake for this region estimated from process models (-1,032 TgC per year). Extending model predictions to warmer conditions up to 2100 indicates that winter CO2 emissions will increase 17% under a moderate mitigation scenario-Representative Concentration Pathway 4.5-and 41% under business-as-usual emissions scenario-Representative Concentration Pathway 8.5. Our results provide a baseline for winter CO2 emissions from northern terrestrial regions and indicate that enhanced soil CO2 loss due to winter warming may offset growing season carbon uptake under future climatic conditions.
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| 5. |
- Björkman, Anne, 1981, et al.
(författare)
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Plant functional trait change across a warming tundra biome
- 2018
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 562:7725, s. 57-62
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Tidskriftsartikel (refereegranskat)abstract
- The tundra is warming more rapidly than any other biome on Earth, and the potential ramifications are far-reaching because of global feedback effects between vegetation and climate. A better understanding of how environmental factors shape plant structure and function is crucial for predicting the consequences of environmental change for ecosystem functioning. Here we explore the biome-wide relationships between temperature, moisture and seven key plant functional traits both across space and over three decades of warming at 117 tundra locations. Spatial temperature–trait relationships were generally strong but soil moisture had a marked influence on the strength and direction of these relationships, highlighting the potentially important influence of changes in water availability on future trait shifts in tundra plant communities. Community height increased with warming across all sites over the past three decades, but other traits lagged far behind predicted rates of change. Our findings highlight the challenge of using space-for-time substitution to predict the functional consequences of future warming and suggest that functions that are tied closely to plant height will experience the most rapid change. They also reveal the strength with which environmental factors shape biotic communities at the coldest extremes of the planet and will help to improve projections of functional changes in tundra ecosystems with climate warming.
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| 6. |
- Björkman, Anne, 1981, et al.
(författare)
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Tundra Trait Team: A database of plant traits spanning the tundra biome
- 2018
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Ingår i: Global Ecology and Biogeography. - : Wiley. - 1466-822X .- 1466-8238. ; 27:12, s. 1402-1411
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Tidskriftsartikel (refereegranskat)abstract
- © 2018 The Authors Global Ecology and Biogeography Published by John Wiley & Sons Ltd Motivation: The Tundra Trait Team (TTT) database includes field-based measurements of key traits related to plant form and function at multiple sites across the tundra biome. This dataset can be used to address theoretical questions about plant strategy and trade-offs, trait–environment relationships and environmental filtering, and trait variation across spatial scales, to validate satellite data, and to inform Earth system model parameters. Main types of variable contained: The database contains 91,970 measurements of 18 plant traits. The most frequently measured traits (>1,000 observations each) include plant height, leaf area, specific leaf area, leaf fresh and dry mass, leaf dry matter content, leaf nitrogen, carbon and phosphorus content, leaf C:N and N:P, seed mass, and stem specific density. Spatial location and grain: Measurements were collected in tundra habitats in both the Northern and Southern Hemispheres, including Arctic sites in Alaska, Canada, Greenland, Fennoscandia and Siberia, alpine sites in the European Alps, Colorado Rockies, Caucasus, Ural Mountains, Pyrenees, Australian Alps, and Central Otago Mountains (New Zealand), and sub-Antarctic Marion Island. More than 99% of observations are georeferenced. Time period and grain: All data were collected between 1964 and 2018. A small number of sites have repeated trait measurements at two or more time periods. Major taxa and level of measurement: Trait measurements were made on 978 terrestrial vascular plant species growing in tundra habitats. Most observations are on individuals (86%), while the remainder represent plot or site means or maximums per species. Software format: csv file and GitHub repository with data cleaning scripts in R; contribution to TRY plant trait database (www.try-db.org) to be included in the next version release.
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| 7. |
- Pereira, M. P., et al.
(författare)
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Position Statement : Linear prurigo is a subtype of chronic prurigo
- 2019
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Ingår i: Journal of the European Academy of Dermatology and Venereology. - : Wiley. - 0926-9959 .- 1468-3083. ; 33:2, s. 263-266
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Tidskriftsartikel (refereegranskat)abstract
- Background: Chronic prurigo (CPG) is a distinct disease characterized by chronic pruritus, history and/or signs of prolonged scratching and multiple pruriginous lesions. It may present with various clinical manifestations, including papules, nodules, plaques or umbilicated lesions. Some patients with chronic pruritus show pruriginous linear and scaring scratch lesions (LSSL) and it is unclear whether these lesions belong to the spectrum of CPG. Objective: To achieve a consensus on the classification of pruriginous LSSL and establish criteria to differentiate them from similar appearing conditions of different nature. Methods: Members of the Task Force Pruritus (TFP) of the European Academy of Dermatology and Venereology participated in the consensus conference, discussing representative clinical cases. Using the Delphi method, consensus was reached when ≥75% of members agreed on a statement. Results: Twenty-one members of the TFP with voting rights participated in the meeting. It was consented that LSSL occurs due to chronic pruritus and prolonged scratching, and share common pathophysiological mechanisms with CPG. LSSL were thus considered as belonging to the spectrum of CPG and the term ‘linear prurigo’ was chosen to describe this manifestation. Conclusion: Considering linear prurigo as belonging to the spectrum of CPG has important clinical implications, since both the diagnostic and therapeutic approach of these patients should be performed as recommended for CPG. Importantly, linear prurigo should be differentiated from self-inflicted skin lesions as factitious disorders or skin picking syndromes. In the latter, artificial manipulation rather than pruritus itself leads to the development of cutaneous lesions, which can show clinical similarities to linear prurigo.
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| 8. |
- Pereira, Manuel P., et al.
(författare)
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Google search trends for itch in Europe : a retrospective longitudinal study
- 2021
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Ingår i: Journal of the European Academy of Dermatology and Venereology : JEADV. - : Wiley. - 1468-3083 .- 0926-9959. ; 35:6, s. 1362-1370
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Itch is a common symptom in the general population. Affected individuals often do not seek medical consultation and rely on Internet searches to obtain information regarding their itch.OBJECTIVES: The aim of this study was to attain insights into common concerns of the general population regarding itch can by analysing itch-related Internet search behaviour.METHODS: Google AdWords Keyword Planner was used to assess search volumes for itch-related terms in 15 European countries between September 2014 and August 2018. All identified keywords were qualitatively categorized. Itch-related terms were descriptively analysed and are shown as number of searches/100 000 inhabitants.RESULTS: The search volume for the keyword 'itch' per 100 000 inhabitants was highest in Northern Europe, followed by Eastern, Central and Southern Europe. In 4/15 countries, itch was searched for more often in the autumn/winter months compared to in the spring/summer months. Most itch-related terms were related to dermatological conditions such as inflammatory skin diseases (e.g. psoriasis, atopic dermatitis), allergic or immunologic conditions (e.g. urticaria), and infectious diseases or infestations (e.g. scabies). In terms of body location, genitoanal itch dominated the searches. Symptoms and signs related to itch, possible non-dermatological aetiologies, and treatment options were also among the most searched terms.CONCLUSIONS: These analyses provided for the first time insights into the search behaviour patterns related to itch across Europe. People from Northern and Eastern Europe are more likely to seek online information regarding itch. Causes for the itch, especially dermatological conditions, and genitoanal itch are the most important concerns for Internet users. This unconventional and inexpensive method identifies medical needs of people beyond the medical setting, including people who do not seek medical consultation. Accordingly, the data could be used to guide public health interventions and manage respective inhabitants' medical needs.
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| 9. |
- Ständer, S., et al.
(författare)
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EADV Task Force Pruritus White Paper on chronic pruritus and chronic prurigo : Current challenges and future solutions
- 2024
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Ingår i: Journal of the European Academy of Dermatology and Venereology. - 0926-9959 .- 1468-3083.
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Tidskriftsartikel (refereegranskat)abstract
- Chronic pruritus (CP) is frequent in general medicine and the most common complaint in general dermatology. The prevalence of CP is expected to rise in the future due to the ageing population. The clinical presentation, underlying aetiology and treatment strategy of CP are heterogeneous. Also, individual treatment aims and physical, psychic and economic burdens of patients might vary. Chronic prurigo (CPG) is the most severe disease in the chronic pruritus spectrum, being associated with long-standing scratch-induced skin lesions and a therapy refractory itch-scratch-cycle. It is thus important to raise disease awareness for CP and CPG in the general public and among decision-makers in the health system. Further, there is a need to support a rational clinical framework to optimize both diagnostics and therapeutics. Currently, there is still a shortcoming regarding approved therapies and understanding CP/CPG as severe medical conditions. Therefore, the EADV Task Force Pruritus decided to publish this white paper based on several consensus meetings. The group consented on the following goals: (a) ensure that CP is recognized as a serious condition, (b) increase public awareness and understanding of CP and CPG as chronic and burdensome diseases that can greatly affect a person's quality of life, (c) clarify that in most cases CP and CPG are non-communicable and not caused by a psychiatric disease, (d) improve the support and treatment given to patients with CP to help them manage their disease and (e) publicize existing therapies including current guidelines. We aim to point to necessary improvements in access and quality of care directed to decision-makers in health policy, among payers and administrations as well as in practical care.
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| 10. |
- Hugelius, Gustaf, et al.
(författare)
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Estimated stocks of circumpolar permafrost carbon with quantified uncertainty ranges and identified data gaps
- 2014
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 11:23, s. 6573-6593
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Tidskriftsartikel (refereegranskat)abstract
- Soils and other unconsolidated deposits in the northern circumpolar permafrost region store large amounts of soil organic carbon (SOC). This SOC is potentially vulnerable to remobilization following soil warming and permafrost thaw, but SOC stock estimates were poorly constrained and quantitative error estimates were lacking. This study presents revised estimates of permafrost SOC stocks, including quantitative uncertainty estimates, in the 0-3m depth range in soils as well as for sediments deeper than 3m in deltaic deposits of major rivers and in the Yedoma region of Siberia and Alaska. Revised estimates are based on significantly larger databases compared to previous studies. Despite this there is evidence of significant remaining regional data gaps. Estimates remain particularly poorly constrained for soils in the High Arctic region and physiographic regions with thin sedimentary overburden (mountains, highlands and plateaus) as well as for deposits below 3mdepth in deltas and the Yedoma region. While some components of the revised SOC stocks are similar in magnitude to those previously reported for this region, there are substantial differences in other components, including the fraction of perennially frozen SOC. Upscaled based on regional soil maps, estimated permafrost region SOC stocks are 217 +/- 12 and 472 +/- 27 Pg for the 0-0.3 and 0-1 m soil depths, respectively (+/- 95% confidence intervals). Storage of SOC in 0-3m of soils is estimated to 1035 +/- 150 Pg. Of this, 34 +/- 16 PgC is stored in poorly developed soils of the High Arctic. Based on generalized calculations, storage of SOC below 3m of surface soils in deltaic alluvium of major Arctic rivers is estimated as 91 +/- 52 Pg. In the Yedoma region, estimated SOC stocks below 3mdepth are 181 +/- 54 Pg, of which 74 +/- 20 Pg is stored in intact Yedoma (late Pleistocene ice-and organic-rich silty sediments) with the remainder in refrozen thermokarst deposits. Total estimated SOC storage for the permafrost region is similar to 1300 Pg with an uncertainty range of similar to 1100 to 1500 Pg. Of this, similar to 500 Pg is in non-permafrost soils, seasonally thawed in the active layer or in deeper taliks, while similar to 800 Pg is perennially frozen. This represents a substantial similar to 300 Pg lowering of the estimated perennially frozen SOC stock compared to previous estimates.
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| 11. |
- Prevey, J. S., et al.
(författare)
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Warming shortens flowering seasons of tundra plant communities
- 2019
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Ingår i: Nature Ecology & Evolution. - : Springer Science and Business Media LLC. - 2397-334X. ; 3:1, s. 45-52
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Tidskriftsartikel (refereegranskat)abstract
- Advancing phenology is one of the most visible effects of climate change on plant communities, and has been especially pronounced in temperature-limited tundra ecosystems. However, phenological responses have been shown to differ greatly between species, with some species shifting phenology more than others. We analysed a database of 42,689 tundra plant phenological observations to show that warmer temperatures are leading to a contraction of community-level flowering seasons in tundra ecosystems due to a greater advancement in the flowering times of late-flowering species than early-flowering species. Shorter flowering seasons with a changing climate have the potential to alter trophic interactions in tundra ecosystems. Interestingly, these findings differ from those of warmer ecosystems, where early-flowering species have been found to be more sensitive to temperature change, suggesting that community-level phenological responses to warming can vary greatly between biomes.
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| 12. |
- Ständer, Sonja, et al.
(författare)
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IFSI-Guideline on Chronic Prurigo including Prurigo nodularis.
- 2020
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Ingår i: ITCH. - : Ovid Technologies (Wolters Kluwer Health). - 2380-5048. ; 5:4, s. 1-13
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Forskningsöversikt (refereegranskat)abstract
- Chronic prurigo (CPG) is a highly burdensome pruritic disease characterized by chronic itch, a prolonged scratching behavior and the development of localized or generalized hyperkeratotic pruriginous lesions. Neuronal sensitization and the development of an itch-scratch cycle contribute to the augmentation of pruritus and the chronicity of the disease. We provide here the first international guideline for a rational diagnostic and therapeutic approach for CPG. Recommendations are based on available evidence and expert opinion. The diagnosis of CPG is made clinically. A detailed medical history together with laboratory and radiological examinations are advised in order to determine the severity of CPG, identify the underlying origin of the itch and assist in the elaboration of a treatment plan. Therapeutically, it is advised to adopt a multimodal approach, including general strategies to control itch, treatment of the underlying pruritic conditions, and of the pruriginous lesions. Topical (corticosteroids, calcineurin inhibitors, capsaicin) and systemic antipruritic agents (eg, gabapentinoids, immunosuppressants, and opioid modulators) as well as physical treatment modalities (phototherapy, cryotherapy) should be employed in a step-wise approach. Psychosomatic or psychological interventions may be recommended in CPG patients with signs of psychiatric/psychological comorbidities.
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| 13. |
- Pereira, M. P., et al.
(författare)
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European academy of dermatology and venereology European prurigo project : Expert consensus on the definition, classification and terminology of chronic prurigo
- 2018
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Ingår i: Journal of the European Academy of Dermatology and Venereology. - : Wiley. - 0926-9959. ; 32:7, s. 1059-1065
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Tidskriftsartikel (refereegranskat)abstract
- Background: The term prurigo has been used for many decades in dermatology without clear definition, and currently used terminology of prurigo is inconsistent and confusing. Especially, itch-related prurigo remains unexplored regarding the epidemiology, clinical profile, natural course, underlying causes, available treatments and economic burden, although burdensome and difficult to treat. Objective: To address these issues, the multicentre European Prurigo Project (EPP) was designed to increase knowledge on chronic prurigo (CPG). In the first step, European experts of the EADV Task Force Pruritus (TFP) aimed to achieve a consensus on the definition, classification and terminology of CPG. Additionally, procedures of the cross-sectional EPP were discussed and agreed upon. Methods: Discussions and surveys between members of the TFP served as basis for a consensus conference. Using the Delphi method, consensus was defined as an agreement ≥75% among the present members. Results: Twenty-four members of the TFP participated in the consensus conference. Experts consented that CPG should be used as an umbrella term for the range of clinical manifestations (e.g. papular, nodular, plaque or umbilicated types). CPG is considered a distinct disease defined by the presence of chronic pruritus for ≥6 weeks, history and/or signs of repeated scratching and multiple localized/generalized pruriginous skin lesions (whitish or pink papules, nodules and/or plaques). CPG occurs due to a neuronal sensitization to itch and the development of an itch-scratch cycle. Conclusion: This new definition and terminology of CPG should be implemented in dermatology to harmonize communication in the clinical routine, clinical trials and scientific literature. Acute/subacute forms of prurigo are separated entities, which need to be differentiated from CPG and will be discussed in a next step. In the near future, the cross-sectional EPP will provide relevant clinical data on various aspects of CPG leading to new directions in the scientific investigation of CGP.
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| 14. |
- Prevey, J., et al.
(författare)
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Greater temperature sensitivity of plant phenology at colder sites: implications for convergence across northern latitudes
- 2017
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 23:7, s. 2660-2671
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Tidskriftsartikel (refereegranskat)abstract
- Warmer temperatures are accelerating the phenology of organisms around the world. Temperature sensitivity of phenology might be greater in colder, higher latitude sites than in warmer regions, in part because small changes in temperature constitute greater relative changes in thermal balance at colder sites. To test this hypothesis, we examined up to 20 years of phenology data for 47 tundra plant species at 18 high-latitude sites along a climatic gradient. Across all species, the timing of leaf emergence and flowering was more sensitive to a given increase in summer temperature at colder than warmer high-latitude locations. A similar pattern was seen over time for the flowering phenology of a widespread species, Cassiope tetragona. These are among the first results highlighting differential phenological responses of plants across a climatic gradient and suggest the possibility of convergence in flowering times and therefore an increase in gene flow across latitudes as the climate warms.
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| 15. |
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| 16. |
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| 17. |
- Prevéy, Janet S., et al.
(författare)
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The tundra phenology database: more than two decades of tundra phenology responses to climate change
- 2022
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Ingår i: Arctic Science. - : Canadian Science Publishing. - 2368-7460. ; 8:3, s. 1026-1039
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Tidskriftsartikel (refereegranskat)abstract
- Observations of changes in phenology have provided some of the strongest signals of the effects of climate change on terrestrial ecosystems. The International Tundra Experiment (ITEX), initiated in the early 1990s, established a common protocol to measure plant phenology in tundra study areas across the globe. Today, this valuable collec-tion of phenology measurements depicts the responses of plants at the colder extremes of our planet to experimental and ambient changes in temperature over the past decades. The database contains 150 434 phenology observations of 278 plant species taken at 28 study areas for periods of 1–26 years. Here we describe the full data set to increase the visibility and use of these data in global analyses and to invite phenology data contributions from underrepresented tundra locations. Portions of this tundra phenology database have been used in three recent syntheses, some data sets are expanded, others are from entirely new study areas, and the entirety of these data are now available at the Polar Data Catalogue (https://doi.org/10.21963/13215).
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| 18. |
- Spulber, S, et al.
(författare)
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Patterns of activity correlate with symptom severity in major depressive disorder patients
- 2022
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Ingår i: Translational psychiatry. - : Springer Science and Business Media LLC. - 2158-3188. ; 12:1, s. 226-
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Tidskriftsartikel (refereegranskat)abstract
- Objective measures, such as activity monitoring, can potentially complement clinical assessment for psychiatric patients. Alterations in rest–activity patterns are commonly encountered in patients with major depressive disorder. The aim of this study was to investigate whether features of activity patterns correlate with severity of depression symptoms (evaluated by Montgomery–Åsberg Rating Scale (MADRS) for depression). We used actigraphy recordings collected during ongoing major depressive episodes from patients not undergoing any antidepressant treatment. The recordings were acquired from two independent studies using different actigraphy systems. Data was quality-controlled and pre-processed for feature extraction following uniform procedures. We trained multiple regression models to predict MADRS score from features of activity patterns using brute-force and semi-supervised machine learning algorithms. The models were filtered based on the precision and the accuracy of fitting on training dataset before undergoing external validation on an independent dataset. The features enriched in the models surviving external validation point to high depressive symptom severity being associated with less complex activity patterns and stronger coupling to external circadian entrainers. Our results bring proof-of-concept evidence that activity patterns correlate with severity of depressive symptoms and suggest that actigraphy recordings may be a useful tool for individual evaluation of patients with major depressive disorder.
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| 19. |
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| 20. |
- Björkman, Mats P., 1978, et al.
(författare)
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A comparison of annual and seasonal carbon dioxide effluxes between sub-Arctic Sweden and High-Arctic Svalbard
- 2010
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Ingår i: Polar Research. - : Norwegian Polar Institute. - 1751-8369. ; 29:1, s. 75-84
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Tidskriftsartikel (refereegranskat)abstract
- Recent climate change predictions suggest altered patterns of winter precipitation across the Arctic. It has been suggested that the presence, timing and amount of snow all affect microbial activity, thus influencing CO2 production in soil. In this study annual and seasonal emissions of CO2 were estimated in High-Arctic Adventdalen, Svalbard, and sub-Arctic Latnjajaure, Sweden, using a new trace gas-based method to track real time diffusion rates through the snow. Summer measurements from snow-free soils were made using a chamber-based method. Measurements were obtained at different snow regimes in order to evaluate the effect of snow depth on winter CO2 effluxes. Total annual emissions of CO2 from the sub-Arctic site (0.662–1.487 kg CO2 m-2 yr-1) were found to be more than double the emissions from the High-Arctic site (0.369–0.591 kg CO2 m-2 yr-1). There were no significant differences in winter effluxes between snow regimes or vegetation types, indicating that spatial variability in winter soil CO2 effluxes are not directly linked to snow cover thickness or soil temperatures. Total winter emissions (0.004–0.248 kg CO2 m-2) were found to be in the lower range of those previously described in the literature. Winter emissions varied in their contribution to total annual production between 1 and 18%. Artificial snow drifts shortened the snow-free period by two weeks and decreased annual CO2 emission by up to 20%. This study suggests that future shifts in vegetation zones may increase soil respiration from Arctic tundra regions.
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| 21. |
- Björkman, Mats P., 1978, et al.
(författare)
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Winter carbon dioxide effluxes from Arctic ecosystems - A presentation of a novel trace gas method and comparison with previously used methodologies
- 2009
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Ingår i: Eos Trans. AGU, 90(52), Fall Meet. Suppl., Abstract A54D-03..
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Konferensbidrag (refereegranskat)abstract
- Winter CO2 efflux from subnivean environments is an important component of annual C budgets in arctic ecosystems and consequently makes prediction and estimations of winter processes as well as incorporations of these processes into existing models important. Several methods have been used for estimating winter CO2 production, by using different snow pack assumptions. Here, measurements from three commonly used methods and one novel trace gas method used during the winter 2007-2008 are compared and discussed: (1) measurements with chamber on snow surface, Fsnow, (2) chamber measurements directly on the soil, Fsoil, after snow removal, (3) diffusion measurements, F2-point, within the snow pack, and (4) a novel trace gas technique, FSF6, with multiple gas sampling within the snow pack. According to measurements in shallow and deep snow cover in High-arctic Svalbard and Sub-arctic Sweden total winter emissions from the trace gas technique, 0.004-0.248 kg CO2 m-2, were found to be in the lower range of those previously described in the literature, however, results from all four methods differ by up to two orders of magnitude. Highest mean winter CO2 effluxes were observed using Fsoil, 7.7-216.8 mg CO2 m-2 h-1, and lowest values using FSF6, 0.8-12.6 mg CO2 m-2 h-1. Fsnow and F2-point were both within the lower range, 2.1-15.1 mg CO2 m-2 h-1 and 6.8-11.2 mg CO2 m-2 h-1, respectively. Differences are considered a result of contrasting methods but also that the assumptions within the methods are not equivalent when quantifying CO2 production and effluxes to the atmosphere. As snow can act as a barrier for CO2, Fsoil is assumed to measure soil production whereas FSF6, Fsnow and F2-point are considered better approaches for quantifying exchange processes between the soil, snow, and the atmosphere. This study indicates that estimation of winter CO2 emissions might vary more due to the method used than due to the actual variation in soil CO2 production or release. This is of major concern, especially when CO2 efflux data is used in climate models or in carbon budget calculations and highlights the need for further development and validation of techniques.
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| 22. |
- Björkman, Mats P., 1978, et al.
(författare)
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Winter carbon dioxide effluxes from Arctic ecosystems: An overview and comparison of methodologies
- 2010
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Ingår i: Global Biogeochemical Cycles. ; 24, s. GB3010-
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Tidskriftsartikel (refereegranskat)abstract
- The winter CO2 efflux from subnivean environments is an important component of annual C budgets in arctic ecosystems and consequently makes prediction and estimations of winter processes as well as incorporations of these processes into existing models important. Several methods have been used for estimating winter CO2 effluxes, involving different assumptions about the snow pack, all aiming to quantify CO2 production. Here, four different methods are compared and discussed: (1) measurements with a chamber on the snow surface, Fsnow; (2) chamber measurements directly on the soil, Fsoil, after snow removal; (3) diffusion measurements, F2-point, within the snow pack; and (4) a trace gas technique, FSF6, with multiple gas sampling within the snow pack. According to measurements collected from shallow and deep snow cover in High-Arctic Svalbard and Sub-Arctic Sweden during the winter of 2007-2008, the four methods differ by up to two orders of magnitude in their estimates of total winter emissions. The highest mean winter CO2 effluxes, 7.7-216.8 mg CO2 m-2 h-1, were observed using Fsoil and lowest values, 0.8-12.6 mg CO2 m-2 h-1, using FSF6. The Fsnow and F2-point methods were both within the lower range, 2.1-15.1 mg CO2 m-2 h-1 and 6.8-11.2 mg CO2 m-2 h-1, respectively. These differences are considered to be a result of contrasting methods, but also because the assumptions within the methods are not the same when quantifying CO2 production and effluxes to the atmosphere. Since snow can act as a barrier to CO2, Fsoil is assumed to measure soil production, whereas FSF6, Fsnow and F2-point are considered better approaches for quantifying exchange processes between the soil, snow, and the atmosphere. This study indicates that estimates of winter CO2 emissions may vary more as a result of the method used than due to the actual variation in soil CO2 production or release. This is a major concern, especially when CO2 efflux data are used in climate models or in carbon budget calculations, thus highlighting the need for further development and validation of accurate and appropriate techniques.
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| 23. |
- Björkman, Mats P., 1978, et al.
(författare)
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Winter fluxes of carbon dioxide – a comparison of current methodology
- 2008
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Ingår i: The 15th ITEX workshop, Reykjavik, Iceland, 9–12 October 2008..
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- During winter as much as 47 % of the land mass of the northern hemisphere may experience the insulating effect of a snow-cover, during which vast areas have a longer snow-covered period than growing season. The snow cover allows soil microbial activities to continue during winter with a production of CO2 as a result. Estimations of winter fluxes are difficult since snow is a highly complex media, with large uncertainties as a result. Using a newly developed trace gas diffusion technique this project aims to improve winter flux estimations and to minimise the uncertainties given by the snow-cover itself. Current methodology for winter CO2 emissions will be presented and evaluated together with a discussion on measurement standardization.
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| 24. |
- Chadburn, Sarah E., et al.
(författare)
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Carbon stocks and fluxes in the high latitudes : using site-level data to evaluate Earth system models
- 2017
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 14:22, s. 5143-5169
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Tidskriftsartikel (refereegranskat)abstract
- It is important that climate models can accurately simulate the terrestrial carbon cycle in the Arctic due to the large and potentially labile carbon stocks found in permafrost-affected environments, which can lead to a positive climate feedback, along with the possibility of future carbon sinks from northward expansion of vegetation under climate warming. Here we evaluate the simulation of tundra carbon stocks and fluxes in three land surface schemes that each form part of major Earth system models (JSBACH, Germany; JULES, UK; ORCHIDEE, France). We use a site-level approach in which comprehensive, high-frequency datasets allow us to disentangle the importance of different processes. The models have improved physical permafrost processes and there is a reasonable correspondence between the simulated and measured physical variables, including soil temperature, soil moisture and snow. We show that if the models simulate the correct leaf area index (LAI), the standard C3 photosynthesis schemes produce the correct order of magnitude of carbon fluxes. Therefore, simulating the correct LAI is one of the first priorities. LAI depends quite strongly on climatic variables alone, as we see by the fact that the dynamic vegetation model can simulate most of the differences in LAI between sites, based almost entirely on climate inputs. However, we also identify an influence from nutrient limitation as the LAI becomes too large at some of the more nutrient-limited sites. We conclude that including moss as well as vascular plants is of primary importance to the carbon budget, as moss contributes a large fraction to the seasonal CO2 flux in nutrient-limited conditions. Moss photosynthetic activity can be strongly influenced by the moisture content of moss, and the carbon uptake can be significantly different from vascular plants with a similar LAI. The soil carbon stocks depend strongly on the rate of input of carbon from the vegetation to the soil, and our analysis suggests that an improved simulation of photosynthesis would also lead to an improved simulation of soil carbon stocks. However, the stocks are also influenced by soil carbon burial (e.g. through cryoturbation) and the rate of heterotrophic respiration, which depends on the soil physical state. More detailed below-ground measurements are needed to fully evaluate biological and physical soil processes. Furthermore, even if these processes are well modelled, the soil carbon profiles cannot resemble peat layers as peat accumulation processes are not represented in the models. Thus, we identify three priority areas for model development: (1) dynamic vegetation including (a) climate and (b) nutrient limitation effects; (2) adding moss as a plant functional type; and an (3) improved vertical profile of soil carbon including peat processes.
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| 25. |
- Christiansen, J. R., et al.
(författare)
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Modelling water balance and nitrate leaching in temperate Norway spruce and beech forests located on the same soil type with the CoupModel
- 2006
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 237:03-jan, s. 545-556
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Tidskriftsartikel (refereegranskat)abstract
- Two contrasting forest ecosystems located in close proximity to each other were selected for evaluating the importance of tree species and afforestation in relation to the water balance and the quality of the water leaving the forest root zone. Measurements included soil water content and the collection of precipitation, canopy throughfall, stem flow and soil solution on a weekly basis during 15 months (1999-2000). Soil solutions were extracted using suction probes installed at all major horizons within the upper 120 cm of a Norway spruce (N. spruce) stand (Picea Abies [L.] Karst.) and a European beech stand (Fagus Sylvatica L.) located on the same soil type. Soil solutions were analyzed for the content of all major ions, including nitrate. A water balance model (CoupModel) was used to estimate percolation rates beneath the root zone. Percolation at the beech stand was 292 mm and only 41 rnm at the N. spruce stand mainly due to differences in the interception loss. The highest annual leaching of Mg, K, Na, Al, Cl, SO4-S was noted in the N. spruce stand while leaching of NO3-N was highest in the beech stand, corresponding to 39 kg ha(-1) year(-1). By contrast, the annual leaching of NO3-N in the N. spruce stand was only 0.5 kg ha(-1) year(-1). The larger amount of NO3-N was leaving the beech forest soil despite the fact that the N. spruce stand had the highest atmospheric N-deposition. Thus, differences in NO3-N leaching between the stands must be related to differences in uptake and accumulation of N in the vegetation and within the upper 120 cm of the soil. Differences in the water balance and NO3-N leaching between beech and N. spruce stands call for further attention to the selection of tree-species on a soil type basis when planning future afforestation projects, particularly when such projects aim to improve the quality of water infiltrating to the groundwater zone.
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