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Publications (10 of 29) Show all publications
Poeppl, R. E., Polvi, L. E. & Turnbull, L. (2023). (Dis)connectivity in hydro-geomorphic systems – emerging concepts and their applications. Earth Surface Processes and Landforms, 48(6), 1089-1094
Open this publication in new window or tab >>(Dis)connectivity in hydro-geomorphic systems – emerging concepts and their applications
2023 (English)In: Earth Surface Processes and Landforms, ISSN 0197-9337, E-ISSN 1096-9837, Vol. 48, no 6, p. 1089-1094Article in journal, Editorial material (Other academic) Published
Abstract [en]

In geomorphology, connectivity has emerged as a framework for understanding the transfer of water and sediment through landscapes. Over the past decade, sessions on (dis)connectivity at the General Assembly of the European Geosciences Union (EGU), and more recently, three mini-conferences in 2020 and 2021 called ‘Connectivity Conversations’, organized by the International Association of Geomorphologists (IAG) working group on ‘Connectivity in Geomorphology’, have created a space for the exchange of ideas relating to (dis)connectivity in geomorphology and related disciplines. The result of these initiatives has been a collection of research articles related to a special issue (SI) entitled ‘(Dis)connectivity in hydro-geomorphic systems – emerging concepts and their applications’. In this article, we provide a synthesis that embraces the SI contributions related to the application of the connectivity concept in different environments and geomorphic process domains, spatial and temporal scales, types and spatial dimensions of connectivity and the role of human impacts and associated river and catchment management aspects.

Place, publisher, year, edition, pages
John Wiley & Sons, 2023
Keywords
catchment, complexity, fluvial, sediment, water
National Category
Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:umu:diva-206459 (URN)10.1002/esp.5574 (DOI)000951727800001 ()2-s2.0-85151000360 (Scopus ID)
Note

This article also appears in: (Dis)connectivity in hydro-geomorphic systems: emerging concepts and their applications (Special Issue).

Available from: 2023-04-06 Created: 2023-04-06 Last updated: 2023-07-12Bibliographically approved
Mason, R. J. & Polvi, L. E. (2023). Unravelling fluvial versus glacial legacy controls on boulder-bed river geomorphology for semi-alluvial rivers in Fennoscandia. Earth Surface Processes and Landforms, 48(14), 2900-2919
Open this publication in new window or tab >>Unravelling fluvial versus glacial legacy controls on boulder-bed river geomorphology for semi-alluvial rivers in Fennoscandia
2023 (English)In: Earth Surface Processes and Landforms, ISSN 0197-9337, E-ISSN 1096-9837, Vol. 48, no 14, p. 2900-2919Article in journal (Refereed) Published
Abstract [en]

River management is founded on predictable self-organisation between river form and catchment controls in alluvial rivers. However, a substantial proportion of rivers are not fully alluvial. In previously glaciated landscapes, boulder-rich glacial till influences river channel form and process. Increasing interest in nature- and process-based river restoration requires knowledge of pre-disturbance natural processes, which does not exist for semi- and non-alluvial rivers in Fennoscandia. We aimed to determine the role of Pleistocene glaciation and subsequent deglaciation versus Holocene fluvial processes in controlling channel form of boulder-bed rivers in Fennoscandia. We quantified morphological characteristics of northern Swedish boulder-bed rivers, in which channel morphology was minimally impacted by humans, and used the degree of alluvial signatures to infer fluvial and legacy glacial controls. We conducted surveys of reach-scale channel geometry, boulder and wood distributions and catchment characteristics for 20 reference reaches (drainage area: 11–114 km2). Reaches ranged in slope from 1% to 8% and were extremely diverse in channel geometry. Rivers showed little self-organisation at the reach scale; no association exists between channel width and channel slope or bed sediment size. Boulders were rarely clustered into bedforms (e.g., step-pools) typical of boulder-bed mountain rivers. Drainage area was positively correlated with channel capacity but not channel width, slope or sediment size. Channel boulder density was best predicted by surveys of terrestrial boulders. Consequently, channel geometry, boulder size and the distribution of boulders were primarily controlled by legacy glacial conditioning rather than current fluvial processes, with some alluvial adjustment of smaller particles within the boulder template. Therefore, restoration of semi-alluvial rivers should take into account local sediment and geomorphic conditions rather than use management principles built for fully alluvial rivers.

Place, publisher, year, edition, pages
John Wiley & Sons, 2023
Keywords
boulder-bed river, glacial legacy, paraglacial, river restoration, semi-alluvial
National Category
Physical Geography
Identifiers
urn:nbn:se:umu:diva-214036 (URN)10.1002/esp.5666 (DOI)2-s2.0-85168909384 (Scopus ID)
Funder
Swedish Agency for Marine and Water ManagementSwedish Research Council Formas, 2014-00484
Available from: 2023-09-06 Created: 2023-09-06 Last updated: 2024-01-09Bibliographically approved
Hof, A. R., Zachrisson, A. & Polvi, L. E. (2021). Forest Restoration: Do Site Selection and Restoration Practices Follow Ecological Criteria? A Case Study in Sweden. Forests, 12(8), Article ID 988.
Open this publication in new window or tab >>Forest Restoration: Do Site Selection and Restoration Practices Follow Ecological Criteria? A Case Study in Sweden
2021 (English)In: Forests, ISSN 1999-4907, E-ISSN 1999-4907, Vol. 12, no 8, article id 988Article in journal (Refereed) Published
Abstract [en]

The speed with which restoration will, or can, be accomplished depends on the initial state and location of the sites. However, many factors can undermine the process of choosing sites that are deemed the best ecological choice for restoration. Little attention has been paid to whether site selection follows ecological criteria and how this may affect restoration success. We used habitat inventory data to investigate whether ecological criteria for site selection and restoration have been followed, focusing on restoration for the white-backed woodpecker (Dendrocopos leucotos B.) in Sweden. In our study region, which is situated in an intensively managed forest landscape with dense and young stands dominated by two coniferous species, purely ecological criteria would entail that sites that are targeted for restoration would (1) initially be composed of older and more deciduous trees than the surrounding landscape, and (2) be at a scale relevant for the species. Furthermore, restoration should lead to sites becoming less dense and less dominated by coniferous trees after restoration, which we investigated as an assessment of restoration progress. To contextualize the results, we interviewed people involved in the restoration efforts on site. We show that although the first criterion for ecological site selection was largely met, the second was not. More research is needed to assess the motivations of actors taking part in restoration efforts, as well as how they interlink with public efforts. This would allow us to identify possible synergies that can benefit restoration efforts.

Place, publisher, year, edition, pages
MDPI, 2021
Keywords
Dendrocopos leucotos, forest restoration, forestry, site selection, project management, public-private partnerships
National Category
Ecology Forest Science
Identifiers
urn:nbn:se:umu:diva-186929 (URN)10.3390/f12080988 (DOI)000690558600001 ()2-s2.0-85112486575 (Scopus ID)
Funder
Swedish Research Council Formas, 2009-450
Available from: 2021-08-26 Created: 2021-08-26 Last updated: 2023-09-05Bibliographically approved
Polvi, L. E. (2021). Morphodynamics of Boulder-Bed Semi-Alluvial Streams in Northern Fennoscandia: A Flume Experiment to Determine Sediment Self-Organization. Water resources research, 57(3), Article ID e2020WR028859.
Open this publication in new window or tab >>Morphodynamics of Boulder-Bed Semi-Alluvial Streams in Northern Fennoscandia: A Flume Experiment to Determine Sediment Self-Organization
2021 (English)In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 57, no 3, article id e2020WR028859Article in journal (Refereed) Published
Abstract [en]

In northern Fennoscandia, semi-alluvial boulder-bed channels with coarse glacial legacy sediment are abundant, and due to widespread anthropogenic manipulation during timber-floating, unimpacted reference reaches are rare. The landscape context of these semi-alluvial rapids—with numerous mainstem lakes that buffer high flows and sediment connectivity in addition to a regional low sediment yield—contribute to low amounts of fine sediment and incompetent flows to transport boulders. To determine the morphodynamics of semi-alluvial rapids and potential self-organization of sediment with multiple high flows, a flume experiment was designed and carried out to mimic conditions in semi-alluvial rapids in northern Fennoscandia. Two slope setups (2% and 5%) were used to model a range of flows (Q1 (summer high flow), Q2, Q10, and Q50) in a 8 × 1.1 m flume with a sediment distribution analogous to field conditions; bed topography was measured using structure-from-motion photogrammetry after each flow to obtain DEMs. No classic steep coarse-bed channel bedforms (e.g., step-pools) developed. However, similarly to boulder-bed channels with low relative submergence, at Q10 and Q50 flows, sediment deposited upstream of boulders and scoured downstream. Because the Q50 flow was not able to rework the channel by disrupting grain-interlocking from preceding lower flows, transporting boulders, or forming channel-spanning boulders, the channel-forming discharge is larger than the Q50. These results have implications for restoration of gravel spawning beds in northern Fennoscandia and highlight the importance of large grains in understanding channel morphodynamics.

Place, publisher, year, edition, pages
American Geophysical Union (AGU), 2021
Keywords
bedforms, boulders, sediment clusters, sediment transport, Sweden
National Category
Environmental Sciences
Identifiers
urn:nbn:se:umu:diva-182093 (URN)10.1029/2020WR028859 (DOI)000635680800055 ()2-s2.0-85103250719 (Scopus ID)
Available from: 2021-04-15 Created: 2021-04-15 Last updated: 2023-09-05Bibliographically approved
Dietze, M., Losee, J., Polvi, L. & Palm, D. (2020). A seismic monitoring approach to detect and quantify river sediment mobilization by steelhead redd-building activity. Earth Surface Processes and Landforms, 45(12), 2840-2849
Open this publication in new window or tab >>A seismic monitoring approach to detect and quantify river sediment mobilization by steelhead redd-building activity
2020 (English)In: Earth Surface Processes and Landforms, ISSN 0197-9337, E-ISSN 1096-9837, Vol. 45, no 12, p. 2840-2849Article in journal (Refereed) Published
Abstract [en]

The role of spawning salmonids in altering river bed morphology and sediment transport is significant, yet poorly understood. This is due, in large part, to limitations in monitoring the redd‐building process in a continuous and spatially extended way. A complementary approach may be provided through the use of a small seismic sensor network analysing the ground motion signals generated by the agitation of sediment during the redd‐building process. We successfully tested the viability of this approach by detecting and locating artificially generated redd signals in a reach of the Mashel River, Washington State, USA. We then utilize records of 17 seismic stations, in which we automatically detected seismic events that were subsequently manually checked, yielding a catalogue of 45 potential redd‐building events. Such redd‐building events typically lasted between 1 and 20 min and consisted of a series of clusters of 50–100 short energetic pulses in the 20–60 Hz frequency range. The majority (>90%) of these redd‐building events occurred within 11 days, predominantly during the early morning and late afternoon. The seismically derived locations of the signals were in agreement with independently mapped redds. Improved network geometry and installation conditions are required for more efficient detection, robust location and improved energetic insights into redd‐building processes in larger reaches. The passive and continuous nature of the seismic approach in detecting redds and describing fish behaviour provides a novel tool for fish biologists and fisheries managers, but also for fluvial geomorphologists, interested in quantifying the amount of sediment mobilized by this ecosystem engineer. When complemented with classic approaches, it could allow for a more holistic picture of the kinetics and temporal patterns (at scales from seconds to multiple seasons) of a key phase of salmonid life cycles.

Place, publisher, year, edition, pages
John Wiley & Sons, 2020
Keywords
environmental seismology, ecosystem engineers, salmonid spawning, gravel-bed rivers, biogeomorphology
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-173899 (URN)10.1002/esp.4933 (DOI)000551689300001 ()2-s2.0-85088382425 (Scopus ID)
Available from: 2020-08-07 Created: 2020-08-07 Last updated: 2023-03-23Bibliographically approved
Lininger, K. B. & Polvi, L. E. (2020). Evaluating floodplain organic carbon across a gradient of human alteration in the boreal zone. Geomorphology, 370, Article ID 107390.
Open this publication in new window or tab >>Evaluating floodplain organic carbon across a gradient of human alteration in the boreal zone
2020 (English)In: Geomorphology, ISSN 0169-555X, E-ISSN 1872-695X, Vol. 370, article id 107390Article in journal (Refereed) Published
Abstract [en]

River corridors play an important role in the carbon cycle as sites of carbon transport, storage, and transformation. Floodplain soil organic carbon (OC) and dead, downed large wood (LW) are two of the largest OC stocks in rivers. Human modifications of river corridors, such as damming and floodplain land-use change, have likely modified floodplain OC storage and retention through removal of LW and potential reduction of OC concentrations in soils. However, the effect of human alterations on floodplain OC storage is poorly understood. We measured floodplain soil OC and downed LW loads on three rivers in northern Sweden that display a gradient in the degree of human alteration. The Muddus River is located in a national park and is unaltered. The Vindel River is free-flowing but has been modified via logging and other land-use changes within the floodplain. The Ume River is dammed along its length and has also experienced floodplain logging and land-use change. We used statistical models to determine which factors are associated with differences in mineral soil OC and LW among rivers with different degrees of human alteration. We find the highest mineral soil OC concentrations on the unaltered Muddus River (mean ± standard error (SE) = 3.70 ± 0.59%; median = 3.81%), with lower soil OC along the Vindel (mean ± SE = 1.44 ± 0.22%; median = 0.72%) and Ume (mean ± SE = 2.47 ± 0.44%; median = 1.12%) Rivers. The Muddus River also has the highest downed LW loads (mean ± SE = 22.25 ± 6.99 m3 ha−1) compared to the Vindel (mean ± SE = 3.10 ± 1.26 m3 ha−1) and Ume (mean ± SE = 7.26 ± 3.53 m3 ha−1) Rivers. Variations in soil OC and downed large wood loads indicate that damming may reduce floodplain OC in these boreal systems through reducing lateral channel-floodplain connectivity and longitudinal connectivity. Logging and other land-use changes likely reduce OC inputs to the floodplain surface through removal of organic matter and LW. Further research is needed to elucidate the impact of human modifications on floodplain OC across diverse regions and to inform river restoration efforts to enhance floodplain OC storage.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Floodplain carbon storage, Rivers and the carbon cycle, Human impacts on rivers, Boreal rivers, Fluvial processes, Floodplain dynamics
National Category
Physical Geography
Identifiers
urn:nbn:se:umu:diva-177253 (URN)10.1016/j.geomorph.2020.107390 (DOI)000589917200007 ()2-s2.0-85091256843 (Scopus ID)
Available from: 2020-12-04 Created: 2020-12-04 Last updated: 2023-03-24Bibliographically approved
Polvi, L. E., Lind, L., Persson, H., Miranda-Melo, A., Pilotto, F., Su, X. & Nilsson, C. (2020). Facets and scales in river restoration: Nestedness and interdependence of hydrological, geomorphic, ecological, and biogeochemical processes. Journal of Environmental Management, 265, Article ID 110288.
Open this publication in new window or tab >>Facets and scales in river restoration: Nestedness and interdependence of hydrological, geomorphic, ecological, and biogeochemical processes
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2020 (English)In: Journal of Environmental Management, ISSN 0301-4797, E-ISSN 1095-8630, Vol. 265, article id 110288Article, review/survey (Refereed) Published
Abstract [en]

Although river restoration has increased rapidly, observations of successful ecological recovery are rare, mostly due to a discrepancy in the spatial scale of the impact and the restoration. Rivers and their ecological communities are a product of four river facets—hydrology, geomorphology, ecology and biogeochemistry—that act and interact on several spatial scales, from the sub-reach to the reach and catchment scales. The four river facets usually affect one another in predictable pathways (e.g., hydrology commonly controls geomorphology), but we show that the order in which they affect each other and can be restored varies depending on ecoregion and hydroclimatic regime. Similarly, processes at different spatial scales can be nested or independent of those at larger scales. Although some restoration practices are dependent of those at higher scales, other reach-scale restoration efforts are independent and can be carried out prior to or concurrently with larger-scale restoration. We introduce a checklist using the four river facets to prioritize restoration at three spatial scales in order to have the largest positive effect on the entire catchment. We apply this checklist to two contrasting regions—in northern Sweden and in southern Brazil—with different anthropogenic effects and interactions between facets and scales. In the case of nested processes that are dependent on larger spatial scales, reach-scale restoration in the absence of restoration of catchment-scale processes can frankly be a waste of money, providing little ecological return. However, depending on the scale-interdependence of processes of the river facets, restoration at smaller scales may be sufficient. This means that the most appropriate government agency should be assigned (i.e., national vs. county) to most effectively oversee river restoration at the appropriate scale; however, this first requires a catchment-scale analysis of feedbacks between facets and spatial scale interdependence.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Brazil, Fluvial geomorphology, River ecology, River restoration, Spatial scales, Sweden
National Category
Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:umu:diva-171804 (URN)10.1016/j.jenvman.2020.110288 (DOI)000533526800025 ()32421567 (PubMedID)2-s2.0-85084186223 (Scopus ID)
Available from: 2020-06-12 Created: 2020-06-12 Last updated: 2023-03-24Bibliographically approved
Polvi, L. E., Dietze, M., Lotsari, E., Turowski, J. M. & Lind, L. (2020). Seismic Monitoring of a Subarctic River: Seasonal Variations in Hydraulics, Sediment Transport, and Ice Dynamics. Journal of Geophysical Research - Earth Surface, 125(7), Article ID e2019JF005333.
Open this publication in new window or tab >>Seismic Monitoring of a Subarctic River: Seasonal Variations in Hydraulics, Sediment Transport, and Ice Dynamics
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2020 (English)In: Journal of Geophysical Research - Earth Surface, ISSN 2169-9003, E-ISSN 2169-9011, Vol. 125, no 7, article id e2019JF005333Article in journal (Refereed) Published
Abstract [en]

High-latitude rivers are commonly covered by ice for up to one third of the year. Our understanding of the effects of ice on channel morphodynamics and bedload transport is hindered by the difficulties of sensing through the ice and dangers of field work on thin ice or during ice break-up. To avoid this drawback, we used seismic signals to interpret processes and quantify water and sediment fluxes. Our objective was to determine seasonal differences in hydraulics and bedload sediment transport under ice-covered versus open-channel flow conditions using a small seismic network and to provide a first-order estimation of sediment flux in a Fennoscandian river. Our study reach was on a straight, low-gradient section of the Savar River in northern Sweden. Interpretations of seismic signals, from a station 40 m away from the river, and inverted physical models of river stage and bedload flux indicate clear seasonal differences between ice-covered and open-channel flow conditions. Diurnal cycles in seismic signals reflecting turbulence and sediment transport are evident directly after ice break-up. Analysis of seismic signals of ice-cracking support our visual interpretation of ice break-up timing and the main ice break-up mechanism as thermal rather than mechanical. Assuming the bulk of sediment moves during ice break-up and the snowmelt flood, we calculate a minimum annual sediment flux of 56.2 +/- 0.7 t/km(2), which drastically reduces the uncertainty from previous estimates (0-50 t/km(2)) that exclude ice-covered or ice break-up periods.

Place, publisher, year, edition, pages
American Geophysical Union (AGU), 2020
Keywords
river ice, environmental seismology, Sweden, sediment transport, sediment flux, ice break‐up
National Category
Geophysics
Identifiers
urn:nbn:se:umu:diva-174345 (URN)10.1029/2019JF005333 (DOI)000555444100003 ()2-s2.0-85088367702 (Scopus ID)
Available from: 2020-08-20 Created: 2020-08-20 Last updated: 2023-03-24Bibliographically approved
Su, X., Polvi, L. E., Lind, L., Pilotto, F. & Nilsson, C. (2019). Importance of landscape context for post-restoration recovery of riparian vegetation. Freshwater Biology, 64(5), 1015-1028
Open this publication in new window or tab >>Importance of landscape context for post-restoration recovery of riparian vegetation
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2019 (English)In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 64, no 5, p. 1015-1028Article in journal (Refereed) Published
Abstract [en]

We tested whether the recovery of riparian vegetation along rapids that have been restored after channelisation for timber floating can be predicted based on floristic and geomorphic characteristics of surrounding landscape units. Our study was located along tributary stream networks, naturally fragmented in rapids, slow-flowing reaches, and lakes (i.e. process domains), in the Vindel River catchment in northern Sweden.

We tested whether landscape characteristics, specifically to what extent the geomorphology (affecting local abiotic conditions), species richness, and species composition (representing the species pool for recolonisation), as well as the proximity to various upstream process domains (determining the dispersal potential), can predict post-restoration recovery of riparian vegetation.

Our results indicate that post-restoration recovery of riparian vegetation richness or composition is not strongly related to landscape-scale species pools in these streams. The restored rapids were most similar to upstream rapids, geomorphically and floristically, including plant traits. Species richness of adjacent landscape units (upstream process domains or lateral upland zone) did not correlate with that of restored rapids, and proximity of upstream rapids or other process domains was only weakly influential, thus diminishing support for the hypothesis that hydrochory or other means of propagule dispersal plays a strong role in riparian vegetation community organisation after restoration in this fragmented stream network.

We conclude that, in these naturally fragmented stream systems with three discrete process domains (rapids, slow-flowing reaches and lakes), hydrochory is probably not the main predictor for short-term riparian vegetation recovery. Therefore, other factors than landscape context can serve in prioritising restoration and, in these systems, local factors are likely to outweigh landscape connectivity in the recovery of riparian vegetation.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
hydrochory, plant dispersal, riparian zone, species pool, streams
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-159391 (URN)10.1111/fwb.13282 (DOI)000466805700016 ()2-s2.0-85063265512 (Scopus ID)
Available from: 2019-06-10 Created: 2019-06-10 Last updated: 2023-03-24Bibliographically approved
Su, X., Lind, L., Polvi, L. E. & Nilsson, C. (2019). Variation in hydrochory among lakes and streams: effects of channel planform, roughness, and currents. Ecohydrology, 12(5), Article ID e2091.
Open this publication in new window or tab >>Variation in hydrochory among lakes and streams: effects of channel planform, roughness, and currents
2019 (English)In: Ecohydrology, ISSN 1936-0584, E-ISSN 1936-0592, Vol. 12, no 5, article id e2091Article in journal (Refereed) Published
Abstract [en]

The configuration of channels in stream networks is vital for their connectivity, biodiversity, and metacommunity dynamics. We compared the capacity of three process domains-lakes, slow-flowing reaches, and rapids-to disperse and retain plant propagules by releasing small wooden cubes as propagule mimics during the spring flood and recording their final locations. We also measured the geomorphic characteristics (planform, longitudinal profile, cross-sectional morphology, and wood) of each process domain. The three process domains all differed in morphology and hydraulics, and those characteristics were important in shaping the transport capacity of mimics. On average, lakes retained more mimics than slow-flowing reaches but did not differ from the retainment of rapids. Living macrophytes were the most efficient element trapping mimics. In rapids and slow-flowing reaches, most trapped mimics remained floating, whereas in lakes, most mimics ended up on the banks. The decay curves of retention varied substantially among and within process domains. The results suggest that managers who rely on natural recovery of restored sites by means of plant immigration may benefit from understanding landscape patterns when deciding upon the location of restoration measures in stream networks.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
connectivity, hydrochory, lakes, northern Sweden, process domains, propagule mimics, streams
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-161838 (URN)10.1002/eco.2091 (DOI)000474658500011 ()2-s2.0-85065187788 (Scopus ID)
Available from: 2019-08-08 Created: 2019-08-08 Last updated: 2023-03-23Bibliographically approved
Projects
Natural stream restoration design in northern Sweden-- analysis of bedload sediment transport [2014-484_Formas]; Umeå UniversityFloodplain organic carbon storage in boreal regions: comparisons between human-altered and unaltered floodplains in Sweden and Alaska [2016-06454_VR]; Umeå University
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6075-9890

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