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  • 51.
    van Woerkom, Anne
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Cryptic refugia vs. Tabula Rasa: Boreal trees in glacial Fennoscandia: Plant growth during the Weichselian glaciation and the early Holocene in northern Europe2016Självständigt arbete på avancerad nivå (masterexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Recent studies applying innovative technologies, such as genetic analysis and carbon dating, contradict the palynological based assumption that Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) vanished from Fennoscandia during the Last Glacial Maximum (c. 20.000 yrs BP) and re-colonized after the cold Younger Dryas (c. 12.000 yrs BP). Instead, those studies indicate glacial survival of boreal trees in ‘cryptic’ refugia within Scandinavia, which is still heavily debated. In this report, I try to get a better grip on the discussion if Norway spruce and Scots pine survived Weichselian glacial periods in isolated ‘cryptic’ refugia within Scandinavia, or either re-colonized Fennoscandia by post-glacial migration from eastern areas such as Russia. To this aim, climatic settings are described and an overview is given on what is already known on the distribution of boreal trees during the Weichselian glaciations and the post-glacial landscape. Several records are important to detect ancient boreal trees: pollen, macrofossils and currently DNA. Macrofossils indicate early post-glacial tree growth in the central Scandes just after the Younger Dryas, aDNA indicates the existence of a ‘cryptic’ refugium on Andøya during the Last Glacial Maximum and modern DNA analysis possibly indicates isolation of spruce in western Norway, which are all contradicted by the current interpretation of low pollen percentages. Altogether, alternative hypotheses supporting glacial survival of plants might have been overlooked and pollen interpretations need revision, which could turn the exclusion from the past into supporting evidence for the glacial survival of P. abies and P. sylvestris in Scandinavia.

  • 52.
    Vedin, Jörgen
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rönnmark, Kjell
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Bunescu, Costel
    Marghitu, Octav
    Estimating properties of concentrated parallel electric fields from electron velocity distributions2007Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 34, nr 16, artikel-id L16107Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Information about the magnitude of the field-aligned potential drop along auroral field lines is usually derived from the velocity distribution of the particles. When the electrons are accelerated by a strong double layer their velocity distribution will have features different from those produced by a weak, spread-out, electric field. Quantifying these features, we obtain information about the strength and thickness of the double layer.

  • 53.
    Vestergren, Johan
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Ouattara, Korodjouma
    Burkina Faso.
    Schleucher, Jurgen
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Gröbner, Gerhard
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Ilstedt, Ulrik
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Effect of Trees on Forms of Soil Phosphorus in an Agroforestry Parkland in Burkina Faso2014Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Phosphorus is commonly a limiting nutrient for crop production, especially in highly weathered tropical soils. In two semi-arid areas in Burkina Faso with high and low aluminum and iron content respectively, we studied the effect of scattered trees within cropping fields (an agroforestry system called “parklands”) on soils from two areas with high and low aluminum and iron content, respectively. The study focused on different P forms using liquid-state 31P NMR, and their relation to soil chemical properties, determined by XRF. We hypothesized that i) There is generally a difference in P forms between under canopies and in openings outside canopies due to higher input and turnover of organic material close to trees; ii) Close to trees there are more P forms of microbial origin due to the increased activity of the microbial community; iii) This difference is more pronounced in the area with higher content of aluminum and iron. We took topsoil samples under tree canopies as well as outside tree canopies. Our results showed that there were generally low levels of organic carbon and P, but under the canopies of the scattered trees the levels were higher. 31P-NMR showed that soil P was composed of similar ratios of inorganic and organic P as has been observed in other ecosystems, and that the organic P pool was composed of P species commonly observed in soils. NMR also revealed that areas outside the canopies had a less diverse P composition. In the area with high Al/Fe content, microbial activity under trees had a more pronounced effect on the soil P composition, by significantly increasing the amounts of P species of biological origin. In conclusion, the study confirmed the importance of soil organic matter and trees for P availability in semi-arid tropical ecosystems.

  • 54.
    Vickers, Kim
    et al.
    Department of Archaeology, University of Sheffield, UK.
    Buckland, Philip I
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet.
    Predicting island beetle faunas by their climate ranges: the tabula rasa/refugia theory in the North Atlantic2015Ingår i: Journal of Biogeography, ISSN 0305-0270, E-ISSN 1365-2699, Vol. 42, nr 11, s. 2031-2048Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Aim: This paper addresses two opposing theories put forward for the origins of the beetle fauna of the North Atlantic islands. The first is that the biota of the isolated oceanic islands of the Faroes, Iceland and Greenland immigrated across a Palaeogene–Neogene land bridge from Europe, and survived Pleistocene glaciations in ameliorated refugia. The second argues for a tabula rasa in which the biota of the islands was exterminated during glaciations and is Holocene in origin. The crux of these theories lies in the ability of the flora and fauna to survive in a range of environmental extremes. This paper sets out to assess the viability of the refugia hypothesis using the climatic tolerances of one aspect of the biota: the beetle fauna. Location: The paper focuses on Iceland, the Faroe Islands and Greenland. Methods: The known temperature requirements of the recorded beetle faunas of the North Atlantic islands were compared with published proxy climate reconstructions for successive climate periods since the severing of a North Atlantic land bridge. We used the MCR (mutual climatic range) method available in the open access BugsCEP database software. Results: We show that most of the MCR faunas of the North Atlantic islands could not have survived in situ since the Palaeogene–Neogene, and are likely to have been exterminated by the Pleistocene glaciations. Main conclusions: The discrepancy between the climatic tolerances of the North Atlantic beetle fauna and the estimated climatic regimes since the severing of a land bridge strongly support the tabula rasa theory and suggests that the North Atlantic coleopteran fauna is Holocene in origin.

  • 55. Wassenaar, Leonard I.
    et al.
    Van Wilgenburg, Steve L.
    Larson, Keith W.
    Klamath Bird Observatory, PO Box 758, Ashland, OR, 97520, USA; Department of Animal Ecology, University of Lund, Lund, Sweden.
    Hobson, Keith A.
    A groundwater isoscape (δD, δ18O) for Mexico2009Ingår i: Journal of Geochemical Exploration, ISSN 0375-6742, E-ISSN 1879-1689, Vol. 102, nr 3, s. 123-136Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Numerous studies have shown that precipitation isocapes drive δD and δ18O patterns in surficial waters and in terrestrial food webs. While the GNIP (Global Network for Isotopes in Precipitation) dataset provided a key foundation for linking precipitation-terrestrial isoscapes globally, it has insufficient spatial coverage in many countries like Mexico. To overcome this limitation, we hypothesized that shallow phreatic groundwaters in Mexico could be used as an isotopic integrator of long-term seasonally weighted precipitation inputs to the landscape to aid in calibrating spatial H and O isotope datasets for terrestrial, biological and hydrological research. Groundwater was sampled from 234 sites in Mexico at ~ 50 km latitudinal spacing to obtain high spatial resolution and country-wide coverage for the construction of a groundwater isoscape. Our data revealed that shallow groundwater infiltration in Mexico appears largely unaffected by evaporation and reflects seasonally weighted precipitation inputs. These precipitation inputs are primarily biased to summertime when highest rainfall occurs, but a small degree of post-precipitation evaporation revealed a lower d-excess zone that corresponded to the interior semi-arid ecozone. We developed a predictive general linear model (GLM) for hydrogen and oxygen isotopic spatial patterns in Mexican groundwater and then compared the results to a validation subset of our field data, as well external data reported in the literature. The GLM used elevation, latitude, drainage basin (Atlantic vs. Pacific), and rainfall as the most relevant predictive variables. The GLM explained 81% of the overall isotopic variance observed in groundwater, 68% of the variance within our validation subset, and 77% of the variance in the external data set. Our predictive GLM is sufficiently accurate to allow for future ecological, hydrological and forensic isoscape applications in Mexico, and may be an approach that is applicable to other countries and regions where GNIP stations are lacking.

  • 56.
    Wieloch, Thomas
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Intramolecular isotope analysis reveals plant ecophysiological signals covering multiple timescales2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Our societies' wellbeing relies on stable and healthy environments. However, our current lifestyles, growth-oriented economic policies and the population explosion are leading to potentially catastrophic degradation of ecosystems and progressive disruption of food chains. Hopefully, more clarity about what the future holds in store will trigger stronger efforts to find, and adopt, problem-focused coping strategies and encourage environmentally friendly lifestyles.

    Forecasting environmental change/destruction is complicated (inter alia) by lack of complete understanding of plant-environment interactions, particularly those involved in slow processes such as plant acclimatisation and adaptation. This stems from deficiencies in tools to analyse such slow processes. The present work aims at developing tools that can provide retrospective ecophysiological information covering timescales from days to millennia.

    Natural archives, such as tree-rings, preserve plant metabolites over long timescales. Analyses of intramolecular isotope abundances in plant metabolites have the potential to provide retrospective information about metabolic processes and underlying environmental controls. Thus, my colleagues and I (hereafter we) analysed intramolecular isotope patterns in tree rings to develop analytical tools that can convey information about clearly-defined plant metabolic processes over multiple timescales. Such tools might help (inter alia) to constrain plants' capacities to sequester excess amounts of anthropogenic CO2; the so-called CO2 fertilisation effect. This, in turn, might shed light on plants' sink strength for the greenhouse gas CO2, and future plant performance and growth under climate change.

    In the first of three studies, reported in appended papers, we analysed intramolecular 13C/12C ratios in tree-ring glucose. In six angiosperm and six gymnosperm species we found pronounced intramolecular 13C/12C differences, exceeding 10‰. These differences are transmitted into major global C pools, such as soil organic matter. Taking intramolecular 13C/12C differences into account might improve isotopic characterisation of soil metabolic processes and soil CO2 effluxes. In addition, we analysed intramolecular 13C/12C ratios in a Pinus nigra tree-ring archive spanning the period 1961 to 1995. These data revealed new ecophysiological 13C/12C signals, which can facilitate climate reconstructions and assessments of plant-environment interactions at higher resolution; thus providing higher quality information. We proposed that 13C/12C signals at glucose C-1 to C-2 derive from carbon injection into the Calvin-Benson cycle via the oxidative pentose phosphate pathway. We concluded that intramolecular 13C/12C measurements provide valuable new information about long-term metabolic dynamics for application in biogeochemistry, plant physiology, plant breeding, and paleoclimatology.

    In the second study, we developed a comprehensive theory on the metabolic and ecophysiological origins of 13C/12C signals at tree-ring glucose C-5 and C-6. According to this theory and theoretical implications of the first study on signals at C-1 to C-3, analysis of such intramolecular signals can provide information about several metabolic processes. At C-3, a well-known signal reflecting CO2 uptake is preserved. The glucose-6-phosphate shunt around the Calvin-Benson cycle affects 13C/12C compositions at C-1 and C-2, while the 13C/12C signals at C-5 and C-6 reflect carbon fluxes into downstream metabolism. This theoretical framework enables further experimental studies to be conducted in a hypothesis-driven manner. In conclusion, the intramolecular approach provides information about carbon allocation in plant leaves. Thus, it gives access to long-term information on key ecophysiological processes, which could not be acquired by previous approaches.

    The abundance of the hydrogen isotope deuterium, δD, is important for linking the water cycle with plant ecophysiology. The main factors affecting δD in plant organic matter are commonly assumed to be the δD in source water and leaf-level evaporative enrichment. Current δD models incorporate biochemical D fractionations as constants. In the third study we showed that biochemical D fractionations respond strongly to low ambient CO2 levels and low light intensity. Thus, models of δD values in plant organic matter should incorporate biochemical fractionations as variables. In addition, we found pronounced leaf-level δD differences between α-cellulose and wax n-alkanes. We explained this by metabolite-specific contributions of distinct hydrogen sources during biosynthesis.

    Overall, this work advances our understanding of isotope distributions and isotope fractionations in plants. It reveals the immense potential of intramolecular isotope analyses for retrospective assessment of plant metabolism and associated environmental controls.

  • 57.
    Wieloch, Thomas
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Sharkey, Thomas David
    Werner, Roland Anton
    Schleucher, Jürgen
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Intramolecular 13C/12C signals reflect carbon allocation in plant leavesManuskript (preprint) (Övrigt vetenskapligt)
  • 58.
    Yeşilbaş, Merve
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Thin water and ice films on minerals: a molecular level study2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Minerals in Earth’s crust and suspended in the atmosphere form water or ice films as thin as a few nanometers to as thick as a few micrometers, and beyond. Mineral-bound water and ice films in terrestrial systems (e.g. vadose zones, permafrosts) can impact the bio(geo)chemistry of nutrients and contaminants, water cycling, as well as possible land-air exchanges in terrestrial environments. In the atmosphere, films are tied to clouds and rain formation, and can influence the absorption and scattering of solar radiation of dust mineral aerosols. Water films are, at the same time, of interest to technology. They are even of interest in the study of asteroids, comets, and planet Mars. Still, their formation on the various types of minerals common to the environment is misunderstood.

    The aim of this thesis is to gain fundamental insight on the roles that minerals play on forming and stabilising thin water and ice films. This work is separated in two parts, with Part A associated with Papers I-II, and Part B with Papers III-V of the appendix of this thesis.

    In Part A of this work (Papers I-II), water loadings and vibrational signatures of thin water films were collected on 21 different minerals (metal oxides, silicates, carbonates) relevant to terrestrial environments, atmosphere and perhaps outer-space. Measurements were made on minerals of varied (i) composition, (ii) structure, (iii) morphology, (iv) particle size and (v) surface roughness. Loadings, measured by a microgravimetric Dynamic Vapour Sorption technique, were of a few monolayers in sub-micrometer-sized particles but of several hundreds to thousands of water layers in micrometer-sized particles (Paper I). This was seen in the Fourier Transform Infrared (FTIR) spectra of sub-micrometer-sized particles with different hydrogen bonding environments than liquid water. Micrometer-sized particles formed liquid-like films regardless of the mineral. Similar observations were made in the spectra of the thinnest water films remaining on these minerals after long periods of sublimation of ice overcoatings at sub-freezing temperatures (Paper II).

    In Part B of this work (Papers III-V), focus on the expandable clay mineral montmorillonite was made to study (i) intercalated water, (ii) ice and cryosalt formation inside microporous gels, and (iii) its interactions with intercalated CO2.  FTIR extracted spectral components reflecting interlayer hydration states of ~0W, 1W and 2W monolayers of water (Paper III). Thermal dehydration/dehydroxylation experiments showed that the driest forms of montmorillonite strongly retained low levels of crystalline water in its structure.  FTIR also showed that frozen wet gels of montmorillonite form ice and the cryosalt mineral hydrohalite. Ice was seen in rigid gels and aggregated compact particles, as well as low particle density with low salt content. In contrast, concentrated (>> 10 g/L) saline gels host hydrohalite, probably between and/or near aggregated clay particle walls. Field-Emission Cryogenic Scanning Electron Microscopy showed that ice microcrystals form in micropores of the gels (Paper IV). Finally, release rates of CO2 trapped in interlayers of montmorillonite, monitored by FTIR spectroscopy, were larger in the presence of 1-2W. The activation energy of CO2 release from~0W montmorillonite (34 kJ/mol) is comparable to other mineral surfaces. This study highlights that the most stabilised CO2 occur in of dry and cold conditions.

    This thesis will hopefully serve as a springboard for further work exploring the chemistry and physics of water and ice films at minerals surfaces. It should contribute to improve our understanding of the geochemistry of Earth’s soils, processes in the atmosphere, and even of space chemistry.

  • 59.
    Yeşilbaş, Merve
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Lee, Cheng Choo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Boily, Jean-François
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Ice and cryosalt formation in saline microporous clay gels2018Ingår i: ACS Earth and Space Chemistry, ISSN 2472-3452, Vol. 2, nr 4, s. 314-319Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hydrated clay minerals that are common to Earth’s atmosphere and terrestrial and aquatic environments can form gels that host saline solutions. Using cryogenic electron microscopy and vibration spectroscopy, we show that saline gels of montmorillonite frozen at < −90 °C host elongated hexagonal ice (Ih) microcrystals embedded in a network of honeycomb micropores. Freezing segregates salts into walls of aggregated clay nanoparticles sharing face-to-face contacts. Above ∼ −50 °C, clay gels that are sufficiently dense (≫10 g/L) and flexible (Na-exchanged montmorillonite) also host the cryosalt mineral hydrohalite (NaCl·2H2O), either co-existing or entirely replacing Ih in the gels. Hydrohalite does not form in gels of low-density (<10 g/L) or rigid (Ca-exchange montmorillonite) clay particles. These results suggest that hydrohalite forms in expandable clay gels that are sufficiently dense and flexible to retain saline solutions within their walls, possibly through interparticle capillary and hydration forces. These forces effectively oppose water diffusion to growing ice microcrystals within micropores, thus prolonging the lifetime of hydrohalite within these hydrated clay gels. Our findings tie the fate of ice and cryosalt nucleation and growth to the water-retention capability of expandable clay gels.

  • 60.
    Östman, Sofi
    et al.
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet.
    Samuel, Eriksson
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet.
    Buckland, Philip I.
    Umeå universitet, Humanistiska fakulteten, Institutionen för idé- och samhällsstudier, Miljöarkeologiska laboratoriet.
    Preliminär rapport om miljöarkeologisk analys av prover från RAÄ 113:1 och Obj.nr 10. Själevad socken, Örnsköldsvik kommun, Västernorrlands län, Ångermanland2017Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Analysen omfattar makrofossilanalys, markkemisk-fysikalisk (geoarkeologisk) analys, samt vedartsanalys för utplock av daterbart material för 14C. Proverna är tagna från ett område med "koncentrationer av skärvsten med fynd av brända ben samt kvartsavslag" (RAÄ 113:1; Smeds 2016) samt en boplats utan RAÄ-nr vid rapportskrivning (Obj.nr 10; RAÄ Dnr 3.4.2-2662-2015). Syftet med analysen är dels att få fram daterbart material, dels att studera om anläggningarna har varit utsatt för direkt eldpåverkan eller andra aktiviteter.

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