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  • 1. Anderson, N. John
    et al.
    Saros, Jasmine E.
    Bullard, Joanna E.
    Cahoon, Sean M. P.
    Mcgowan, Suzanne
    Bagshaw, Elizabeth A.
    Barry, Christopher D.
    Bindler, Richard
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Burpee, Benjamin T.
    Carrivick, Jonathan L.
    Fowler, Rachel A.
    Fox, Anthony D.
    Fritz, Sherilyn C.
    Giles, Madeleine E.
    Hamerlik, Ladislav
    Ingeman-Nielsen, Thomas
    Law, Antonia C.
    Mernild, Sebastian H.
    Northington, Robert M.
    Osburn, Christopher L.
    Pla-Rabes, Sergi
    Post, Eric
    Telling, Jon
    Stroud, David A.
    Whiteford, Erika J.
    Yallop, Marian L.
    Yde, Jacob C.
    The Arctic in the Twenty-First Century: Changing Biogeochemical Linkages across a Paraglacial Landscape of Greenland2017Inngår i: BioScience, ISSN 0006-3568, E-ISSN 1525-3244, Vol. 67, nr 2, s. 118-133Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Kangerlussuaq area of southwest Greenland encompasses diverse ecological, geomorphic, and climate gradients that function over a range of spatial and temporal scales. Ecosystems range from the microbial communities on the ice sheet and moisture-stressed terrestrial vegetation (and their associated herbivores) to freshwater and oligosaline lakes. These ecosystems are linked by a dynamic glacio-fluvial-aeolian geomorphic system that transports water, geological material, organic carbon and nutrients from the glacier surface to adjacent terrestrial and aquatic systems. This paraglacial system is now subject to substantial change because of rapid regional warming since 2000. Here, we describe changes in the eco-and geomorphic systems at a range of timescales and explore rapid future change in the links that integrate these systems. We highlight the importance of cross-system subsidies at the landscape scale and, importantly, how these might change in the near future as the Arctic is expected to continue to warm.

  • 2. Blackburn, M.
    et al.
    Ledesma, Jose L. J.
    Näsholm, Torgny
    Laudon, Hjalmar
    Sponseller, Ryan A.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Evaluating hillslope and riparian contributions to dissolved nitrogen (N) export from a boreal forest catchment2017Inngår i: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 122, nr 2, s. 324-339Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Catchment science has long held that the chemistry of small streams reflects the landscapes they drain. However, understanding the contribution of different landscape units to stream chemistry remains a challenge which frequently limits our understanding of export dynamics. For limiting nutrients such as nitrogen (N), an implicit assumption is that the most spatially extensive landscape units (e.g., uplands) act as the primary sources to surface waters, while near-stream zones function more often as sinks. These assumptions, based largely on studies in high-gradient systems or in regions with elevated inputs of anthropogenic N, may not apply to low-gradient, nutrient-poor, and peat-rich catchments characteristic of many northern ecosystems. We quantified patterns of N mobilization along a hillslope transect in a northern boreal catchment to assess the extent to which organic matter-rich riparian soils regulate the flux of N to streams. Contrary to the prevailing view of riparian functioning, we found that near-stream, organic soils supported concentrations and fluxes of ammonium (NH4+) and dissolved organic nitrogen that were much higher than the contributing upslope forest soils. These results suggest that stream N chemistry is connected to N mobilization and mineralization within the riparian zone rather than the wider landscape. Results further suggest that water table fluctuation in near-surface riparian soils may promote elevated rates of net N mineralization in these landscapes.

  • 3. Buckland, Paul C.
    et al.
    Panagiotakopulu, Eva
    University of Edinburgh, Scotland.
    Skidmore, Peter
    Snæsdóttir, Mjöll
    Institute of Archaeology, Iceland.
    Buckland, Philip I.
    Umeå universitet, Humanistiska fakulteten, Arkeologi och samiska studier, Miljöarkeologiska laboratoriet.
    Insect faunas from Stóraborg, a farm mound in Southern Iceland2004Rapport (Annet vitenskapelig)
  • 4.
    Buckland, Philip
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet.
    Lessons from extinctions2017Inngår i: Wood Wise, s. 22-27Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    Many beetles are very good at colonising new areas when changes in the landscape open up new possibilities. Equally, they are highly susceptible to local extinction in the face of landscape scale changes in their environment.

  • 5.
    Buckland, Philip I.
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet. Umeå universitet, Humanistiska fakulteten, Humlab.
    The Bugs Coleopteran Ecology Package (BugsCEP) database: 1000 sites and half a million fossils later2014Inngår i: Quaternary International, ISSN 1040-6182, E-ISSN 1873-4553, Vol. 341, s. 272-282Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 6.
    Buckland, Philip I.
    et al.
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet. Umeå universitet, Humanistiska fakulteten, Humlab.
    Buckland, Paul C.
    BugsCEP, an entomological database twenty-five years on2014Inngår i: Antenna (Journal of the Royal Entomological Society), ISSN 0140-1890, Vol. 38, nr 1, s. 21-28Artikkel i tidsskrift (Fagfellevurdert)
  • 7.
    Buckland, Philip I.
    et al.
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet.
    Buckland, Paul C.
    Species found as fossils in Quaternary sediments2018Inngår i: Checklist of beetles of the British Isles: with a chapter on fossil beetles / [ed] Andrew G. Duff, Iver: Pemberley Books , 2018, 3, s. 171-174Kapittel i bok, del av antologi (Annet vitenskapelig)
  • 8.
    Buckland, Philip I.
    et al.
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet.
    Buckland, Paul C.
    Olsson, Fredrik
    Paleoentomology: insects and other arthropods in environmental archaeology2018Inngår i: Encyclopedia of global archaeology / [ed] Claire Smith, Cham: Springer, 2018, 2Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Insects are the most diverse group of animals on the planet and as such are present in a wider variety of habitats than most other complex organisms. This diversity, in addition to a long evolutionary history (Grimaldi and Engel 2005), and together with a propensity to be preserved in both desiccating and anaerobic environments, has provided an excellent tool for the reconstruction of both Quaternary and more immediate archaeological environments. Insect remains often provide proxy environmental information on the immediate context from which the fossils are derived, and as such may be either complementary to the more regional picture provided by palynology or indicate site conditions, such as levels of hygiene and evidence of trading connections, which are rarely available from any other palaeoecological source. They therefore provide information on a broad range of habitats and conditions, on- and off-site, and in addition, in appropriate contexts, also climate. Processing of samples is essentially simple, requiring readily available materials, yet is time consuming, and identification of the usually disarticulated fragments (sclerites) requires diligence and patience and access to well-curated reference collections. Fortunately, abundant literature, computer software, and database tools now exist to aid in their interpretation.

  • 9.
    Buckland, Philip I.
    et al.
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet.
    Eriksson, Erik J.
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet.
    Palm, Fredrik
    Umeå universitet, Humanistiska fakulteten, Humlab.
    SEAD - The Strategic Environmental Archaeology Database: Progress Report Spring 20142014Rapport (Annet vitenskapelig)
    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.

  • 10.
    Buckland, Philip I.
    et al.
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet.
    Linderholm, Johan
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet.
    Östman, Sofi
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet.
    Samuel, Ericson
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet.
    Wallin, Jan-Erik
    Pollenlaboratoriet i Umeå AB.
    Engelmark, Roger
    Environmental archaeological analysis from the archaeological excavations at Ørland kampflybase, Vik 70/1, Ørland, Sør-Trøndelag, Norway. 2015-20162017Rapport (Annet vitenskapelig)
    Abstract [en]

    A total of 322 bulk samples, 267 bulk subsamples and 1632 survey samples from the excavation of Iron Age settlements at Ørland, Vik, Sør-Trondelag, were analysed at the Environmental Archaeology Laboratory (MAL) at Umeå University. The overall aim of these analyses was to look for evidence which could help identify possible prehistoric activity areas, understand building functions and divisions, and shed light on land management around the farmsteads.

  • 11.
    Buckland, Philip I.
    et al.
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet.
    Sjölander, Mattias
    Blombocken avslöjar forntiden: Databaser.2017Inngår i: Populär arkeologi, ISSN 0281-014, nr 5, s. 28-31Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
    Abstract [sv]

    Databaser. Fossila insekter och förkolnade fröer kan ge mycket information om de miljöer som människor har levt i och kan liksom annan biologisk information tjäna arkeologi

  • 12.
    Buckland, Philip I.
    et al.
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet.
    Wallin, Jan-Erik
    Pollenlaboratoriet i Umeå AB.
    Pollen analysis of samples from the defensive ditch (vollgrav) at Site FO4 Klypen-Øst, Follobanen, Oslo2017Rapport (Annet vitenskapelig)
    Abstract [en]

    Nine samples were submitted for pollen analyses from three profiles from the "Vollgrav"defensive ditch feature, at the Follobanen FO4 Klypen-Øst excavation in Oslo. These samples were investigated with respect to their pollen contents and, in a separate investigation, soil micromorphology. The micromorphological methods and results are described in detail in a separate report from Richard Macphail (2016). Where relevant, these findings are commented on with respect to the other analysis results below.

  • 13.
    Buckland, Philip I.
    et al.
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet.
    Östman, Sofi
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet.
    Wallin, Jan-Erik
    Pollenlaboratoriet i Umeå AB.
    Samuel, Ericson
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet.
    Linderholm, Johan
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet.
    Pollen, plant macrofossil and geoarchaeological analyses of profile 11632, Follobanen FO3, Oslo2017Rapport (Annet vitenskapelig)
  • 14.
    Buckland, Philip
    et al.
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet.
    Wallin, Jan-Erik
    Pollenlaboratoriet i Umeå AB.
    Pollenanalys från Rörbäcksnäs, Sälen, Dalarna2017Rapport (Annet vitenskapelig)
    Abstract [sv]

    Miljöarkeologiska Laboratoriet anlitades för att undersöka ett flertal torvmossar innanför föreslagna alternativa vägkorridorer i området nordöst om byn Rörbäcksnäs i Malung-Sälens kommun, Dalarna. Målen var att 1) undersöka den arkeologiska potentialen av våtmarkssediment som skulle förstöras av det föreslagna vägbygget och 2) utföra analyser på ett urval av materialet om det bedömdes vara tillräckligt välbevarat och av vetenskapligt intresse för området.

  • 15. Cael, B. B.
    et al.
    Seekell, David A.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    The size-distribution of Earth's lakes2016Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, artikkel-id 29633Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Globally, there are millions of small lakes, but a small number of large lakes. Most key ecosystem patterns and processes scale with lake size, thus this asymmetry between area and abundance is a fundamental constraint on broad-scale patterns in lake ecology. Nonetheless, descriptions of lake size-distributions are scarce and empirical distributions are rarely evaluated relative to theoretical predictions. Here we develop expectations for Earth's lake area-distribution based on percolation theory and evaluate these expectations with data from a global lake census. Lake surface areas >= 8.5 km(2) are power-law distributed with a tail exponent (T = 1.97) and fractal dimension (d = 1.38), similar to theoretical expectations (T = 2.05; d = 4/3). Lakes <8.5 km(2) are not power-law distributed. An independently developed regional lake census exhibits a similar transition and consistency with theoretical predictions. Small lakes deviate from the power-law distribution because smaller lakes are more susceptible to dynamical change and topographic behavior at sub-kilometer scales is not self-similar. Our results provide a robust characterization and theoretical explanation for the lake size-abundance relationship, and form a fundamental basis for understanding and predicting patterns in lake ecology at broad scales.

  • 16.
    Cunningham, Laura
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten. Climate Impacts Research Centre (CIRC), Umeå University, 98107 Abisko, Sweden.
    Vogel, Hendrik
    Nowaczyk, Norbert
    Wennrich, Volker
    Juschus, Olaf
    Persson, Per
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Rosen, Peter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Climate Impacts Research Centre (CIRC), Umeå University, 98107 Abisko, Sweden.
    Climatic variability during the last interglacial inferred from geochemical proxies in the Lake El'gygytgyn sediment record2013Inngår i: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 386, s. 408-414Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Last Interglacial Period (LIP) is often regarded as a good analogue for potential climatic conditions under predicted global warming scenarios. Despite this, there is still debate over the nature, duration and frequency of climatic changes during this period. One particularly contentious issue has been the apparent evidence of climatic instability identified in many marine cores but seemingly lacking from many terrestrial archives, especially within the Arctic, a key region for global climate change research. In this paper, geochemical records from Lake El'gygytgyn, north-eastern Russia, are used to infer past climatic changes during the LIP from within the high Arctic. With a sampling resolution of similar to 20-similar to 90 years, these records offer the potential for detailed, high-resolution palaeoclimate reconstruction. This study shows that the LIP commenced in central Chukotka similar to 129 thousand years ago (ka), with the warmest climatic conditions occurring between similar to 128 and 127 ka before being interrupted by a short-lived cold reversal. Mild climatic conditions then persisted until similar to 122 ka when a marked reduction in the sedimentation rate suggests a decrease in precipitation. A further climatic deterioration at similar to 118 ka marks the return to glacial conditions. This study highlights the value of incorporating several geochemical proxies when inferring past climatic conditions, thus providing the potential to identify signals related to environmental change within the catchment. We also demonstrate the importance of considering how changes in sedimentation rate influence proxy records, in order to develop robust palaeoenvironmental reconstructions. (C) 2013 Elsevier B.V. All rights reserved.

  • 17.
    Ekeberg, Jonas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Swedish Institute of Space Physics, P.O. Box 812, SE-981 28 Kiruna, Sweden.
    Wannberg, Gudmund
    Swedish Institute of Space Physics, P.O. Box 812, SE-981 28 Kiruna, Sweden.
    Eliasson, Lars
    Swedish Institute of Space Physics, P.O. Box 812, SE-981 28 Kiruna, Sweden.
    Häggström, Ingemar
    EISCAT Scientific Association, P.O. Box 812, SE-981 28 Kiruna, Sweden.
    Soliton-induced spectrally uniform ion line power enhancements at the ionospheric F region peak2012Inngår i: Earth Planets and Space, ISSN 1343-8832, E-ISSN 1880-5981, Vol. 64, nr 7, s. 605-611Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present European incoherent scatter (EISCAT) observations of spectrally uniform ion line power enhancements (SUIPE), where the up- and downshifted shoulder and the spectral valley between them are enhanced simultaneously and equally. We have identified 48 cases of this type of ion line enhancements in data from the EISCAT Svalbard radar taken during the International Polar Year (extending from March 2007 to the end of February 2008). The SUIPEs are observed at altitudes between 210 km and 280 km with a standard deviation of 9% of the average occurrence height 230 km. The power enhancements are one order of magnitude above the thermal level. The SUIPEs occur at the ionospheric F region peak with 85% of the cases located within 10 km of the peak. The occurrence shows a clear preference for magnetically disturbed conditions, with the likelihood of occurrence increasing with increasing K index. A majority of the events occur in the magnetic evening to pre-midnight sector.

  • 18. Faucherre, Samuel
    et al.
    Jørgensen, Christian Juncher
    Blok, Daan
    Weiss, Niels
    Siewert, Matthias Benjamin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Department of Physical Geography, Stockholm University,Stockholm, Sweden.
    Bang-Andreasen, Toke
    Hugelius, Gustaf
    Kuhry, Peter
    Elberling, Bo
    Short and Long-Term Controls on Active Layer and Permafrost Carbon Turnover Across the Arctic2018Inngår i: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 123, nr 2, s. 372-390Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Decomposition of soil organic matter (SOM) in permafrost terrain and the production of greenhouse gases is a key factor for understanding climate change-carbon feedbacks. Previous studies have shown that SOM decomposition is mostly controlled by soil temperature, soil moisture, and carbon-nitrogen ratio (C:N). However, focus has generally been on site-specific processes and little is known about variations in the controls on SOM decomposition across Arctic sites. For assessing SOM decomposition, we retrieved 241 samples from 101 soil profiles across three contrasting Arctic regions and incubated them in the laboratory under aerobic conditions. We assessed soil carbon losses (C-loss) five times during a 1year incubation. The incubated material consisted of near-surface active layer (AL(NS)), subsurface active layer (AL(SS)), peat, and permafrost samples. Samples were analyzed for carbon, nitrogen, water content, C-13, N-15, and dry bulk density (DBD). While no significant differences were observed between total AL(SS) and permafrost C-loss over 1year incubation (2.32.4% and 2.51.5% C-loss, respectively), AL(NS) samples showed higher C-loss (7.94.2%). DBD was the best explanatory parameter for active layer C-loss across sites. Additionally, results of permafrost samples show that C:N ratio can be used to characterize initial C-loss between sites. This data set on the influence of abiotic parameter on microbial SOM decomposition can improve model simulations of Arctic soil CO2 production by providing representative mean values of CO2 production rates and identifying standard parameters or proxies for upscaling potential CO2 production from site to regional scales.

  • 19.
    Holmgren, Bror
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Soil organic carbon pools of the Torneträsk catchment area: The importance of soil depth and stone and boulder content for carbon inventories in formerly glaciated subarctic soils2013Independent thesis Basic level (degree of Bachelor), 20 poäng / 30 hpOppgave
    Abstract [en]

    High latitude soils are estimated to store a considerable part of the global pool of soil organic carbon (SOC). Studies of global and regional SOC pools have estimated total inventories in northern Sweden’s subarctic region to fall within 10-50 kg m-2. However, correction factors for stone and boulder content of soils are often overlooked in SOC-studies and soil profiles are commonly normalized to a depth of 1 m, which can result in substantial overestimates of the SOC pool if a large part of the soil volume is occupied by stones/boulders or if the soil depth is shallower than 1 m. This study was performed to quantify SOC in soils of the Torneträsk catchment area using detailed measures of soil depth and stone/boulder contents. Two non-destructive sampling methods, ground penetrating radar (GPR) and rod penetration, were used to measure soil depth and stone and boulder content in the catchment area. Results show that average soil depth (n = 52344) varied between 0.95 – 2.14 m depending on elevation and the average mire depth was 0.63 m. Stone and boulder content of the soil was estimated to 49 – 68 % depending on elevation. The results were added to existing carbon and soil density data from the Torneträsk catchment area and total SOC inventories were calculated to 6.8 – 13.1 kg m-2. The results of this study indicate that previous studies on regional and global scale may have overestimated the SOC pools in the subarctic regions of northern Sweden.

  • 20.
    Holmgren, Bror
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Tracing the source of colourless carbon in an arctic lake on SW Greenland: Insights of organic matter origin from hydrogen isotope analyses of samples prepared using steam equilibration2016Independent thesis Advanced level (degree of Master (Two Years)), 40 poäng / 60 hpOppgave
    Abstract [en]

    Lakes play an important role in the global carbon (C) cycle as they process carbon from terrestrial (allochthonous) and within lake (autochthonous) sources and may store C over long periods of time. Some arctic lakes contain high concentrations of dissolved organic carbon (DOC) that does not absorb light and thus remains colourless. The origin of this DOC remains unknown, but the sediment of these lakes have been suggested to accumulate primarily autochthonous (algal) C. I developed an experimental chamber for hydrogen (H) isotope pre-treatments and applied a novel H isotope tracing approach to determine the origin of the DOC and sediment C of a lake on SW Greenland known to contain colourless DOC. I hypothesized that autochthonous C was the prime source of DOC and sediment C, in line with previous theories. Analyses of algae and soil samples from the catchment revealed that local allochthonous and autochthonous C sources had a δ2H composition of -139 ‰ and -209 ‰, respectively. In contrast to my hypothesis, the analysed DOC had a mean δ2H isotopic composition of -147 ‰ indicating a dominance (ca 80-90 %) of allochthonous C. Similarly, the sediment had a mean δ2H isotopic composition of -155 ‰, suggesting that about 84 % of the C accumulating in the sediment was derived from terrestrial sources. The terrestrial origin was supported by field observations of high DOC seepage water (up to 70 mg L-1) with uncharacteristically low light absorption values entering the lake during high precipitation events. My results indicate that terrestrial processes are fundamental C sources for arctic lakes, even in regions with very low precipitation.

  • 21.
    Hotchkiss, E. R.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Hall, R. O., Jr.
    Sponseller, R. A.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Butman, D.
    Klaminder, J.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Laudon, H.
    Rosvall, Martin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Karlsson, J.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Sources of and processes controlling CO2 emissions change with the size of streams and rivers2015Inngår i: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908, Vol. 8, nr 9, s. 696-699Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Carbon dioxide (CO2) evasion from streams and rivers to the atmosphere represents a substantial flux in the global carbon cycle(1-3). The proportions of CO2 emitted from streams and rivers that come from terrestrially derived CO2 or from CO2 produced within freshwater ecosystems through aquatic metabolism are not well quantified. Here we estimated CO2 emissions from running waters in the contiguous United States, based on freshwater chemical and physical characteristics and modelled gas transfer velocities at 1463 United States Geological Survey monitoring sites. We then assessed CO2 production from aquatic metabolism, compiled from previously published measurements of net ecosystem production from 187 streams and rivers across the contiguous United States. We find that CO2 produced by aquatic metabolism contributes about 28% of CO2 evasion from streams and rivers with flows between 0.0001 and 19,000 m(3) s(-1). We mathematically modelled CO2 flux from groundwater into running waters along a stream-river continuum to evaluate the relationship between stream size and CO2 source. Terrestrially derived CO2 dominates emissions from small streams, and the percentage of CO2 emissions from aquatic metabolism increases with stream size. We suggest that the relative role of rivers as conduits for terrestrial CO2 efflux and as reactors mineralizing terrestrial organic carbon is a function of their size and connectivity with landscapes.

  • 22.
    Hotchkiss, Erin
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Program in Ecology and Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, USA.
    Hall, R. O., Jr.
    Baker, M. A.
    Rosi-Marshall, E. J.
    Tank, J. L.
    Modeling priming effects on microbial consumption of dissolved organic carbon in rivers2014Inngår i: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 119, nr 5, s. 982-995Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Rivers receive and process large quantities of terrestrial dissolved organic carbon (DOC). Biologically available (unstable) DOC leached from primary producers may stimulate (i.e., prime) the consumption of more stable terrestrially derived DOC by heterotrophic microbes. We measured microbial DOC consumption (i.e., decay rates) from contrasting C sources in 10 rivers in the western and Midwestern United States using short-term bioassays of river water, soil and algal leachates, glucose, and commercial humate. We added inorganic nutrients (ammonium and phosphorus) to a subset of bioassays. We also amended a subset of river, soil, and commercial humate bioassays with glucose or algal leachates to test the hypothesis that unstable DOC primes consumption of more stable DOC. We used prior measurements of source-specific DOC bioavailability, linked with a Bayesian process model, to estimate means and posterior probability distributions for source-specific DOC decay rates in multisource bioassays. Modeled priming effects ranged from a -130 to +370% change in more stable DOC decay when incubated with unstable DOC. Glucose increased modeled river DOC decay by an average of 87% among all rivers. Glucose and algal leachates increased soil leachate and commercial humate decay by an average of 25% above background rates. Inorganic nutrient additions did not have consistent effects on DOC decay, likely because most of the study rivers had high ambient background nutrients. Our results demonstrate that the priming effect can augment DOC decay in rivers. In addition, Bayesian models can be used to estimate mechanisms driving aquatic ecosystem processes that are difficult to measure directly.

  • 23. Karlsson, Tomas
    et al.
    Hamrin, Maria
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Nilsson, Hans
    Kullen, Anita
    Pitkänen, Timo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Magnetic forces associated with bursty bulk flows in Earth's magnetotail2015Inngår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 42, nr 9, s. 3122-3128Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present the first direct measurements of magnetic forces acting on bursty bulk flow plasma in the magnetotail. The magnetic forces are determined using Cluster multispacecraft measurements. We analyze 67 bursty bulk flow (BBF) events and show that the curvature part of the magnetic force is consistently positive, acting to accelerate the plasma toward Earth between approximately 10 and 20 R-E geocentrical distances, while the magnetic field pressure gradient increasingly brakes the plasma as it moves toward Earth. The net result is that the magnetic force accelerates the plasma at distances greater than approximately 14 R-E, while it acts to decelerate it within that distance. The magnetic force, together with the thermal pressure gradient force, will determine the dynamics of the BBFs as they propagate toward the near-Earth tail region. The determination of the former provides an important clue to the ultimate fate of BBFs in the inner magnetosphere.

  • 24. Karnachuk, Olia V
    et al.
    Pimenov, Nikolay V
    Yusupov, Sandjar K
    Frank, Yulia A
    Kaksonen, Anna H
    Puhakka, Jaakko A
    Ivanov, Mikhail V
    Lindström, E Börje
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Tuovinen, Olli H
    Sulfate reduction potential in sediments in the Norilsk mining area, northern Siberia2005Inngår i: Geomicrobiology Journal, ISSN 0149-0451, E-ISSN 1521-0529, Vol. 22, nr 1-2, s. 11-25Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The purpose of this study was to characterize the distribution and activity of sulfate-reducing bacteria in tailings and sediments impacted by effluents from mining and smelting operations in the Norilsk area in northern Siberia. The Norilsk mining complex involves three smelter operations, a hydrometallurgical plant, and extensive tailings areas located in the permafrost zone. Sulfate reduction rates measured with a (35)SO(4)(2-) tracer technique under various in-situ conditions ranged from 0.05 to 30 nmol S cm(-3) day(-1). Acetate and glucose addition greatly stimulated sulfate reduction, whereas lactate had less effect. The most pronounced stimulation of sulfate reduction (6.5-fold) was observed with phosphate amendment. Most-probable-number (MPN) counts of sulfate-reducing bacteria in media with glucose, ethanol, lactate, and acetate as electron donors were generally highest at around 10(7) cells ml(-1). The actual MPN counts varied with the sample, electron donor, and incubation conditions (pH 7.2 vs. pH 3.5; 28 degrees C vs. 4 degrees C). Enrichment cultures of sulfate-reducing bacteria were established from a sample that showed the highest rate of sulfate reduction. After multiple serial transfers, the dominant sulfate-reducers were identified by fluorescence in situ hybridization using genus and group-specific 16S rRNA-targeted oligonucleotide probes. Desulfobulbus spp. prevailed in ethanol and lactate enrichments and the Desulfosarcina-Desulfococcus group dominated in acetate and benzoate enrichments. Psychrophilic Desulfotalea-Desulfofustis and moderately psychrophilic Desulforhopalus spp. were identified in enrichments incubated at 4 degrees C, but they were also found in mesophilic enrichments.

  • 25.
    Kashian, Alireza
    et al.
    Dept. of Infrastructure Engineering, University of Melbourne, Parkville, Australia.
    Rajabifard, Abbas
    Dept. of Infrastructure Engineering, University of Melbourne, Parkville, Australia.
    Chen, Yiqun
    Dept. of Infrastructure Engineering, University of Melbourne, Parkville, Australia.
    Richter, Kai-Florian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    OSM POI Analyzer: A Platform for Assessing Position of POIs in OpenStreetMap2017Inngår i: ISPRS Geospatial Week 2017 / [ed] D. Li, J. Gong, B. Yang, H. Wu, L. Wu, Z. Gui, X. Cheng, H. Wu, S. Li, R. Lindenbergh, J. Boehm, M. Rutzinger, W. Yao, M. Weinmann, Z. Kang, K. Khoshelham, M. Peter, L. Díaz-Vilariño, W. Shi, B. Lu, H. Abdulmuttalib, M. R. Delavar, T. Balz, B. Osmanoglu, F. Rocca, U. Sörgel, J. Zhang, P. Li, S. Du, L. Zhao, X. Lin, K. Qin, C. Kang, X. Li, C. Chen, R. Li, G. Qiao, H. Wu, and C. Heipke, 2017, Vol. XLII-2/W7, s. 497-504Konferansepaper (Fagfellevurdert)
    Abstract [en]

     In recent years, more and increased participation in Volunteered Geographical Information (VGI) projects provides enough data coverage for most places around the world for ordinary mapping and navigation purposes, however, the positional credibility of contributed data becomes more and more important to bring a long-term trust in VGI data. Today, it is hard to draw a definite traditional boundary between the authoritative map producers and the public map consumers and we observe that more and more volunteers are joining crowdsourcing activities for collecting geodata, which might result in higher rates of man-made mistakes in open map projects such as OpenStreetMap. While there are some methods for monitoring the accuracy and consistency of the created data, there is still a lack of advanced systems to automatically discover misplaced objects on the map. One feature type which is contributed daily to OSM is Point of Interest (POI). In order to understand how likely it is that a newly added POI represents a genuine real-world feature scientific means to calculate a probability of such a POI existing at that specific position is needed. This paper reports on a new analytic tool which dives into OSM data and finds co-existence patterns between one specific POI and its surrounding objects such as roads, parks and buildings. The platform uses a distance-based classification technique to find relationships among objects and tries to identify the high-frequency association patterns among each category of objects. Using such method, for each newly added POI, a probabilistic score would be generated, and the low scored POIs can be highlighted for editors for a manual check. The same scoring method can be used for existing registered POIs to check if they are located correctly. For a sample study, this paper reports on the evaluation of 800 pre-registered ATMs in Paris with associated scores to understand how outliers and fake entries could be detected automatically.

  • 26. Khorasani, Sara
    et al.
    Panagiotakopulu, Eva
    Engelmark, Roger
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier.
    Ralston, Ian
    Late Holocene beetle assemblages and environmental change in Gammelhemmet, northern Sweden2015Inngår i: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 44, nr 2, s. 368-382Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 27. Krickov, Ivan V.
    et al.
    Lim, Artem G.
    Manasypov, Rinat M.
    Loiko, Sergey V.
    Shirokova, Liudmila S.
    Kirpotin, Sergey N.
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Pokrovsky, Oleg S.
    Riverine particulate C and N generated at the permafrost thaw front: case study of western Siberian rivers across a 1700km latitudinal transect2018Inngår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 15, nr 22, s. 6867-6884Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In contrast to numerous studies on the dynamics of dissolved (< 0.45 mu m) elements in permafrost-affected highlatitude rivers, very little is known of the behavior of river suspended (> 0.45 mu m) matter (RSM) in these regions. In order to test the effect of climate, permafrost and physiogeographical landscape parameters (bogs, forest and lake coverage of the watershed) on RSM and particulate C, N and P concentrations in river water, we sampled 33 small and medium-sized rivers (10-100 000 km(2) watershed) along a 1700 km N-S transect including both permafrost-affected and permafrost-free zones of the Western Siberian Lowland (WSL). The concentrations of C and N in RSM decreased with the increase in river watershed size, illustrating (i) the importance of organic debris in small rivers which drain peatlands and (ii) the role of mineral matter from bank abrasion in larger rivers. The presence of lakes in the watershed increased C and N but decreased P concentrations in the RSM. The C V N ratio in the RSM reflected the source from the deep soil horizon rather than surface soil horizon, similar to that of other Arctic rivers. This suggests the export of peat and mineral particles through suprapermafrost flow occurring at the base of the active layer. There was a maximum of both particulate C and N concentrations and export fluxes at the beginning of permafrost appearance, in the sporadic and discontinuous zone (62-64 degrees N). This presumably reflected the organic matter mobilization from newly thawed organic horizons in soils at the active latitudinal thawing front. The results suggest that a northward shift of permafrost boundaries and an increase in active layer thickness may increase particulate C and N export by WSL rivers to the Arctic Ocean by a factor of 2, while P export may remain unchanged. In contrast, within a long-term climate warming scenario, the disappearance of permafrost in the north, the drainage of lakes and transformation of bogs to forest may decrease C and N concentrations in RSM by 2 to 3 times.

  • 28.
    Kullman, Leif
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Early postglacial appearance of tree species in northern Scandinavia: review and perspective2008Inngår i: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 27, nr 27-28, s. 2467-2472Artikkel i tidsskrift (Fagfellevurdert)
    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".

  • 29. Kylander, Malin E.
    et al.
    Martínez-Cortizas, A.
    Bindler, Richard
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Kaal, Joeri
    Sjöström, Jenny K.
    Hansson, Sophia V.
    Silva-Sánchez, Noemi
    Greenwood, Sarah L.
    Gallagher, Kerry
    Rydberg, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Mörth, Carl-Magnus
    Rauch, Sebastien
    Mineral dust as a driver of carbon accumulation in northern latitudes2018Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, artikkel-id 6876Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Peatlands in northern latitudes sequester one third of the world's soil organic carbon. Mineral dusts can affect the primary productivity of terrestrial systems through nutrient transport but this process has not yet been documented in these peat-rich regions. Here we analysed organic and inorganic fractions of an 8900-year-old sequence from Store Mosse (the "Great Bog") in southern Sweden. Between 5420 and 4550 cal yr BP, we observe a seven-fold increase in net peat-accumulation rates corresponding to a maximum carbon-burial rate of 150 g C m-2 yr-1 - more than six times the global average. This high peat accumulation event occurs in parallel with a distinct change in the character of the dust deposited on the bog, which moves from being dominated by clay minerals to less weathered, phosphate and feldspar minerals. We hypothesize that this shift boosted nutrient input to the bog and stimulated ecosystem productivity. This study shows that diffuse sources and dust dynamics in northern temperate latitudes, often overlooked by the dust community in favour of arid and semi-arid regions, can be important drivers of peatland carbon accumulation and by extension, global climate, warranting further consideration in predictions of future climate variability.

  • 30.
    Kübler, Isabella
    et al.
    Department of Geography, University of Zürich.
    Richter, Kai-Florian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Fabrikant, Sara Irina
    Department of Geography, University of Zürich.
    How does the visualization of uncertainty influence decision making with hazard prediction maps?2017Annet (Annet vitenskapelig)
    Abstract [en]

    A wealth of design strategies has been proposed by an interdisciplinary scientific community to visually communicate data uncertainty in maps, with the aim to support spatio-temporal decision-making under uncertainty (MacEachren et al., 2012). However, very few researchers have looked at whether and how uncertainty depictions might influence people’s reasoning processes and decision making outcomes, especially in problem contexts for which uncertainty truly matters, i.e., in life-threatening situations, or for dilemmatic decisions. We report on a map-based multi-criteria decision making study where participants (N=35) were asked to imagine purchasing a house shown on map stimuli inspired by Swiss National hazard prediction maps (SFOEN, 2016). These area-classed maps show the probability and intensity of natural disasters occurring in areas with varying danger levels in a pre-defined color scheme (i.e., red=high, blue=moderate, and yellow=low danger). Current hazard prediction maps do not depict prediction uncertainties, even though suggestions have been proposed in the cartographic literature (Kunz and Hurni, 2011). However, because there are uncertainties associated with the areal extent of the classed danger zones, we modified the zonal boundaries to show this locational uncertainty using the visual variables color value, focus, and texture, as suggested by prior empirical research (MacEachren, 2012). In a within-subject design, participants were repeatedly asked to decide which house they wished to buy, given varying house location characteristics, and respective purchase price information. The houses were depicted on a series of hazard prediction maps showing an area unknown to participants, with/without data uncertainty depicted. The maps showing uncertainty varied in the visual variables (i.e., color value|focus|texture) used to convey the locational uncertainty of the zonal boundaries. We recorded participants’ house selections, response times, and eye movements during the experiment. The task asked for participants’ preferences; there were no right or wrong answers. As hypothesized, our results show that participants’ decision making outcomes were indeed influenced by the depicted uncertainty information. Participants decided to buy different houses, as they weighted selection criteria differently, depending on whether uncertainty was shown on the map or not. We thus provide rare evidence on how uncertainty and the type of uncertainty visualization (i.e., varying color value, focus, or texture) can influence people’s reasoning to arrive at a complex, multi-criteria-based decision. We also find that participants’ individual differences with respect to their risk taking behavior tested with a standardised questionnaire influences their decision making. Risk takers underestimate the dangers of natural hazards when prediction uncertainties are depicted. With this unique study we are able to shed additional light on how people use visualized uncertainty information to make complex map-based decisions. Echoing Hegarty et al.'s (2016) findings, we again demonstrate that not only display design characteristics are relevant for map-based reasoning and decision making outcomes, but also the decision makers’ individual background, and the map-based decision-making task and context. References: Hegarty, M., Friedman, A., Boone, A.P., Barrett, T.J. (2016). Where Are You? The Effect of Uncertainty and Its Visual Representation on Location Judgments in GPS-Like Displays. Journal of Experimental Psychology, Applied, DOI: 10.1037/xap0000103. Kunz, M. and Hurni, L. (2011). How to Enhance Cartographic Visualisations of Natural Hazards Assessment Results. The Cartographic Journal, 48(1): 60-71. MacEachren, A. M., Roth, R. E., O'Brien, J., Li, B., Swingley, D., Gahegan, M. (2012). Visual Semiotics & Uncertainty Visualization: An Empirical Study. IEEE Transactions on Visualization and Computer Graphics, 18(12): 2496-2505. Swiss Federal Office for the Environment (SFOEN). Gefahrenkarten, Intensitätskarten und Gefahrenhinweiskarten. (Natural Hazard Maps), http://www.bafu.admin.ch/naturgefahren/14186/14801/15746/ (not available in English, accessed Oct. 2016).

  • 31. Lapierre, Jean-Francois
    et al.
    Seekell, David A.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    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 lakes2017Inngår i: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 122, nr 4, s. 875-885Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 32.
    Lidberg, William
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Moshyttan: Sweden’s oldest known blast furnace?: A multiproxy study based on geochemical and pollen analyses2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Radiocarbon datings in a previous study suggested that Moshyttan in Nora bergslag is the oldest blast furnace in Sweden and Europe. The aim of this study was specifically to study the origin of the Moshyttan blast furnace to answer the question: when was the blast furnace at Moshyttan established? To this end, a 2.5 m sediment record was collected from Fickeln, a lake 600 m downstream of Moshyttan, in March 2012. The geochemical properties of the sediment record were analyzed for major and trace elements using XRF. The organic content was calculated from the ash residue following the mercury analyses as a proxy for organic matter. Pollen and charcoal were analyzed using a standardized method. A age- depth model was created based on four radiocarbon datings of the sediment profile. The pollen data suggest that early land use consisted of forest grazing from about AD 220, and agriculture from about AD 880. An increase in Pb and charcoal particles about AD 880 indicates early metallurgy in the area. The first significant evidence of the establishment of a blastfurnace was between AD 1020 and AD 1090 marked by a decrease in organic content combined with a strong increase of ore related metals such as Pb, Zn, Cu and a strong increase of charcoal particles. Within the uncertainty of the age-depth modeling, the results from this study offers support to Wetterholms radiocarbon datings, thus making Moshyttan the oldest known blast furnace in Sweden and Europe. 

  • 33. Lindstedt, T
    et al.
    Khotyaintsev, YV
    Vaivads, A
    André, M
    Nilsson, H
    Waara, Martin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Oxygen energization by localized perpendicular electric fields at the cusp boundary2010Inngår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 37, nr 9, artikkel-id L09103Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report Cluster observations of oxygen energization by several keV at the boundary between the high latitude cusp and lobe. A localized electric field at the cusp/lobe boundary is responsible for a significant part of the observed energization. Such electric fields can be related to the separatrix region of reconnection at the magnetopause. Ions are accelerated as they move non-adiabatically in the spatially inhomogeneous electric field. Additional heating may be provided by low frequency waves at the oxygen gyrofrequency. Citation: Lindstedt, T., Y. V. Khotyaintsev, A. Vaivads, M. Andre, H. Nilsson, and M. Waara (2010), Oxygen energization by localized perpendicular electric fields at the cusp boundary.

  • 34.
    Lundin, Erik
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Klaminder, Jonatan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Bastviken, David
    Department of Thematic Studies–Water and Environmental Studies, Linköping University, Linköping, Sweden.
    Olid, Carolina
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Hansson, Sophia
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Strong climate impact on the carbon emission – burial balance inhigh latitude lakesManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Lakes play an important role in the global carbon (C) cycle by burying C in sediments and emitting CO2 and CH4 to the atmosphere. The strengths of these fundamentally different pathways are critical for quantifying effects of lakes upon the climate system. In this study, based on new high-resolution estimates in combination with literature data, we show a generally ten times higher emission:burial ratio in boreal compared to subarctic-arctic lakes. These results suggest a major bioclimatic impact on C cycling in lakes, as lakes in warmer boreal regions emit more and store relatively less C than lakes in colder arctic regions. Thus, our results reveal a previously unforeseen longterm climate feedback: if predictions of the northward expansion of the boreal biome are correct, C emissions of high latitude lakes may increase four-fold, corresponding to 14% of present global lake C evasion to the atmosphere. Such effects are of major importance for understanding feedbacks of climate warming on the continental source-sink function at high latitudes

     

     

  • 35. Nakamura, R.
    et al.
    Karlsson, T.
    Hamrin, Maria
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Nilsson, H.
    Swedish Inst Space Phys, S-98128 Kiruna, Sweden.
    Marghitu, O.
    Amm, O.
    Bunescu, C.
    Constantinescu, V.
    Frey, H. U.
    Keiling, A.
    Semeter, J.
    Sorbalo, E.
    Vogt, J.
    Forsyth, C.
    Kubyshkina, M. V.
    Low- altitude electron acceleration due to multiple flow bursts in the magnetotail2014Inngår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 41, nr 3, s. 777-784Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    At 10:00 UT on 25 February 2008, Cluster 1 spacecraft crossed the near-midnight auroral zone, at about 2R(E) altitude, while two of the Time History of Events and Macroscale Interactions During Substorms (THEMIS) spacecraft, THD and THE, observed multiple flow bursts on the near-conjugate plasma sheet field lines. The flow shear pattern at THEMIS was consistent with the vortical motion at duskside of a localized flow channel. Coinciding in time with the flow bursts, Cluster 1 observed bursts of counterstreaming electrons with mostly low energies (441eV), accompanied by short time scale (<5s) magnetic field disturbances embedded in flow-associated field-aligned current systems. This conjugate event not only confirms the idea that the plasma sheet flows are the driver of the kinetic Alfven waves accelerating the low-energy electrons but is a unique observation of disturbances in the high-altitude auroral region relevant to the multiple plasma sheet flows. Key Points <list list-type="bulleted"> <list-item id="grl51326-li-0001">First observation of multiple flow signatures on near-conjugate flux tubes <list-item id="grl51326-li-0002">Low-energy electron profile suggests Alfvenic acceleration due to fast flow <list-item id="grl51326-li-0003">Multiple flow bursts are obtained to extend over large radial distance in tail

  • 36.
    Ninnes, Sofia
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Tolu, Julie
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Meyer-Jacob, Carsten
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Mighall, Tim M.
    Bindler, Richard
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Investigating molecular changes in organic matter composition in two Holocene lake-sediment records from central Sweden using pyrolysis-GC/MS2017Inngår i: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 122, nr 6, s. 1423-1438Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Organic matter (OM) is a key component of lake sediments, affecting carbon, nutrient, and trace metal cycling at local and global scales. Yet little is known about long-term (millennial) changes in OM composition due to the inherent chemical complexity arising from multiple OM sources and from secondary transformations. In this study we explore how the molecular composition of OM changes throughout the Holocene in two adjacent boreal lakes in central Sweden and compare molecular-level information with conventional OM variables, including total carbon, total nitrogen, C:N ratios, delta C-13, and delta N-15. To characterize the molecular OM composition, we employed a new method based on pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), which yields semiquantitative data on > 100 organic compounds of different origin and degradation status. We identify large changes in OM composition after deglaciation (circa 8500 +/- 500 B.C.), associated with early landscape development, and during the most recent 4050 years, driven by degradation processes. With molecular(-)level information we can also distinguish between natural landscape development and human catchment disturbance during the last 1700 years. Our study demonstrates that characterization of the molecular OM composition by the high-throughput PyGC/MS method is an efficient complement to conventional OM variables for identification and understanding of past OM dynamics in lake-sediment records. Holocene changes observed for pyrolytic compounds and compound classes known for having different reactivity indicate the need for further paleo-reconstruction of the molecular OM composition to better understand both past and future OM dynamics and associated environmental changes.

  • 37.
    Parsons, Malcolm
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Herbivore pressure of reindeer, rodents and invertebrates in the Fennoscandian tundra: a comparison of three methods.2016Independent thesis Advanced level (degree of Master (Two Years)), 40 poäng / 60 hpOppgave
    Abstract [en]

    Estimating herbivore density is an important part of understanding their impact on vegetation.  Many studies have been carried out on the impact of reindeer and other herbivores on arctic and sub-arctic vegetation, but they are difficult to compare as they typically use different methods to estimate herbivore activities.  The aim of this study was to compare three methods that were based on the recent International Tundra Experiment herbivory protocol to measure the activities of three herbivore groups: reindeer, rodents and invertebrates. The robustness of the methods themselves was then evaluated.  Fieldwork was carried out at 12 sites in the Fennoscandian mountain area, with controls inside reindeer exclosures.  The results showed that the methods were the most robust when measuring reindeer activities.  The reindeer measurements were also well correlated with a reindeer-density estimate calculated from official reindeer population data.  This study recommends considering the use of photographs to increase the time-efficiency of pellet-counts.  The rodent activity estimates were good, but the patterns inside exclosures differed to the patterns outside exclosures.  The results for invertebrates were deemed to be less reliable as the measurements for one method were not recorded at an appropriate scale.  In conclusion, the findings of this study will help improve the comparability of future studies on the impact of reindeer herbivory and other herbivores, and gives suggestions for more accurate ways of measuring herbivore pressure in arctic and sub-arctic vegetation.

  • 38.
    Robinson, G. M.
    et al.
    University of South Australia, Australia.
    Carson, D. A.
    University of South Australia, Australia.
    Applying Landscape Science to Natural Resource Management2013Inngår i: Ecology & society, ISSN 1708-3087, E-ISSN 1708-3087, Vol. 18, nr 1, s. 32-Artikkel i tidsskrift (Fagfellevurdert)
  • 39.
    Rocher-Ros, Gerard
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Biophysical controls on CO2 evasion from Arctic inland waters2019Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    CO2 evasion to the atmosphere from inland waters is a major component of the global carbon (C) cycle. Yet spatial patterns of CO2 evasion and the sources of C that fuel evasion remain poorly understood. In this thesis, I use detailed measurements of biological and physical drivers of CO2 evasion to assess how C is transformed and evaded from inland waters in the Arctic (Northern Scandinavia and Alaska). I found that lake size was a master variable controlling lake CO2 evasion in an Arctic catchment and that large lakes play a major role at the landscape scale. In stream networks, I found that catchment topography shapes patterns of CO2 evasion by dictating unique domains with high lateral inputs of C, other domains where biological processes were dominant, and domains where physical forces promoted degassing to the atmosphere. Together, these topographically driven domains created a strong spatial heterogeneity that biases regional and global estimates of CO2 evasion. Further, I found that photosynthetic activity in Arctic streams can produce a large change in CO2 concentrations from night to day, and as a result CO2 evasion is up to 45% higher during night than day. The magnitude of the diel change in CO2 was also affected by the turbulence of the stream and photo-chemical production of CO2. Overall, this thesis offers important insights to better understand landscape patterns of CO2 evasion from inland waters, and suggests that stream metabolic processes largely determine the fate of the C delivered from Arctic soils.

  • 40. Rocher-Ros, Gerard
    et al.
    Harms, Tamara K.
    Sponseller, Ryan A.
    Väisänen, Maria
    Mörth, Carl-Magnus
    Giesler, Reiner
    Photosynthesis overrides photo-oxidation in CO2 dynamics of Arctic permafrost streamsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Global warming is mobilising large amounts of organic carbon (C) from arctic soils into streams, where it can be mineralized to CO2 and released to the atmosphere. Photo-chemical degradation is thought to drive this mineralization, yet this process has not been quantitatively integrated with biological processes, like photosynthesis and respiration, that also influence CO2 dynamics in aquatic ecosystems. We measured CO2 and δ13C-DIC concentrations at diel resolution in two northern Alaska streams, and coupled this with whole-system metabolism estimates to assess the effect of different light-dependent processes on stream C dynamics. CO2 concentrations decreased by up to 500 ppm from night to day, a pattern counter to the hypothesis that photodegradation is the dominant source of dissolved CO2. Instead, the observed decrease in CO2 concentration during daytime was explained by photosynthetic rates in streams, which ranged from 0.04 to 0.17 g C m-2 d-1, and were also strongly correlated with diurnal changes in the isotopic composition of dissolved inorganic C. However, photosynthetic rates were larger than the observed diel change in CO2, suggesting that metabolic estimates are partly masked by CO2 production from photo-oxidation. The difference between expected and observed daytime CO2 concentrations suggests 1 – 30 mmol C m3 d-1 may be generated from photo-oxidation, a range that corresponds well to laboratory measurements of this process. Overall, stream net ecosystem production was a source of CO2, with rates ten times greater than published photo-oxidation rates for arctic aquatic ecosystems and accounted for 27-83% of CO2 evasion. Our results suggest that aquatic metabolic activity has a significant effect on CO2 dynamics and emissions from arctic stream networks.

  • 41. Rocher-Ros, Gerard
    et al.
    Sponseller, Ryan A.
    Bergström, Ann-Kristin
    Myrstener, Maria
    Giesler, Reiner
    Stream metabolism controls diel patterns and evasion of CO2 in Arctic streamsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Streams play an important role in the global carbon (C) cycle, accounting for a large portion of CO2 evaded from inland waters despite their small areal coverage. However, the relative importance of different terrestrial and aquatic processes driving CO2 production and evasion from streams remains poorly understood. In this study, we measured O2 and CO2 continuously in tundra-dominated streams in northern Sweden to estimate daily metabolic rates and CO2 evasion simultaneously and thus provide insight into the role of stream metabolism as a driver of C dynamics in Arctic streams. Our results show that aquatic biological processes control CO2 concentrations and evasion at multiple time scales. Photosynthesis caused a marked decrease in CO2 concentrations during the day, with up to a 900-ppm difference between day- and night-time values with the magnitude of this diel variation being strongest at the low-turbulence streams. These diel patterns in CO2 concentrations in turn influenced evasion, with up to 45% higher rates at night. Throughout the summer, CO2 evasion was sustained by ecosystem respiration, which was one order of magnitude higher than gross primary production. Furthermore, in most cases the contribution of stream respiration exceeded CO2 evasion, suggesting that some stream reaches serve as net sources of CO2, creating longitudinal heterogeneity in C production and loss within this stream network. Overall, our results provide the first link between stream metabolism and CO2 evasion in the Arctic and demonstrate that stream metabolic processes are key drivers of the transformation and fate of terrestrial organic matter exported from these landscapes.

  • 42.
    Rocher-Ros, Gerard
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Sponseller, Ryan A.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Lidberg, William
    SLU.
    Mörth, Carl-Magnus
    Stockholm University.
    Giesler, Reiner
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Landscape process domains drive patterns of CO2 evasion from river networks2019Inngår i: Limnology and Oceanography Letters, ISSN 2378-2242, Vol. 4, nr 4, s. 87-95Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Streams are important emitters of CO2 but extreme spatial variability in their physical properties can make upscaling very uncertain. Here, we determined critical drivers of stream CO2 evasion at scales from 30 to 400 m across a 52.5 km2 catchment in northern Sweden. We found that turbulent reaches never have elevated CO2 concentrations, while less turbulent locations can potentially support a broad range of CO2 concentrations, consistent with global observations. The predictability of stream pCO2 is greatly improved when we include a proxy for soil‐stream connectivity. Catchment topography shapes network patterns of evasion by creating hydrologically linked “domains” characterized by high water‐atmosphere exchange and/or strong soil‐stream connection. This template generates spatial variability in the drivers of CO2 evasion that can strongly bias regional and global estimates. To overcome this complexity, we provide the foundations of a mechanistic framework of CO2 evasion by considering how landscape process domains regulate transfer and supply.

  • 43. Roux, A.
    et al.
    Robert, P.
    Le Contel, O.
    Angelopoulos, V.
    Auster, U.
    Bonnell, J.
    Cully, C. M.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Ergun, R. E.
    McFadden, J. P.
    A mechanism for heating electrons in the magnetopause current layer and adjacent regions2011Inngår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 29, nr 12, s. 2305-2316Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Taking advantage of the string-of-pearls configuration of the five THEMIS spacecraft during the early phase of their mission, we analyze observations taken simultaneously in the magnetosheath, the magnetopause current layer and the magnetosphere. We find that electron heating coincides with ultra low frequency waves. It seems unlikely that electrons are heated by these waves because the electron thermal velocity is much larger than the Alfven velocity (V-a). In the short transverse scale (k (perpendicular to) rho(i) >> 1) regime, however, short scale Alfven waves (SSAWs) have parallel phase velocities much larger than V-a and are shown to interact, via Landau damping, with electrons thereby heating them. The origin of these waves is also addressed. THEMIS data give evidence for sharp spatial gradients in the magnetopause current layer where the highest amplitude waves have a large component delta B perpendicular to the magnetopause and k azimuthal. We suggest that SSAWs are drift waves generated by temperature gradients in a high beta, large T-i/T-e magnetopause current layer. Therefore these waves are called SSDAWs, where D stands for drift. SSDAWs have large k(perpendicular to) and therefore a large Doppler shift that can exceed their frequencies in the plasma frame. Because they have a small but finite parallel electric field and a magnetic component perpendicular to the magnetopause, they could play a key role at reconnecting magnetic field lines. The growth rate depends strongly on the scale of the gradients; it becomes very large when the scale of the electron temperature gradient gets below 400 km. Therefore SSDAW's are expected to limit the sharpness of the gradients, which might explain why Berchem and Russell (1982) found that the average magnetopause current sheet thickness to be similar to 400-1000 km (similar to 500 km in the near equatorial region).

  • 44.
    Sarneel, J. M. Judith
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Ecology & Biodiversity Group and Plant Ecophysiology Group, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
    Veen, G. F. Ciska
    Legacy effects of altered flooding regimes on decomposition in a boreal floodplain2017Inngår i: Plant and Soil, ISSN 0032-079X, E-ISSN 1573-5036, Vol. 421, nr 1-2, s. 57-66Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Since long-term experiments are scarce, we have poor understanding of how changed flooding regimes affect processes such as litter decomposition. We simulated short- and long-term changed flooding regimes by transplanting turfs between low (frequently flooded) and high (in-frequently flooded) elevations on the river bank in 2000 (old turfs) and 2014 (young turfs). We tested how incubation elevation, turf origin and turf age affected decomposition of standard litter (tea) and four types of local litter. For tea, we found that the initial decomposition rate (k) and stabilization (S) of labile material during the second decomposition phase were highest at high incubation elevation. We found intermediate values for k and S in young transplanted turfs, but turf origin was not important in old turfs. Local litter mass loss was generally highest at high incubation elevations, and effects of turf origin and turf age were litter-specific. We conclude that incubation elevation, i.e., the current flooding regime, was the most important factor driving decomposition. Soil origin (flooding history) affected decomposition of tea only in young turfs. Therefore, we expect that changes in flooding regimes predominantly affect decomposition directly, while indirect legacy effects are weaker and litter- or site-specific.

  • 45.
    Schmidt, Julian
    Umeå universitet, Samhällsvetenskapliga fakulteten, Institutionen för geografi och ekonomisk historia. JLU Giessen.
    Does IKEA keep its promises?: Impact of large retail chains on medium-sized citiesusing the example of IKEA in Sweden2013Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Large investments in sparsely populated areas have the reputation to increase the attractiveness of these areas. This is said to lead to more investments, followed by growths in population, unemployment rates and tax revenues. Usually, city officials in Sweden trust in this formula and have the tendency to provide financial and other incentives for companies to start large investment projects in their towns (Hrelja, Isaksson, and Richardson, 2012). This thesis investigates the actual impact of such projects by the example of the large retail chain IKEA in Sweden. The development of three medium-sized cities in sparsely populated areas in Sweden which recently opened IKEA stores are compared to close-by cities and benchmark cities of a comparable size with respect to their unemployment rates, income, population, retail sales and trade indexes. The results will be used to predict the impact of the new IKEA store planned in Umeå.

  • 46.
    Schmidt, Julian
    Umeå universitet, Samhällsvetenskapliga fakulteten, Institutionen för geografi och ekonomisk historia, Kulturgeografi.
    Interaction Effects of Specialization and Relatedness on Regional Productivity: A Long-term Study on Swedish Labor Market Regions between 1975 and 20102015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The key factors that are driving the economic development of regions are a vital question in economic geography, urban planning, and regional policy. Both specialization and relatedness are assumed to boost regional productivity. Specialization means the focus on a limited range of employment sectors while relatedness describes the extent to which the expertise and skills that are necessary in one sector can be translated to other sectors in a region. This thesis studies the combined effects of specialization and relatedness on productivity of Swedish labor-market regions between 1975 and 2010. It is shown that an increase in absolute as well as in relative specialization is accompanied by an increase in regional productivity. However, the positive effect of relative specialization is not observed in unrelated sectors. My results suggest that regional policy should generally aim at specialization in related, rather than unrelated, industries to support sustainable economic growth.

  • 47. Sobek, Sebastian
    et al.
    Gudasz, Cristian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Arktiskt centrum vid Umeå universitet (Arcum). Department of Ecology and Genetics/Limnology, Uppsala University, Uppsala, Sweden.
    Koehler, Birgit
    Tranvik, Lars J.
    Bastviken, David
    Morales-Pineda, Maria
    Temperature dependence of apparent respiratory quotients and oxygen penetration depth in contrasting lake sediments2017Inngår i: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 122, nr 11, s. 3076-3087Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Lake sediments constitute an important compartment in the carbon cycle of lakes, by burying carbon over geological timescales and by production and emission of greenhouse gases. The degradation of organic carbon (OC) in lake sediments is linked to both temperature and oxygen (O-2), but the interactive nature of this regulation has not been studied in lake sediments in a quantitative way. We present the first systematic investigation of the effects of temperature on the apparent respiratory quotient (RQ, i.e., the molar ratio between carbon dioxide (CO2) production and O-2 consumption) in two contrasting lake sediments. Laboratory incubations of sediment cores of a humic lake and an eutrophic lake across a 1-21 degrees C temperature gradient over 157days revealed that both CO2 production and O-2 consumption were positively, exponentially, and similarly dependent on temperature. The apparent RQ differed significantly between the lake sediments (0.630.26 and 0.990.28 in the humic and the eutrophic lake, respectively; meanSD) and was significantly and positively related to temperature. The O-2 penetration depth into the sediment varied by a factor of 2 over the 1-21 degrees C temperature range and was significantly, negatively, and similarly related to temperature in both lake sediments. Accordingly, increasing temperature may influence the overall extent of OC degradation in lake sediments by limiting O-2 supply to aerobic microbial respiration to the topmost sediment layer, resulting in a concomitant shift to less effective anaerobic degradation pathways. This suggests that temperature may represent a key controlling factor of the OC burial efficiency in lake sediments.

  • 48.
    Song, Xiaowei
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Surface and Bulk Reactivity of Iron Oxyhydroxides: A Molecular Perspective2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Iron oxyhydroxide (FeOOH) mineral plays an important role in a variety of atmospheric, terrestrial and technological settings. Molecular resolution of reactions involving these minerals is thereby required to develop a fundamental understanding of their contributions in processes taking place in the atmosphere, Earth’s upper crust as well as the hydrosphere. This study resolves interactions involving four different types of synthetic FeOOH particles with distinct and well-defined surfaces, namely lath- and rod-shaped lepidocrocite (γ), goethite (α) and akaganéite (β). The surface and bulk reactivities of these particles are controlled by their distinct structures. When exposed to ambient atmospheric or aqueous conditions their surfaces are populated with different types of (hydr)oxo functional groups acting as reaction centers. These sites consist of hydroxyl groups that can be singly- (≡FeOH, -OH), doubly- (≡Fe2OH, μ-OH), or triply-coordinated (≡Fe3OH, μ3-OH) with underlying Fe atoms. Moreover, these sites exhibit different types, densities, distributions, as well as hydrogen bonding patterns on different crystal planes for each mineral. Knowledge of the types and distributions of hydroxyl groups on minerals with different surface structures is fundamental for building a molecular-scale understanding of processes taking place at FeOOH particle surfaces.

    In this thesis, Fourier transform infrared (FTIR) spectroscopy was used to resolve the interactions between (hydr)oxo groups of FeOOH particles with (in)organic acids, salts, water vapor as well as carbon dioxide. The focus on such compounds was justified by their importance in natural environments. This thesis is based on 9 articles and manuscripts that can be found in the appendices.

    FTIR spectroscopic signatures of hydroxyl groups in the bulk of well crystallized FeOOH minerals were characterized for structural differences and thermal stabilities. Those of akaganéite were particularly resolved for the variable bond strength of bulk hydroxyls induced by the incorporation of HCl through nanostructured channels at the terminations of the particles. FTIR bands of hydroxyl groups at all particle surfaces were monitored for responses to thermal gradients and proton loadings, providing experimental validation to previous theoretical accounts on surface site reactivity. This site reactivity was resolved further in the fluoride (F-) and phosphate (PO43-) ions adsorption study to follow the site selectivity for ligand-exchange reactions. These efforts showed that singly-coordinated groups are the primary adsorption centers for ligands, doubly-coordinated groups can only be exchanged at substantially higher ligand loadings, while triply coordinated groups are largely resilient to any ligand-exchange reaction.

    These findings helped consolidate fundamental knowledge that can be used in investigating sorption processes involving atmospherically and geochemically important gases. The latter parts of this thesis were therefore focused on water vapor and carbon dioxide interactions with these FeOOH particles. These efforts showed how surface structure and speciation affect sorption loadings and configurations, as well as how water diffused into and through the akaganéite bulk. Hydrogen bonding is one of the most important forms of interactions between gas phase and minerals. It plays a crucial role in the formation of thin water films and in stabilizing surface (bi)carbonate species. The affinity of surface hydroxyl groups for water and carbon dioxide is strongly dependent on their abilities to form hydrogen bonds. These are controlled by coordination number and site accessibility/steric constraints. In agreement with the aforementioned ligand-exchange studies, surfaces dominated by singly coordinated groups have stronger ability to accumulate water layers than the ones terminated by groups of larger coordination number. Collectively, these efforts consolidate further the concept for structure-controlled reactivities in iron oxyhydroxides, and pave the way for new studies along such lines.

  • 49.
    Strawhacker, Colleen
    et al.
    University of Colorado, Boulder, CO USA.
    Buckland, Philip I.
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet. Umeå universitet, Humanistiska fakulteten, Humlab.
    Palsson, Gisli
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet. Umeå universitet, Humanistiska fakulteten, Humlab.
    Fridrikkson, Adolf
    Institute of Archaeology, Reykjavik, Iceland.
    Lethbridge, Emily
    Centre for Medieval Studies, University of Iceland, Reykjavik, Iceland.
    Brin, Adam
    Arizona State University, Tempe, USA.
    Opitz, Rachel
    University of Arkansas, Fayetteville, USA.
    Dawson, Thomas
    School of History, St. Andrews University, Scotland.
    Building Cyberinfrastructure from the Ground Up for the North Atlantic Biocultural Organization: Introducing the cyberNABO Project2015Inngår i: 2015 Digital Heritage: Volume 2 / [ed] Gabriele Guidi, Roberto Scopigno, Juan Carlos Torres, Holger Graf et al., Institute of Electrical and Electronics Engineers (IEEE), 2015, Vol. 2, s. 457-460, artikkel-id 7419547Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The cyberNABO Project is designed to solidify a developing multidisciplinary community through the development of cyberinfrastructure (CI) to study the long-term human ecodynamics of North Atlantic, a region that is especially vulnerable to ongoing climate and environmental change. It builds build upon prior sustained field and laboratory research, rich and diverse datasets, and a strong involvement by local communities and institutions. cyberNABO is currently hosting a series of workshops aimed at taking these collaborators and stakeholder communities to a new level of integration and to develop capacity for building CI and visualizations in subsequent funding cycles. Research on the long-term sustainability in the Arctic requires compiling data from over thousands of square miles, hundreds of years, and multiple disciplines, from climatology to archaeology to folklore. The complexity of datasets of this scale presents a unique challenge to create a CI system that results in interoperability and accessibility of data – a task that needs an explicit plan and extensive expertise from a variety of fields. Investing in a comprehensive CI system provides the opportunity to integrate collaborators and data from the natural sciences, social sciences, and the humanities, thus providing the opportunity for a holistic approach to long-term human ecodynamics in the context of rapid social and environmental change and for the creation of digital tools for expanded northern community involvement in global change research. In order to address questions of this scale, however, this collaborative group needs to integrate multiple sources, types, and formats of data to address multidisciplinary questions and provide effective support for visualization and modeling efforts that can connect knowledge systems.

  • 50. Tang, Jing
    et al.
    Yurova, Alla Y.
    Schurgers, Guy
    Miller, Paul A.
    Olin, Stefan
    Smith, Benjamin
    Siewert, Matthias B.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Department of Physical Geography, Stockholm University, Sweden.
    Olefeldt, David
    Pilesjö, Petter
    Poska, Anneli
    Drivers of dissolved organic carbon export in a subarctic catchment: Importance of microbial decomposition, sorption-desorption, peatland and lateral flow2018Inngår i: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 622, s. 260-274Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Tundra soils account for 50% of global stocks of soil organic carbon (SOC), and it is expected that the amplified climate warming in high latitude could cause loss of this SOC through decomposition. Decomposed SOC could become hydrologically accessible, which increase downstream dissolved organic carbon (DOC) export and subsequent carbon release to the atmosphere, constituting a positive feedback to climate warming. However, DOC export is often neglected in ecosystem models. In this paper, we incorporate processes related to DOC production, mineralization, diffusion, sorption-desorption, and leaching into a customized arctic version of the dynamic ecosystem model LPJ-GUESS in order to mechanistically model catchment DOC export, and to link this flux to other ecosystem processes. The extended LPJ-GUESS is compared to observed DOC export at Stordalen catchment in northern Sweden. Vegetation communities include flood-tolerant graminoids (Eriophorum) and Sphagnum moss, birch forest and dwarf shrub communities. The processes, sorption-desorption and microbial decomposition (DOC production and mineralization) are found to contribute most to the variance in DOC export based on a detailed variance-based Sobol sensitivity analysis (SA) at grid cell-level. Catchment-level SA shows that the highest mean DOC exports come from the Eriophorum peatland (fen). A comparison with observations shows that the model captures the seasonality of DOC fluxes. Two catchment simulations, one without water lateral routing and one without peatland processes, were compared with the catchment simulations with all processes. The comparison showed that the current implementation of catchment lateral flow and peatland processes in LPJ-GUESS are essential to capture catchment-level DOC dynamics and indicate the model is at an appropriate level of complexity to represent the main mechanism of DOC dynamics in soils. The extended model provides a new tool to investigate potential interactions among climate change, vegetation dynamics, soil hydrology and DOC dynamics at both stand-alone to catchment scales. 

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