| 1. |
- Berg, Sofia, et al.
(författare)
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Ekologisk funktionalitet av värdekärnor för barrskogar inom Västra Götalands län : Ett strategiskt underlag för planering av förändrad skogsskötsel av barrskogsområden inom Västra Götalands län i syfte att stärka skogarnas förutsättningar att stödja biologisk mångfald och skogens klimatnytta
- 2022
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Rapport (populärvet., debatt m.m.)abstract
- Skogsstyrelsen redovisar i sin utvärdering av miljömålet Levande skogar 2019 att centrala hinder för uppfyllelse av miljömålet är minskande och fragmenterade livsmiljöer och minskande och/eller små populationer av ett antal hotade arter knutna till skogsekosystemet. En väg framåt för att vända denna trend är att framtidens skogsbruk bland annat bör utvecklas utifrån ett landskapsperspektiv och där hyggesfria skogsbruksmetoder ökar i omfattning.Länsstyrelserna i Sverige har genom sitt arbete med regionala handlingsplaner för grön infrastruktur identifierat så kallade värdekärnor – områden av stor betydelse för skogsarternas överlevnad. I denna studie har Västra Götalands läns värdekärnor analyserats med avseende på deras förmåga att stödja biologisk mångfald i ett landskapsperspektiv. Arbetet har gjorts i samverkan med Länsstyrelsen för Västra götalands län.Metoden som använts är Biotope Biodiversity Capacity Indicator (BBCI). Metoden har utvecklats inom forskningsprojektet “Landscape biodiversity capacity: a tool for measuring, monitoring and managing” finansierat av Naturvårdsverkets miljöforskningsanslag (2019-2022).Resultaten visar vilka geografiskt avgränsade värdekärnor som idag har hög ekologisk funktionalitet och som utgör biologiska överlevnads- och spridningshotspots för arter knutna till barrskogar. Vidare visar resultaten att endast sju kommuner har BBCI-värden över 1, det vill säga, ett hållbart skogslandskap som kan hålla fokusarten i ett 100-årsperspektiv.För att nå de svenska miljömålen Levande skogar och Ett rikt växt- och djurliv samt skapa bättre förutsättningar för skogens biologiska mångfald att fortleva behöver nuvarande skogsmetoder med trakthyggesbruk anpassas till brukningsformer som tar större hänsyn till skogens ekosystem. Resultaten från denna studie kan ge prioriteringsunderlag för inom vilka produktionsskogar en så kallad återvildning genom förändrad brukningsmetod skulle kunna resultera i betydelsefull ökad ekologisk funktionalitet på landskapsnivå för de västgötska barrskogarna.
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| 2. |
- Curtsdotter, Alva, et al.
(författare)
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Ecosystem function in predator-prey food webs : confronting dynamic models with empirical data
- 2019
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Ingår i: Journal of Animal Ecology. - : John Wiley & Sons. - 0021-8790 .- 1365-2656. ; 88:2, s. 196-210
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Tidskriftsartikel (refereegranskat)abstract
- Most ecosystem functions and related services involve species interactions across trophic levels, for example, pollination and biological pest control. Despite this, our understanding of ecosystem function in multitrophic communities is poor, and research has been limited to either manipulation in small communities or statistical descriptions in larger ones. Recent advances in food web ecology may allow us to overcome the trade-off between mechanistic insight and ecological realism. Molecular tools now simplify the detection of feeding interactions, and trait-based approaches allow the application of dynamic food web models to real ecosystems. We performed the first test of an allometric food web model's ability to replicate temporally nonaggregated abundance data from the field and to provide mechanistic insight into the function of predation. We aimed to reproduce and explore the drivers of the population dynamics of the aphid herbivore Rhopalosiphum padi observed in ten Swedish barley fields. We used a dynamic food web model, taking observed interactions and abundances of predators and alternative prey as input data, allowing us to examine the role of predation in aphid population control. The inverse problem methods were used for simultaneous model fit optimization and model parameterization. The model captured >70% of the variation in aphid abundance in five of ten fields, supporting the model-embodied hypothesis that body size can be an important determinant of predation in the arthropod community. We further demonstrate how in-depth model analysis can disentangle the likely drivers of function, such as the community's abundance and trait composition. Analysing the variability in model performance revealed knowledge gaps, such as the source of episodic aphid mortality, and general method development needs that, if addressed, would further increase model success and enable stronger inference about ecosystem function. The results demonstrate that confronting dynamic food web models with abundance data from the field is a viable approach to evaluate ecological theory and to aid our understanding of function in real ecosystems. However, to realize the full potential of food web models, in ecosystem function research and beyond, trait-based parameterization must be refined and extended to include more traits than body size. © 2018 The Authors. Journal of Animal Ecology © 2018 British Ecological Society
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| 3. |
- Fick, Jerker, et al.
(författare)
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Screening of benzodiazepines in thirty European rivers
- 2017
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Ingår i: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 176, s. 324-332
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Tidskriftsartikel (refereegranskat)abstract
- Pharmaceuticals as environmental contaminants have received a lot of interest over the past decade but, for several pharmaceuticals, relatively little is known about their occurrence in European surface waters. Benzodiazepines, a class of pharmaceuticals with anxiolytic properties, have received interest due to their behavioral modifying effect on exposed biota. In this study, our results show the presence of one or more benzodiazepine(s) in 86% of the analyzed surface water samples (n = 138) from 30 rivers, representing seven larger European catchments. Of the 13 benzodiazepines included in the study, we detected 9, which together showed median and mean concentrations (of the results above limit of quantification) of 5.4 and 9.6 ng L-1, respectively. Four benzodiazepines (oxazepam, temazepam, clobazam, and bromazepam) were the most commonly detected. In particular, oxazepam had the highest frequency of detection (85%) and a maximum concentration of 61 ng L-1. Temazepam and clobazam were found in 26% (maximum concentration of 39 ng L-1) and 14% (maximum concentration of 11 ng L-1) of the samples analyzed, respectively. Finally, bromazepam was found only in Germany and in 16 out of total 138 samples (12%), with a maximum concentration of 320 ng L-1. This study clearly shows that benzodiazepines are common micro-contaminants of the largest European river systems at ng L-1 levels. Although these concentrations are more than a magnitude lower than those reported to have effective effects on exposed biota, environmental effects cannot be excluded considering the possibility of additive and sub-lethal effects.
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| 4. |
- Grut, Viktor, et al.
(författare)
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Cytomegalovirus seropositivity is associated with reduced risk of multiple sclerosis : a presymptomatic case-control study
- 2021
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Ingår i: European Journal of Neurology. - : Blackwell Publishing. - 1351-5101 .- 1468-1331. ; 28:9, s. 3072-3079
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Epstein-Barr virus (EBV) and Human herpesvirus 6A (HHV-6A) are associated with increased risk of multiple sclerosis (MS). Conversely, infection with Cytomegalovirus (CMV) has been suggested to reduce the risk of MS but supporting data from presymptomatic studies are lacking. Here, we sought to increase the understanding of CMV in MS aetiology.METHODS: We performed a nested case-control study with presymptomatically collected blood samples identified through cross-linkage of MS registries and Swedish biobanks. Serological antibody response against CMV, EBV and HHV-6A was determined using a bead-based multiplex assay. Odds ratio (OR) with 95 % confidence intervals (CI) for CMV seropositivity as risk factor for MS was calculated by conditional logistic regression and adjusted for EBV and HHV-6A seropositivity. Potential interactions on the additive scale were analysed by calculating attributable proportion due to interaction (AP).RESULTS: Serum samples from 670 pairs of matched cases and controls were included. CMV seropositivity was associated with a reduced risk for MS (OR = 0.70, 95% CI 0.56-0.88, p = 0.003). Statistical interactions on the additive scale were observed between seronegativity for CMV and seropositivity against HHV-6A (AP 0.34, 95% CI 0.06-0.61) and EBV antigen EBNA-1 (amino acid 385-420) at age 20-39 years (AP 0.37, 95% CI 0.09-0.65).CONCLUSIONS: CMV seropositivity is associated with a decreased risk for MS. The protective role for CMV infection in MS aetiology is further supported by the interactions between CMV seronegativity and EBV and HHV-6A seropositivity.
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| 5. |
- Heuvelmans, Matthijs, 1982-, et al.
(författare)
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Power Semiconductors for Voltage Source Converters in HVDC and STATCOM Applications
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- With a steady increase in electricity consumption in both developed and developing regions combined with demand for sustainable energy infrastructure, trends towards more renewable energy sources and more open electricity markets are becoming more prominent. High Voltage DC (HVDC) connections and Static Synchronous Compensators (STATCOM) are two technologies that play a part in fulfilling this increasing demand. HVDC is beneficial in cases where production and consumption are geographically separated or for sub-sea cable transmissions. STATCOM helps to increase the capacity of AC transmission in addition to enhancing ac-grid voltage quality. A key component in both HVDC and STATCOM converters are the semiconductor switching devices. Switching devices have a fundamental impact on performance levels that can be obtained in terms of efficiency, reliability and functionality. This paper serves two purposes. The first is to give a historical overview of switching devices employed in HVDC transmission systems and STATCOMs. This starts with the use of mercury arc valves some 100 years ago and it continues with the semiconductor switching devices that are currently being employed in HVDC and STATCOM applications. A second purpose of this paper is to indicate developments in switching technology that are of interest for HVDC and STATCOM. In order to do this in a structured manner, the technologies are compared in terms of efficiency, reliability and functionality. Developments that are discussed in this paper are the emergence of Silicon Carbide (SiC) devices and the improvement of Insulated Gate Bipolar Transistor (IGBT) and Integrated Gate Commutated Thyristor (IGCT) devices in silicon. Currently, applications are based on silicon based thyristors or IGBT technology. Line commutated converters based on thyristors are cost-effective and efficient; however, due to lack of controlled turn-off capability, functionality is limited. Using voltage source converter technology with semiconductors having turn-off capability, such as the IGBT, increased functionality is obtained. The IGCT, a gate controlled thyristor with turn-off capability, has lower conduction losses compared to an IGBT with the same active area. In case a modular multilevel converter is used, the switching frequency of the individual switches can be reduced for the same performance. This leads to a shift towards the importance of having low conduction losses as opposed to low switching losses. A further shift can be achieved by using soft-switching techniques. Regarding SiC devices, different maturity is reached for unipolar and bipolar devices. Unipolar devices in SiC have been marketed successfully at low voltages (≤ 1700V). An example is SiC Schottky diodes for power factor correctors. For the voltages typically applied in HVDC and STATCOM, the drift region resistance would impose serious limitations on efficiency (if high current densities are used). Bipolar devices such as SiC IGBTs and IGCTs have been demonstrated in laboratory setups and results have been published; however, reliable operation is currently impeded due to the propagation of crystal lattice defects which causes rapid degradation of such devices.
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| 6. |
- Jonsson, Annie, et al.
(författare)
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Landskapets förmåga att hålla biologisk mångfald : – en indikator för biologisk mångfald och ett planeringsverktyg för prioritering av markanvändning
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Rapporten beskriver ett nytt verktyg framtaget för att underlätta planering av grön infrastruktur på landskapsnivå och ger via fallstudier exempel på hur verktyget kan användas. Projektet har utförts i ett samarbete med expertis inom teoretisk ekologi, ekologi, biodiversitetsinformatik och tillämpad matematik.Forskningsprojektet har utvecklat en modell för att uppskatta ett landskaps för-måga att hålla biologisk mångfald i dess olika biotoper (Biotope Biodiversity Capacity Indicator, BBCI). Ett teoretiskt ramverk baserat på ekologisk kunskap har tagits fram som grund för modellen.Syftet med BBCI är att modellen ska kunna användas som ett planeringsverktyg för att:stärka biologisk mångfald i ett landskap,förbättra förutsättningarna för arter att använda hela landskapet ochskapa bättre förutsättningar för hänsyn till biologisk mångfald i samband med samhällsutveckling.För att testa och beskriva verktygets användbarhet har fyra fallstudier genomförts med olika fokus:Analys av fragmenteringen i ett barrskogslandskap som sköts med särskild naturhänsyn i Västernorrlands län.Analys av barrskogsvärdekärnors kapacitet för biologisk mångfald inom Västra Götalands län som synliggör vikten av kommunöverskridande samverkan.Analys av potentiella målkonflikter mellan två biotoper, ädellövskog och öppen mark med skyddsvärda träd i Valle.Analys av kapacitet för biologisk mångfald hos äldre ädellövträd i ett landskap mixat med urbana miljöer och landsbygd, Mjölby kommun.Parallellt med utvcklingen av BBCI har en tät dialog och samverkan skett med olika intressenter och slutanvändare. Den breda dialogen har medfört ett effektivt kun-skapsutbyte mellan olika parter.Rapporten avslutas med att beskriva utmaningar och verktygets utvecklings-potential både avseende pedagogik och teknik men även hur modellen kan byggas på och utvecklas med ytterligare funktioner för en breddad tillämpning.
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| 7. |
- Jonsson, Anders, et al.
(författare)
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Limitations of acyclic causal graphs for planning
- 2014
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Ingår i: Artificial Intelligence. - : Elsevier. - 0004-3702 .- 1872-7921. ; 210, s. 36-55
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Tidskriftsartikel (refereegranskat)abstract
- Causal graphs are widely used in planning to capture the internal structure of planning instances. Researchers have paid special attention to the subclass of planning instances with acyclic causal graphs, which in the past have been exploited to generate hierarchical plans, to compute heuristics, and to identify classes of planning instances that are easy to solve. This naturally raises the question of whether planning is easier when the causal graph is acyclic. In this article we show that the answer to this question is no, proving that in the worst case, the problem of plan existence is PSPACE-complete even when the causal graph is acyclic. Since the variables of the planning instances in our reduction are propositional, this result applies to STRIPS planning with negative preconditions. We show that the reduction still holds if we restrict actions to have at most two preconditions. Having established that planning is hard for acyclic causal graphs, we study two subclasses of planning instances with acyclic causal graphs. One such subclass is described by propositional variables that are either irreversible or symmetrically reversible. Another subclass is described by variables with strongly connected domain transition graphs. In both cases, plan existence is bounded away from PSPACE, but in the latter case, the problem of bounded plan existence is hard, implying that optimal planning is significantly harder than satisficing planning for this class.
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| 8. |
- Jonsson, Annie, et al.
(författare)
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Utvärdering av Hornborgasjöns restaurering : måluppfyllelse och effekter på biologisk mångfald med fokus på vegetation och fågelfauna
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Hornborgasjön räknas idag som en av Sveriges rikaste fågelsjöar och är internationellt utpekad som en av Sveriges värdefullaste våtmarker. Sjön har stor betydelse som både rast- och häckplats för en mängd fågelarter. Området är också av stort intresse för friluftslivet och som ett levande kulturlandskap. Under de senaste 150 åren har Hornborgasjön genomgått stora förändringar. En serie av sjösänkningar under 1800 och 1900-talen ledde till kraftig igenväxning och följdes av ett storskaligt restaureringsprojekt i senare tid. Syftet med Hornborgasjöns restaurering var att säkerställa Hornborgasjöns framtid som fågelsjö. Restaureringen är ett av Sveriges största naturvårdsprojekt. I denna rapport har vi utvärderat hur Hornborgasjöns restaurering påverkat vegetation och fågelfauna. Syftet var att analysera om och till vilken grad de biologiska målen med restaureringen uppnåtts.För att utvärdera måluppfyllelsen har vi i första hand jämfört olika naturtypers utbredning mellan åren 1905 och 2010 samt förändringar i fågelfaunan under flera tidsperioder. Analyser av vegetationskartor visar att vass- och buskområden kraftigt reducerats och att en stor öppen vattenspegel och omgivande mader återskapats. Våtmarksfåglarnas numerär har generellt sett återhämtat sig från igenväxningsperioden och är för vissa arter till och med större än vid förra sekelskiftet. För vissa naturtyper och fågelarter, som till exempel vassområden och häckande vadare, är dagens situation dock inte i linje med målen. Det står ändå klart att det övergripande målet och många av de mer specifika delmålen har uppfyllts så att Hornborgasjön idag är en levande våtmark med stort antal häckande och rastande fågelarter.I analyser av fågeldata från senare tid finns indikationer på negativa trender som man behöver vara observant på för att för framtiden säkra en biologiskt rik Hornborgasjö. En utmaning för denna utvärdering har dock varit bristen på högkvalitativa och jämförbara data att basera analyserna på. Vi belyser därför vikten av att ha ett fungerande övervakningssystem som kontinuerligt följer upp statusen i ekosystemet.
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| 9. |
- Jonsson, Anders, et al.
(författare)
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When Acyclicity is not Enough: Limitations of the Causal Graph
- 2013
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Ingår i: Proceedings of the Twenty-Third International Conference on Automated Planning and Scheduling. - : AAAI Press. - 9781577356097 ; , s. 117-125
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Konferensbidrag (refereegranskat)abstract
- Causal graphs are widely used in planning to capture the internal structure of planning instances. In the past, causal graphs have been exploited to generate hierarchical plans, to compute heuristics, and to identify classes of planning instances that are easy to solve. It is generally believed that planning is easier when the causal graph is acyclic. In this paper we show that this is not true in the worst case, proving that the problem of plan existence is PSPACE-complete even when the causal graph is acyclic. Since the variables of the planning instances in our reduction are propositional, this result applies to STRIPS planning with negative pre-conditions. Having established that planning is hard for acyclic causal graphs, we study a subclass of planning instances with acyclic causal graphs whose variables have strongly connected domain transition graphs. For this class, we show that plan existence is easy, but that bounded plan existence is hard, implying that optimal planning is significantly harder than satisficing planning for this class.
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| 10. |
- Jonsson, Tomas, et al.
(författare)
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Food web structure affects the extinction risk of species in ecological communities
- 2006
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Ingår i: Ecological Modelling. - : Elsevier. - 0304-3800 .- 1872-7026. ; 199:1, s. 93-106
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Tidskriftsartikel (refereegranskat)abstract
- This paper studies the effect of food web structure on the extinction risk of species. We examine 793 different six-species food web structures with different number, position and strength of trophic links and expose them to stochasticity in a model with Lotka–Volterra predator–prey dynamics. The characteristics of species (intrinsic rates of increase as well as intraspecific density dependence) are held constant, but the interactions with other species and characteristics of the food web are varied.Extinctions of producer species occurred but were rare. Species at all trophic levels went extinct in communities with strong interactions as compared to communities with no strong interactions where only the secondary consumer went extinct. Extinction of a species directly involved in a strong interaction was more frequent than extinctions of species not directly involved in strong interactions (here termed direct and indirect extinctions, respectively). In model webs where both direct and indirect extinctions occurred, roughly 20% were indirect extinctions. The probability of indirect extinctions decreased with number of links. It is concluded that not just the presence of strong interactions but also their position and direction can have profound effects on extinction risk of species.Three principal components, based on 11 different food web metrics, explained 76.6% of the variation in trophic structure among food webs that differed in the number and position, but not strength, of trophic links. The extinction risk of consumer species was closely correlated to at least two of the three principal components, indicating that extinction risk of consumer species were affected by food web structure. The existence of a relationship between food web structure and extinction risk of a species was confirmed by a regression tree analysis and a complementary log-linear analysis. These analyses showed that extinction of consumer species were affected by the position of strong interactions and a varying number of other food web metrics, different for intermediate and top species. Furthermore, the degree to which the equilibrium abundance of a species is affected by a press perturbation is an indication of the risk of extinction that this species faces when exposed to environmental stochasticity. It is concluded that extinction risk of a species is determined in a complicated way by an interaction among species characteristics, food web structure and the type of disturbance.
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