| 1. |
- 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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| 2. |
- Abbott, Benjamin W., et al.
(författare)
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Biomass offsets little or none of permafrost carbon release from soils, streams, and wildfire : an expert assessment
- 2016
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 11:3
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Tidskriftsartikel (refereegranskat)abstract
- As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release will be offset by increased production of Arctic and boreal biomass; however, the lack of robust estimates of net carbon balance increases the risk of further overshooting international emissions targets. Precise empirical or model-based assessments of the critical factors driving carbon balance are unlikely in the near future, so to address this gap, we present estimates from 98 permafrost-region experts of the response of biomass, wildfire, and hydrologic carbon flux to climate change. Results suggest that contrary to model projections, total permafrost-region biomass could decrease due to water stress and disturbance, factors that are not adequately incorporated in current models. Assessments indicate that end-of-the-century organic carbon release from Arctic rivers and collapsing coastlines could increase by 75% while carbon loss via burning could increase four-fold. Experts identified water balance, shifts in vegetation community, and permafrost degradation as the key sources of uncertainty in predicting future system response. In combination with previous findings, results suggest the permafrost region will become a carbon source to the atmosphere by 2100 regardless of warming scenario but that 65%-85% of permafrost carbon release can still be avoided if human emissions are actively reduced.
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| 3. |
- Franke, Vera, et al.
(författare)
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Chemical composition and source analysis of carbonaceous aerosol particles at a mountaintop site in central Sweden
- 2017
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Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 69
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Tidskriftsartikel (refereegranskat)abstract
- The chemical composition of atmospheric particulate matter at Mt. angstrom reskutan, a mountaintop site in central Sweden, was analysed with a focus on its carbonaceous content. Filter samples taken during the Cloud and Aerosol Experiment at angstrom re (CAEsAR 2014) were analysed by means of a thermo-optical method and ion chromatography. Additionally, the particle light absorption and particle number size distribution measurements for the entire campaign were added to the analysis. Mean airborne concentrations of organic and elemental carbon during CAEsAR 2014 were OC= 0.85 +/- 0.8 mu gm(-3) and EC = 0.06 +/- 0.06 mu gm(-3), respectively. Elemental to organic carbon ratios varied between EC/OC = 0.02 and 0.19. During the study a large wildfire occurred in Vastmanland, Sweden, with the plume reaching our study site. This led to significant increases in OC and EC concentrations (OC = 3.04 +/- 0.03 mu gm(-3) and EC = 0.24 +/- 0.00 mu gm(-3)). The mean mass-specific absorption coefficient observed during the campaign was sigma(BC)(abs) = 9.1 +/- 7.3 m(2)g(-1) (at wavelength lambda= 637 nm). In comparison to similarly remote European sites, Mt. angstrom reskutan experienced significantly lower carbonaceous aerosol loadings with a clear dominance of organic carbon. A mass closure study revealed a missing chemical mass fraction that likely originated from mineral dust. Potential regional source contributions of the carbonaceous aerosol were investigated using modelled air mass back trajectories. This source apportionment pointed to a correlation between high EC concentrations and air originating from continental Europe. Particles rich in organic carbon most often arrived from highly vegetated continental areas. However, marine regions were also a source of these aerosol particles. The source contributions derived during this study were compared to emission inventories of an Earth system model. This comparison highlighted a lack of OC and EC point-sources in the model's emission inventory which could potentially lead to an underestimation of the carbonaceous aerosol reaching Mt. angstrom reskutan in the simulation of this Earth system model.
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| 4. |
- Messori, Gabriele, et al.
(författare)
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Atmospheric jet stream variability reflects vegetation activity in Europe
- 2022
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Ingår i: Agricultural and Forest Meteorology. - : Elsevier. - 0168-1923 .- 1873-2240. ; 322
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Tidskriftsartikel (refereegranskat)abstract
- Jet streams are a key component of the climate system, whose dynamics couple closely to regional climate variability. Yet, the link between jet stream variability and vegetation activity has received little attention. Here, we leverage our understanding of the mid-latitude jet stream dynamics over the Euro-Atlantic sector to probe climate-vegetation interactions across Europe. We link indices related to the meridional location of the jet and the large-scale zonal wind speed with remotely-sensed vegetation greenness anomalies during locally-defined growing seasons. Correlations between greenness anomalies and jet latitude anomalies point to a control of the jet stream's variability on vegetation activity over large parts of Europe. This potential control is mediated by the jet latitude anomalies' correlations with temperature, soil moisture and downward surface solar radiation. The sign and strength of these correlations depend on location and time of the year. Furthermore, jet stream variability modulates conditions at the onset and end of the growing season. The link between jet latitude anomalies and vegetation greenness is not only specific to the climate zone, but also to the landclass and subperiod within the growing season. It is thus important to use a locally-defined growing season for interpreting the atmospheric controls on regional vegetation phenology. Results consistent with the correlation analysis emerge when focussing on local high or low greenness months only or on zonal wind speed anomalies, confirming the relevance of jet variability for vegetation activity.
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| 5. |
- Blennow, Kristina
(författare)
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Evaluating the Local Climate Impacts Profile tool for assessing local impacts of extreme weather events
- 2014
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Ingår i: Journal of Geography and Natural Disasters. - : OMICS Publishing Group. - 2167-0587. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- The climate change adaptation tool Local Climate Impacts Profile (LCLIP), developed and previously widely usedin the UK, was systematically evaluated in terms of its transferability to Sweden and its usefulness as a catalyst forawareness-raising and action with respect to climate change adaptation. The tool includes scoping, media trawl,interviews and reporting and was applied in three Swedish municipalities. It was found that after some adjustment,the tool can be applied successfully under Swedish conditions. The municipalities involved found the results useful forstimulating local adaptation work. However, the municipalities concluded that LCLIP is primarily a beginner's tool thatcan be applied at a low cost and that other, more costly investigations on vulnerability to extreme weather typically needto be conducted for successful adaptation to climate change at municipal level. An advantage of the LCLIP tool is thatit involves civil servants from all departments in the municipality and thus the resulting vulnerability discussions alsoinvolve departments dealing with ‘soft' issues, such as administration and care.
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| 6. |
- Blennow, Kristina
(författare)
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Simulating wind disturbance impacts on forest landscapes: Tree-level heterogeneity matters
- 2014
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Ingår i: Environmental Modelling and Software. - : Elsevier BV. - 1364-8152 .- 1873-6726. ; 51, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Wind is the most detrimental disturbance agent in Europe's forest ecosystems. In recent years, disturbance frequency and severity have been increasing at continental scale, a trend that is expected to continue under future anthropogenic climate change. Disturbance management is thus increasingly important for sustainable stewardship of forests, and requires tools to evaluate the effects of management alternatives and climatic changes on disturbance risk and ecosystem services. We here present a process-based model of wind disturbance impacts on forest ecosystems, integrated into the dynamic landscape simulation model iLand. The model operates at the level of individual trees and simulates wind disturbance events iteratively, i.e., dynamically accounting for changes in forest structure and newly created edges during the course of a storm. Both upwind gap size and local shelter from neighboring trees are considered in this regard, and critical wind speeds for uprooting and stem breakage are distinguished. The simulated disturbance size, pattern, and severity are thus emergent properties of the model. We evaluated the new simulation tool against satellite-derived data on the impact of the storm Gudrun (January 2005) on a 1391 ha forest landscape in south central Sweden. Both the overall damage percentage (observation: 21.7%, simulation: 21.4%) as well as the comparison of spatial damage patterns showed good correspondence between observations and predictions (prediction accuracy: 60.4%) if the full satellite-derived structural and spatial heterogeneity of the landscape was taken into account. Neglecting within-stand heterogeneity in forest conditions, i.e., the state-of-the-art in many stand-level risk models, resulted in a considerable underestimation of simulated damage, supporting the notion that tree-level complexity matters for assessing and modeling large-scale disturbances. A sensitivity analysis further showed that changes in wind speed and soil freezing could have potentially large impacts on disturbed area and patch size. The model presented here is available as open source. It can be used to study the effects of different silvicultural systems and future climates on wind risk, as well as to quantify the impacts of wind disturbance on ecosystem services such as carbon sequestration. It thus contributes to improving our capacity to address changing disturbance regimes in ecosystem management. (C) 2013 Elsevier Ltd. All rights reserved.
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| 7. |
- Blennow, Kristina, et al.
(författare)
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Societal impacts of storm damage
- 2013
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Ingår i: Living with Storm Damage to Forests. What science can tell us. - 9789525980097 ; :3, s. 70-77
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 8. |
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| 9. |
- Helbig, M., et al.
(författare)
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Warming response of peatland CO2 sink is sensitive to seasonality in warming trends
- 2022
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Ingår i: Nature Climate Change. - : Springer Science and Business Media LLC. - 1758-6798 .- 1758-678X. ; 12:8, s. 743-749
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Tidskriftsartikel (refereegranskat)abstract
- Peatlands have acted as net CO2 sinks over millennia, exerting a global climate cooling effect. Rapid warming at northern latitudes, where peatlands are abundant, can disturb their CO2 sink function. Here we show that sensitivity of peatland net CO2 exchange to warming changes in sign and magnitude across seasons, resulting in complex net CO2 sink responses. We use multiannual net CO2 exchange observations from 20 northern peatlands to show that warmer early summers are linked to increased net CO2 uptake, while warmer late summers lead to decreased net CO2 uptake. Thus, net CO2 sinks of peatlands in regions experiencing early summer warming, such as central Siberia, are more likely to persist under warmer climate conditions than are those in other regions. Our results will be useful to improve the design of future warming experiments and to better interpret large-scale trends in peatland net CO2 uptake over the coming few decades.
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| 10. |
- Pavelka, M., et al.
(författare)
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Standardisation of chamber technique for CO2, N2O and CH4 fluxes measurements from terrestrial ecosystems
- 2018
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Ingår i: International Agrophysics. - : Walter de Gruyter GmbH. - 0236-8722 .- 2300-8725. ; 32:4, s. 569-587
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Tidskriftsartikel (refereegranskat)abstract
- Chamber measurements of trace gas fluxes between the land surface and the atmosphere have been conducted for almost a century. Different chamber techniques, including static and dynamic, have been used with varying degrees of success in estimating greenhouse gases (CO2, CH4, N2O) fluxes. However, all of these have certain disadvantages which have either prevented them from providing an adequate estimate of greenhouse gas exchange or restricted them to be used under limited conditions. Generally, chamber methods are relatively low in cost and simple to operate. In combination with the appropriate sample allocations, chamber methods are adaptable for a wide variety of studies from local to global spatial scales, and they are particularly well suited for in situ and laboratory-based studies. Consequently, chamber measurements will play an important role in the portfolio of the Pan-European long-term research infrastructure Integrated Carbon Observation System. The respective working group of the Integrated Carbon Observation System Ecosystem Monitoring Station Assembly has decided to ascertain standards and quality checks for automated and manual chamber systems instead of defining one or several standard systems provided by commercial manufacturers in order to define minimum requirements for chamber measurements. The defined requirements and recommendations related to chamber measurements are described here.
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