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- Abadikhah, Marie, 1992
(författare)
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Influence of electrode material and stochastic factors on the performance and microbial community assembly in microbial electrochemical systems
- 2022
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Microbial electrolysis cells (MECs) are systems with microbial communities in the form of biofilms on electrode surfaces. The electrogenic bacteria in the anode biofilm act as catalysts for the oxidization of organic compounds, leading to release of electrons, generation of electrical current, and production of hydrogen and methane at the cathode. In addition to production of energy carriers, MECs can be used for other applications as well; for example, as biosensors to monitor biochemical oxygen demand or toxicity. The performance of MECs is determined by both deterministic and stochastic factors influencing the microbial communities on the electrode surfaces, most of which as still poorly understood. In this thesis, the effects of electrode materials on microbial community assembly and MEC performance was investigated. Two experiments were carried out. In the first, three cathode materials (carbon nanoparticles, titanium, and steel) were compared. In the second, three anode materials (carbon cloth, graphene, and nickel) were compared. The cathode materials had no significant effect on the performance of the MECs, as opposed to the anode materials where carbon cloth MECs had the highest current density and the shortest lag time during startup. The differences seen in lag time of replicate systems at the start of the experiment indicated a stochastic initial attachment of the electrogenic bacteria on the anode. Different microbial communities develop in the biofilms on the anodes and cathodes. Electrogens from the Desulfobacterota phylum dominated the anode, while various hydrogenotrophic methanogens, e.g., Methanobacterium, were found to dominate on the cathodes. Diversity and null model analysis of the electrode communities highlighted stochasticity and not electrode material as the important factor in the community assembly. Network analysis showed that the cathode communities had fewer negative interactions between taxa in comparison to the anode. Since hydrogen gas generated at the cathode surface can diffuse through the biofilm, all microorganisms on the cathode have access to the substrate, reducing the need for competition between species. In contrast, electrogens require a short distance to the anode to be able to use it as electron acceptor. Limited space on the anode and competition between electrogens shaped the anode communities and explain the higher number of negative interactions observed. Based on the findings in this thesis, it is suggested that stochastic factors have more influence than electrode material on the anode community even though there is a selective pressure for electrogenic bacteria.
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| 2. |
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| 3. |
- Ahlbäck Widenfalk, Lina
(författare)
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Traits or species – space or environment : how to understand the spatial structure of springtail community composition
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- How communities are structured and the processes shaping species composition are among the basic questions in ecology. Knowledge about these processes is essential to predict changes in community composition in response to changes in for example climate or land use practices. Soil communities are considered to be both remarkably species-rich and to have many generalist species with seemingly similar niche requirements. Soil fauna composition shows a large variation even at small spatial scales and both local environment and spatial configuration of habitats are regarded as important forces shaping the community composition. In this thesis, I examine the factors influencing small-scale community composition of springtails (Collembola) in two habitats, a variable and dynamic salt marsh and a more stable mature pine forest. The functional traits of species determine both their responses to the environment and their effects on ecosystem processes. The current knowledge on environment - species - traits relationship is limited in spite of its potential importance for ecosystem function. I show that by combining perspectives from two closely linked theoretical frameworks – metacommunity ecology and community assembly theory – we get a better understanding of the important ecological factors operating in this system. I found that the factors influencing community composition was context dependent, but in a predictable way. In the environmentally variable habitat, salt marsh, with spatial and temporal heterogeneity, there was evidence of strong environmental filtering. Small-scale topography was the strongest predictor of community composition, likely due to disturbances restricting where habitat-generalists can persist. In contrast, in the more stable habitat, mature pine forest, environmental filtering appeared weaker and biotic interactions seemed to have a stronger impact. Coexisting species were more similar in traits related to resource utilisation and sensory ability than expected, and variation in species composition was explained mainly by spatial factors like the distance between samples, i.e. each local community seemed to depend on the composition of the surrounding communities.
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| 4. |
- Andersson, Anders, 1980-
(författare)
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Catch and effort from a recreational trolling fishery in a large lake
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Over recent decades recreational fisheries have grown substantially throughout the world. Despite this increase, catches from recreational fisheries have often been ignored in fisheries management, although this is now being remedied. Monitoring recreational fisheries can be expensive, and the primary means used for monitoring is angler (creel) surveys, typically funded from sales of fishing licences. The studies presented in this thesis examine different approaches to monitoring recreational trolling fisheries’ catch and effort, where fishing licenses are not required and there are no reporting requirements. I present results from a complemented roving/mail-in survey undertaken during 2013-2014 to estimate recreational effort and catch of Atlantic salmon (Salmo salar) and brown trout (S. trutta) in the largest lake in the European Union, Lake Vänern, Sweden. I also evaluate different angler catch reporting methods (mail-in, tournament reports and face-to-face interviews) and compare catch rates within and among spring and fall fishing periods. In addition, mail-in survey data are examined for recall bias. I estimate that 28.7 tonnes of salmon and trout combined were harvested by the recreational trolling fishery in 2014, more than the commercial and subsistence fisheries combined. Seasonal differences in both recreational effort and catch were observed. Effort, in boat hours, was significantly higher in spring than in fall. Catch rates of trout were higher in fall than in spring, but there were no seasonal differences in catches of salmon. Harvest per boat day did not differ significantly among catch reporting methods, indicating that all three methods could be useful for managers interested in harvest rates. In contrast, total and released catch per boat day differed among reporting methods, with tournament anglers catching more fish in total. Finally, there was little evidence for recall bias in mail-in surveys, indicating that mail-in surveys are useful for collecting unbiased catch data. My study is the most comprehensive angler survey to date for Lake Vänern, and my results should be of immediate use to local fisheries managers and should also be of interest to researchers and managers interested in estimating catch and effort for fisheries at large spatial scales.
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| 5. |
- Beier, Ulrika
(författare)
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Habitat selection and indirect interactions in fish communities : mechanisms to explain spatial distribution of perch, roach, and vendace
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- To increase the understanding of freshwater lake ecosystems, I have studied the habitat selection of perch (Perca fluviatilis L.), roach (Rutilus rutilus (L.)), and vendace (Coregonus albula (L.)). These fish species use the pelagic and the littoral-benthic habitats in lakes to different extents. Perch and roach are omnivorous, and perch become piscivorous at larger sizes. Vendace is a pelagic species specialized in eating zooplankton. Vendace was expected to affect biotic interactions and habitat use of roach and perch, both directly and indirectly. I used monitoring data to examine how species distribution patterns, as well as population structures, depended on species composition. In a predation experiment, I studied the relative predation sensitivity as well as evasive behaviours of roach and vendace, with piscivorous perch used as predators. In foraging experiments in aquaria, I studied foraging efficiencies and swimming performances of roach and vendace eating zooplankton in different temperature and light treatments. I then applied metabolic models for roach and vendace, respectively, to compare their net energy gain in different abiotic conditions. Roach used the pelagic habitat less, and the biomass of roach was lower in lakes with vendace. Results did not support the prediction that perch populations would benefit from the presence of vendace. However, results indicated that a release of competition for small perch may be mediated by vendace, through changed habitat use of roach, increasing the possibilities for predation. Roach and vendace were similar in their sensitivity to predation, indicating that energy gain can explain their habitat use. Foraging efficiencies did not explain the habitat use of roach and vendace in the field. However, the net energy gain in different abiotic conditions, could explain observed patterns of their habitat use in lakes. This thesis shows how the trade-off between mortality and net energy gain is manifested in habitat use. Including habitat selection in ecological studies may increase our understanding of biotic interactions. Metabolic costs as well as foraging abilities in different abiotic conditions are important for explaining the habitat use of species. Such knowledge can make it possible to forecast how interacting fish species may be affected by environmental change.
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| 6. |
- Bell, David
(författare)
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Forest restoration guided by an umbrella species : will measures to protect the white-backed woodpecker benefit saproxylic beetles?
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Management shortcuts in conservation biology, like the umbrella species concept, have been debated worldwide. Umbrella species have been used to identify and delineate protective areas, but habitat requirements of umbrella species can also provide tangible targets in ecological restoration. In Sweden, forest habitats have been restored for the white-backed woodpecker (WBW, Dendrocopos leucotos) under the assumption that it will benefit other habitat-associated (background) species. In this thesis, the umbrella species concept was evaluated based on the response of wood-inhabiting (saproxylic) beetles to forest restoration for the WBW. The WBW is a top-predator in saproxylic food webs associated with broadleaved trees, but it is also critically endangered in Sweden because of commercial forestry practices that disadvantage broadleaved trees and reduce dead wood availability. Spruce trees (Norway spruce, Picea abies) were selectively harvested during forest restoration to make way for broadleaved trees like birch (Betula spp.) and European aspen (Populus tremula). Some broadleaved trees were also killed to create high-stumps (snags) and downed logs. Commercially managed forests were compared with restored forests; either directly in comparative studies, or before and after forest restoration. Two types of flight-intercept traps were used to catch saproxylic beetles: IBL2-traps and trunk-window traps. Results presented in this thesis show that habitat requirements of an umbrella species can be used to guide forest restoration. There were many beneficiary species at the stand-level. Commercially managed and restored forests were inhabited by different communities of saproxylic beetles, and species positively associated with broadleaved trees and sun-exposed substrates were particularly responsive. This was reflected by an increased species richness and abundance. Several near-threatened and vulnerable species were also attracted to substrates created for the WBW. This shows that efforts to bring back the WBW can benefit other resource-limited groups of conservation concern. Saproxylic beetles might even facilitate restoration efforts since many important prey species for the WBW were attracted to restored sites. Umbrella species, like the WBW, will require landscape-level efforts to recover. This is a strength of the umbrella species concept, but also a weakness since landscape-level efforts are time consuming. The WBW is still struggling in Sweden, and failed attempts to re-establish viable populations might undermine conservation incentives. Early signs of progress, however, are sometimes provided by less demanding species, like many saproxylic beetles in this thesis. Background species can also provide much needed examples of restoration success at the stand-level.
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| 7. |
- Bergstedt, Johan, 1953-
(författare)
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Boreal vegetation responses to forestry as reflected in field trial and survey data
- 2004
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis had two objectives: the first objective was to evaluate the response of forest ground vegetation to selected forestry operations, i.e. cutting of different intensities and scarification; the second objective was to compare the use of survey data in vegetation research with that of more traditional research using field trials - i.e. can survey data be used and produce results that comply with those emerging from field trials? Here, the results from an analysis of survey data has been compared with results emerging from a field trial.Survey data was analysed from the National Forest Inventory (NFI), using 789 sample plots in central and northern Sweden visited twice at an interval of 10-11 years, 294 of which had been subjected to logging between inventories. This was compared with a field trial in central Sweden: a complete block design with four replicates - three treatments and conventional harvesting as the control.The cutting intensity was found to have an impact on the ground-layer flora, the change being mostly differences in abundance rather than change in species richness. Those increasing were early successional species, i.e. crustose lichens, Deschampsia flexuosa. In contrast, Vaccinium myrtillus was decreasing substantially in response to increased cutting intensity. A number of species appeared to be indifferent to cutting, i.e. Vaccinium vitisidaea, Trientalis europaea.Scarification had a different impact on the flora than cutting: only Polytrichum spp. increased substantially, while many decreased.For those effects that were possible to compare in both studies, the results from survey data comply with those from the field trial, indicating that survey data is possible to use in forest vegetation research.
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| 8. |
- Bergsten, Arvid, 1981-
(författare)
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Fragmented landscapes : Assessment and communication of landscape connectivity in human-dominated landscapes
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This licentiate thesis summarizes the first half of my PhD on the theme of management of fragmented landscapes. The thesis applies – and reflects on the use of – network analysis of connectivity in relation to landscape planning. Relevant theory on knowledge management and spatial ecology is summarized and discussed in connection with two papers.Paper I centers on municipal ecologists and environmental planners in the Stockholm region. They state that connectivity is rarely considered enough in planning and that assessment tools are lacking. Paper I studies the benefits and difficulties of using network analysis to manage connectivity in land-use planning. Among the main difficulties was the choice of model species and access to input data. The main strengths were the graphical and quantitative results, the potential for social learning, identification of critical sites and to relate local planning and ecology to the regional landscape.Paper II applies network methodology to quantify habitat availability of fragmented lichen-type forests in protected areas in northern Sweden. It studies a dynamic landscape that is continuously rearranged by forestry, with consequences that depend on species’ abilities to compete for resources in protected habitats, and to disperse through unprotected mature forest stands. We discuss the results with reference to the planning of forestry and protected areas, and to the resilience of species to patchy disturbance regimes.To end I propose a continuation of research, including a methodological development of network analysis; a sociological study of the acceptance of ecological advice in urban planning; and an integration of social and ecological network analysis to compare patterns of cross-municipal collaboration with landscape connectivity.
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| 10. |
- Danell, Anna
(författare)
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Predator management : space use and monitoring of Lynx in the reindeer husbandry area
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Successful legislation during the 20th century has led to recovering populations of large carnivores in Europe and we are now facing the challenges of managing the populations to fulfil both national and international conservation goals as well as minimizing the conflicts resulting from depredation on domestic animals on a national level. I investigated the space use by Eurasian lynx (Lynx lynx) in relation to their migrating main prey, the semi-domesticated reindeer (Rangifer t. tarandus). Based on data from radio-collared lynx individuals seasonal activity range use did not seem to be affected by the seasonal migrations of the reindeer. For example, the mean distance from the centre of a lynx’s activity range one season, to the centre point in the season immediately following, did not differ significantly between seasons. The distances between centre points were about one order of magnitude shorter than the distance of the reindeer migration. Hence, lynx in northern Sweden do not appear to move with the migrating reindeer and likely sustain on stray reindeer and alternative prey during part of the year. Successful management of wildlife populations also requires appropriate monitoring of population size to make new management decisions and evaluate the consequences of previous decisions and management actions. I evaluated the effect of varying accuracy and interval of population estimates on management success. When funding is limited, managers would be better off focusing on surveys with higher precision even if that means that the interval between surveys is longer.
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