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  • 1.
    Algesten, Grete
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Regulation of carbon dioxide emission from Swedish boreal lakes and the Gulf of Bothnia2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The global carbon cycle is subject to intense research, where sources and sinks for greenhouse gases, carbon dioxide in particular, are estimated for various systems and biomes. Lakes have previously been neglected in carbon balance estimations, but have recently been recognized to be significant net sources of CO2.

    This thesis estimates emission of carbon dioxide (CO2) from boreal lakes and factors regulating the CO2 saturation from field measurements of CO2 concentration along with a number of chemical, biological and physical parameters. Concentration of dissolved organic carbon (DOC) was found to be the most important factor for CO2 saturation in lake water, whereas climatic parameters such as precipitation, temperature and global radiation were less influential. All lakes were supersaturated with and, thus, sources of CO2. Sediment incubation experiments indicated that in-lake mineralization processes during summer stratification mainly occurred in the pelagial. Approximately 10% of the CO2 emitted from the lake surface was produced in epilimnetic sediments.

    The mineralization of DOC and emission of CO2 from freshwaters was calculated on a catchment basis for almost 80,000 lakes and 21 major catchments in Sweden, together with rates of sedimentation in lakes and export of organic carbon to the sea. The total export of terrestrial organic carbon to freshwaters could thereby be estimated and consequently also the importance of lakes for the withdrawal of organic carbon export from terrestrial sources to the sea. Lakes removed 30-80% of imported terrestrial organic carbon, and mineralization and CO2 emission were much more important than sedimentation of carbon. The carbon loss was closely related to water retention time, where catchments with short residence times (<1 year) had low carbon retentions, whereas in catchments with long residence times (>3 years) a majority of the imported TOC was removed in the lake systems.

    The Gulf of Bothnia was also studied in this thesis and found to be a net heterotrophic system, emitting large amounts of CO2 to the atmosphere on an annual basis. The rate of CO2 emission was depending on the balance between primary production and bacterial respiration, and the system was oscillating between being a source and a sink of CO2.

  • 2.
    Andersson, Tord
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Mercury and radiocesium in Swedish lakes1993Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Two large, nationwide monitoring data sets were compiled and statistically treated in order to create a national picture of the problems with high contents of mercury (Hg) and radiocesium (137Cs) in fish. Beside these two data sets, 75 lakes in four counties (Västernorrland, Gävleborg, Örebro and Kronoberg) were studied in connection to an evaluation of different measures to decrease the content of Hg and 137Cs in fish. An important objective was to investigate and determine the relationship between the content in fish and the load of the elements and how this relationship was affected by different abiotic lake characteristics. Several alternatives to measure the lake doses of Hg and 137Cs were evaluated (concentration in different fractions in lake water, in settling particles, and in surface sediments).

    About 10000 Swedish lakes were calculated to have a mean Hg content in 1-kg pike (FHg) above 1 mg kg-1 (wet weight) in the end of 1980’s, that is a 5-fold increase compared to the calculated preindustrial mean value. The cumulated domestic Hg- sources of emission make the largest contribution to the presently high mercury levels in pike and particularly so in central and northern Sweden.The second most important cause is acidification and thirdly Hg emissions from European sources. The content of 137Cs in fish normalized to 100 g perch (FCs) was above the limit for commercial sale, 1500 Bq kg-k in about 14000 Swedish lakes during autumn of 1987.

    An empirical model including Chernobyl fallout, hydraulic residence time and ionic strength explained almost 60 % of the inter-lake variation in FCs. At the same level of fallout, this difference in lake sensitivity, gave a tenfold difference in the initial transfer from fallout to small perch. A significant relationship was demonstrated between the lake dose of 137Cs and the content in fish. No such clear relationship existed for Hg due to the much more complex chemical and biological behaviour of Hg, where especially factors affecting méhylation and food web structure seems crucial. Lakes with a low relative sedimentation of Hg did also have a low relative sedimentation of 137Cs due to differences in particle sedimentation rates between the lakes. The sedimentation rate of radiocesium was well correlated to the natural concentration of major base cations and intercorrelated parameters such as pH, alkalinity and conductivity. The higher scavenging capacity in lakes with higher concentration of major base cations was due to higher particle sedimentation rates and higher K<i values in these lakes. However, the water chemistry was probably not causal in this respect, despite the high correlation, the distribution and sedimentation coefficients for radiocesium was not notably affected of the increased mean concentration of major base cations after liming and potash addition. It is suggested that a likely causal factor rather would be the amount and nature of scavenging agents (possibly clay minerals), which in these lakes was indicated by the natural concentration of base cations in the water.

    In general, the remedial measures gave the intended water chemical response with substantially increased mean values of alkalinity, hardness and pH. Two years after the start of the remedies, the Hg concentration in small perch (Hg-pe) was reduced by about 30% on average. The sedimentation rate of Hg decreased during 1988 and 1989 (i.e. after remedial measures) in contrast to the mean concentration of total Hg in water, thus, the retention decreased. None of the methods applied gave any rapid and clear reduction in the concentrations of 137Cs in fish, in comparison with lakes where the water chemical or biological conditions not were changed.

  • 3.
    Ask, Jenny
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Carbon metabolism in clear-water and brown-water lakes2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The trophic state of lakes is commonly defined by the concentration of nutrients in the water column. High nutrient concentrations generate high phytoplankton production, and lakes with low nutrient concentrations are considered low-productive. This simplified view of lake productivity ignores the fact that benthic primary producers and heterotrophic bacteria can be important basal producers in lake ecosystems.

    In this thesis I have studied clear-water and brown-water lakes with respect to primary production, respiration and bacterial production based on allochthonous organic carbon. These processes were quantified in pelagic and benthic habitats on temporal and spatial scales. I also calculated the net ecosystem production of the lakes, defined as the difference between gross primary production (GPP) and respiration (R). The net ecosystem production indicates whether a lake is net heterotrophic (GPP < R), net autotrophic (GPP > R) or in metabolic balance (GPP = R). Net heterotrophic lakes are sources of carbon dioxide (CO2) to the atmosphere since respiration in these lakes, by definition, is subsidized by an external organic carbon source. External organic carbon is transported to lakes from the terrestrial environment via inlets, and can serve as a carbon source for bacteria but it also limits light availability for primary producers by absorbing light.

    On a seasonal scale, four of the clear-water lakes studied in this thesis were dominated by primary production in the soft-bottom benthic habitat and by respiration in the pelagic habitat. Concentrations of dissolved organic carbon (DOC) were low in the lakes, but still high enough to cause the lakes to be net heterotrophic. However, the lakes were not low-productive due to the high production in the benthic habitat. One of the clear-water lakes was studied also during the winter and much of the respiration under ice was supported by the benthic primary production from the previous summer. This is in contrast to brown-water lakes where winter respiration is suggested to be supported by allochthonous organic carbon.

    By studying lakes in a DOC gradient (i.e. from clear-water to brown-water lakes) I could draw two major conclusions. The lakes became less productive since benthic primary production decreased with increasing light extinction, and the lakes became larger sources of CO2 to the atmosphere since pelagic respiration was subsidized by allochthonous organic carbon. Thus, lake carbon metabolism can have an important role in the global carbon cycle due to their processing of terrestrial organic carbon and to their possible feedback effects on the climate system.

  • 4. Barrio, I. C.
    et al.
    Bueno, C. G.
    Gartzia, M.
    Soininen, E. M.
    Christie, K. S.
    Speed, J. D. M.
    Ravolainen, V. T.
    Forbes, B. C.
    Gauthier, G.
    Horstkotte, Tim
    Hoset, K. S.
    Høye, T. T.
    Jónsdóttir, I. S.
    Lévesque, E.
    Mörsdorf, M. A.
    Olofsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Wookey, P. A.
    Hik, D. S.
    Biotic interactions mediate patterns of herbivore diversity in the Arctic2016In: Global Ecology and Biogeography, ISSN 1466-822X, E-ISSN 1466-8238, Vol. 25, no 9, 1108-1118 p.Article in journal (Refereed)
    Abstract [en]

    Aim: Understanding the forces shaping biodiversity patterns, particularly for groups of organisms with key functional roles, will help predict the responses of ecosystems to environmental changes. Our aim was to evaluate the relative role of different drivers in shaping the diversity patterns of vertebrate herbivores, a group of organisms exerting a strong trophic influence in terrestrial Arctic ecosystems. This biome, traditionally perceived as homogeneous and low in biodiversity, includes wide variation in biotic and physical conditions and is currently undergoing major environmental change. Location: The Arctic (including the High Arctic, Low Arctic and Subarctic) MethodsWe compiled available data on vertebrate (birds and mammals) herbivore distribution at a pan-Arctic scale, and used eight variables that represent the most relevant hypotheses for explaining patterns of species richness. We used range maps rasterized on a 100kmx100km equal-area grid to analyse richness patterns of all vertebrate herbivore species combined, and birds and mammalian herbivores separately. Results: Overall, patterns of herbivore species richness in the Arctic were positively related to plant productivity (measured using the normalized difference vegetation index) and to the species richness of predators. Greater species richness of herbivores was also linked to areas with a higher mean annual temperature. Species richness of avian and mammalian herbivores were related to the distance from the coast, with the highest avian richness in coastal areas and mammalian richness peaking further inland. Main conclusions: Herbivore richness in the Arctic is most strongly linked to primary productivity and the species richness of predators. Our results suggest that biotic interactions, with either higher or lower trophic levels or both, can drive patterns of species richness at a biome-wide scale. Rapid ongoing environmental changes in the Arctic are likely to affect herbivore diversity through impacts on both primary productivity and changes in predator communities via range expansion of predators from lower latitudes.

  • 5.
    Bigler, Christian
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Diatoms as indicators of Holocene climate and environmental change in northern Sweden2001Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The objective of the thesis was to explore the potential of diatoms (Bacillariophyceae) as indicators of Holocene climate and environmental change in northern Sweden (Abisko region, 68°21'N, 18°49'E). A modern surface-sediment calibration set including 100 lakes was developed and lake-water pH, sedimentary organic content (assessed by loss-on-ignition) and temperature were identified as most powerful environmental variables explaining the variance within the diatom assemblages. Transfer functions based on unimodal species response models (WA-PLS) were developed for lake-water pH and mean July air temperature (July T), yielding coefficients of determination of 0.77 and 0.70, and prediction errors based on leave-one-out cross-validation of 0.19 pH units and 0.96 °C for lake-water pH and July T, respectively. The transfer functions were validated with monitoring data covering two open-water seasons (lake-water pH) and meteorological records covering the 20th century (July T). The good agreement between diatom-based inferences and measured monitoring data confirmed the prediction ability of the developed transfer functions.

    Analysing a Holocene sediment core from a lake nearby Abisko (Vuoskkujávri), diatoms infer a linearly decreasing July T trend (1.5 °C) since 6,000 cal. BP, which compares well with inferences based on chironomids and pollen from the same sediment core. The lake-water pH inference shows a pattern of moderate natural acidification (c. 0.5 pH units) since the early Holocene, reaching present-day pH values at c. 5,000 cal. BP. By fitting fossil diatom samples to the modern calibration set by means of residual distance assessment within canonical correspondence analysis (CCA), the early Holocene (between 10,600 and 6,000 cal. BP) was identified as a problematic time-period for diatom-based inferences and, consequently, reconstructions during this period are tentative. Pollen-based inferences also show 'poor' fit between 10,600 and 7,500 cal. BP and chironomids probably provide the most reliable July T reconstruction at Vuoskkujávri, with 'poor' fit only during the initial part of the Holocene (between 10,600 and 10,250 cal. BP).

    Possible factors confounding diatom-based July T inferences were investigated. Using detrended CCA (DCCA), Holocene sediment sequences from five lakes indicate that during the early Holocene, mainly physical factors such as high minerogenic erosion rates, high temperature and low light availability may have regulated diatom assemblages, favouring Fragilaria species. In all five lakes, diatom assemblages developed in a directional manner, but timing and scale of development differed substantially between lakes. The differences are attributed primarily to the geological properties of the lake catchments (with strong effects on lake-water pH), but other factors such as climatic change, vegetation, hydrologic setting and in-lake processes appear to regulate diatom communities in each lake differently. The influence of long-term natural acidification on diatom assemblages progressively declined during the Holocene with corresponding increase of the influence of climatic factors.

  • 6.
    Bigler, Christian
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Hall, Roland I
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Diatoms as quantitative indicators of July temperature: a century-scale validation with meteorological data from northern Sweden2003In: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 189, no 3-4, 147-160 p.Article in journal (Refereed)
  • 7.
    Bigler, Christian
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Larocque, Isabelle
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Peglar, S. M.
    Birks, H. J. B.
    Hall, Roland I.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Quantitative multiproxy assessment of long-term patterns of Holocene environmental change from a small lake near Abisko, northern Sweden2002In: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 12, no 4, 481-496 p.Article in journal (Refereed)
    Abstract [en]

    Quantitative reconstructions are made of Holocene changes in climatic and environmental conditions from analyses of pollen, chironomids and diatoms in identical stratigraphic levels of a sediment core from Vuoskku-javri (68degrees20'43 N, 19degrees06'00 E, 348 m a.s.l.) near Abisko in northern Sweden (Lapland). Transfer functions, based on regional calibration sets, are applied to reconstruct Holocene patterns in mean July air temperature (using all three indicators). mean January air temperature (pollen), annual precipitation (pollen) and lakewater pH (diatoms). During periods with 'good' fit to the modern calibration sets all mean July air-temperature inferences based on the three proxy indicators reveal a general trend of decreasing temperature: pollen-inferred mean July air temperature shows a decrease of c, 1.1degreesC since 7500 cal. yrs BP; the chironomids show a decrease of c. 1.2degreesC since the early Holocene whereas the diatoms show a decrease of c. 1.5degreesC since 6000 cal. yrs BP. Pollen-inferred mean January air temperature indicates that winters may have been warmer by c. 3.0degreesC during the early Holocene, followed by a gradual cooling until 8500 cal. yrs BP (c. 1.0degreesC warmer than today) and a subsequent warming until 7000 cal. yrs BP (c. 2.0degreesC warmer than today). Since 7000 cal, yrs BP, a gradual cooling towards the present-day values is inferred. According to the pollen, annual precipitation may have been considerably higher during the early Holocene than today (c. +150 mm) and increased until 7000 cal. yrs BP (c. +320 mm). Since 7000 cal. yrs BP, annual precipitation decreased continuously towards present-day values. Diatom-inferred pH trends show that natural acidification of c. 0.5 pH units followed deglaciation; present-day values were reached c. 5000 cal. yrs BP. The early Holocene is identified as a problematic time period for the application of modern calibration sets. as diatoms show 'poor' fit to the calibration set from 10 600 to 6000 cal. yrs BP. pollen from 10 600 to 7500 cal. yrs BP, and chironomids from 10 250 to 10 000 cal. yrs BP. Compared with estimates from the COHMAP GCM model, mean July air-temperature inferences based on biological proxies at Vuoskkujavri suggest a more moderate decrease in temperature over the past 9000 years.

  • 8.
    Blume-Werry, Gesche
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Wilson, Scott D.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Biology, University of Regina, Regina, Saskatchewan S4S 0A2 Canada.
    Kreyling, Juergen
    Milbau, Ann
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Research Institute for Nature and Forest INBO, Kliniekstraat 25, 1070 Brussels, Belgium.
    The hidden season: growing season is 50% longer below than above ground along an arctic elevation gradient2016In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 209, no 3, 978-986 p.Article in journal (Refereed)
    Abstract [en]

    There is compelling evidence from experiments and observations that climate warming prolongs the growing season in arctic regions. Until now, the start, peak, and end of the growing season, which are used to model influences of vegetation on biogeochemical cycles, were commonly quantified using above-ground phenological data. Yet, over 80% of the plant biomass in arctic regions can be below ground, and the timing of root growth affects biogeochemical processes by influencing plant water and nutrient uptake, soil carbon input and microbial activity. We measured timing of above- and below-ground production in three plant communities along an arctic elevation gradient over two growing seasons. Below-ground production peaked later in the season and was more temporally uniform than above-ground production. Most importantly, the growing season continued c. 50% longer below than above ground. Our results strongly suggest that traditional above-ground estimates of phenology in arctic regions, including remotely sensed information, are not as complete a representation of whole-plant production intensity or duration, as studies that include root phenology. We therefore argue for explicit consideration of root phenology in studies of carbon and nutrient cycling, in terrestrial biosphere models, and scenarios of how arctic ecosystems will respond to climate warming.

  • 9.
    Bogren, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    LIDAR-analys av flygsanddyner i Västerbottens inland: Har dynmorfologi bildad under tidigare interstadialer bevarats i landskapet?2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The aim of this study was to map the prevalence of aeolian sand dunes in Västerbotten, northern Sweden to find dunes formed during earlier deglaciation phases, which was then preserved in cold-based conditions during the youngest stadial of the Weichselian glaciation. These preserved dunes were expected to be covered by a layer of till and have a rather faint morphology compared to dunes formed during the Holocene. Consequently, high resolution LIDAR-derived images from the Swedish mapping, cadastral and land registration authority (Lantmäteriet) was used to detect the dunes throughout an area covering most of Västerbotten, above the highest coastline and below the mountain range. The analysis resulted in several new findings of aeolian dunes compared to the findings in the quaternary soil map created by the Geological Survey of Sweden. Despite the fact some of the dunes at the LIDAR-derived image had a strange faint appearance, it was quickly evident during the fieldwork that the aeolian sand was not covered by till on any of the dunes visited. The common view during the last decades has been that cold-based ice will not erode or alter the morphology of the landscape beneath the ice. However, this study suggests that hypothesis may not be entirely correct, and therefore it can be hard to use geomorphological implications to reconstruct past glacial environments. Thus, it can be concluded that even under cold-based conditions, preservation of aeolian sand dunes in Västerbotten is probably not very common.

  • 10. Buckland, Paul C.
    et al.
    Buckland, Philip I.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    The Alder Leaf Beetle Agelastica alni (L.) (Col.: Chrysomelidae) in the Dearne Valley. Climate change or poor quarantine.2014In: Sorby Record, ISSN 0260-2245, no 50, 2-6 p.Article in journal (Other academic)
  • 11.
    Buckland, Philip I.
    Department of Archaeology and Prehistory, University of Sheffield, Sheffield, UK.
    Lichenometry and Soil Erosion in Northwest Iceland1994In: Environmental Change in Iceland, München: nstitut für Geographie der Universität München , 1994, 31-40 p.Conference paper (Other (popular science, discussion, etc.))
  • 12.
    Buckland, Philip I.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    The Bugs Coleopteran Ecology Package (BugsCEP): the development and implementation of software for palaeoenvironmental and palaeoclimatological research2009Book (Other academic)
    Abstract [en]

    This book describes the development and practical application of a unique database orientated software package, BugsCEP, for environmental, climatic and biodiversity reconstruction from beetle assemblages. BugsCEP consists of a database of ecology and distribution data for over 9400 insect taxa, and includes temperature tolerance data for 436 species. It contains abundance and summary data for over 770 sites, most of the known European Quaternary fossil coleopteran record, supported by a bibliography of over 3700 sources. Built in statistics, including a specially developed habitat classification system, provide semi-quantitative environmental reconstructions to aid in the interpretation of sites. BugsCEP's querying and reporting functions also increase the efficiency with which analyses can be undertaken, including the facility to explore the fossil record of species by searching ecology and distribution data. The Mutual Climatic Range (MCR) reconstruction method is implemented and improved upon, including predictive modelling and the graphical output of reconstructions and climate space maps. BugsCEP is available from www.bugscep.com.

  • 13.
    Buckland, Philip I.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab. Umeå University, Faculty of Arts, Humlab.
    The Bugs Coleopteran Ecology Package (BugsCEP) database: 1000 sites and half a million fossils later2014In: Quaternary International, ISSN 1040-6182, E-ISSN 1873-4553, Vol. 341, 272-282 p.Article in journal (Refereed)
    Abstract [en]

    The Bugs database project started in the late 1980s as what would now be considered a relatively simple system, albeit advanced for its time, linking fossil beetle species lists to modern habitat and distribution information. Since then, Bugs has grown into a complex database of fossils records, habitat and distribution data, dating and climate reference data wrapped into an advanced software analysis package. At the time of writing, the database contains raw data and metadata for 1124 sites, and Russell Coope directly contributed to the analysis of over 154 (14%) of them, some 98790 identifications published in 231 publications. Such quantifications are infeasible without databases, and the analytical power of combining a database of modern and fossil insects with analysis tools is potentially immense for numerous areas of science ranging from conservation to Quaternary geology.

    BugsCEP, The Bugs Coleopteran Ecology Package, is the latest incarnation of the Bugs database project. Released in 2007, the database is continually added too and is available for free download from http://www.bugscep.com. The software tools include quantitative habitat reconstruction and visualisation, correlation matrices, MCR climate reconstruction, searching by habitat and retrieving, among other things, a list of taxa known from the selected habitat types. It also provides a system for entering, storing and managing palaeoentomological data as well as a number of expert system like reporting facilities.

    Work is underway to create an online version of BugsCEP, implemented through the Strategic Environmental Archaeology Database (SEAD) project (http://www.sead.se). The aim is to provide more direct access to the latest data, a community orientated updating system, and integration with other proxy data. Eventually, the tools available in the offline BugsCEP will be duplicated and Bugs will be entirely in the web.

    This paper summarises aspects of the current scope, capabilities and applications of the BugsCEP database and software, with special reference to and quantifications of the contributions of Russell Coope to the field of palaeoentomology as represented in the database. The paper also serves to illustrate the potential for the use of BugsCEP in biographical studies, and discusses some of the issues relating to the use of large scale sources of quantitative data.

    All datasets used in this article are available through the current version of BugsCEP available at http://www.bugscep.com.

  • 14.
    Buckland, Philip I.
    et al.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab. Umeå University, Faculty of Arts, Humlab.
    Buckland, Paul C.
    BugsCEP, an entomological database twenty-five years on2014In: Antenna (Journal of the Royal Entomological Society), ISSN 0140-1890, Vol. 38, no 1, 21-28 p.Article in journal (Refereed)
  • 15.
    Buckland, Philip I.
    et al.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Eriksson, Erik J.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Palm, Fredrik
    Umeå University, Faculty of Arts, Humlab.
    SEAD - The Strategic Environmental Archaeology Database: Progress Report Spring 20142014Report (Other academic)
    Abstract [en]

    This report provides an overview of the progress and results of the VR:KFI infrastructure projects 2007-7494 and (825-)2010-5976. It should be considered as a status report in an on-going long-term research infrastructure development project.

  • 16.
    Buckland, Philip I.
    et al.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Lemdahl, Geoffrey
    Linnaeus University, Sweden.
    Explaining Late Quaternary beetle extinctions in the UK using palaeoenvironmental databases for quantitative environmental reconstruction2015Conference paper (Refereed)
    Abstract [en]

    The comparison of palaeoenvironmental and archaeological records of fossil insects with modern red data books can provide a picture of local extinctions. Buckland & Buckland (2012) performed such a study on the Coleoptera of the British Isles, using the BugsCEP database for the fossil data, and looking at broad chronological divisions. The ecology of these regionally extinct beetles, all of which are extant in other parts of the World, may be used to investigate the environmental and climatic changes which may have lead to their extirpation. This process can be semi-automated and habitats quantified through the use of ecological classification and a database infrastructure which links fossil and modern ecological and climate data (Buckland & Buckland 2006; http://www.bugscep.com). Preliminary results indicate that the majority of extirpated species with mid-Holocene records were dependent on woodland environments (Buckland 2014). These investigations can be refined by using narrower time-slices, interpolating dating evidence and including more comprehensive archaeological dating evidence. The expansion of the analysis to include the full assemblages found in the samples containing the extirpated species also allows for a more comprehensive picture of the long-term relationships between biodiversity, environmental and climatic change and human activity.

  • 17. Chambers, Frank M.
    et al.
    Booth, Robert K.
    De Vleeschouwer, Francois
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Lamentowicz, Mariusz
    Le Roux, Gael
    Mauquoy, Dmitri
    Nichols, Jonathan E.
    van Geel, Bas
    Development and refinement of proxy-climate indicators from peats2012In: Quaternary International, ISSN 1040-6182, Vol. 268, 21-33 p.Article in journal (Refereed)
    Abstract [en]

    Peat, especially from acidic mires (bogs), is a natural archive of past environmental change. Reconstructions of past climate from bogs commenced in the 19th Century through examination of visible peat stratigraphy, and later formed the basis for a postglacial climatic scheme widely used in Northwest Europe. Nevertheless, misconceptions as to how bogs grow led to a 50-year lacuna in peat-climate study, before the concept of 'cyclic regeneration' in bogs was refuted. In recent decades, research using proxy-climate indicators from bogs has burgeoned. A range of proxies for past hydrological change has been developed, as well as use of pollen, bog oaks and pines and other data to reconstruct past temperatures. Most of this proxy-climate research has been carried out in Northern Europe, but peat-based research in parts of Asia and North America has increased, particularly during the last decade, while research has also been conducted in Australia, New Zealand and South America. This paper reviews developments in proxy-climate reconstructions from peatlands; chronicles use of a range of palaeo-proxies such as visible peat stratigraphy, plant macrofossils, peat humification, testate amoebae and non-pollen palynomorphs: and explains the use of wiggle-match radiocarbon dating and relationship to climate shifts. It details other techniques being used increasingly, such as biomarkers, stable-isotopes, inorganic geochemistry and estimation of dust flux: and points to new proxies under development. Although explicit protocols have been developed recently for research on ombrotrophic mires, it must be recognised that not all proxies and techniques have universal applicability, owing to differences in species assemblages, mire formation, topographic controls, and geochemical characteristics. (C) 2011 Elsevier Ltd and INQUA. All rights reserved.

  • 18.
    Deininger, Anne
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Effects of inorganic nitrogen and organic carbon on pelagic food webs in boreal lakes2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Anthropogenic activities are increasing inorganic nitrogen (N) loadings to lakes in the northern hemisphere. In many boreal lakes phytoplankton are N limited, wherefore enhanced N input may affect the productivity of pelagic food webs. Simultaneously, global change causes increased inflows of terrestrial dissolved organic carbon (DOC) to boreal lakes. Between clear and humic lakes, whole lake primary and consumer production naturally differs. However, research is inconclusive as to what controls pelagic production in these lakes. Further, it is unclear how DOC affects the response of the pelagic food web to enhanced inorganic N availability. The overarching goal of this thesis was to study the effects of inorganic N and organic C for pelagic food webs in boreal lakes. In the thesis, I first identified the main drivers of pelagic production during summer in eight non-manipulated Swedish boreal lakes with naturally low or high DOC. Then I investigated how increased N availability affects the pelagic food chain, and how the response differs with DOC. Therefore, whole lake inorganic N fertilization experiments were conducted in six Swedish boreal lakes across a DOC gradient (low, medium, high) divided into three lake pairs (control, N enriched) with one reference and two impact years. In each lake, I also investigated the response of zooplankton growth using in situ mesocosm experiments excluding planktivores. I found that humic boreal lakes had lower phytoplankton production and biomass than clear water lakes. Further, phytoplankton community composition and food quality differed with DOC. However, high DOC did not reduce pelagic energy mobilization or zooplankton biomass, but promoted a higher dominance of cladoceran relative to copepod species. N addition clearly enhanced phytoplankton biomass and production in the experimental lakes. However, this stimulating N effect decreased with DOC as caused by light limitation. Further, the newly available phytoplankton energy derived from N addition was not efficiently transferred to zooplankton, which indicates a mismatch between producer energy supply and consumer energy use. Indeed, the mesocosm experiment revealed that decreased food quality of phytoplankton in response to N addition resulted in reduced food web performance, especially in clearer lakes. In humic lakes, zooplankton production and food web efficiency were clearly more resilient to N addition. In summary, my thesis suggests that any change in the landscape that enhances inorganic N availability will especially affect pelagic food webs in clear water lakes. In contrast, brownification will result in more lakes being resilient to eutrophication caused by enhanced N deposition.

  • 19.
    Engelmark, Roger
    et al.
    Umeå University, Faculty of Arts, Archaeology and Sami Studies, Environmental Archaeology Lab.
    Buckland, Philip I.
    Umeå University, Faculty of Arts, Archaeology and Sami Studies, Environmental Archaeology Lab.
    The Early Holocene Environment of North Fennoscandia and its Implications for Colonisation2005In: Pioneer settlements and colonization processes in the Barents region, Vuollerim: Vuollerim 6000 år , 2005, 97-108 p.Conference paper (Refereed)
    Abstract [en]

    This paper uses the currently available data on the immediate post-glacial landscape of Fennoscandia, along with relevant palaeoenvionmental reconstructions for the Barents region, to paint a picture of the landscape and resources available to the early colonisers of this area. In addition, the aim is to provide a source of up to date references for those interested in integrating the archaeological and environmental evidence, towards an holistic model of the Early Holocene landscape.

  • 20.
    Foghagen, Christer
    Umeå University, Faculty of Social Sciences, Department of Social and Economic Geography.
    Algae blooms and their consequences on camping tourism on Öland, SwedenManuscript (preprint) (Other academic)
    Abstract [en]

    In Sweden camping tourism holds the position as one of the largest niches within the tourism accommodation sector. The camping sector represents more than 17 million or 35% of commercial overnight stays in total. On the island of Öland which is located in Kalmar county, and in Kalmar county itself, the camping sector represents more than 1.75 million or 65% of the annual overnight stays which positions Kalmar and Öland as the second largest camping region in Sweden. However, tourism businesses, and especially island tourism systems, can be vulnerable to shifting environmental conditions. In recent years, the media has highlighted the issue of harmful algae blooms frequently affecting coastlines in the Baltic Sea. Based on structured interviews, this article investigates the perceptions of campground managers and camping tourists on Öland have of the impact of algae blooms on tourism. The results show that both among campground managers and visitors, algae blooms are perceived as an environmental concern that might affect tourism in negative ways.

  • 21.
    Forsman, Mona
    et al.
    Department of Forest Resource Management, Swedish University of Agricultural Sciences.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Holmgren, Johan
    Department of Forest Resource Management, Swedish University of Agricultural Sciences.
    Estimation of tree stem attributes using terrestrial photogrammetry2012In: International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Copernicus Gesellschaft , 2012, B5-261-B5-265 p.Conference paper (Other academic)
    Abstract [en]

    The objective of this work was to create a method to measure stem attributes of standing trees on field plots in the forest using terrestrial photogrammetry. The primary attributes of interest are the position and the diameter at breast height (DBH).

    The developed method creates point clouds from image from three or more calibrated cameras attached to a calibrated rig. SIFT features in multiple images in combination with epipolar line filtering are used to make high quality matching in images with large amounts of similar features and many occlusions. After projection of the point cloud to a simulated ground plane, RANSAC filtering is applied, followed by circle fitting to the remaining points.

    To evaluate the algorithm, a camera rig of five Canon digital system cameras with a baseline of 123 cm and up to 40 cm offset in height was constructed. The rig was used in a field campaign at the Remningstorp forest test area in southern Sweden. Ground truth was collected manually by surveying and manual measurements.

    Initial results show estimated tree stem diameters within 10% of the ground truth. This suggest that terrestrial photogrammetry is a viable method to measure tree stem diameters on circular field plots.

  • 22.
    Irl, Severin D. H.
    et al.
    Univ Bayreuth, BayCEER, Dept Disturbance Ecol, D-95447 Bayreuth, Germany.
    Steinbauer, Manuel J.
    Univ Bayreuth, BayCEER, Dept Biogeog, D-95447 Bayreuth, Germany.
    Messinger, Jana
    Univ Bayreuth, BayCEER, Dept Biogeog, D-95447 Bayreuth, Germany.
    Blume-Werry, Gesche
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Univ Bayreuth, BayCEER, Dept Biogeog, D-95447 Bayreuth, Germany.
    Palomares-Martinez, Angel
    Parque Nacl Caldera Taburiente, El Paso 38750, Spain.
    Beierkuhnlein, Carl
    Univ Bayreuth, BayCEER, Dept Biogeog, D-95447 Bayreuth, Germany.
    Jentsch, Anke
    Univ Bayreuth, BayCEER, Dept Disturbance Ecol, D-95447 Bayreuth, Germany.
    Burned and devoured-Introduced herbivores, fire, and the endemic flora of the high-elevation ecosystem on La Palma, Canary Islands2014In: Arctic, Antarctic and Alpine research, ISSN 1523-0430, Vol. 46, no 4, 859-869 p.Article in journal (Refereed)
    Abstract [en]

    Novel disturbance regimes (e.g., introduced herbivores and fire) are among the major drivers of degradation in island ecosystems. High-elevation ecosystems (HEEs) on islands might be especially vulnerable to these disturbances due to high endemism. Here, data from an 11-year exclosure experiment in the HEE of La Palma (Canary Islands) are presented where mammalian herbivores have been introduced. We investigate the combined effect of herbivory and fire on total species richness, seedling richness, and seedling establishment on the whole system and a subset of highly endangered species (target species). Total species richness, seedling species richness, and seedling establishment decreased with herbivory. Five out of eight target species were exclusively found inside the exclosures indicating the negative impact of introduced herbivores on endemic high elevation flora. Target species were generally affected more negatively by introduced herbivores and were subject to significantly higher browsing pressure, probably owing to their lack of defense strategies. A natural wildfire that occurred six years before data sampling substantially increased total species richness and seedling richness in both herbivory exclosure and reference conditions. We conclude that species composition of the HEE has been severely altered by the introduction of non-native herbivores, even though fire seems to have a positive effect on this system.

  • 23.
    Ivarsson, Hans
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Glacial dynamics and till genesis in hilly terrain: A study in the Tallträsk area, central-northern Sweden2007Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This study deals with the influence of topography on glacial dynamics and the genesis of till in an area of moder-ate bedrock relief. An area 25 km west of Lycksele, northern Sweden, was investigated using geomorphological and sedimentological methods. The bedrock is dominated by coarse-grained granites and the topography, ranging in altitude between 310 and 490 m. a.s.l., is characterized by relatively wide, free-lying hills.

    The erosional and depositional features provide evidence of several glacial events, with regional ice flows from approximately the same direction (NW-NNW). The gravel fraction of the till is dominated by material transported more than 10 km. However, the total glacial erosion has been modest, as indicated by the frequent occurrence of residual pre-glacial weathering features. There is no evidence of warm-based conditions during the period when the ice divide of the Late Weichselian ice sheet was situated E-SE of the study area. The major mor-phological impact is most likely by pre-Late Weichselian ice sheets.

    The general stratigraphy at the valley floors is a complex sequence of heterogeneous till and beds of sorted sediments with some evidence of glacial deformation covered by an up to 2.5-m-thick, texturally homogeneous till layer with distinct fissility structure and clast fabric orientation. The lower unit is interpreted as pre-Late Weichselian marginal deposits, and the upper till as mainly formed during rigid-bed conditions, i.e. by lodgement, during the last deglaciation. The role of pervasive deformation and melt-out in the formation of the upper till are discussed. Inferred mainly from till fabrics it is evident that the ice flow was strongly topographically controlled within a relatively wide marginal zone of the retreating ice.

    At the summits of the hills there are only signs of very weak glacial abrasive and depositional activity, sug-gesting frozen based conditions over the summits until a very late stage of the deglaciation. The very thin till at the summits, which also lay as a drape over the thick lee-side deposits, consists of a mixture of relatively fine-grained, distantly derived debris and of local bedrock fragments entrained during a very late phase of plucking.

    On the stoss- and lateral slopes of the hills the till is thin and discontinuous. The irregular bedrock surface in these areas created a “mosaic” of small-scale subglacial depositional environments, which were superimposed on the changes in the conditions for deposition along the hillslope. This till is comparatively coarse-grained, which is interpreted as an effect of syn-depositional winnowing of fines, and locally also because of the incorporation of local bedrock material largely from pre-glacially weathered zones.

    On the lee-sides of the hills the deposits are considerably thicker than on slopes facing other directions. They are characterized by highly variable texture and structure, suggesting a depositional environment characterized by large temporal and spatial variations in meltwater activity and stress/strain conditions. The lee-side tills are inter-preted as mainly pre-Late Weichselian in age.

    The overall conclusion is that the local topography strongly controlled the basal ice flow and produced a com-plex pattern of thermal variations within a relatively wide marginal zone of the ice sheet during the last deglacia-tion. The study supports the view that there are complete transitions between the different genetical types of sub-glacial tills, although the role of deformation by pervasive shearing is uncertain in this type of coarse-grained till.

  • 24.
    Jacobson, Holger
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Near-surface stratigraphy of till and glacifluvium near Knaften, northern Sweden: Identifying small-scale stratigraphy using ground-penetrating radar2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The aim of the study was to assess the possibilities in using ground-penetrating radar to identify small-scale stratigraphy in the upper 1 m of a soil profile and to statistically identify differences in the stratigraphic units discovered using the GPR unit. The study area is ca 15 km southwest of Lycksele near a gravel pit on the banks of Örån. It was located on top of a large (>5 m thick) glacifluvial deposit of indeterminate age overlayed by till from the latest deglaciation. The data sampled included 22 radargrams depicting a total length of >1000 m as well as soil samples from three stratigraphic units from three different trenches (9 samples in total). Visual analysis of the stratigraphy took place via trenches as well as by studying the radar images. The radar images show that three stratigraphic units can be identified clearly (ablation till, S1, a transitional layer of mixed till and glacifluvium, S2, and the underlying glacifluvium, S3) but that the border between the two lower units can be opaque at times. Field observations showed this to be due to the genesis of the topmost unit, the ablation till. Observations in the field also showed relict podsolization in a kettle in the northern part of the study area. Grain-size comparison of the three stratigraphic units identified was performed via sieving. Calculations of the weight percentage were then used for statistical analysis to identify any differences between the strata. Results show that there are differences regarding fine material (ø <0.074 mm, p=0.038), gravel (ø > 2 mm, p<0.0001) and sand (p=0.027) within these three stratigraphic units. 

  • 25.
    Jørgensen, Dolly
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Rethinking rewilding2015In: Geoforum, ISSN 0016-7185, E-ISSN 1872-9398, Vol. 65, 482-488 p.Article in journal (Refereed)
    Abstract [en]

    The term 'rewilding' sounds as if it should have a straightforward meaning 'to make wild again'. But in truth the term has a complex history and a host of meanings have been ascribed to it. Rewilding as a specific scientific term has its beginnings as a reference to the Wildlands Project, which was founded in 1991 and aimed to create North American core wilderness areas without human activity that would be connected by corridors. Words, however, do not stand still they change over time and take on new meanings, while sometimes simultaneously retaining the older sense. Employing Foucault's idea of historical genealogy, this article examines how the term rewilding was historically adopted and modified in ecological scientific discourse over the last two decades. This investigation probes what and, by extension, when and where, rewilding refers to as it has moved into various geographies across the globe. It then examines how the term has moved outside of science and been adopted by environmental activists as a plastic word. Taken as a whole, rewilding discourse seeks to erase human history and involvement with the land and flora and fauna. Such an attempted split between nature and culture may prove unproductive and even harmful. A more inclusive rewilding is a preferable strategy.

  • 26.
    Kampezidou, Dimitra
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Spatial distribution of heavy metals in surface marine sediments in the Mediterranean region2015Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Several scientific articles were mainly reviewed from Umeå’ s university database in order to determine the distribution, degree of contamination, and the sources of 7 selected heavy metals (Cr, Pb, Cu, Zn, Cd, Hg, Ni) in surface sediments along the coasts of the Mediterranean Sea. The Enrichment factor (EF) was used as pollution indicator to evaluate the extent of metal contamination in all the investigated areas. According to Abrahim and Parker (2008) the EF is defined as the ratio of the determined metal to Al (or Fe) in the sample divided by the ratio of background metal to background Al (or Fe) ratio. According to the results of this study, EF values for Cr, Pb, Cu, Cd and Ni presented an upward trend along the west to east shoreline of the Mediterranean sea, whereas Zn and Hg EF values showed a downward trend along this region. Cr generally exhibited no enrichment in places to the west (EF<1.5) whereas in the eastern side displayed moderate enrichment (EF=1.95). Pb EF values showed moderate enrichment (EF=5) along the western section of the sea, whilst in the eastern part revealed significant enrichment (5.45). Zn pollution levels were minimal (EF=1.6) in places to the west and moderate (EF=2.2) to the east. The enrichment for Cd was considered moderate in the western part of the basin and significant in the eastern section. These heavy metals distribution can be explained by the fact that different inputs (mainly due to anthropogenic activities) from the inshore environment may take place in each area of the sea. However, Cu and Ni presented the same degree of pollution (moderate) in the whole sea, presumably indicating similar Cu and Ni inputs from the terrestrial environment. However, conclusions for Hg were not possible to be drawn as the collected data were not sufficient. 

    The full text will be freely available from 2021-01-01 09:00
  • 27. Khorasani, Sara
    et al.
    Panagiotakopulu, Eva
    Engelmark, Roger
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies.
    Ralston, Ian
    Late Holocene beetle assemblages and environmental change in Gammelhemmet, northern Sweden2015In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 44, no 2, 368-382 p.Article in journal (Refereed)
    Abstract [en]

    Analysis of insect fossil remains retrieved from a bog close to the abandoned farm at Gammelhemmet, near Lycksele in Swedish Lapland, enabled the reconstruction of environmental changes at the site over the last 2500years. These results represent the first late Holocene palaeoentomological succession studied for insect remains in the Vasterbotten interior, and they provide new evidence for landscape change in the area. Around 2000years ago, at the end of the early Iron Age, disappearance of the tree and leaf litter fauna and an increase in aquatic species indicate the expansion of wetlands in the area. Patches of a multi-aged mixed woodland with a diverse assemblage of forest-dwelling beetles succeeded the wetland approximate to 1500years ago, at the beginning of the late Iron Age. A marked change to open and drier conditions, and the presence of species often found in grassland and cultivated ground took place during the post-Medieval period. Our evidence indicates drainage of the area prior to the 18th century, placing the initiation of agricultural activities in Gammelhemmet earlier than the documentary record. Our research shows the potential of the use of fossil insects for understanding environmental change and also human impact on the landscape, even of limited scale, from natural contexts.

  • 28.
    Klaus, Marcus
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Environmental effects on cryoturbation along bioclimatic gradients in subarctic Sweden: The importance of soil disturbance proxy, spatial scale and mesoclimatic regime2012Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    Cryoturbation is a fundamental soil forming process with large importance for ecosystem functioning in the Arctic. Recent investigations have emphasized the effect of climate change on cryoturbation, but contrast in their predictions on cryoturbation under future climate warming. This study analyzed to what extent conclusions on the response of cryoturbation to environmental conditions depend on: 1) the proxy of cryogenic activity used; 2) the spatial scale of environmental predictor variables; and 3) the mesoclimatic regime of the study site. As an example of cryoturbated soil, 48 non-sorted patterned-ground features were sampled at eight sites along an elevational and a precipitation gradient and vegetation gradients nested within each site in the Abisko area, northernmost Sweden. To quantify cryogenic activity, eight proxies of cryogenic activity were used. In addition, environmental data were obtained at two spatial scales from field surveys and existing geodata. The results suggest a significant correlation between most activity proxies. Cryogenic activity increased along the precipitation gradient and peaked at intermediate elevations, while within-site variation was similar to between-site variation. The response of cryogenic activity to environmental factors was largly independent of the proxy used but varied with the spatial scale of predictor variables and across mesoclimatic regimes, with precipitation and vegetation cover being the most important predictors. The study indicates that spatial scale and mesoclimate should be considered when assessing the sensitivity of cryoturbation to climate changes. The results therefore provide possible explanations for contrasting previous predictions on the fate of cryoturbated patterned-ground ecosystems under future climate warming.

  • 29.
    Klaus, Marcus
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Land use effects on greenhouse gas emissions from boreal inland waters2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Anthropogenic activities perturb the global carbon and nitrogen cycle with large implications for the earth’s climate. Land use activities deliver excess carbon and nitrogen to aquatic ecosystems. In the boreal biome, this is mainly due to forestry and atmospheric deposition. Yet, impacts of these anthropogenically mediated inputs of carbon and nitrogen on the processing and emissions of greenhouse gases from recipient streams and lakes are largely unknown. Understanding the ecosystem-scale response of aquatic greenhouse gas cycling to land use activities is critical to better predict anthropogenic effects on the global climate system and design more efficient climate change mitigation measures.

    This thesis assesses the effects of forest clearcutting and nitrate enrichment on greenhouse gas emissions from boreal inland waters. It also advances methods to quantify sources and sinks of these emissions. Short-term clearcut and nitrate enrichment effects were assessed using two whole-ecosystem experiments, carried out over four years in nine headwater catchments in boreal Sweden. In these experiments, I measured or modeled air-water fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), combining concentration, ebullition and gas-transfer velocity measurements in groundwater, streams and lakes. By using Swedish national monitoring data, I also assessed broad-scale effects of forest clearcutting by relating CO2 concentrations in 439 forest lakes to the areal proportion of catchment forest clearcuts. To improve quantifications of CO2 sources and sinks in lakes, I analyzed time series of oxygen concentrations and water temperature in five lakes on conditions under which whole-lake metabolism estimates can be inferred from oxygen dynamics given the perturbing influence of atmospheric exchange, mixing and internal waves.

    The experiments revealed that aquatic greenhouse gas emissions did not respond to nitrate addition or forest clearcutting. Importantly, riparian zones likely buffered clearcut-induced increases in groundwater CO2 and CH4 concentrations. Experimental results were confirmed by monitoring data showing no relationship between CO2 patterns across Swedish lakes and clearcut gradients. Yet, conclusions on internal vs. external CO2 controls largely depended on whether spatially or temporally resolved data was used. Partitioning CO2 sources and sinks in lakes using time series of oxygen was greatly challenged by physical transport and mixing processes.

    Conclusively, ongoing land use activities in the boreal zone are unlikely to have major effect on headwater greenhouse gas emissions. Yet, system- and scale specific effects cannot be excluded. To reveal these effects, there is a large need of improved methods and design of monitoring programs that account for the large spatial and temporal variability in greenhouse gas dynamics and its controls by abiotic and biotic factors.

  • 30.
    Klaus, Marcus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bergström, Ann-Kristin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Jonsson, Anders
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Deininger, Anne
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Geibrink, Erik
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Weak response of greenhouse gas emissions to whole lake N enrichmentManuscript (preprint) (Other academic)
    Abstract [en]

    Global warming and land use scenarios suggest increased 21st century nitrogen (N) inputs to boreal lakes. Nitrogen affects in-lake processing and, potentially, atmospheric exchange of greenhouse gases. However, we miss evidence from whole-lake experiments addressing the net effect of N inputs on greenhouse gas exchange of lake ecosystems. Here, we test for the first time the effect of a whole-lake experimental increase (three-fold) in external nitrate loads on the atmospheric emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) from six N-limited unproductive boreal lakes. Nitrogen enrichment effects were assessed within a paired Before-After/Control-Impact framework based on 2-hourly to biweekly surface-water sampling of dissolved gas concentrations, and monthly whole-lake inventory surveys, carried out over four years. Responses of gas emissions during the summer stratification period to nitrate additions were small in all lakes and not statistically significant; this was also true for changes in summer and winter inventories and emphasizes the modest role of internal carbon fixation for the CO2 dynamics of unproductive boreal lakes. A global synthesis of 54 published studies revealed a wide range of N fertilization effects on greenhouse gas emissions depending on the spatiotemporal scale of the study system and if N was added alone or in combination with phosphorous. Combined, our results suggest that N enrichment effects on greenhouse gas dynamics are small on a whole-lake scale and that greenhouse gas emissions from unproductive boreal lakes are robust against changes in N supply.

  • 31.
    Klaus, Marcus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Geibrink, Erik
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Jonsson, Anders
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bergström, Ann-Kristin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bastviken, David
    The Department of Thematic Studies - Environmental Change, Linköping University, Linköping, Sweden.
    Laudon, Hjalmar
    Department of Forest Ecology and Management, Swedish University of Agricultural Science, Umeå, Sweden.
    Klaminder, Jonatan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Does clearcut forestry influence aquatic greenhouse gas emissions?Manuscript (preprint) (Other academic)
    Abstract [en]

    Forest clearcutting generally increase exports of carbon and nitrogen to downstream aquatic systems. Although these losses affect the greenhouse gas budget of managed forests, it is unknown if they modify greenhouse gas emissions of recipient inland waters. To assess this question, we quantified atmospheric fluxes of carbon dioxide (CO2) methane (CH4) and nitrous oxide (N2O) of humic lakes and their inlet streams in four boreal catchments of which two were treated with forest clearcuts (18% and 44% of the catchment area) using a Before-After/Control-Impact-experiment. We measured gas concentrations and hydrological and physicochemical water characteristics in hillslope groundwater, along stream transects and at multiple locations in lakes at 2-hourly to biweekly intervals throughout the snow-free season over a four year period. These measurements were combined with atmospheric gas transfer measurements and models to calculate aquatic greenhouse gas emissions. Forest clearcutting did not change greenhouse gas emissions from streams or lakes, despite significant increases of CO2 and CH4 concentrations in hillslope groundwater. Clearcut effects on groundwater were likely buffered in the riparian zone. Hence, the greenhouse gas budget of forests initially after clearcutting is unlikely to be confounded by aquatic greenhouse gas emissions. However, our findings should be extrapolated with caution to other environments. Here, site-specific conditions makes our study system representative for systems where clearcutting causes only a limited initial impact on catchment hydrology and biogeochemistry.

  • 32.
    Klaus, Marcus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hotchkiss, Erin
    Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA.
    Bergström, Ann-Kristin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    MacIntyre, Sally
    Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA, USA.
    Estimates of ecosystem metabolism in unproductive lakes with inclusion of physical oxygen fluxesManuscript (preprint) (Other academic)
    Abstract [en]

    Whole-lake metabolism estimates based on free-water oxygen measurements may be compromised in unproductive lakes if the transport of oxygen by physical processes is neglected and large relative to biologically induced changes. Here, we quantify how oxygen fluxes associated with atmospheric exchange, vertical mixing and internal waves modify metabolism estimates in five unproductive boreal, brown water lakes. Water temperature and dissolved oxygen concentrations were measured at five minute intervals at 5-8 depths for 8-70 days per lake from May to September 2015. We estimated daily metabolism using three inverse Bayesian models accounting for atmospheric gas exchange using a (1) conventional wind-speed model and a (2) surface renewal model based on near-surface turbulence, and (3) accounting for within lake mixing by deepening of the actively mixing layer and the coefficient of eddy diffusivity. Gross primary production (GPP), ecosystem respiration (ER) and net ecosystem production (NEP) ranged from 0 to 0.9, -0.3 to -2.5 and -0.2 to -1.6 g C m-3 d-1, respectively. Metabolism estimates were reduced by up to 400% if oxygen time series were filtered to remove effects of internal waves and thermocline up- and downwelling, which have likely caused large changes in concentrations. Metabolism estimates differed by 0-25% depending on the atmospheric gas transfer model used and by 0-120% depending on whether fluxes from vertical mixing were considered. Almost half of the metabolism estimates were unreasonable (GPP<0 or ER>0), and these largely coincided with enhanced (up to 300%) diel cycles in physical oxygen fluxes. We conclude that physical processes should be explicitly assessed in three dimensions when using the free-water oxygen method to model metabolism in unproductive lakes.

  • 33.
    Klaus, Marcus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Seekell, David
    Climate Impacts Research Centre, Department of Ecology and Environmental Science, Umeå University, Umeå, Sweden.
    Lidberg, William
    Department of Forest Ecology and Management, Swedish University of Agricultural Science, Umeå, Sweden.
    Karlsson, Jan
    Climate Impacts Research Centre, Department of Ecology and Environmental Science, Umeå University, Umeå, Sweden.
    Neglecting seasonality causes biased view of climate and forestry impacts on lake CO2 cyclingManuscript (preprint) (Other academic)
    Abstract [en]

    Lakes emit carbon dioxide (CO2) at globally significant rates. These emissions may be controlled by land use and climate. Disentangling these interactions is a prerequisite to accurately predicting anthropogenic impacts on carbon cycling in lake rich regions. We used environmental monitoring data of lakes collected in autumn (n = 439) and throughout the whole open-water season (n = 22) from a wet and a dry year in Swedish forest catchments to evaluate direct and indirect effects of temperature, precipitation, wind speed, forest productivity and forest clearcutting on lake CO2 concentrations. We found that trends in CO2 concentrations along climate and forestry gradients do not always correspond between autumn and open-water season averages, implying the need of validation of patterns derived from snap-shot data alone. According to spatially resolved data, autumn CO2 concentrations increased with mean annual air temperature (dry year) or catchment forest productivity (wet year) but were not coupled to colored dissolved organic matter (CDOM) concentrations. In contrast, open-water season averaged CO2 concentrations were constant across temperature and productivity gradients but increased with CDOM. These antagonistic results suggest that our fundamental understanding of the controls of CO2 in lakes depends on whether spatially or temporally resolved data is used. Hence, trade-offs in sampling efforts clearly limit the questions that can be addressed regarding climate and land use effects on lake carbon cycling.

  • 34.
    Kullman, Leif
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Early postglacial appearance of tree species in northern Scandinavia: review and perspective2008In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 27, no 27-28, 2467-2472 p.Article in journal (Refereed)
    Abstract [en]

    This paper reviews megafossil evidence for the first postglacial records of different tree species in northern Scandinavia. Betula pubescens coll. appeared at the Arctic coast of northern Norway by 16. 900 yr BR In addition, Betula Pubescens (14, 000 yr BP), Pinus sylvestris (11, 700 yr BP) and Picea abies (11, 000 yr BP) existed on early ice- free mountain peaks (nunataks) at different locations in the Scandes during the Lateglacial. Larix sibirica, currently not native to Fennoscandia, and several thermophilous broadleaved tree species were recorded in the earliest part of the Holocene. The conventional interpretation of pollen and macrofossil records from peat and sediment stratigraphies do not consider the Occurrence of the species mentioned above that early at these northern and high altitude sites. This very rapid arrival after the local deglaciation implies that the traditional model of far distant glacial refugial areas for tree species has to be challenged. The Current results are more compatible with a situation involving scattered "cryptic" refugia quite close to margin of the ice sheet at its full-glacial extension. This fits a more general pattern currently emerging on different continents. In general, "cryptic" refugia should be considered in connection with modelling extinction risks related to modern and possible future "climatic crises".

  • 35. Lapierre, Jean-Francois
    et al.
    Seekell, David A.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Filstrup, Christopher T.
    Collins, Sarah M.
    Fergus, C. Emi
    Soranno, Patricia A.
    Cheruvelil, Kendra S.
    Continental-scale variation in controls of summer CO2 in United States lakes2017In: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 122, no 4, 875-885 p.Article in journal (Refereed)
    Abstract [en]

    Understanding the broad-scale response of lake CO2 dynamics to global change is challenging because the relative importance of different controls of surface water CO2 is not known across broad geographic extents. Using geostatistical analyses of 1080 lakes in the conterminous United States, we found that lake partial pressure of CO2 (pCO(2)) was controlled by different chemical and biological factors related to inputs and losses of CO2 along climate, topography, geomorphology, and land use gradients. Despite weak spatial patterns in pCO(2) across the study extent, there were strong regional patterns in the pCO(2) driver-response relationships, i.e., in pCO(2) regulation. Because relationships between lake CO2 and its predictors varied spatially, global models performed poorly in explaining the variability in CO2 for U.S. lakes. The geographically varying driver-response relationships of lake pCO(2) reflected major landscape gradients across the study extent and pointed to the importance of regional-scale variation in pCO(2) regulation. These results indicate a higher level of organization for these physically disconnected systems than previously thought and suggest that changes in climate and land use could induce shifts in the main pathways that determine the role of lakes as sources and sinks of atmospheric CO2. Plain Language Summary In this study we show that changes in climate and terrestrial landscapes could affect which are the main mechanisms responsible for the widespread emissions of CO2 by lakes. Although mechanisms such as aquatic primary production, respiration by microorganisms, or terrestrial loadings of carbon have been studied extensively, their relative importance across broad geographic extents with different climate or land use remains unknown. Based on an analysis of 1080 lakes distributed across the continental U.S., we show that lake CO2 dynamics depend on the climate and landscape context where these lakes are found, such as precipitation, elevation, percent agriculture, or wetlands in the lakes catchments. We observed a widespread effect of in-lake primary production, while the color of water, which has often been identified as one of the main controls of lake CO2 in northern lakes, was important in only a small fraction of the lakes studied. Our results show that controls on lake CO2 dynamics vary geographically and that considering that variation will be important for creating accurate global carbon models.

  • 36.
    Larsson, Cecilia
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Metod för inventering av underhållsbehov för skogsdiken2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Large areas have been ditched in Sweden during the past 100 years to improve the forest production. Ditching and also maintenance of old ditches are operations having mainly negative effects on water quality, flora and fauna and changing characteristics of soil. The purpose of this study was to suggest a method for inventory of the need for ditching maintenance in old forest ditches that takes biodiversity, water protection and forest production into consideration. Inventory methods from five Swedish and Finnish forest companies, agencies and organisations were compared. Their employees were interviewed about their handling with ditches, forest production and nature conservation. The results show that there are four major questions that have to be answered in order to decide whether old ditches should be left as they are, maintained or if there are other operations that could be needed. First, it is important to know whether the original ditches has had an improving effect on forest production and second, what effect a cleaning of the ditch would have on the growth at present. The third and fourth theme that has to be valued is what the effects could be on biodiversity and the environment and all this has to be weighted together. Maintenance of old ditches is a complex subject. It is of major concern to have a comprehensive view and to look outside the specific object for eventual causes and effects. A method for inventory of need for ditching maintenance is a good tool in the planning.

  • 37. Linkowski, Weronika Axelsson
    et al.
    Kvarnstrom, Marie
    Westin, Anna
    Moen, Jon
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ostlund, Lars
    Wolf and Bear Depredation on Livestock in Northern Sweden 1827-2014: Combining History, Ecology and Interviews2017In: Land, ISSN 2073-445X, E-ISSN 2073-445X, Vol. 6, no 3, 63Article in journal (Refereed)
    Abstract [en]

    During the twenty-first century, large carnivores have increased in human dominated landscapes after being extinct or nearly extinct. This has resulted in increasing numbers of livestock killed by large carnivores. The intent of this paper is to give a land use-historical perspective on the recent livestock-carnivore conflict in boreal Sweden. More specifically we address: (1) depredation risks (livestock killed by carnivores) and (2) local knowledge of how to protect livestock from predation and whether it survived among pastoralists until the present. This study provides numeric information on carnivores, livestock and depredation, combined with oral information from summer farmers about livestock protection. We compare recent (since 1998) and historical (late nineteenth century) depredation rates in two Swedish counties. In Dalarna recent depredation rates are higher than historical rates while the opposite pattern is seen in Jamtland. Recent depredation rates in Dalarna are twice the recent rates in Jamtland, in contrast to the historical situation. Recent and historical depredation rates are of the same order. Summer farmers traditionally graze their livestock in forested areas where carnivores reside. Interviews show that traditional knowledge of how to protect livestock from carnivores was lost during the twentieth century, but recently new knowledge has developed leading to changes in summer farming practices. The carnivore-livestock situation today differs from the historical situation, not so much in levels of depredation, but mainly regarding the possibilities of farmers to face challenges associated with increasing carnivore populations.

  • 38.
    Myrstener, Maria
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Konduktivitet i vattendrag som indikator på sura sulfatjordar2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Increasing attention is being given to acid sulphate soils wherever they occur. The problems that leaching sulphate soils gives with significant lowerings of pH and mobilization of heavy metals influence large spectra of our society from fisheries to agriculture to construction. Mapping these soils is consequently of great importance and the methods of doing this is very much lacking in function and precision. This study was therefore carried out to investigate whether conductivity in running water can be used as a simple instrument to identify acid sulphate soils in the catchment. 31 coastal streams in the county of Västerbotten were analyzed for different catchment properties such as occurence of marine sediments and basic water chemistry including conductivity and sulphate. Sulphate proved to be the dominant factor controling conductivity in most streams, constituting up to 90 % of the anions. The results also showed that the concentrations of sulphate correlated to 67 % with marine sediments in the catchment. Where conductivity values exceeded 90 µS/cm the influence of acid sulphate soils could be determined for certain. The major conclusion drawn from this study is that high conductivity values serves as a reliable indicator of leaching acid sulphate soils whereas lower values can not exclude them.

  • 39. Plue, Jan
    et al.
    De Frenne, Pieter
    Acharya, Kamal
    Brunet, Jorg
    Chabrerie, Olivier
    Decocq, Guillaume
    Diekmann, Martin
    Graae, Bente J.
    Heinken, Thilo
    Hermy, Martin
    Kolb, Annette
    Lemke, Isgard
    Liira, Jaan
    Naaf, Tobias
    Shevtsova, Anna
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Verheyen, Kris
    Wulf, Monika
    Cousins, Sara A. O.
    Climatic control of forest herb seed banks along a latitudinal gradient2013In: Global Ecology and Biogeography, ISSN 1466-822X, E-ISSN 1466-8238, Vol. 22, no 10, 1106-1117 p.Article in journal (Refereed)
    Abstract [en]

    Aim Seed banks are central to the regeneration strategy of many plant species. Any factor altering seed bank density thus affects plant regeneration and population dynamics. Although seed banks are dynamic entities controlled by multiple environmental drivers, climatic factors are the most comprehensive, but still poorly understood. This study investigates how climatic variation structures seed production and resulting seed bank patterns. Location Temperate forests along a 1900km latitudinal gradient in north-western (NW) Europe. Methods Seed production and seed bank density were quantified in 153 plots along the gradient for four forest herbs with different seed longevity: Geum urbanum, Milium effusum, Poa nemoralis and Stachys sylvatica. We tested the importance of climatic and local environmental factors in shaping seed production and seed bank density. Results Seed production was determined by population size, and not by climatic factors. G.urbanum and M.effusum seed bank density declined with decreasing temperature (growing degree days) and/or increasing temperature range (maximum-minimum temperature). P.nemoralis and S.sylvatica seed bank density were limited by population size and not by climatic variables. Seed bank density was also influenced by other, local environmental factors such as soil pH or light availability. Different seed bank patterns emerged due to differential seed longevities. Species with long-lived seeds maintained constant seed bank densities by counteracting the reduced chance of regular years with high seed production at colder northern latitudes. Main conclusions Seed bank patterns show clear interspecific variation in response to climate across the distribution range. Not all seed banking species may be as well equipped to buffer climate change via their seed bank, notably in short-term persistent species. Since the buffering capacity of seed banks is key to species persistence, these results provide crucial information to advance climatic change predictions on range shifts, community and biodiversity responses.

  • 40. Rosqvist, Gunhild C
    et al.
    Leng, Melanie J.
    Goslar, Tomasz
    Sloane, Hilary J.
    Bigler, Christian
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Cunningham, Laura
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Dadal, Anna
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bergman, Jonas
    Berntsson, Annika
    Jonsson, Christina
    Wastegard, Stefan
    Shifts in precipitation during the last millennium in northern Scandinavia from lacustrine isotope records2013In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 66, 22-34 p.Article in journal (Refereed)
    Abstract [en]

    Here we present delta P-18(diatom) data from two high-latitude lakes; one has short residence time and a water isotopic composition (delta O-18(lake)) that fluctuate due to seasonal variations in precipitation and temperature, and the other has delta O-18(lake) that is influenced by longer lake water residence times and evaporation. The delta O-18(diatom) records reveal common responses to precipitation forcing over the past millennium. Relatively wet summers are inferred from delta O-18(diatom) between 1000 and 1080 AD, 1300 and 1440 AD, and during the early 19th century, coincided with periods of high cloud cover inferred from tree-ring carbon isotopes, and other data for high Arctic Oscillation index. While relatively dry summers with increasing influence of winter snow are indicated between 1600 and 1750 AD. The co-response between carbon isotopes in trees and oxygen isotopes in diatoms strengthens the relationship between cloud cover and precipitation and the hypothesis that these changes were the result of significant regional shifts in atmospheric circulation. (C) 2012 Elsevier Ltd. All rights reserved.

  • 41.
    Thompson, Megan Shera
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Giesler, Reiner
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Klaminder, Jonatan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Size and characteristics of the DOC pool in near-surface subarctic mire permafrost as a potential source for nearby freshwaters2015In: Arctic, Antarctic and Alpine research, ISSN 1523-0430, E-ISSN 1938-4246, Vol. 47, no 1, 49-58 p.Article in journal (Refereed)
    Abstract [en]

    Subarctic peatlands are rich sources of organic carbon for freshwater ecosystems. Where those peatlands are underlain by permafrost, permafrost thaw may cause an initial release of bioavailable dissolved organic carbon (DOC) to surrounding freshwaters. In this study, we measured icebound and potentially leachable (extracted) DOC quantities and indices of DOC quality in active layer and permafrost layers from two subarctic peat mires, Stord-alen and Storflaket. Most of the permafrost layers did not contain more organic matter or exportable DOC (as g kg(-1) dry soil) than the overlying active layer, and there was no difference in aromaticity, molecular weight, or the ratio between labile and recalcitrant DOC extracted from the permafrost and active layer. However, DOC held in segregated ice of the near-surface permafrost had relatively low aromaticity compared to extracted DOC from the same depth. Total icebound and potentially leachable DOC in the Stordalen mire permafrost that is predicted to experience active layer deepening during each of the next 50 years corresponded to about 0.1% of the current annual aquatic export of DOC from the mire. We conclude that the pool of potentially leachable DOC currently stored in permafrost layers is small. We also highlight differences in permafrost organic material between the two studied mire systems, which has an effect on the pool and properties of leachable DOC that is potentially available for export during thaw. Moreover, the geomorphological form of permafrost thaw will influence future hydrological connectedness and DOC production, in turn determining future DOC export from the mires.

  • 42.
    van Woerkom, Anne
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ancient DNA from soils and sediments from the Krigstjärn area, northern Sweden: Preservation and detection of Holocene mammal sedaDNA2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Current knowledge of past vegetation and faunal diversity has been based on pollen and macrofossil analysis from lake sediments. The innovative method of sedimentary ancient DNA (sedaDNA) is a promising, complementary proxy to reconstruct information about past environments. However, to what extent animal DNA can be extracted from old sediments and soils has not been frequently studied. This study explored if ancient DNA of moose (Alces alces), reindeer (Rangifer tarangus), goat (Capra aegagrus) and plants could be extracted from millennia old lake sediments of Lake Krigstjärn and archaeological soil samples in northern Sweden. SedaDNA was successfully extracted and detected from both reindeer and plants DNA, while goats sedaDNA was absent in all sediments. Moose ancient DNA (aDNA) was only detected in the archaeological soils. Yet, there were signs that the applied moose primer set was not optimal for heavily degraded DNA and the validity of this primer needs further research. Earliest detections of reindeer DNA can be dated to ~6500 c. years ago. Oldest sediments contained DNA, indicating sufficient DNA preservation conditions in the sediments of Lake Krigstjärn. Finds of plants DNA in pre-deglaciational sediments may indicate the existence of >9500 year old glacial vegetation. Altogether is sedaDNA a highly promising tool to reconstruct diversity, origin and immigration routes of mammals, but technical issues such as primer set specificity and its purpose should be considered and tested carefully in advance. 

  • 43. Wallensten, Anders
    et al.
    Munster, Vincent J
    Osterhaus, Albert DME
    Waldenström, Jonas
    Bonnedahl, Jonas
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Infectious Diseases.
    Broman, Tina
    Fouchier, Ron AM
    Olsen, Björn
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Infectious Diseases.
    Mounting evidence for the presence of influenza A virus in the avifauna of the Antarctic region2006In: Antarctic Science, ISSN 0954-1020, E-ISSN 1365-2079, Vol. 18, no 3, 353-356 p.Article in journal (Refereed)
    Abstract [en]

    Penguin blood samples collected at Bird Island, sub-Antarctic South Georgia, and faecal samples taken from penguins at several localities along the Antarctic Peninsula were analysed in order to investigate if influenza A virus is present in penguin populations in the South Atlantic Antarctic region. Serology was performed on the blood samples while the faecal samples were screened by a RT-PCR method directed at the matrix protein gene for determining the presence of influenza A virus. All faecal samples were negative by PCR, but the blood samples gave serologic indications that influenza A virus is present amongst these penguin species, confirming previous studies, although the virus has still not been isolated from any bird in the Antarctic region.

  • 44. Winder, Monika
    et al.
    Bouquet, Jean-Marie
    Bermudez, J. Rafael
    Berger, Stella A.
    Hansen, Thomas
    Brandes, Jay
    Sazhin, Andrey F.
    Nejstgaard, Jens C.
    Båmstedt, Ulf
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Jakobsen, Hans H.
    Dutz, Joerg
    Frischer, Marc E.
    Troedsson, Christofer
    Thompson, Eric M.
    Increased appendicularian zooplankton alter carbon cycling under warmer more acidified ocean conditions2017In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 62, no 4, 1541-1551 p.Article in journal (Refereed)
    Abstract [en]

    Anthropogenic atmospheric loading of CO2 raises concerns about combined effects of increasing ocean temperature and acidification, on biological processes. In particular, the response of appendicularian zooplankton to climate change may have significant ecosystem implications as they can alter biogeochemical cycling compared to classical copepod dominated food webs. However, the response of appendicularians to multiple climate drivers and effect on carbon cycling are still not well understood. Here, we investigated how gelatinous zooplankton (appendicularians) affect carbon cycling of marine food webs under conditions predicted by future climate scenarios. Appendicularians performed well in warmer conditions and benefited from low pH levels, which in turn altered the direction of carbon flow. Increased appendicularians removed particles from the water column that might otherwise nourish copepods by increasing carbon transport to depth from continuous discarding of filtration houses and fecal pellets. This helps to remove CO2 from the atmosphere, and may also have fisheries implications.

  • 45. Young, Amanda B.
    et al.
    Cairns, David M.
    Lafon, Charles W.
    Moen, Jon
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Geometrid moth outbreaks and their climatic relations in northern Sweden2014In: Arctic, Antarctic and Alpine research, ISSN 1523-0430, Vol. 46, no 3, 659-668 p.Article in journal (Refereed)
    Abstract [en]

    The alpine treeline in northern Fennoscandia is composed primarily of mountain birch (Betula pubescens ssp. czerepanovii), a deciduous tree that experiences episodic defoliation due to outbreaks of the autumnal moth (Epirrita autumnata) and winter moth (Operophtera brumata). Here, we use an extensive dendroecological data set to reconstruct historic defoliating outbreaks and relate them to climatic conditions. Our data are from 25 sites in eight valleys in northern Sweden. We used the computer program OUTBREAK to reconstruct moth outbreaks. The reconstructed outbreak record matches the historical record well. There is a significant, but weak relationship between the outbreak severity and temperatures in February, April, July, and August of the outbreak year. Temperatures in the previous May and November were also positively correlated with outbreak severity. For seasonally aggregated temperatures, only autumn temperatures are correlated with outbreak severity. There was no significant correlation between NAO index and outbreak severity. A spatiotemporal semivariogram analysis showed that sites within approximately 100 km of each other show similar patterns in outbreak severity. Our analyses suggest that moths are affected by climatic variations. The influence of climate on outbreaks is weak because background climatic conditions alone cannot induce an outbreak. Outbreaks also depend on nonclimatic factors, such as tree age, and the outbreak status of neighboring areas.

  • 46.
    Zale, Rolf
    Umeå University.
    Lake sediments around the Antarctic Peninsula: archives of climatic and environmental changes1993Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Lakes and lake sediments from four areas around the Antarctic Peninsula are described.

    The concentrations of trace metals in sediment are found to be a useful tool in distinguishing between the different sedimentary phases during a transition from marine to limnic environment.

    A tephrochronology based on Deception Island tephra is developed, and used to cross date sediments from different lakes in order to overcome the radiocarbon dating problem of the area.

    The fluctuating concentrations of copper and phosphorus from penguin guano in the sediment of Lake Boeckella are used as a proxy for the penguin inpact on the sediment, and the size of the penguin rookery on the shores of the lake. Anthropogenic activities in the area, as well as climatic changes are discussed in relation to the rookery size.

    A radiocarbon dating model developed for the sediment of Lake Boeckella showed that the radiocarbon correction factor in the sediment depends on the amount and apparent age of the penguin guano washed down into the lake, and the amount of particulate carbon from the watershed present in the sediment. Neither the "old" meltwater from the glaciers nor dissolved carbonates contributes significantly to the correction factor. The model is used to achieve more accurate radiocarbon dates of the Lake Boeckella sediment. This model, or a modified version, may contribute to a higher dating accuracy and a better understanding of the dating problems in Antarctica.

    Deglaciation dates, as well as data on the climatic and environmental history of Byers Peninsula on Livingston Island, South Shetland Islands, of Hope Bay, Antarctic Peninsula and of Hidden Lake area, James Ross Island are given.

  • 47.
    Åberg, Jan
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Production and emission of CO2 in two unproductive lakes in northern Sweden2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Unproductive lakes are one of few natural landscape compartments with net release of carbon to the atmosphere. Lakes also generally decrease the net terrestrial carbon uptake, since most of the CO2 production in unproductive lakes are derived from organic carbon produced on land (e.g. in forests). High latitude lakes are predicted to be particularly affected by the global climate change. The carbon cycling in these lakes and their role in the landscape are therefore important to study.

    In this thesis, carbon turnover processes were studied in two lakes above the arctic circle (Lake Diktar-Erik and Lake Merasjärvi) in year 2004 and 2005. Both lakes were net heterotrophic, with large variations in CO2 concentrations both on shorter (30min) and longer (24h) time-scales. The pelagic habitat supported a major part of the net production of CO2, with larger dynamics in the CO2 production than the sediments. The CO2 variations of the surface water were related to respiration of allochthonous organic carbon, and were affected by the concentration and quality of the DOC, as well as the whole lake water temperatures, and vertical water movements.

    The emission of CO2 from Lake Merasjärvi was measured with the eddy covariance tech­nique. The results showed that the gas transfer rate during moderate winds were higher than expected, causing the two most commonly used models to underestimate the long term fluxes of CO2 from the lake.

    Taken together, the results of the thesis show that the studied lakes contributed to bring terrestrial organic carbon back into the atmosphere, driven by a substantial internal CO2 production based on mineralization of allochthonous organic carbon. Major results are that the eddy covariance technique indicated that commonly used models tend to underestimate the net release rate of CO2 from lakes to the atmosphere, and that the lake CO2 dynamics can be the results of interactions between biogeochemical and physical processes in the lake water.

  • 48.
    Ågren, Anneli
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Seasonal variation and landscape regulation of dissolved organic carbon concentrations and character in Swedish boreal streams2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The seasonal variation and landscape regulation of dissolved organic carbon (DOC) concentrations in streams have been studied in two watersheds in the boreal zone. The seasonal variation was found to be highly correlated to variations in runoff. An increase in runoff was always accompanied with an increase in DOC concentration. However, there were indications that the TOC concentration was restricted by the soil TOC pool during snowmelt.

    The main factors affecting DOC exports varied between seasons. During winter baseflow the spatial variation in DOC exports was strongly influenced by wetland coverage, during snowmelt the exports were correlated to factors describing the size and location of the catchment, and during the snow-free season they were heavily affected by the proportions of wetlands and forests in the catchments. Small headwaters had the highest terrestrial DOC export, per unit area.

    The properties of the DOC changed during spring flood, towards lower molecular weight and more aliphatic compounds. These changes affected the bioavailability of the DOC, which increased during spring flood. There were also differences in the DOC properties between wetlands and forest soils; the forested soils yielded DOC with lower molecular weight (measured as 254 nm/365 nm light absorbance ratios), largely from superficial layers that were activated during high flow events, while wetland soils generally provided a more constant carbon source with higher molecular weight. The majority of the DOC was exported by wetlands, but most of the short-term bioavailable DOC (BP7) was derived from the forests, during the spring flood period, indicating that bacterial production in streams and lakes is likely to be almost entirely based on DOC exported from forested areas during, and some time after, the spring flood event.

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