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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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  • 4. Atkin, Owen K
    et al.
    Atkinson, Lindsey J
    Fischer, Rosie A
    Campbell, Catherine
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Zaragoza-Castells, Joana
    Pitchford, Jon W
    Woodward, F Ian
    Hurry, Vaughan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Using temperature-dependent changes in leaf scaling relationships to quantitatively account forthermal acclimation of respiration in a coupled global climate-vegetation model2008In: Global Change Biology, Vol. 14, p. 2709-2726Article in journal (Refereed)
    Abstract [sv]

    The response of plant respiration (R) to temperature is an important component of the biosphere's response to climate change. At present, most global models assume that R increases exponentially with temperature and does not thermally acclimate. Although we now know that acclimation does occur, quantitative incorporation of acclimation into models has been lacking. Using a dataset for 19 species grown at four temperatures (7, 14, 21, and 28 °C), we have assessed whether sustained differences in growth temperature systematically alter the slope and/or intercepts of the generalized log–log plots of leaf R vs. leaf mass per unit leaf area (LMA) and vs. leaf nitrogen (N) concentration. The extent to which variations in growth temperature account for the scatter observed in log–log R–LMA–N scaling relationships was also assessed. We show that thermal history accounts for up to 20% of the scatter in scaling relationships used to predict R, with the impact of thermal history on R–LMA–N generalized scaling relationships being highly predictable. This finding enabled us to quantitatively incorporate acclimation of R into a coupled global climate–vegetation model. We show that accounting for acclimation of R has negligible impact on predicted annual rates of global R, net primary productivity (NPP) or future atmospheric CO2 concentrations. However, our analysis suggests that accounting for acclimation is important when considering carbon fluxes among thermally contrasting biomes (e.g. accounting for acclimation decreases predicted rates of R by up to 20% in high-temperature biomes). We conclude that acclimation of R needs to be accounted for when predicting potential responses of terrestrial carbon exchange to climatic change at a regional level.

  • 5. Attermeyer, Katrin
    et al.
    Casas-Ruiz, Joan Pere
    Fuss, Thomas
    Pastor, Ada
    Cauvy-Fraunie, Sophie
    Sheath, Danny
    Nydahl, Anna C.
    Doretto, Alberto
    Portela, Ana Paula
    Doyle, Brian C.
    Simov, Nikolay
    Roberts, Catherine Gutmann
    Niedrist, Georg H.
    Timoner, Xisca
    Evtimova, Vesela
    Barral-Fraga, Laura
    Basic, Tea
    Audet, Joachim
    Deininger, Anne
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Busst, Georgina
    Fenoglio, Stefano
    Catalan, Nuria
    de Eyto, Elvira
    Pilotto, Francesca
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Mor, Jordi-Rene
    Monteiro, Juliana
    Fletcher, David
    Noss, Christian
    Colls, Miriam
    Nagler, Magdalena
    Liu, Liu
    Gonzalez-Quijano, Clara Romero
    Romero, Ferran
    Pansch, Nina
    Ledesma, Jose L. J.
    Pegg, Josephine
    Klaus, Marcus
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Freixa, Anna
    Ortega, Sonia Herrero
    Mendoza-Lera, Clara
    Bednarik, Adam
    Fonvielle, Jeremy A.
    Gilbert, Peter J.
    Kenderov, Lyubomir A.
    Rulik, Martin
    Bodmer, Pascal
    Carbon dioxide fluxes increase from day to night across European streams2021In: Communications Earth & Environment, E-ISSN 2662-4435, Vol. 2, no 1, article id 118Article in journal (Refereed)
    Abstract [en]

    Globally, inland waters emit over 2 Pg of carbon per year as carbon dioxide, of which the majority originates from streams and rivers. Despite the global significance of fluvial carbon dioxide emissions, little is known about their diel dynamics. Here we present a large-scale assessment of day- and night-time carbon dioxide fluxes at the water-air interface across 34 European streams. We directly measured fluxes four times between October 2016 and July 2017 using drifting chambers. Median fluxes are 1.4 and 2.1mmolm(-2) h(-1) at midday and midnight, respectively, with night fluxes exceeding those during the day by 39%. We attribute diel carbon dioxide flux variability mainly to changes in the water partial pressure of carbon dioxide. However, no consistent drivers could be identified across sites. Our findings highlight widespread day-night changes in fluvial carbon dioxide fluxes and suggest that the time of day greatly influences measured carbon dioxide fluxes across European streams. Diel patterns can greatly impact total stream carbon dioxide emissions, with 39% greater carbon dioxide flux during the night-time relative to the day-time, according to a study of 34 streams across Europe.

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

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

  • 7.
    Bartels, Pia
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ask, Jenny
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Climate Impacts Research Centre (CIRC), Department of Ecology and Environmental Science, Umeå University, Abisko, Sweden.
    Giesler, Reiner
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Climate Impacts Research Centre (CIRC), Department of Ecology and Environmental Science, Umeå University, Abisko, Sweden.
    Allochthonous Organic Matter Supports Benthic but Not Pelagic Food Webs in Shallow Coastal Ecosystems2018In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 21, no 7, p. 1459-1470Article in journal (Refereed)
    Abstract [en]

    Rivers transport large amounts of allochthonous organic matter (OM) to the ocean every year, but there are still fundamental gaps in how allochthonous OM is processed in the marine environment. Here, we estimated the relative contribution of allochthonous OM (allochthony) to the biomass of benthic and pelagic consumers in a shallow coastal ecosystem in the northern Baltic Sea. We used deuterium as a tracer of allochthony and assessed both temporal variation (monthly from May to August) and spatial variation (within and outside river plume). We found variability in allochthony in space and time and across species, with overall higher values for zoobenthos (26.2 +/- 20.9%) than for zooplankton (0.8 +/- 0.3%). Zooplankton allochthony was highest in May and very low during the other months, likely as a result of high inputs of allochthonous OM during the spring flood that fueled the pelagic food chain for a short period. In contrast, zoobenthos allochthony was only lower in June and remained high during the other months. Allochthony of zoobenthos was generally higher close to the river mouth than outside of the river plume, whereas it did not vary spatially for zooplankton. Last, zoobenthos allochthony was higher in deeper than in shallower areas, indicating that allochthonous OM might be more important when autochthonous resources are limited. Our results suggest that climate change predictions of increasing inputs of allochthonous OM to coastal ecosystems may affect basal energy sources supporting coastal food webs.

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  • 8.
    Barthelemy, Hélène
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Stark, Sari
    Michelsen, Anders
    Olofsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Urine is an important nitrogen source for plants irrespective of vegetation composition in an Arctic tundra: Insights from a N-15-enriched urea tracer experiment2018In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 106, no 1, p. 367-378Article in journal (Refereed)
    Abstract [en]

    1. Mammalian herbivores can strongly influence nitrogen (N) cycling and herbivore urine could be a central component of the N cycle in grazed ecosystems. Despite its potential role for ecosystem productivity and functioning, the fate of N derived from urine has rarely been investigated in grazed ecosystems. 2. This study explored the fate of N-15-enriched urea in tundra sites that have been either lightly or intensively grazed by reindeer for more than 50years. We followed the fate of the N-15 applied to the plant canopy, at 2weeks and 1year after tracer addition, in the different ecosystem N pools. 3. N-15-urea was rapidly incorporated in cryptogams and in above-ground parts of vascular plants, while the soil microbial pool and plant roots sequestered only a marginal proportion. Furthermore, the litter layer constituted a large sink for the N-15-urea, at least in the short term, indicating a high biological activity in the litter layer and high immobilization in the first phases of organic matter decomposition. 4. Mosses and lichens still constituted the largest sink for the N-15-urea 1year after tracer addition at both levels of grazing intensity demonstrating their large ability to capture and retain N from urine. Despite large fundamental differences in their traits, deciduous and evergreen shrubs were just as efficient as graminoids in taking up the N-15-urea. The total recovery of N-15-urea was lower in the intensively grazed sites, suggesting that reindeer reduce ecosystem N retention. 5. Synthesis. The rapid incorporation of the applied N-15-urea indicates that arctic plants can take advantage of a pulse of incoming N from urine. In addition, N-15 values of all taxa in the heavily grazed sites converged towards the N-15 values for urine, bringing further evidence that urine is an important N source for plants in grazed tundra ecosystems.

  • 9.
    Berggren, Martin
    et al.
    Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden.
    Ye, Linlin
    Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden; School of Geographic Sciences, Nantong University, Nantong, China.
    Sponseller, Ryan A.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bergström, Ann-Kristin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Verheijen, Hendricus
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hensgens, Geert
    Department of Earth Sciences, Vrije Universiteit, Amsterdam, Netherlands.
    Nutrient limitation masks the dissolved organic matter composition effects on bacterial metabolism in unproductive freshwaters2023In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 68, no 9, p. 2059-2069Article in journal (Refereed)
    Abstract [en]

    Aquatic microbial responses to changes in the amount and composition of dissolved organic carbon (DOC) are of fundamental ecological and biogeochemical importance. Parallel factor (PARAFAC) analysis of excitation–emission fluorescence spectra is a common tool to characterize DOC, yet its ability to predict bacterial production (BP), bacterial respiration (BR), and bacterial growth efficiency (BGE) vary widely, potentially because inorganic nutrient limitation decouples microbial processes from their dependence on DOC composition. We used 28-d bioassays with water from 19 lakes, streams, and rivers in northern Sweden to test how much the links between bacterial metabolism and fluorescence PARAFAC components depend on experimental additions of inorganic nutrients. We found a significant interaction effect between nutrient addition and fluorescence on carbon-specific BP, and weak evidence for influence on BGE by the same interaction (p = 0.1), but no corresponding interaction effect on BR. A practical implication of this interaction was that fluorescence components could explain more than twice as much of the variability in carbon-specific BP (R2 = 0.90) and BGE (R2 = 0.70) after nitrogen and phosphorus addition, compared with control incubations. Our results suggest that an increased supply of labile DOC relative to ambient phosphorus and nitrogen induces gradually larger degrees of nutrient limitation of BP, which in turn decouple BP and BGE from fluorescence signals. Thus, while fluorescence does contain precise information about the degree to which DOC can support microbial processes, this information may be hidden in field studies due to nutrient limitation of bacterial metabolism.

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  • 10.
    Bigler, Christian
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Diatoms as indicators of Holocene climate and environmental change in northern Sweden2001Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

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

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

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

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  • 11.
    Bigler, Christian
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Hall, Roland I
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Diatoms as quantitative indicators of July temperature: a century-scale validation with meteorological data from northern Sweden2003In: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 189, no 3-4, p. 147-160Article in journal (Refereed)
  • 12.
    Bigler, Christian
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Larocque, Isabelle
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Peglar, S. M.
    Birks, H. J. B.
    Hall, Roland I.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Quantitative multiproxy assessment of long-term patterns of Holocene environmental change from a small lake near Abisko, northern Sweden2002In: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 12, no 4, p. 481-496Article in journal (Refereed)
    Abstract [en]

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

  • 13.
    Blume-Werry, Gesche
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Wilson, Scott D.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Biology, University of Regina, Regina, Saskatchewan S4S 0A2 Canada.
    Kreyling, Juergen
    Milbau, Ann
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Research Institute for Nature and Forest INBO, Kliniekstraat 25, 1070 Brussels, Belgium.
    The hidden season: growing season is 50% longer below than above ground along an arctic elevation gradient2016In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 209, no 3, p. 978-986Article in journal (Refereed)
    Abstract [en]

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

  • 14. Bogard, Matthew J.
    et al.
    St-Gelais, Nicolas F.
    Vachon, Dominic
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Groupe de recherche interuniversitaire en limnologie, Département des sciences biologiques, Université du Québec à Montréal, Montreal, Québec, Canada.
    del Giorgio, Paul A.
    Patterns of Spring/Summer Open-Water Metabolism Across Boreal Lakes2020In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 23, p. 1581-1597Article in journal (Refereed)
    Abstract [en]

    Northern regions host the greatest density of surface water globally, but knowledge of lake metabolism in this vast yet remote landscape is limited. Here, we used an oxygen stable isotope approach to quantify patterns and drivers of surface layer metabolism in lakes throughout an approximately 10(6) km(2) tract of boreal Canada. Ecosystem gross primary production (GPP) and respiration rates (R) were much higher than previously assumed for spring and summer months. Both rates were strongly linked to nitrogen (N) concentrations, not light availability, despite earlier work showing community-level light effects. Net ecosystem production (NEP = GPP - R) was negative for most lakes. Hierarchical modeling revealed that although NEP is strongly stabilized via similar effects of N on both GPP and R, NEP decreases with increasing dissolved organic carbon (DOC). These interactive controls on NEP were not predictable from bivariate regressions linking NEP to physical, chemical or habitat-specific drivers. In contrast to expectations, NEP was higher in warmer waters due to increased temperature dependency of GPP, not R. Temperature and DOC content had opposing effects on NEP in all but the most dystrophic lakes, possibly implying a muted response of metabolic balances to future shifts in both regional climate and OC delivery.

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

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

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  • 16. Buckland, Paul
    et al.
    Buckland, Philip I.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Prosser, Tim
    Edlington Wood: using Lidar to put ancient fields and old excavations into their contemporary landscape2020In: Transactions of the Hunter Archaeological Society, ISSN 0966-2251, Vol. 29, p. 84-101Article in journal (Refereed)
    Abstract [en]

    The Roman sites in Edlington Wood, three miles west-south-west of Doncaster, South Yorkshire, first came to wider notice as a result of finds by the woodman in the 1930s and the material was of sufficient interest for Philip Corder to use it as the basis for a paper in a festschrift to O. G. S. Crawford. Most of these finds and later material were deposited in Doncaster Museum, although others went to the owners and local metal detectorists. In 1970 a threat of quarrying led to a detailed survey of the site by the Royal Commission on Historical Monuments and limited excavation on one site. Two large areas within the Wood were cleared but remain as improved grassland. The recent availability of Lidar imagery allows the occupation sites and fragments of field system located by ground survey to be placed in a broader context of small rectangular fields and some attempt at a landscape chronology to be made. The cultivation of the fields in a system of cord rig is discussed.

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  • 17. Buckland, Paul C.
    et al.
    Buckland, Philip I.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    The Alder Leaf Beetle Agelastica alni (L.) (Col.: Chrysomelidae) in the Dearne Valley. Climate change or poor quarantine.2014In: Sorby Record, ISSN 0260-2245, no 50, p. 2-6Article in journal (Other academic)
  • 18.
    Buckland, Philip I.
    Department of Archaeology and Prehistory, University of Sheffield, Sheffield, UK.
    Lichenometry and Soil Erosion in Northwest Iceland1994In: Environmental Change in Iceland: mit 18 Tabellen / [ed] Stötter, Johann, München: Münchener Universitätsschriften , 1994, p. 31-40Conference paper (Other (popular science, discussion, etc.))
  • 19.
    Buckland, Philip I.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    The Bugs Coleopteran Ecology Package (BugsCEP): the development and implementation of software for palaeoenvironmental and palaeoclimatological research2009Book (Other academic)
    Abstract [en]

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

  • 20.
    Buckland, Philip I.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab. Umeå University, Faculty of Arts, Humlab.
    The Bugs Coleopteran Ecology Package (BugsCEP) database: 1000 sites and half a million fossils later2014In: Quaternary International, ISSN 1040-6182, E-ISSN 1873-4553, Vol. 341, p. 272-282Article in journal (Refereed)
    Abstract [en]

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

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

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

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

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

  • 21.
    Buckland, Philip I.
    et al.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab. Umeå University, Faculty of Arts, Humlab.
    Buckland, Paul C.
    BugsCEP, an entomological database twenty-five years on2014In: Antenna (Journal of the Royal Entomological Society), ISSN 0140-1890, Vol. 38, no 1, p. 21-28Article in journal (Refereed)
  • 22.
    Buckland, Philip I.
    et al.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Eriksson, Erik J.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Palm, Fredrik
    Umeå University, Faculty of Arts, Humlab.
    SEAD - The Strategic Environmental Archaeology Database: Progress Report Spring 20142014Report (Other academic)
    Abstract [en]

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

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    SEAD - Progress Report Spring 2014
  • 23.
    Buckland, Philip I.
    et al.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Lemdahl, Geoffrey
    Linnaeus University, Sweden.
    Explaining Late Quaternary beetle extinctions in the UK using palaeoenvironmental databases for quantitative environmental reconstruction2015Conference paper (Refereed)
    Abstract [en]

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

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    Presentation
  • 24.
    Buckland, Philip I.
    et al.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Nyqvist, Roger
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Alexander, Benedict
    WSP, Sweden.
    Palsson, Gisli
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Eriksson, Samuel
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    The Swedish Transport Administration’s Toolbox and its Potential in Archaeological and Cultural Heritage Survey: Including a brief review of remote sensing, prospection and geodata analysis methods for archaeology and cultural heritage2018Report (Other academic)
    Abstract [en]

    This report provides an overview of the main remote sensing methods and geodata types used in archaeological prospection and cultural heritage survey. Based on a literature review, it provides an initial survey of the state of the art nationally and internationally, followed by details on the potential usage of different methods in a Swedish context. The details include pros and cons of methods as well as information on considerations that should be taken into account when applying the methods in different situations. Examples are provided where relevant to explain specific details or illustrate important points. Particular attention has been paid to laser scanning (LiDAR) data due to its increasing prevalence and prominence in landscape and archaeological surveys.

    The report continues with a preliminary evaluation of the possibilities for using data provided by Swedish Transport Administration (Trafikverket), obtained for other stages of the planning process, in archaeological and cultural heritage work. Specifically, the report looks at a number of geodata types obtained from The Geological Survey of Sweden (Sveriges geologiska undersökning/SGU), a nature conservation survey in report form, a ground penetrating radar technical report, terrain laser scanning (LiDAR) and orthophotos (geometrically corrected aerial photographs). The SGU geodata consist of a number of Geographical Information System (GIS) layers describing bedrock and soil types, and the nature conservation survey included accompanying, but incomplete, GIS data. This section consists of concise descriptions of the potential of each group of GIS layers or data, and is complemented by brief, bullet point summaries along with additional technical information in Appendix 1. Comments have been made where additional, related, data sources would be useful. Swedish terms are included in parenthesis where the term differs significantly from the English equivalent.

    A final summary provides a compact overview of the main points of the report before providing some conclusions and ideas for further work. This is in turn followed by a list of ideas for enhancing the efficiency with which the types of data discussed can be used in infrastructure projects which have a potential to impact on archaeology/cultural heritage.

    References are provided to support important or potentially contentious points or where further reading or research would be advised for a more comprehensive understanding of relevant issues.

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  • 25. Callaghan, Terry V.
    et al.
    Johansson, Margareta
    Brown, Ross D.
    Groisman, Pavel Ya.
    Labba, Niklas
    Radionov, Vladimir
    Barry, Roger G.
    Blangy, Sylvie
    Bradley, Raymond S.
    Bulygina, Olga N.
    Christensen, Torben R.
    Colman, Jonathan
    Essery, Richard L.H.
    Forbes, Bruce C.
    Forchhammer, Mads C.
    Frolov, Dimitry M.
    Golubev, Vladimir N.
    Grenfell, Thomas C.
    Honrath, Richard E.
    Juday, Glenn P.
    Melloh, Rae
    Meshcherskaya, Anna V.
    Petrushina, Marina N.
    Phoenix, Gareth K.
    Pomeroy, John
    Rautio, Arja
    Razuvaev, Vyacheslav N.
    Robinson, David A.
    Romanov, Peter
    Schmidt, Niels M.
    Serreze, Mark C.
    Shevchenko, Vladimir
    Shiklomanov, Alexander I.
    Shindell, Drew
    Shmakin, Andrey B.
    Sköld, Peter
    Umeå University, Faculty of Arts, Centre for Sami Research.
    Sokratov, Sergey A.
    Sturm, Matthew
    Warren, Stephen
    Woo, Ming-ko
    Wood, Eric F.
    Yang, Daquing
    Changing snow cover and its impacts2011In: Snow, Water, Ice and Permafrost in the Arctic (SWIPA): Climate Change and the Cryosphere, Oslo: Arctic Monitoring and Assessment Programme, 2011, p. 4:1-4:58Chapter in book (Refereed)
  • 26.
    Capo, Eric
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Marine Biology, Institut de Ciències del Mar, CSIC, Barcelona, Spain.
    Rydberg, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Tolu, Julie
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland.
    Domaizon, Isabelle
    Debroas, Didier
    Bindler, Richard
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bigler, Christian
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    How Does Environmental Inter-annual Variability Shape Aquatic Microbial Communities?: A 40-Year Annual Record of Sedimentary DNA From a Boreal Lake (Nylandssjon, Sweden)2019In: Frontiers in Ecology and Evolution, E-ISSN 2296-701X, Vol. 7, article id 245Article in journal (Refereed)
    Abstract [en]

    To assess the sensitivity of lakes to anthropogenically-driven environmental changes (e.g., nutrient supply, climate change), it is necessary to first isolate the effects of between-year variability in weather conditions. This variability can strongly impact a lake's biological community especially in boreal and arctic areas where snow phenology play an important role in controlling the input of terrestrial matter to the lake. Identifying the importance of this inherent variability is difficult without time series that span at least several decades. Here, we applied a molecular approach (metabarcoding on eukaryotic 18S rRNA genes and qPCR on cyanobacterial 16S rRNA genes) to sedimentary DNA (sed-DNA) to unravel the annual variability of microbial community in 40 years' sediment record from the boreal lake Nylandssjon which preserve annually-laminated sediments. Our comparison between seasonal meteorological data, sediment inorganic geochemistry (X-ray fluorescence analyses) and organic biomarkers (pyrolysis-gas chromatography/mass spectrometry analyses), demonstrated that inter-annual variability strongly influence the sediment composition in Nylandssjon. Spring temperature, snow and ice phenology (e.g., the percentage of snow loss in spring, the timing of lake ice-off) were identified as important drivers for the inputs of terrestrial material to the lake, and were therefore also important for shaping the aquatic biological community. Main changes were detected in the late-80s/mid-90s and mid-2000s associated with increases in algal productivity, in total richness of the protistan community and in relative abundances of Chlorophyta, Dinophyceae as well as Cyanobacteria abundance. These changes could be linked to a decline in terrestrial inputs to the lake during the snow melt and run-off period, which in turn was driven by warmer winter temperatures. Even if our data shows that meteorological factors do affect the sediment composition and microbial communities, they only explain part of the variability. This is most likely a consequence of the high inter-annual variability in abiotic and biotic parameters highlighting the difficulty to draw firm conclusions concerning drivers of biological changes at an annual or sub-annual resolution even with the 40-year varved sediment record from Nylandssjon. Hence, it is necessary to have an even longer time perspective in order to reveal the full implications of climate change.

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  • 27. Chambers, Frank M.
    et al.
    Booth, Robert K.
    De Vleeschouwer, Francois
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Lamentowicz, Mariusz
    Le Roux, Gael
    Mauquoy, Dmitri
    Nichols, Jonathan E.
    van Geel, Bas
    Development and refinement of proxy-climate indicators from peats2012In: Quaternary International, ISSN 1040-6182, E-ISSN 1873-4553, Vol. 268, p. 21-33Article in journal (Refereed)
    Abstract [en]

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

  • 28.
    de la Barreda-Bautista, Betsabe
    et al.
    School of Biosciences, University of Nottingham, Sutton Bonington, Loughborough, United Kingdom; School of Geography, University of Nottingham, University Park, Nottingham, United Kingdom.
    Boyd, Doreen S.
    School of Geography, University of Nottingham, Nottingham, United Kingdom.
    Ledger, Martha
    School of Biosciences, University of Nottingham, Sutton Bonington, Loughborough, United Kingdom.
    Siewert, Matthias B.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Chandler, Chris
    School of Geography, University of Nottingham, Nottingham, United Kingdom.
    Bradley, Andrew V.
    Department of Chemical and Environmental Engineering, Faculty of Engineering, Nottingham Geospatial Institute, Nottingham, United Kingdom.
    Gee, David
    Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham, Nottingham, United Kingdom.
    Large, David J.
    Department of Chemical and Environmental Engineering, Faculty of Engineering, Nottingham Geospatial Institute, Nottingham, United Kingdom; Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham, Nottingham, United Kingdom.
    Olofsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Sowter, Andrew
    Terra Motion Ltd, Ingenuity Centre, Nottingham, United Kingdom.
    Sjögersten, Sofie
    School of Biosciences, University of Nottingham, Sutton Bonington, Loughborough, United Kingdom.
    Towards a Monitoring Approach for Understanding Permafrost Degradation and Linked Subsidence in Arctic Peatlands2022In: Remote Sensing, E-ISSN 2072-4292, Vol. 14, no 3, article id 444Article in journal (Refereed)
    Abstract [en]

    Permafrost thaw resulting from climate warming is threatening to release carbon from high latitude peatlands. The aim of this research was to determine subsidence rates linked to permafrost thaw in sub-Arctic peatlands in Sweden using historical orthophotographic (orthophotos), Unoccupied Aerial Vehicle (UAV), and Interferometric Synthetic Aperture Radar (InSAR) data. The orthophotos showed that the permafrost palsa on the study sites have been contracting in their areal extent, with the greatest rates of loss between 2002 and 2008. The surface motion estimated from differential digital elevation models from the UAV data showed high levels of subsidence (maxi-mum of −25 cm between 2017 and 2020) around the edges of the raised palsa plateaus. The InSAR data analysis showed that raised palsa areas had the greatest subsidence rates, with maximum subsidence rates of 1.5 cm between 2017 and 2020; however, all wetland vegetation types showed sub-sidence. We suggest that the difference in spatial units associated with each sensor explains parts of the variation in the subsidence levels recorded. We conclude that InSAR was able to identify the areas most at risk of subsidence and that it can be used to investigate subsidence over large spatial extents, whereas UAV data can be used to better understand the dynamics of permafrost degradation at a local level. These findings underpin a monitoring approach for these peatlands.

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  • 29.
    Deininger, Anne
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Effects of inorganic nitrogen and organic carbon on pelagic food webs in boreal lakes2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

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

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  • 30.
    Ehnvall, B.
    et al.
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Ratcliffe, J.L.
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden; North Highland College, Environmental Research Institute, University of the Highlands and Islands, Thurso, United Kingdom; Unit for Field-Based Forest Research, Swedish University of Agricultural Sciences, Vindeln, Sweden.
    Nilsson, M.B.
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Öquist, M.G.
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Sponseller, Ryan A.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Grabs, T.
    Department of Earth Sciences, Geocentrum, Uppsala University, Uppsala, Sweden.
    Topography and time shape mire morphometry and large-scale mire distribution patterns in the northern boreal landscape2024In: Journal of Geophysical Research - Earth Surface, ISSN 2169-9003, E-ISSN 2169-9011, Vol. 129, no 2, article id e2023JF007324Article in journal (Refereed)
    Abstract [en]

    Peatlands are major terrestrial soil carbon stores, and open mires in boreal landscapes hold a considerable fraction of the global peat carbon. Despite decades of study, large-scale spatiotemporal analyses of mire arrangement have been scarce, which has limited our ability to scale-up mire properties, such as carbon accumulation to the landscape level. Here, we use a land-uplift mire chronosequence in northern Sweden spanning 9,000 years to quantify controls on mire distribution patterns. Our objectives include assessing changes in the spatial arrangement of mires with land surface age, and understanding modifications by upland hydrotopography. Characterizing over 3,000 mires along a 30 km transect, we found that the time since land emergence from the sea was the dominant control over mire coverage, especially for the establishment of large mire complexes. Mires at the youngest end of the chronosequence were small with heterogenous morphometry (shape, slope, and catchment-to-mire areal ratios), while mires on the oldest surfaces were variable in size, but included larger mires with more complex shapes and smaller catchment-to-mire ratios. In general, complex topography fragmented mires by constraining the lateral expansion, resulting in a greater number of mires, but reduced total mire area regardless of landscape age. Mires in this study area occurred on slopes up to 4%, indicating a hydrological boundary to peatland expansion under local climatic conditions. The consistency in mire responses to spatiotemporal controls illustrates how temporal limitation in peat initiation and accumulation, and topographic constraints to mire expansion together have shaped present day mire distribution patterns.

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  • 31.
    Ehnvall, Betty
    et al.
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Skogsmarksgränd 17, Umeå, Sweden.
    Ågren, Anneli M.
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Skogsmarksgränd 17, Umeå, Sweden.
    Nilsson, Mats B.
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Skogsmarksgränd 17, Umeå, Sweden.
    Ratcliffe, Joshua L.
    Unit for Field-Based Forest Research, Swedish University of Agricultural Sciences, Vindeln, Sweden.
    Noumonvi, Koffi Dodji
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Skogsmarksgränd 17, Umeå, Sweden.
    Peichl, Matthias
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Skogsmarksgränd 17, Umeå, Sweden.
    Lidberg, William
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Skogsmarksgränd 17, Umeå, Sweden.
    Giesler, Reiner
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Mörth, Carl-Magnus
    Department of Geological Sciences, Stockholm University, Svante Arrheniusväg 8, Stockholm, Sweden.
    Öquist, Mats G.
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Skogsmarksgränd 17, Umeå, Sweden.
    Catchment characteristics control boreal mire nutrient regime and vegetation patterns over ~5000 years of landscape development2023In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 895, article id 165132Article in journal (Refereed)
    Abstract [en]

    Vegetation holds the key to many properties that make natural mires unique, such as surface microtopography, high biodiversity values, effective carbon sequestration and regulation of water and nutrient fluxes across the landscape. Despite this, landscape controls behind mire vegetation patterns have previously been poorly described at large spatial scales, which limits the understanding of basic drivers underpinning mire ecosystem services. We studied catchment controls on mire nutrient regimes and vegetation patterns using a geographically constrained natural mire chronosequence along the isostatically rising coastline in Northern Sweden. By comparing mires of different ages, we can partition vegetation patterns caused by long-term mire succession (<5000 years) and present-day vegetation responses to catchment eco-hydrological settings. We used the remote sensing based normalized difference vegetation index (NDVI) to describe mire vegetation and combined peat physicochemical measures with catchment properties to identify the most important factors that determine mire NDVI. We found strong evidence that mire NDVI depends on nutrient inputs from the catchment area or underlying mineral soil, especially concerning phosphorus and potassium concentrations. Steep mire and catchment slopes, dry conditions and large catchment areas relative to mire areas were associated with higher NDVI. We also found long-term successional patterns, with lower NDVI in older mires. Importantly, the NDVI should be used to describe mire vegetation patterns in open mires if the focus is on surface vegetation, since the canopy cover in tree-covered mires completely dominated the NDVI signal. With our study approach, we can quantitatively describe the connection between landscape properties and mire nutrient regime. Our results confirm that mire vegetation responds to the upslope catchment area, but importantly, also suggest that mire and catchment aging can override the role of catchment influence. This effect was clear across mires of all ages, but was strongest in younger mires.

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  • 32.
    Engelmark, Roger
    et al.
    Umeå University, Faculty of Arts, Archaeology and Sami Studies, Environmental Archaeology Lab.
    Buckland, Philip I.
    Umeå University, Faculty of Arts, Archaeology and Sami Studies, Environmental Archaeology Lab.
    The Early Holocene Environment of North Fennoscandia and its Implications for Colonisation2005In: Pioneer settlements and colonization processes in the Barents region / [ed] Helena Knutsson, Vuollerim: Vuollerim 6000 år , 2005, p. 97-106Conference paper (Refereed)
    Abstract [en]

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

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  • 33.
    Fjällberg, Martina
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Characteristics of instream wood following alluvial river restoration: Using Uncrewed Aerial Vehicles2023Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    River restoration is something that is often used to help restore watercourses that were historically used for timber floating. In these restorations, instream wood (IW) plays a big role in increasing biodiversity and habitat heterogeneity in watercourses. Uncrewed Aerial Vehicles (UAVs) have proven to be useful when monitoring changes following river restoration but there is a need for less time-consuming methods to detect IW. This study’s objective was to investigate IW following a river restoration in an alluvial reach in Vargån, Northern Sweden and how well UAVs can be used to do this. Manual digitizing of IW was done in GIS from orthomosaics of three different flight occasions: pre-restoration, directly after and one year after restoration. An object- and color-based automated image thresholding was done to investigate if it could be used to automatically detect IW. The results showed that there were differences in number of IW, volume, width, and length between the different flight occasions. There was also indication that there had been movement of IW as well as changes in cluster composition, with more clusters with a higher number of wood pieces in the latest flight occasion. The automated image thresholding was able to accurately detect IW with an accuracy of 47,4 %, but it had limitations due to natural conditions. However, it showed the possibility of using automated methods to detect IW and with improvements it could become a faster and more accessible way of detecting IW in river monitoring. 

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  • 34.
    Foghagen, Christer
    Umeå University, Faculty of Social Sciences, Department of Social and Economic Geography.
    Algae blooms and their consequences on camping tourism on Öland, SwedenManuscript (preprint) (Other academic)
    Abstract [en]

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

  • 35.
    Forsman, Mona
    et al.
    Department of Forest Resource Management, Swedish University of Agricultural Sciences.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Holmgren, Johan
    Department of Forest Resource Management, Swedish University of Agricultural Sciences.
    Estimation of tree stem attributes using terrestrial photogrammetry2012In: International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Copernicus Gesellschaft , 2012, p. B5-261-B5-265Conference paper (Other academic)
    Abstract [en]

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

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

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

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

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  • 36.
    Hansen Österlund, Sara Emilie
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Spatialanalys av markgeokemi: Hur utlakningshalter av markgeokemin varierar i Sveriges morän enligt interpolationsmetoder2023Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of this study was to evaluate the spatial distribution of geochemistry in Swedish till and whether interpolations could predict unknown values of geochemistry between samples at a national spatial level, Sweden, and a regional, the county of Västerbotten. The information of the spatial distribution of the elements and the interpolations accurateness has several applications. For example, the establishing of infrastructure.  Which, in Sweden, is regulated by Naturvårdsverkets guidelines for sensitive land management (KM) and less sensitive land management (MKM) since elements can be harmful for the environment and health above certain levels. The guidelines for waste disposal of soil with levels of less than slight risk (MRR) does also acquire knowledge about the background levels of an area which are found in the C-horizon. The aim of the study was therefore to answer the following questions 1) Which interpolation method provides the most accurate prediction for the various elements at the national and regional level? 2) How does the calculated levels of geochemistry differ from the sampled ones for the two spatial levels? The study was conducted by studying the levels of ten elements in the C-horizon at the two spatial levels were the regional had greater sample density than the national. The interpolations that were used for these elements were the local interpolation methods kriging, inverse distance weighting (IDW), natural neighbour, thiessen polygons and triangular irregular network (TIN). Samples were gathered from Sweden’s geological Surveys (SGU) for the elements that are regulated by Naturvårdsverkets guidelines which was why these ten elements were studied: arsenic, barium, cobalt, chromium, copper, nickel, lead, antimony, vanadium, and zinc. The interpolations were done with two thirds of  the data. A validation was done with the remaining third by calculating root mean square error (RMSE). For the interpolation method with the lowest RMSE, the mean absolute square error (MAPE) was calculated for all the validation points to see how the calculated levels differed from the samples. The result showed that kriging and IDW were the most accurate interpolation methods for the data but that some of the studied elements need even greater sample density to become more correct. This can be solved by doing a cross-validation of the existing data. Furthermore, the interpolations were more accurate at the regional level for elements except antimony. The higher accuracy can be explained by the higher sample density at the regional level. At the national level the interpolations worked better in the north of Sweden than in the south which needs further studying. Overall, the interpolations were the least accurate when the levels of the elements were low, which may be the reason why antimony showed higher RMSE at the regional level. In conclusion the study showed that it is possible to use interpolations to predict values at unknown places with different accurateness.

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  • 37. Harms, Tamara K.
    et al.
    Rocher-Ros, Gerard
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Godsey, Sarah E.
    Emission of Greenhouse Gases From Water Tracks Draining Arctic Hillslopes2020In: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 125, no 12, article id e2020JG005889Article in journal (Refereed)
    Abstract [en]

    Experimental and ambient warming of Arctic tundra results in emissions of greenhouse gases to the atmosphere, contributing to a positive feedback to climate warming. Estimates of gas emissions from lakes and terrestrial tundra confirm the significance of aquatic fluxes in greenhouse gas budgets, whereas few estimates describe emissions from fluvial networks. We measured dissolved gas concentrations and estimated emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) from water tracks, vegetated depressions that hydrologically connect hillslope soils to lakes and streams. Concentrations of trace gases generally increased as ground thaw deepened through the growing season, indicating active production of greenhouse gases in thawed soils. Wet antecedent conditions were correlated with a decline in CO2 and CH4 concentrations. Dissolved N2O in excess of atmospheric equilibrium occurred in drier water tracks, but on average water tracks took up N2O from the atmosphere at low rates. Estimated CO2 emission rates for water tracks were among the highest observed for Arctic aquatic ecosystems, whereas CH4 emissions were of similar magnitude to streams. Despite occupying less than 1% of total catchment area, surface waters within water tracks were an estimated source of up to 53–85% of total CH4 emissions from their catchments and offset the terrestrial C sink by 5–9% during the growing season. Water tracks are abundant features of tundra landscapes that contain warmer soils and incur deeper thaw than adjacent terrestrial ecosystems and as such might contribute to ongoing and accelerating release of greenhouse gases from permafrost soils to the atmosphere.

  • 38.
    Harrie, Lars
    et al.
    Physical Geography and Ecosystem Science, Lund University, Sweden.
    Touya, Guillaume
    LASTIG, Univ Gustave Eiffel, IGN-ENSG, France.
    Oucheikh, Rachid
    Physical Geography and Ecosystem Science, Lund University, Sweden.
    Ai, Tinghua
    School of Resource and Environmental Sciences, Wuhan University, China.
    Courtial, Azelle
    LASTIG, Univ Gustave Eiffel, IGN-ENSG, France.
    Richter, Kai-Florian
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Machine learning in cartography2024In: Cartography and Geographic Information Science, ISSN 1523-0406, E-ISSN 1545-0465, Vol. 51, no 1, p. 1-19Article in journal (Other academic)
    Abstract [en]

    Machine learning is increasingly used as a computing paradigm in cartographic research. In this extended editorial, we provide some background of the papers in the CaGIS special issue Machine Learning in Cartography with a special focus on pattern recognition in maps, cartographic generalization, style transfer, and map labeling. In addition, the paper includes a discussion about map encodings for machine learning applications and the possible need for explicit cartographic knowledge and procedural modeling in cartographic machine learning models.

  • 39.
    Helmens, Karin
    et al.
    Swedish Museum of Natural History and Värriö Research Station, Institute for Atmospheric and Earth System Research INAR/Physics, University of Helsinki.
    Katrantsiotis, Christos
    Department of Physical Geography, Stockholm University, Sweden.
    Kuosmanen, Niina
    Department of Geosciences and Geography, University of Helsinki.
    Luoto, Tomi
    Ecosystems and Environment Research Programme, Faculty of Biological and Environmental Sciences, University of Helsinki.
    Salonen, Sakari
    Department of Geosciences and Geography, University of Helsinki.
    Väliranta, Minna
    Ecosystems and Environment Research Programme, ECRU, Faculty of Biological and Environmental Sciences, University of Helsinki.
    Prolonged interglacial warmth during the Last Glacial in northern Europe2021In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 50, no 2, p. 331-350Article in journal (Refereed)
    Abstract [en]

    Few fossil‐based environmental and climate records in northern Europe are dated to Marine Isotope Stage (MIS) 5a around 80 ka BP. We here present multiple environmental and climate proxies obtained from a lake sequence of MIS 5a age in the Sokli basin (northern Finland). Pollen/spores, plant macrofossils, NPPs (e.g. green algae), bryozoa, diatoms and chironomids allowed an exceptionally detailed reconstruction of aquatic and telmatic ecosystem successions related to the development of the Sokli Ice Lake and subsequent infilling of a relatively small and shallow lake confined to the Sokli basin. A regional vegetation development typical for the early half of an interglacial is recorded by the pollen, stomata and plant macrofossil data. Reconstructions of July temperatures based on pollen assemblages suffer from a large contribution of local pollen from the lake's littoral zone. Summer temperatures reaching present‐day values, inferred for the upper part of the lake sequence, however, agree with the establishment of pine‐dominated boreal forest indicated by the plant fossil data. Habitat preferences also influence the climate record based on chironomids. Nevertheless, the climate optima of the predominant intermediate‐ to warm‐water chironomid taxa suggest July temperatures exceeding present‐day values by up to several degrees, in line with climate inferences from a variety of aquatic and wetland plant indicator species. The disequilibrium between regional vegetation development and warm, insolation‐forced summers is also reported for Early Holocene records from northern Fennoscandia. The MIS 5a sequence is the last remaining fossil‐bearing deposit in the late Quaternary basin infill at Sokli to be studied using multi‐proxy evidence. A unique detailed climate record for MIS 5 is now available for formerly glaciated northern Europe. Our studies indicate that interglacial conditions persisted into MIS 5a, in agreement with data for large parts of the European mainland, shortening the Last Glacial by some 50 ka to MIS 4‐2.

  • 40. Hough, Moira
    et al.
    McCabe, Samantha
    Vining, S. Rose
    Pickering Pedersen, Emily
    Wilson, Rachel M.
    Lawrence, Ryan
    Chang, Kuang-Yu
    Bohrer, Gil
    Riley, William J.
    Crill, Patrick M.
    Varner, Ruth K.
    Blazewicz, Steven J.
    Dorrepaal, Ellen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Tfaily, Malak M.
    Saleska, Scott R.
    Rich, Virginia, I
    Coupling plant litter quantity to a novel metric for litter quality explains C storage changes in a thawing permafrost peatland2022In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 28, no 3, p. 950-968Article in journal (Refereed)
    Abstract [en]

    Permafrost thaw is a major potential feedback source to climate change as it can drive the increased release of greenhouse gases carbon dioxide (CO2) and methane (CH4). This carbon release from the decomposition of thawing soil organic material can be mitigated by increased net primary productivity (NPP) caused by warming, increasing atmospheric CO2, and plant community transition. However, the net effect on C storage also depends on how these plant community changes alter plant litter quantity, quality, and decomposition rates. Predicting decomposition rates based on litter quality remains challenging, but a promising new way forward is to incorporate measures of the energetic favorability to soil microbes of plant biomass decomposition. We asked how the variation in one such measure, the nominal oxidation state of carbon (NOSC), interacts with changing quantities of plant material inputs to influence the net C balance of a thawing permafrost peatland. We found: (1) Plant productivity (NPP) increased post-thaw, but instead of contributing to increased standing biomass, it increased plant biomass turnover via increased litter inputs to soil; (2) Plant litter thermodynamic favorability (NOSC) and decomposition rate both increased post-thaw, despite limited changes in bulk C:N ratios; (3) these increases caused the higher NPP to cycle more rapidly through both plants and soil, contributing to higher CO2 and CH4 fluxes from decomposition. Thus, the increased C-storage expected from higher productivity was limited and the high global warming potential of CH4 contributed a net positive warming effect. Although post-thaw peatlands are currently C sinks due to high NPP offsetting high CO2 release, this status is very sensitive to the plant community's litter input rate and quality. Integration of novel bioavailability metrics based on litter chemistry, including NOSC, into studies of ecosystem dynamics, is needed to improve the understanding of controls on arctic C stocks under continued ecosystem transition.

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  • 41. Högberg, Peter
    et al.
    Högberg, M. N.
    Göttlicher, S. G.
    Betson, N. R.
    Keel, S. G.
    Metcalfe, D. B.
    Campbell, Catherine
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Schindlbacher, A.
    Hurry, Vaughan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Lundmark, Thomas
    Linder, Sune
    Näsholm, Torgny
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    High temporal resolution tracing of photosynthate carbon from the tree canopy to forest soil microorganisms2008In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 177, no 1, p. 220-228Article in journal (Refereed)
    Abstract [en]

    • Half of the biological activity in forest soils is supported by recent tree photosynthate, but no study has traced in detail this flux of carbon from the canopy to soil microorganisms in the field.

    • Using 13CO2, we pulse-labelled over 1.5 h a 50-m2 patch of 4-m-tall boreal Pinus sylvestris forest in a 200-m3 chamber.

    • Tracer levels peaked after 24 h in soluble carbohydrates in the phloem at a height of 0.3 m, after 2–4 d in soil respiratory efflux, after 4–7 d in ectomycorrhizal roots, and after 2–4 d in soil microbial cytoplasm. Carbon in the active pool in needles, in soluble carbohydrates in phloem and in soil respiratory efflux had half-lives of 22, 17 and 35 h, respectively. Carbon in soil microbial cytoplasm had a half-life of 280 h, while the carbon in ectomycorrhizal root tips turned over much more slowly. Simultaneous labelling of the soil with showed that the ectomycorrhizal roots, which were the strongest sinks for photosynthate, were also the most active sinks for soil nitrogen.

    • These observations highlight the close temporal coupling between tree canopy photosynthesis and a significant fraction of soil activity in forests.

  • 42.
    Irl, Severin D. H.
    et al.
    Univ Bayreuth, BayCEER, Dept Disturbance Ecol, D-95447 Bayreuth, Germany.
    Steinbauer, Manuel J.
    Univ Bayreuth, BayCEER, Dept Biogeog, D-95447 Bayreuth, Germany.
    Messinger, Jana
    Univ Bayreuth, BayCEER, Dept Biogeog, D-95447 Bayreuth, Germany.
    Blume-Werry, Gesche
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Univ Bayreuth, BayCEER, Dept Biogeog, D-95447 Bayreuth, Germany.
    Palomares-Martinez, Angel
    Parque Nacl Caldera Taburiente, El Paso 38750, Spain.
    Beierkuhnlein, Carl
    Univ Bayreuth, BayCEER, Dept Biogeog, D-95447 Bayreuth, Germany.
    Jentsch, Anke
    Univ Bayreuth, BayCEER, Dept Disturbance Ecol, D-95447 Bayreuth, Germany.
    Burned and devoured-Introduced herbivores, fire, and the endemic flora of the high-elevation ecosystem on La Palma, Canary Islands2014In: Arctic, Antarctic and Alpine research, ISSN 1523-0430, E-ISSN 1938-4246, Vol. 46, no 4, p. 859-869Article in journal (Refereed)
    Abstract [en]

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

  • 43.
    Ivarsson, Hans
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Glacial dynamics and till genesis in hilly terrain: A study in the Tallträsk area, central-northern Sweden2007Doctoral thesis, monograph (Other academic)
    Abstract [en]

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

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

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

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

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

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

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

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  • 44.
    Jacobson, Holger
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Near-surface stratigraphy of till and glacifluvium near Knaften, northern Sweden: Identifying small-scale stratigraphy using ground-penetrating radar2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

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

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    Near-surface stratigraphy of till and glacifluvium near Knaften, northern Sweden
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  • 45.
    Jansson, Mats
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hickler, T.
    Jonsson, Anders
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Links between terrestrial primary production and bacterial production and respiration in lakes in a climate gradient in subarctic Sweden2008In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 11, p. 367-376Article in journal (Refereed)
    Abstract [en]

    We compared terrestrial net primary production (NPP) and terrestrial export of dissolved organic carbon (DOC) with lake water heterotrophic bacterial activity in 12 headwater lake catchments along an altitude gradient in subarctic Sweden. Modelled NPP declined strongly with altitude and annual air temperature decreases along the altitude gradient (6ºC between the warmest and the coldest catchment). Estimated terrestrial DOC export to the lakes was closely correlated to NPP. Heterotrophic bacterial production (BP) and respiration (BR) were mainly based on terrestrial organic carbon and strongly correlated with the terrestrial DOC export. Excess respiration over PP of the pelagic system was similar to net emission of CO2 in the lakes. BR and CO2 emission made up considerably higher shares of the terrestrial DOC input in warm lakes than in cold lakes, implying that respiration and the degree of net heterotrophy in the lakes were dependant not only on terrestrial export of DOC, but also on characteristics in the lakes which changed along the gradient and affected the bacterial metabolization of allochthonous DOC. The study showed close links between terrestrial primary production, terrestrial DOC export and bacterial activity in lakes and how these relationships were dependant on air temperature. Increases in air temperature in high latitude unproductive systems might have considerable consequences for lake water productivity and release of CO2 to the atmosphere, which are ultimately determined by terrestrial primary production.

  • 46. Jelinski, Nicolas A.
    et al.
    Yoo, Kyungsoo
    Klaminder, Jonatan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Utilising a suite of isotopic and elemental tracers to constrain cryoturbation rates and patterns in a non-sorted circle2017In: Permafrost and Periglacial Processes, ISSN 1045-6740, E-ISSN 1099-1530, Vol. 28, no 4, p. 634-648Article in journal (Refereed)
    Abstract [en]

    The empirical quantification of rates of material movement in cryoturbated soils has lagged behind the physical and chemical characterisation of these materials. We applied a novel suite of elemental (C, Hg), stable isotope (C-13) and radioisotope (Cs-137, Pb-210, C-14, Be-10) tracers in conjunction with analytical and numerical models to constrain the rates and patterns of soil movement due to cryoturbation in a non-sorted circle (NSC) near Abisko, Sweden. We present the first observations of the variability of Be-10 across a patterned-ground feature, which facilitate the interpretation of subsurface peaks in soil organic carbon, Hg and C-13 and provide constraints on the surficial histories of cryoturbated materials. Apparent rates of surficial lateral movement across the NSC estimated from Cs-137 and Pb-210 (0-2.55cm year(-1)) decreased with distance from its centre and were an order of magnitude greater than rates of subduction and subsurface movement estimated from C-14 (0.04-0.27cm year(-1)). Novel estimates of the original surficial residence times of cryoturbated parcels based on excess Be-10 and Hg inventories ranged from 238 to 3940years. Our results demonstrate the utility of the spatially explicit application of elemental and radioisotopic tracer suites to constrain cryoturbation rates in Arctic patterned ground.

  • 47.
    Jørgensen, Dolly
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Rethinking rewilding2015In: Geoforum, ISSN 0016-7185, E-ISSN 1872-9398, Vol. 65, p. 482-488Article in journal (Refereed)
    Abstract [en]

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

  • 48.
    Kampezidou, Dimitra
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Spatial distribution of heavy metals in surface marine sediments in the Mediterranean region2015Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

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

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  • 49.
    Karlsson, Jan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Giesler, Reiner
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Persson, Jenny
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Lundin, Erik
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    High emission of carbon dioxide and methane during ice thaw in high latitude lakes2013In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 40, no 6, p. 1123-1127Article in journal (Refereed)
    Abstract [en]

    The winter period is seldom included in the estimates of aquatic-atmospheric carbon exchange. In this study we quantified the flux of carbon dioxide (CO2) and methane (CH4) over 3 years from 12 small subarctic lakes. The lakes accumulated consistent and high amounts of CO2 and CH4 (56–97% as CO2) over the winter, resulting in a high flux during ice thaw. The CO2 flux during ice thaw increased with increasing mean depth of the lakes, while the CH4 flux was high in lakes surrounded by mires. The ice thaw period was quantitatively important to the annual gas balances of the lakes. For nine of the lakes, 11 to 55% of the annual flux occurred during thaw. For three of the lakes with an apparent net annual CO2 uptake, including the thaw period reversed the balance from sink to source. Our results suggest that the ice thaw period is critically important for the emissions of CO2 and CH4 in small lakes.

  • 50.
    Karlsson, Jan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Verheijen, Hendricus
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Seekell, David A.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Vachon, Dominic
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Klaus, Marcus
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Ice-melt period dominates annual carbon dioxide evasion from clear-water Arctic lakes2024In: Limnology and Oceanography Letters, E-ISSN 2378-2242, Vol. 9, no 2, p. 112-118Article in journal (Refereed)
    Abstract [en]

    Current estimates of carbon dioxide (CO2) evasion from Arctic lakes are highly uncertain because few studies integrate seasonal variability, specifically evasion during spring ice-melt. We quantified annual CO2 evasion for 14 clear-water Arctic lakes in Northern Sweden through mass balance (ice-melt period) and high-frequency loggers (open-water period). On average, 80% (SD: ± 18) of annual CO2 evasion occurred within 10 d following ice-melt. The contribution of the ice-melt period to annual CO2 evasion was high compared to earlier studies of Arctic lakes (47% ± 32%). Across all lakes, the proportion of ice-melt : annual CO2 evasion was negatively related to the dissolved organic carbon concentration and positively related to the mean depth of the lakes. The results emphasize the need for measurements of CO2 exchange at ice-melt to accurately quantify CO2 evasion from Arctic lakes.

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