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  • 1.
    Becher, Marina
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Cryogenic soil processes in a changing climate2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    A considerable part of the global pool of terrestrial carbon is stored in high latitude soils. In these soils, repeated cycles of freezing and thawing creates soil motion (cryoturbation) that in combination with other cryogenic disturbance processes may play a profound role in controlling the carbon balance of the arctic soil. Conditions for cryogenic soil processes are predicted to dramatically change in response to the ongoing climate warming, but little is known how these changes may affect the ability of arctic soils to accumulate carbon. In this thesis, I utilize a patterned ground system, referred to as non-sorted circles, as experimental units and quantify how cryogenic soil processes affect plant communities and carbon fluxes in arctic soils. I show that the cryoturbation has been an important mechanism for transporting carbon downwards in the studied soil over the last millennia. Interestingly, burial of organic material by cryoturbation appears to have mainly occurred during bioclimatic events occurring around A.D. 900-1250 and A.D. 1650-1950 as indicated by inferred 14C ages. Using a novel photogrammetric approach, I estimate that about 0.2-0.8 % of the carbon pool is annually subjected to a net downward transport induced by the physical motion of soil. Even though this flux seems small, it suggests that cryoturbation is an important transporter of carbon over centennial and millennial timescales and contributes to translocate organic matter to deeper soil layers where respiration proceeds at slow rates. Cryogenic processes not only affect the trajectories of the soil carbon, but also generate plant community changes in both species composition and abundance, as indicated by a conducted plant survey on non-sorted circles subjected to variable differential frost heave during the winter. Here, disturbance-tolerant plant species, such as Carex capillaris and Tofieldia pusilla, seem to be favoured by disturbance generated by the differential heave. Comparison with findings from a previous plant survey on the site conducted in the 1980s suggest that the warmer temperatures during the last decades have resulted in decreased differential heave in the studied non-sorted circles. I argue that this change in cryogenic activity has increased abundance of plants present in the 1980s. The fact that the activity and function of the non-sorted circles in Abisko are undergoing changes is further supported by their contemporary carbon dioxide (CO2) fluxes. Here, my measurements of CO2 fluxes suggest that all studied non-sorted circles act as net CO2 sources and thus that the carbon balance of the soils are in a transition state. My results highlight the complex but important relationship between cryogenic soil processes and the carbon balance of arctic soils.

  • 2.
    Campeau, Audrey
    Uppsala universitet, Luft-, vatten och landskapslära.
    Carbon in Boreal Streams: Isotopic Tracing of Terrestrial Sources2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The boreal biome comprises vast areas of coniferous forests, dotted with millions of peatlands. Plants harbouring these ecosystems fix CO2 from the atmosphere, which is later incorporated into the vegetation biomass and subsequently buried in soils. Over the course of millennia, this process has led to the formation of a large repository of organic C, currently stored in boreal soils. Streams draining this landscape are typically enriched with carbon dioxide (CO2), methane (CH4) and dissolved organic carbon (DOC). As a consequence, streams tend to emit CO2 and CH4 to the atmosphere, two potent greenhouse gases, and thus contribute positively to radiative climate forcing. The sources fuelling C to boreal streams are not well understood. This thesis aims to unravel these sources, and promote a better consolidation of terrestrial and aquatic C biogeochemical processes. The work is largely based on stable and radiogenic C isotope characterization of various dissolved C forms in stream and groundwater, within contrasting ecosystem types across Sweden.

    This thesis identifies boreal soils as the main source of CO2 in streams. Soil respiration (i.e. biogenic sources) overwhelmingly supply CO2 to streams, leaving only a few exceptions where geogenic CO2 sources were present. An array of biological processes also transform CO2 during its transport from soils to streams. These include; methanogenesis, aquatic DOC mineralization and primary production. The majority of C in boreal streams is sustained by the decomposition of recent photosynthates, with ancient C substrates holding a negligible share of the total C export. While these results suggest that the repository of ancient soil organic C is currently stable, within boreal forests and peatlands, the close connection with recently occurring photosynthesis suggest that forecasted alterations in plant C allocation patterns, driven by climate and land-use changes, will produce a rapid response in stream CO2 emissions. Isotopic characterization of C in stream and groundwater can help reveal these sources and transformation processes, but its interpretation must be made with care.

    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 3.
    Jantunen, Liisa
    et al.
    Environment Canada, Canada.
    Wong, Fiona
    Stockholm University.
    Gawor, Anya
    Environment Canada.
    Kylin, Henrik
    Linköpings universitet, Tema Miljöförändring.
    Helm, Paul
    Ontario Ministry of the Environment, Canada.
    Stern, Gary
    University of Manitoba, Canada.
    Strachan, William
    Environment Canada, Canada.
    Burniston, Deborah
    Environment Canada, Canada.
    Bidleman, Terry
    Umeå University.
    20 Years of Air-Water Gas Exchange Observations for Pesticides in the Western Arctic Ocean2015Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 49, nr 23, s. 13844-13852Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Arctic has been contaminated by legacy organochlorine pesticides (OCPs) and currently used pesticides (CUPs) through atmospheric transport and oceanic currents. Here we report the time trends and air−water exchange of OCPs and CUPs from research expeditions conducted between 1993 and 2013. Compounds determined in both air and water were trans- and cis-chlordanes (TC, CC), trans- and cis-nonachlors (TN, CN), heptachlor exo-epoxide (HEPX), dieldrin (DIEL), chlorobornanes (ΣCHBs and toxaphene), dacthal (DAC), endosulfans and metabolite endosulfan sulfate (ENDO-I, ENDO-II, and ENDO SUL), chlorothalonil (CHT), chlorpyrifos (CPF), and trifluralin (TFN). Pentachloronitrobenzene (PCNB and quintozene) and its soil metabolite pentachlorothianisole (PCTA) were also found in air. Concentrations of most OCPs declined in surface water, whereas some CUPs increased (ENDO-I, CHT, and TFN) or showed no significant change (CPF and DAC), and most compounds declined in air. Chlordane compound fractions TC/(TC + CC) and TC/(TC + CC + TN) decreased in water and air, while CC/(TC + CC + TN) increased. TN/(TC + CC + TN) also increased in air and slightly, but not significantly, in water. These changes suggest selective removal of more labile TC and/or a shift in chlordane sources. Water−air fugacity ratios indicated net volatilization (FR > 1.0) or near equilibrium (FR not significantly different from 1.0) for most OCPs but net deposition (FR < 1.0) for ΣCHBs. Net deposition was shown for ENDO-I on all expeditions, while the net exchange direction of other CUPs varied. Understanding the processes and current state of air−surface exchange helps to interpret environmental exposure and evaluate the effectiveness of international protocols and provides insights for the environmental fate of new and emerging chemicals.

  • 4.
    Lundkvist, Markus
    Uppsala universitet, Institutionen för geovetenskaper.
    Accident Risk and Environmental Assessment: Development of an Assessment Guideline with Examination in Northern Scandinavia2005Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    In environmental impact assessment (EIA), accident risk should be considered as one impact. However, few studies have compared assessed risk levels with documented accidents. There is thus a need for assessing accuracy of risk assessment methodologies. The aim of this study was to develop and examine a risk assessment guideline based on environmental assessment. The guideline examination was carried out along the railway and the road between Kiruna and Narvik, Northern Scandinavia. The examined hazards were avalanches, debris flows, rock falls, slush flows, torrents, moose and reindeer. Documented accidents were quantified into an accident level. For each hazard type, six sections/sites were assessed. The propensities of these hazards were analysed through environmental assessments, especially by utilising geomorphology. Then, the accident densities along the sections/sites were compared with assessed accident phase indices describing risk and hazard in both spatial and temporal dimensions. The average uncertainty factors for both the risk and the hazard indices were about 5. This implies a fairly good precision. Risk and hazard indices were also rated and compared to the accident density rates. Thereafter, railway and road information was split up as different proposal alternatives in an EIA context. The total risk for each proposal was compared with the total accident density. The risk assessment guideline proved to be cost-efficient, rapid and relatively reliable in comparing accident risk.

  • 5.
    McLoughlin, Stephen
    et al.
    Naturhistoriska riksmuseet, Enheten för paleobiologi.
    Bomfleur, Benjamin
    Naturhistoriska riksmuseet, Enheten för paleobiologi.
    Thomas, Mörs
    Naturhistoriska riksmuseet, Enheten för paleobiologi.
    The wierd world of fossil worm cocoons2016Ingår i: Deposits Magazine, ISSN 1744-9588, Vol. 46, s. 399-406Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    Curious fossils in continental sedimentary strata that range from about a millimetre in diameter up to the size of a fingernail and appear to have a net-like coating on the surface have reported for over 150 years and have been variously interpreted as the eggs of insects, parts of lichens, the food-catching devices of ancient invertebrates, the membranous coatings of seeds, or the linings of clubmoss sporangia. Many early palaeobiologists simply labelled them as ‘red eggs’ and avoided assigning them to any particular biological group. However, these fossils match the characteristics of the egg-bearing cocoons of modern leeches and their relatives. During cocoon secretion, micro-organisms from the surrounding environment can become entrapped and entombed in the sticky threads of the cocoon wall, thus escaping decay, and ultimately becoming part of the fossil record.

  • 6.
    McLoughlin, Stephen
    et al.
    Naturhistoriska riksmuseet, Enheten för paleobiologi.
    Vajda, Vivi
    Naturhistoriska riksmuseet, Enheten för paleobiologi.
    Topper, Timothy
    Naturhistoriska riksmuseet, Enheten för paleobiologi.
    Crowley, James L.
    Isotope Geology Laboratory, Boise State University, Boise, ID, USA.
    Liu, Fan
    Naturhistoriska riksmuseet, Enheten för paleobiologi.
    Johansson, Ove
    Naturhistoriska riksmuseet, Enheten för paleobiologi.
    Skovsted, Christian
    Naturhistoriska riksmuseet, Enheten för paleobiologi.
    Trace fossils, algae, invertebrate remains and new U-Pb detrital zircon geochronology from the lower Cambrian Torneträsk Formation, northern Sweden2021Ingår i: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 143, nr 2-3, s. 103-133Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nineteen ichnotaxa, together with algal and invertebrate remains, and various pseudo-traces and sedimentary structures are described from the Torneträsk Formation exposed near Lake Torneträsk, Lapland, Sweden, representing a marked increase in the diversity of biotic traces recorded from this unit. The “lower siltstone” interval of the Torneträsk Formation contains mostly simple pascichnia, fodinichnia and domichnia burrows and trails of low-energy shoreface to intertidal settings. The assemblage has very few forms characteristic of high-energy, soft-sediment, foreshore or upper shoreface environments (representative of the Skolithos ichnofacies).

    Uranium-lead (U-Pb) LA-ICPMS analysis of zircon from a thin claystone layer within the “lower siltstone” interval yielded a maximum depositional age of 584 ± 13 Ma, mid-Ediacaran. Most of the zircon is represented by rounded detrital grains that yield dates between 3.3 and 1.0 Ga. Although the age of the basal sandstone-dominated interval of the Torneträsk Formation remains elusive owing to the absence of fossils, the ichnofossil suite from the overlying “lower siltstone” interval lacks deep arthropod trackways, such as Rusophycus and Cruziana, and is suggestive of a very early (Terreneuvian, possibly Fortunian) Cambrian age. The ichnofauna is otherwise similar to early Cambrian trace fossil assemblages from other parts of Baltica, regions further south in modern Europe, and from Greenland.

  • 7.
    Skovsted, Christian
    et al.
    Naturhistoriska riksmuseet, Enheten för paleobiologi.
    Topper, Timothy, P.
    Naturhistoriska riksmuseet, Enheten för paleobiologi.
    McLoughlin, Stephen
    Naturhistoriska riksmuseet, Enheten för paleobiologi.
    Johansson, Ove
    Naturhistoriska riksmuseet, Enheten för paleobiologi.
    Liu, Fan
    Naturhistoriska riksmuseet, Enheten för paleobiologi.
    Vajda, Vivi
    Naturhistoriska riksmuseet, Enheten för paleobiologi.
    First discovery of Small Shelly Fossils and new occurrences of brachiopods and trilobites from the early Cambrian (Stage 4) of the Swedish Caledonides, Lapland2021Ingår i: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 143, nr 2-3, s. 134-150Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    New fossil discoveries are reported from the Grammajukku Formation at Luobákte south of Lake Torneträsk in northern Swedish Lapland, including a fauna of Small Shelly Fossils (SSF) from a limestone bed in the uppermost part of the formation and new occurrences of brachiopods and trilobites in siltstones of the lower part of the formation. The moderately diverse SSF fauna is the first of its kind reported from the Swedish Caledonides and includes the first record of the tommotiid Lapworthella schodackensis and the bradoriid spine Mongolitubulus spinosus from Baltica, together with fragmentary specimens of Bradoria sp. and remains of one additional bradoriid arthropod, a protoconodont and a helcionelloid mollusc. In addition, the limestone bed yields abundant specimens of the brachiopods Botsfordia cf. caelata and Eoobolus cf. priscus and an unidentified ellipsocephalid trilobite. Lower down in the Grammajukku Formation, specimens of both brachiopod taxa, orthothecid hyoliths, the trilobite Ellipsocephalus cf. gripi and an unidentified holmiid trilobite were found at several levels in a siltstone, previously regarded as unfossiliferous. These discoveries markedly increase the known diversity of the palaeobiota from the Grammajukku Formation in northern Lapland and provide new insights into the biostratigraphy and palaeoenvironment of the lower Cambrian in Scandinavia and the palaeobiogeography of Cambrian faunas in general.

  • 8.
    Sulej, Tomasz
    et al.
    Polish Acad Sci, Inst Paleobiol, PL-00818 Warsaw, Poland.
    Krzesinski, Grzegorz
    Warsaw Univ Technol, Inst Aeronaut & Appl Mech, Fac Power & Aeronaut Engn, PL-00665 Warsaw, Poland.
    Talanda, Mateusz
    Univ Warsaw, Biol & Chem Res Ctr, Fac Biol, Dept Paleobiol & Evolut, PL-02089 Warsaw, Poland.
    Wolniewicz, Andrzej S.
    Polish Acad Sci, Inst Paleobiol, PL-00818 Warsaw, Poland; Univ Oxford, Dept Earth Sci, Oxford OX1 3AN, England.
    Blazejowski, Blazej
    Polish Acad Sci, Inst Paleobiol, PL-00818 Warsaw, Poland.
    Bonde, Niels
    Univ Copenhagen, Nat Hist Museum Denmark, Geol Sect, DK-2100 Copenhagen, Denmark; Fur Museum, DK-7884 Fur, Denmark.
    Gutowski, Piotr
    Med Univ Warsaw, Dept Craniomaxillofacial Surg Oral Surg & Implant, PL-02091 Warsaw, Poland.
    Sienkiewicz, Maksymilian
    Warsaw Univ Technol, Inst Aeronaut & Appl Mech, Fac Power & Aeronaut Engn, PL-00665 Warsaw, Poland.
    Niedzwiedzki, Grzegorz
    Uppsala universitet, Evolution och utvecklingsbiologi.
    The earliest-known mammaliaform fossil from Greenland sheds light on origin of mammals2020Ingår i: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 117, nr 43, s. 26861-26867Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Synapsids are unique in having developed multirooted teeth and complex occlusions. These innovations evolved in at least two lineages of mammaliamorphs (Tritylodontidae and Mammaliaformes). Triassic fossils demonstrate that close to the origins of mammals, mammaliaform precursors were "experimenting" with tooth structure and function, resulting in novel patterns of occlusion. One of the most surprising examples of such adaptations is present in the haramiyidan Glade, which differed from contemporary mammaliaforms in having two rows of cusps on molariform crowns adapted to omnivorous/herbivorous feeding. However, the origin of the multicusped tooth pattern present in haramiyidans has remained enigmatic. Here we describe the earliest-known mandibular fossil of a mammaliaform with double molariform roots and a crown with two rows of cusps from the Late Triassic of Greenland. The crown morphology is intermediate between that of morganucodontans and haramiyidans and suggests the derivation of the multicusped molariforms of haramiyidans from the triconodont molar pattern seen in morganucodontids. Although it is remarkably well documented in the fossil record, the significance of tooth root division in mammaliaforms remains enigmatic. The results of our biomechanical analyses (finite element analysis [FEA]) indicate that teeth with two roots can better withstand stronger mechanical stresses like those resulting from tooth occlusion, than teeth with a single root.

  • 9.
    Zaton, Michal
    et al.
    Univ Silesia, Fac Earth Sci, Bedzinska 60, PL-41200 Sosnowiec, Poland.;KNOW Leading Natl Res Ctr, Ctr Polar Studies, Sosnowiec, Poland..
    Niedzwiedzki, Grzegorz
    Uppsala universitet, Evolution och utvecklingsbiologi.
    Blom, Henning
    Uppsala universitet, Evolution och utvecklingsbiologi.
    Kear, Benjamin P.
    Uppsala universitet, Evolutionsmuseet.
    Boreal earliest Triassic biotas elucidate globally depauperate hard substrate communities after the end-Permian mass extinction2016Ingår i: Scientific Reports, E-ISSN 2045-2322, Vol. 6, artikel-id 36345Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The end-Permian mass extinction constituted the most devastating biotic crisis of the Phanerozoic. Its aftermath was characterized by harsh marine conditions incorporating volcanically induced oceanic warming, widespread anoxia and acidification. Bio-productivity accordingly experienced marked fluctuations. In particular, low palaeolatitude hard substrate communities from shallow seas fringing Western Pangaea and the Tethyan Realm were extremely impoverished, being dominated by monogeneric colonies of filter-feeding microconchid tubeworms. Here we present the first equivalent field data for Boreal hard substrate assemblages from the earliest Triassic (Induan) of East Greenland. This region bordered a discrete bio-realm situated at mid-high palaeolatitude (> 30 degrees N). Nevertheless, hard substrate biotas were compositionally identical to those from elsewhere, with microconchids encrusting Claraia bivalves and algal buildups on the sea floor. Biostratigraphical correlation further shows that Boreal microconchids underwent progressive tube modification and unique taxic diversification concordant with changing habitats over time. We interpret this as a post-extinction recovery and adaptive radiation sequence that mirrored coeval subequatorial faunas, and thus confirms hard substrate ecosystem depletion as a hallmark of the earliest Triassic interval globally.

    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 10.
    Zaton, Michal
    et al.
    Univ Silesia Katowice, Fac Earth Sci, Bedzinska 60, PL-41200 Sosnowiec, Poland.
    Niedzwiedzki, Grzegorz
    Uppsala universitet, Institutionen för organismbiologi.
    Rakocinski, Michal
    Univ Silesia Katowice, Fac Earth Sci, Bedzinska 60, PL-41200 Sosnowiec, Poland.
    Blom, Henning
    Uppsala universitet, Institutionen för organismbiologi.
    Kear, Benjamin P.
    Uppsala universitet, Evolutionsmuseet.
    Earliest Triassic metazoan bioconstructions from East Greenland reveal a pioneering benthic community in the immediate aftermath of the end-Permian mass extinction2018Ingår i: Global and Planetary Change, ISSN 0921-8181, E-ISSN 1872-6364, Vol. 167, s. 87-98Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Marine benthic ecosystems collapsed during the catastrophic end-Permian mass extinction, and subsequently endured a protracted phase of biotic recovery under harsh environmental conditions. In particular, metazoan reef communities almost totally disappeared and were replaced by microbe-dominated mounds during the latest Permian-earliest Triassic. Here we report the stratigraphically oldest exclusively metazoan bioconstructions from earliest Triassic (mid-Induan) strata in East Greenland - these formed within the first ca 300 ka after the Permian-Triassic boundary. Unlike the multitaxic sponge-microbe and bivalve-based buildups recorded from the Early Triassic peri-paleoequatorial Panthalassan and Tethyan margins, the East Greenland bioaccumulations developed within a restricted Boreal mid-paleolatitude seaway, and comprised a monospecific primary framework of microconchid 'lophophorate tubes with shell fragments and phosphatic debris cemented by biogenic calcite. Prostrate growth of the microconchids likely facilitated their accretion into successive sheet-like biostromes and small bioherms. These are associated with a regional paleoenvironmental shift towards well-oxygenated bottom waters, and locally punctuated sedimentation that created a favorable habitat. Although microconchids were both abundant and geographically widespread throughout the earliest Triassic, such buildups formed solely by these metazoans have not been reported from that time frame outside the Boreal Realm. These apparently flourished in the absence of more stable complex communities, and suggest that a locally variable, rather than ubiquitously sequential revival of metazoan bioconstruction activity took place in the immediate aftermath of the end-Permian extinction. However, these may also suggest that ecological recovery of benthic marine ecosystems following the end-Permian mass extinction might have started earlier in higher paleolatitudes.

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