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  • Ahlberg, Erik, et al. (författare)
  • "Vi klimatforskare stödjer Greta och skolungdomarna"
  • Ingår i: Dagens nyheter (DN debatt). - 1101-2447.
  • Tidskriftsartikel (populärvet., debatt m.m.)abstract
    • DN DEBATT 15/3. Sedan industrialiseringens början har vi använt omkring fyra femtedelar av den mängd fossilt kol som får förbrännas för att vi ska klara Parisavtalet. Vi har bara en femtedel kvar och det är bråttom att kraftigt reducera utsläppen. Det har Greta Thunberg och de strejkande ungdomarna förstått. Därför stödjer vi deras krav, skriver 270 klimatforskare.
  • Alfonsson, Sven, 1977-, et al. (författare)
  • Differences in motivation and adherence to a prescribed assignment after face-to-face and online psychoeducation : A randomized experiment
  • 2017
  • Ingår i: BMC Psychology. - 2050-7283. ; 5:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Adherence to treatment homework is associated with positive outcomes in behavioral psychotherapy but compliance to assignments is still often moderate. Whether adherence can be predicted by different types of motivation for the task and whether motivation plays different roles in face-to-face compared to online psychotherapy is unknown. If models of motivation, such as Self-determination theory, can be used to predict patients’ behavior, it may facilitate further research into homework promotion. The aims of this study were, therefore, to investigate whether motivation variables could predict adherence to a prescribed assignment in face-to-face and online interventions using a psychotherapy analog model. Methods: A total of 100 participants were included in this study and randomized to either a face-to-face or online intervention. Participants in both groups received a psychoeducation session and were given an assignment for the subsequent week. The main outcome measurements were self-reported motivation and adherence to the assignment. Results: Participant in the face-to-face condition reported significantly higher levels of motivation and showed higher levels of adherence compared to participants in the online condition. Adherence to the assignment was positively associated with intrinsic motivation and intervention credibility in the whole sample and especially in the online group. Conclusions: This study shows that intrinsic motivation and intervention credibility are strong predictors of adherence to assignments, especially in online interventions. The results indicate that intrinsic motivation may be partly substituted with face-to-face contact with a therapist. It may also be possible to identify patients with low motivation in online interventions who are at risk of dropping out. Methods for making online interventions more intrinsically motivating without increasing external pressure are needed.
  • Buker, P., et al. (författare)
  • DO3SE modelling of soil moisture to determine ozone flux to forest trees
  • 2012
  • Ingår i: Atmospheric Chemistry and Physics. - : Copernicus Gesellschaft mbH. - 1680-7316 .- 1680-7324. ; 12:12, s. 5537-5562
  • Tidskriftsartikel (refereegranskat)abstract
    • The DO3SE (Deposition of O-3 for Stomatal Exchange) model is an established tool for estimating ozone (O-3) deposition, stomatal flux and impacts to a variety of vegetation types across Europe. It has been embedded within the EMEP (European Monitoring and Evaluation Programme) photochemical model to provide a policy tool capable of relating the flux-based risk of vegetation damage to O-3 precursor emission scenarios for use in policy formulation. A key limitation of regional flux-based risk assessments has been the assumption that soil water deficits are not limiting O-3 flux due to the unavailability of evaluated methods for modelling soil water deficits and their influence on stomatal conductance (g(sto)), and subsequent O-3 flux. This paper describes the development and evaluation of a method to estimate soil moisture status and its influence on g(sto) for a variety of forest tree species. This DO3SE soil moisture module uses the Penman-Monteith energy balance method to drive water cycling through the soil-plant-atmosphere system and empirical data describing g(sto) relationships with pre-dawn leaf water status to estimate the biological control of transpiration. We trial four different methods to estimate this biological control of the transpiration stream, which vary from simple methods that relate soil water content or potential directly to g(sto), to more complex methods that incorporate hydraulic resistance and plant capacitance that control water flow through the plant system. These methods are evaluated against field data describing a variety of soil water variables, g(sto) and transpiration data for Norway spruce (Picea abies), Scots pine (Pinus sylvestris), birch (Betula pendula), aspen (Populus tremuloides), beech (Fagus sylvatica) and holm oak (Quercus ilex) collected from ten sites across Europe and North America. Modelled estimates of these variables show consistency with observed data when applying the simple empirical methods, with the timing and magnitude of soil drying events being captured well across all sites and reductions in transpiration with the onset of drought being predicted with reasonable accuracy. The more complex methods, which incorporate hydraulic resistance and plant capacitance, perform less well, with predicted drying cycles consistently underestimating the rate and magnitude of water loss from the soil. A sensitivity analysis showed that model performance was strongly dependent upon the local parameterisation of key model drivers such as the maximum g(sto), soil texture, root depth and leaf area index. The results suggest that the simple modelling methods that relate g(sto) directly to soil water content and potential provide adequate estimates of soil moisture and influence on g(sto) such that they are suitable to be used to assess the potential risk posed by O-3 to forest trees across Europe.
  • Coste, S, et al. (författare)
  • Assessing foliar chlorophyll contents with the SPAD-502 chlorophyll meter: 165 a calibration test with thirteen tree species of tropical rainforest in French Guiana
  • 2010
  • Ingår i: Annals of Forest Science. - : Springer. - 1286-4560. ; 67:6, s. 607p1-607p5
  • Tidskriftsartikel (refereegranskat)abstract
    • • Chlorophyll meters such as the SPAD-502 offer a simple, inexpensive and rapid method to estimate foliar chlorophyll content. However, values provided by SPAD-502 are unitless and require empirical calibrations between SPAD units and extracted chlorophyll values. • Leaves of 13 tree species from the tropical rain forest in French Guiana were sampled to select the most appropriate calibration model among the often-used linear, polynomial and exponential models, in addition to a novel homographic model that has a natural asymptote. • The homographic model best accurately predicted total chlorophyll content (µg cm-2) from SPAD units (R² = 0.89). Inter-specific differences in the homographic model parameters explain less than 7% of the variation in chlorophyll content in our dataset. • The utility of the general homographic model for a variety of research and management applications clearly outweighs the slight loss of model accuracy due to the abandon of the species-effect.
  • Jaramillo, Fernando, et al. (författare)
  • Dominant effect of increasing forest biomass on evapotranspiration: Interpretations of movement in Budyko space
  • 2018
  • Ingår i: Hydrology and Earth System Sciences. - : European Geosciences Union (EGU) / Copernicus Publications. - 1027-5606 .- 1607-7938. ; 22, s. 567-580
  • Tidskriftsartikel (refereegranskat)abstract
    • During the last 6 decades, forest biomass has increased in Sweden mainly due to forest management, with a possible increasing effect on evapotranspiration. However, increasing global CO 2 concentrations may also trigger physiological water-saving responses in broadleaf tree species, and to a lesser degree in some needleleaf conifer species, inducing an opposite effect. Additionally, changes in other forest attributes may also affect evapotranspiration. In this study, we aimed to detect the dominating effect(s) of forest change on evapotranspiration by studying changes in the ratio of actual evapotranspiration to precipitation, known as the evaporative ratio, during the period 1961-2012. We first used the Budyko framework of water and energy availability at the basin scale to study the hydroclimatic movements in Budyko space of 65 temperate and boreal basins during this period. We found that movements in Budyko space could not be explained by climatic changes in precipitation and potential evapotranspiration in 60% of these basins, suggesting the existence of other dominant drivers of hydroclimatic change. In both the temperate and boreal basin groups studied, a negative climatic effect on the evaporative ratio was counteracted by a positive residual effect. The positive residual effect occurred along with increasing standing forest biomass in the temperate and boreal basin groups, increasing forest cover in the temperate basin group and no apparent changes in forest species composition in any group. From the three forest attributes, standing forest biomass was the one that could explain most of the variance of the residual effect in both basin groups. These results further suggest that the water-saving response to increasing CO 2 in these forests is either negligible or overridden by the opposite effect of the increasing forest biomass. Thus, we conclude that increasing standing forest biomass is the dominant driver of long-term and large-scale evapotranspiration changes in Swedish forests.
  • Klingberg, Jenny, 1978, et al. (författare)
  • Ozone risk for vegetation in the future climate of Europe based on stomatal ozone uptake calculations
  • 2011
  • Ingår i: Tellus A. - : Wiley-Blackwell. ; 63:1, s. 174-187
  • Tidskriftsartikel (refereegranskat)abstract
    • The negative impacts of surface ozone (O3) on vegetation are determined by external exposure, leaf gas exchange and plant antioxidant defence capacity, all dependent on climate and CO2 concentrations. In this study the influence of climate change on simulated stomatal O3 uptake of a generic crop and a generic deciduous tree at ten European sites was investigated, using the LRTAP Mapping Manual stomatal flux model. O3 concentrations are calculated by a chemistry transport model (MATCH) for three 30-year time-windows (1961-1990, 2021-2050, 2071-2100), with constant precursor emissions and meteorology from a regional climate model (RCA3). Despite substantially increased modelled future O3 concentrations in central and southern Europe, the flux-based risk for O3 damage to vegetation is predicted to remain unchanged or decrease at most sites, mainly as a result of projected reductions in stomatal conductance under rising CO2 concentrations. Drier conditions in southern Europe are also important for this result. At northern latitudes, the current parameterisation of the stomatal conductance model suggest O3 uptake to be mainly limited by temperature. This study demonstrates the importance of accounting for the influences by climate and CO2 on stomatal O3 uptake, and of developing their representation in models, for risk assessment involving climate change.
  • Stenseke, Marie, et al. (författare)
  • Kris i naturen – vår existens har blivit sårbar
  • Ingår i: Svenska Dagbladet, Stockholm. - : Svenska Dagbladet. - 1101-2412.
  • Tidskriftsartikel (populärvet., debatt m.m.)abstract
    • Fler arter än någonsin i mänsklighetens historia hotas av utrotning och den biologiska mångfalden lokalt har förändrats kraftigt i en stor del av världens ekosystem. Grundläggande förändringar behövs både i samhället och för individer, för att bromsa den negativa trenden, skriver en rad debattörer.
  • Adolfsson, Lisa, 1984, et al. (författare)
  • Mycorrhiza Symbiosis Increases the Surface for Sunlight Capture in Medicago truncatula for Better Photosynthetic Production
  • 2015
  • Ingår i: PLoS ONE. - 1932-6203. ; 10:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Arbuscular mycorrhizal (AM) fungi play a prominent role in plant nutrition by supplying mineral nutrients, particularly inorganic phosphate (Pi), and also constitute an important carbon sink. AM stimulates plant growth and development, but the underlying mechanisms are not well understood. In this study, Medicago truncatula plants were grown with Rhizophagus irregularis BEG141 inoculum (AM), mock inoculum (control) or with Pi fertilization. We hypothesized that AM stimulates plant growth through either modifications of leaf anatomy or photosynthetic activity per leaf area. We investigated whether these effects are shared with Pi fertilization, and also assessed the relationship between levels of AM colonization and these effects. We found that increased Pi supply by either mycorrhization or fertilization led to improved shoot growth associated with increased nitrogen uptake and carbon assimilation. Both mycorrhized and Pi-fertilized plants had more and longer branches with larger and thicker leaves than the control plants, resulting in an increased photosynthetically active area. AM-specific effects were earlier appearance of the first growth axes and increased number of chloroplasts per cell section, since they were not induced by Pi fertilization. Photosynthetic activity per leaf area remained the same regardless of type of treatment. In conclusion, the increase in growth of mycorrhized and Pi-fertilized Medicago truncatula plants is linked to an increase in the surface for sunlight capture, hence increasing their photosynthetic production, rather than to an increase in the photosynthetic activity per leaf area.
  • af Ekenstam, Angelica, et al. (författare)
  • Leaf respiration rates are increased by warm season as well as by elevated temperature treatment in Eucalyptus globulus
  • 2014
  • Ingår i: EGU General Assembly 2014, held 27 April - 2 May, 2014 in Vienna, Austria.
  • Konferensbidrag (övrigt vetenskapligt)abstract
    • Plant leaf respiration is one of the major CO2 fluxes between terrestrial biosphere and the atmosphere, and its responses to elevated CO2 and temperature thus have important implications for the carbon cycle and rate on ongoing climate change. Non-photorespiratory leaf respiration is reduced in light, Rlight, compared with the rate in the dark, Rdark. It is therefore important to consider both Rlight and Rdark when estimating the exchange of CO2 between the biosphere and the atmosphere, during current and future climates. This study was conducted at the Hawkesbury Forest Experiment, HFE, in Richmond, NSW, Australia. Trees of Tasmanian Blue Gum (Eucalyptus globulus Labill.) were exposed in whole tree chambers (WTC) to a complete factorial combination of ambient and elevated temperature and CO2 (+3 °C and +240 ppm CO2, respectively). The measurements of Rlight and Rdark were made in 2011 after 15 month exposure in the WTCs. The measurements were made in March (after the year’s hottest months) and October (after the coldest period). Rlight was determined at four temperatures ranging between 20 and 40 °C on attached leaves using a portable gas exchange system (LI-6400XT). Rdark was measured at 20-40 °C in October and at 25 °C in March. Rdark was measured after dark acclimation for at least 30 min and Rlight was determined from the intersection of the photosynthetic CO2 responses measured at three different light intensities using the Laisk metod. Trees grown in elevated temperature had a considerably higher Rdark (+53% across all measurement temperatures in October). However, Rlight did not respond significantly to either CO2 or temperature. In October, the Rlight to Rdark ratio indicated an overall light inhibition of respiration of 31% across all temperatures and in March the light inhibition was 22 % at 25 °C. The seasonal comparisons showed that both Rlight and Rdark were considerably higher after the warm compared to cold season, especially when measured at high temperature. These results points out the importance to account for Rlight as well as seasonal thermal respiratory acclimation when improving predictions of the carbon exchange between tree canopies and the atmosphere. If not taking light inhibition into account, leaf respiration is being overestimated and if not taking the seasonal acclimation into account the errors are potentially very large.
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