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Publications (10 of 96) Show all publications
Campeau, A., Bishop, K., Amvrosiadi, N., Billett, M., Garnett, M., Laudon, H., . . . Wallin, M. (2019). Current forest carbon fixation fuels stream CO2 emissions. Nature Communications, 10, Article ID 1876.
Open this publication in new window or tab >>Current forest carbon fixation fuels stream CO2 emissions
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2019 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 10, article id 1876Article in journal (Refereed) Published
Abstract [en]

Stream CO2 emissions contribute significantly to atmospheric climate forcing. While there are strong indications that groundwater inputs sustain these emissions, the specific biogeochemical pathways and timescales involved in this lateral CO2 export are still obscure. Here, via an extensive radiocarbon (C-14) characterisation of CO2 and DOC in stream water and its groundwater sources in an old-growth boreal forest, we demonstrate that the C-14-CO2 is consistently in tune with the current atmospheric C-14-CO2 level and shows little association with the C-14-DOC in the same waters. Our findings thus indicate that stream CO2 emissions act as a shortcut that returns CO2 recently fixed by the forest vegetation to the atmosphere. Our results expose a positive feedback mechanism within the C budget of forested catchments, where stream CO2 emissions will be highly sensitive to changes in forest C allocation patterns associated with climate and land-use changes.

National Category
Other Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-381845 (URN)10.1038/s41467-019-09922-3 (DOI)000465201500009 ()31015439 (PubMedID)
Funder
Swedish Research Council, 2012-3919Knut and Alice Wallenberg Foundation
Available from: 2019-04-15 Created: 2019-04-15 Last updated: 2019-05-14Bibliographically approved
Jingying, X., Buck, M., Eklöf, K., Ahmed Osman, O., Schaefer, J. K., Bishop, K., . . . Bravo, A. G. (2019). Mercury methylating microbial communities of boreal forest soils. Scientific Reports, 9, Article ID 518.
Open this publication in new window or tab >>Mercury methylating microbial communities of boreal forest soils
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2019 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 518Article in journal (Refereed) Published
Abstract [en]

The formation of the potent neurotoxic methylmercury (MeHg) is a microbially mediated process that has raised much concern because MeHg poses threats to wildlife and human health. Since boreal forest soils can be a source of MeHg in aquatic networks, it is crucial to understand the biogeochemical processes involved in the formation of this pollutant. High-throughput sequencing of 16S rRNA and the mercury methyltransferase, hgcA, combined with geochemical characterisation of soils, were used to determine the microbial populations contributing to MeHg formation in forest soils across Sweden. The hgcA sequences obtained were distributed among diverse clades, including Proteobacteria, Firmicutes, and Methanomicrobia, with Deltaproteobacteria, particularly Geobacteraceae, dominating the libraries across all soils examined. Our results also suggest that MeHg formation is linked to the composition of also non-mercury methylating bacterial communities, likely providing growth substrate (e.g. acetate) for the hgcA-carrying microorganisms responsible for the actual methylation process. While previous research focused on mercury methylating microbial communities of wetlands, this study provides some first insights into the diversity of mercury methylating microorganisms in boreal forest soils.

National Category
Forest Science
Research subject
Biology with specialization in Limnology
Identifiers
urn:nbn:se:uu:diva-346175 (URN)10.1038/s41598-018-37383-z (DOI)000456553400083 ()
Funder
Swedish Research Council, 2011-7192Swedish Research Council, 2012-3892Swedish Research Council, 2013-6978Swedish Energy Agency, 36155-1
Available from: 2018-03-15 Created: 2018-03-15 Last updated: 2019-02-18Bibliographically approved
Karlsen, R., Bishop, K., Grabs, T. J., Ottosson-Lofvenius, M., Laudon, H. & Seibert, J. (2019). The role of landscape properties, storage and evapotranspiration on variability in streamflow recessions in a boreal catchment. Journal of Hydrology, 570, 315-328
Open this publication in new window or tab >>The role of landscape properties, storage and evapotranspiration on variability in streamflow recessions in a boreal catchment
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2019 (English)In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 570, p. 315-328Article in journal (Refereed) Published
Abstract [en]

Streamflow recession analysis provides valuable insights into catchment functioning that can be related to runoff generation, storage retention and baseflow dynamics. As an integrated characteristic, recession analysis is particularly useful in catchment comparison studies to help explain drivers of spatial and temporal variability in hydrological behavior. Here, five years of hourly streamflow data from 14, partly nested, catchments within a 68 km(2) boreal forest landscape in Northern Sweden were used to explore spatiotemporal variation in hydrological processes through recession analysis. The aim of this study was to better understand spatial variation in runoff generation and storage-discharge dynamics across the landscape, as well as the relation to landscape properties. Due to high collinearity between variables, partial least square regression was used to quantify the associations between recession characteristics and catchment properties, as well as to identify key variables controlling recession behavior. We analyzed recession characteristics using both an aggregated approach including all recession data and individual recession events. The analyses based on individual recession events, indicated that catchment topography, quantified by indices such as mean slope or elevation above the stream network, is a primary control on the recession behavior during relatively high flows, whereas catchment area gains importance when flows are relatively low. The proportion of sediment and deep soils also controlled recession behavior. Furthermore, we found that recession characteristics are influenced by both evapotranspiration (ET) and proxies of antecedent catchment storage, but that the patterns were different depending on catchment properties. ET was less influential in catchments with deeper soils and larger catchment area. Shifts in recession rates were primarily related to variation in storage, with faster streamflow recessions occurring during periods with low storage. The results demonstrate the influence of catchment properties on recession behavior, and we found great value in analyzing individual recession events for an increased understanding of spatial and temporal recession characteristics. When recession properties were lumped together, the relationships to catchment characteristics were obscured. This indicates the value of more detailed analyses, at least under the strongly seasonal hydroclimatic conditions of this site.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2019
Keywords
Recession curves, Spatio-temporal variability, Landscape analysis, Runoff, Krycklan
National Category
Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:uu:diva-380487 (URN)10.1016/j.jhydrol.2018.12.065 (DOI)000460709400025 ()
Funder
Swedish Research CouncilSwedish Research Council FormasThe Kempe Foundations
Available from: 2019-04-02 Created: 2019-04-02 Last updated: 2019-04-02Bibliographically approved
Wu, P., Bishop, K., von Brömssen, C., Eklöf, K., Futter, M., Hultberg, H., . . . Åkerblom, S. (2018). Does forest harvest increase the mercury concentrations in fish?: Evidence from Swedish lakes. Science of the Total Environment, 622-623, 1353-1362
Open this publication in new window or tab >>Does forest harvest increase the mercury concentrations in fish?: Evidence from Swedish lakes
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2018 (English)In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 622-623, p. 1353-1362Article in journal (Refereed) Published
Abstract [en]

A number of studies have evaluated the effects of forest harvest on mercury (Hg) concentrations and exports in surface waters, but few studies have tested the effect from forest harvest on the change in fish Hg concentrations over the course of several years after harvest. To address this question, mercury (Hg) concentrations in perch (Perca fluviatilis) muscle tissue from five lakes were analyzed for two years before (2010-2011) and three years after (2013-2015) forest harvest conducted in 2012. Fish Hg concentrations in the clear-cut catchments (n = 1373 fish specimens) were related to temporal changes of fish Hg in reference lakes (n = 1099 fish specimen) from 19 lakes in the Swedish National Environmental Monitoring Programme. Small (length < 100 mm) and large perch (length >= 100 mm) were analyzed separately, due to changing feeding habitats of fish over growing size. There was considerable year-to-year and lake-to-lake variation in fish Hg concentrations (-14%-121%) after forest harvest in the clearcut lakes, according to our first statistical model that count for fish Hg changes. While the effect ascribed to forest harvest varied between years, after three years (in 2015), a significant increase of 26% (p < 0.0001) in Hg concentrations of large fish was identified in our second statistical model that pooled all 5 clearcut lakes. The large fish Hg concentrations in the 19 reference lakes also varied, and in 2015 had decreased by 7% (p = 0.03) relative to the concentrations in 2010-2011. The majority of the annual changes in fish Hg concentrations in the clearcut lakes after harvest were in the lower range of earlier predictions for high-latitude lakes extrapolated primarily from the effects of forest harvest operations on Hg concentrations in water. Since the risk of forest harvest impacts on Hg extends to fish and not just surface water concentrations, there is even more reason to consider Hg effects in forestry planning, alongside other ecosystem effects.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2018
Keywords
Fish hg, Forest harvest, Perch, Forestry practices, Clearcutting
National Category
Fish and Aquacultural Science
Identifiers
urn:nbn:se:uu:diva-350271 (URN)10.1016/j.scitotenv.2017.12.075 (DOI)000426349000132 ()
Funder
Swedish Research Council, 39-2013-6978Mistra - The Swedish Foundation for Strategic Environmental Research
Available from: 2018-05-15 Created: 2018-05-15 Last updated: 2018-05-15Bibliographically approved
Teutschbein, C., Grabs, T. J., Laudon, H., Karlsen, R. & Bishop, K. (2018). Simulating streamflow in ungauged basins under a changing climate: The importance of landscape characteristics. Journal of Hydrology, 561, 160-178
Open this publication in new window or tab >>Simulating streamflow in ungauged basins under a changing climate: The importance of landscape characteristics
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2018 (English)In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 561, p. 160-178Article in journal (Refereed) Published
Abstract [en]

In this paper we explored how landscape characteristics such as topography, geology, soils and land cover influence the way catchments respond to changing climate conditions. Based on an ensemble of 15 regional climate models bias-corrected with a distribution-mapping approach, present and future streamflow in 14 neighboring and rather similar catchments in Northern Sweden was simulated with the HBV model. We established functional relationships between a range of landscape characteristics and projected changes in streamflow signatures. These were then used to analyze hydrological consequences of physical perturbations in a hypothetically ungauged basin in a climate change context. Our analysis showed a strong connection between the forest cover extent and the sensitivity of different components of a catchment's hydrological regime to changing climate conditions. This emphasizes the need to redefine forestry goals and practices in advance of climate change-related risks and uncertainties.

Keywords
Hydrological modeling, Streamflow signatures, Climate change, Forest, Clear-cut, Ungauged
National Category
Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:uu:diva-387455 (URN)10.1016/j.jhydrol.2018.03.060 (DOI)000439401800013 ()
Funder
Swedish Research CouncilSwedish Research Council FormasEU, Horizon 2020, 505539
Available from: 2019-06-25 Created: 2019-06-25 Last updated: 2019-06-25Bibliographically approved
Olsson, B. A., Åkerblom, S., Bishop, K., Eklöf, K. & Ring, E. (2017). Does the harvest of logging residues and wood ash application affect the mobilization and bioavailability of trace metals?. Forest Ecology and Management, 383, 61-72
Open this publication in new window or tab >>Does the harvest of logging residues and wood ash application affect the mobilization and bioavailability of trace metals?
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2017 (English)In: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 383, p. 61-72Article in journal (Refereed) Published
Abstract [en]

Residue biomass from conventional forestry, such as slash (i.e., tree tops and branches) and stumps, are used at an increasing rate for energy purposes in Sweden. This review examined current knowledge on how extraction of forest biomass for large-scale energy production, including the practice of ash application for nutrient recycling, influences the mobility and stocks of trace metals in the forest environment at different time scales. The study focussed on Swedish energy production systems and contemporary forest management practices, as well as the heavy metals lead (Pb), cadmium (Cd) and mercury (Hg). The historic accumulation of these elements in forest soils has mainly originated from diffuse, long-term atmospheric deposition. There is little conclusive evidence that slash harvest generally increases the risk for mobilization of trace metals from soils during the regeneration phase, compared with stem-only harvesting. However, microbial transformation of mercury into the highly toxic methyl mercury (MeHg) species is facilitated in suboxic soil conditions that may increase during the regeneration,phase. Therefore it has been hypothesized that stump harvest could result in increased mercury methylation and transport to surface waters, owing to stump harvest effects on soil physical conditions and hydrological pathways. The few studies available on the stump harvest effects of Hg showed no consistent difference in runoff from clear felled and stump harvested catchments compared to clear-felled and soil-scarified catchments in terms of concentrations or fluxes of MeHg. Assuming that the highest trace metal concentrations in wood ash recommended by the Swedish Forest Authority are not exceeded, wood ash application does not currently increase metal loads at the national scale, because trace metal export in harvested biomass is much larger than that returned in wood ash. The net load of Pb, Cd, and Cu will not increase at the local scale if ash doses do not greatly exceed the compensation for nutrients exported in harvested biomass. Biomass harvest and ash application have negligible effects on the load of mercury to forest soils. A large number of studies have examined the effects of wood ash on trace metal content in soil, water and biota. Most studies showed no effect of wood ash application. When increased concentrations were found (Cd, Cr, Cu, Zn), this was in soils where concentrations remained well below harmful levels. Relatively fewer reports of increased concentrations are reported for soil water and plants, and no effects were reported for edible berries or fungi.

Keywords
Bioenergy, Cadmium, Mercury, Lead, Stump harvesting
National Category
Forest Science
Identifiers
urn:nbn:se:uu:diva-312027 (URN)10.1016/j.foreco.2016.09.017 (DOI)000389163500007 ()
Funder
Swedish Energy Agency
Available from: 2017-01-05 Created: 2017-01-04 Last updated: 2017-11-29Bibliographically approved
Teutschbein, C., Sponseller, R. A., Grabs, T., Blackburn, M., Boyer, E. W., Hytteborn, J. K. & Bishop, K. (2017). Future Riverine Inorganic Nitrogen Load to the Baltic Sea From Sweden: An Ensemble Approach to Assessing Climate Change Effects. Global Biogeochemical Cycles, 31(11), 1674-1701
Open this publication in new window or tab >>Future Riverine Inorganic Nitrogen Load to the Baltic Sea From Sweden: An Ensemble Approach to Assessing Climate Change Effects
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2017 (English)In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 31, no 11, p. 1674-1701Article in journal (Refereed) Published
Abstract [en]

The dramatic increase of bioreactive nitrogen entering the Earth’s ecosystems continues toattract growing attention. Increasingly large quantities of inorganic nitrogen are flushed from land towater, accelerating freshwater, and marine eutrophication. Multiple, interacting, and potentiallycountervailing drivers control the future hydrologic export of inorganic nitrogen. In this paper, we attempt toresolve these land-water interactions across boreal/hemiboreal Sweden in the face of a changing climatewith help of a versatile modeling framework to maximize the information value of existing measurementtime series. We combined 6,962 spatially distributed water chemistry observations spread over 31 years withdaily streamflow and air temperature records. An ensemble of climate model projections, hydrologicalsimulations, and several parameter parsimonious regression models was employed to project future riverineinorganic nitrogen dynamics across Sweden. The median predicted increase in total inorganic nitrogenexport from Sweden (2061–2090) due to climate change was 14% (interquartile range 0–29%), based on theensemble of 7,500 different predictions for each study site. The overall export as well as the seasonal patternof inorganic nitrogen loads in a future climate are mostly influenced by longer growing seasons and morewinter flow, which offset the expected decline in spring flood. The predicted increase in inorganic nitrogenloading due to climate change means that the political efforts for reducing anthropogenic nitrogen inputsneed to be increased if ambitions for reducing the eutrophication of the Baltic Sea are to be achieved.

Place, publisher, year, edition, pages
American Geophysical Union (AGU), 2017
Keywords
streamflow, climate change, nitrogen, Baltic Sea, Sweden, eutrophication
National Category
Oceanography, Hydrology and Water Resources Geosciences, Multidisciplinary Climate Research
Research subject
Hydrology
Identifiers
urn:nbn:se:uu:diva-335388 (URN)10.1002/2016GB005598 (DOI)000418082000004 ()08866236 (ISBN)
Available from: 2017-12-05 Created: 2017-12-05 Last updated: 2018-01-29Bibliographically approved
Osterwalder, S., Bishop, K., Alewell, C., Fritsche, J., Laudon, H., Akerblom, S. & Nilsson, M. B. (2017). Mercury evasion from a boreal peatland shortens the timeline for recovery from legacy pollution. Scientific Reports, 7, Article ID 16022.
Open this publication in new window or tab >>Mercury evasion from a boreal peatland shortens the timeline for recovery from legacy pollution
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2017 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 16022Article in journal (Refereed) Published
Abstract [en]

Peatlands are a major source of methylmercury that contaminates downstream aquatic food webs. The large store of mercury (Hg) in peatlands could be a source of Hg for over a century even if deposition is dramatically reduced. However, the reliability of Hg mass balances can be questioned due to missing long-term land-atmosphere flux measurements. We used a novel micrometeorological system for continuous measurement of Hg peatland-atmosphere exchange to derive the first annual Hg budget for a peatland. The evasion of Hg (9.4 mu g m(-2) yr(-1)) over the course of a year was seven times greater than stream Hg export, and over two times greater than wet bulk deposition to the boreal peatland. Measurements of dissolved gaseous Hg in the peat pore water also indicate Hg evasion. The net efflux may result from recent declines in atmospheric Hg concentrations that have turned the peatland from a net sink into a source of atmospheric Hg. This net Hg loss suggests that open boreal peatlands and downstream ecosystems can recover more rapidly from past atmospheric Hg deposition than previously assumed. This has important implications for future levels of methylmercury in boreal freshwater fish and the estimation of historical Hg accumulation rates from peat profiles.

National Category
Climate Research
Identifiers
urn:nbn:se:uu:diva-361243 (URN)10.1038/s41598-017-16141-7 (DOI)000416118300046 ()29167528 (PubMedID)
Funder
Swedish Research Council, 2009-15586-68819-37
Available from: 2018-09-26 Created: 2018-09-26 Last updated: 2018-09-26Bibliographically approved
Habiba, G., Abebe, G., Bravo, A. G., Ermias, D., Staffan, Ǻ. & Bishop, K. (2017). Mercury Human Exposure in Populations Living Around Lake Tana (Ethiopia). Biological Trace Element Research, 175(2), 237-243
Open this publication in new window or tab >>Mercury Human Exposure in Populations Living Around Lake Tana (Ethiopia)
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2017 (English)In: Biological Trace Element Research, ISSN 0163-4984, E-ISSN 1559-0720, Vol. 175, no 2, p. 237-243Article in journal (Refereed) Published
Abstract [en]

A survey carried out in Lake Tana in 2015 found that Hg levels in some fish species exceeded internationally accepted safe levels for fish consumption. The current study assesses human exposure to Hg through fish consumption around the Lake Tana. Of particular interest was that a dietary intake of fishes is currently a health risk for Bihar Dar residents and anglers. Hair samples were collected from three different groups: anglers, college students and teachers, and daily laborers. A questionary includes gender, age, weight, activity. Frequency of fish consumption and origin of the eaten fish were completed by each participant. Mercury concentrations in hair were significantly higher (P value <0.05) for anglers (mean ± standard deviation 0.120 ± 0.199 μg/g) than college students (mean ± standard deviation 0.018 ± 0.039 μg/g) or daily workers (mean ± standard deviation 16 ± 9.5 ng/g). Anglers consumed fish more often than daily workers and college group. Moreover, there was also a strong correlation (P value <0.05) between the logarithms of total mercury and age associated with mercury concentration in scalp hair. Mercury concentrations in the hair of men were on average twice the value of the women. Also, users of skin lightening soap on a daily basis had 2.5 times greater mercury in scalp hair than non-users. Despite the different sources of mercury exposure mentioned above, the mercury concentrations of the scalp hair of participants of this study were below levels deemed to pose a threat to health.

Keywords
Bihar Dar, Fish, Hair, Mercury, Occupation, Residents
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-304389 (URN)10.1007/s12011-016-0745-9 (DOI)000392336200001 ()27278962 (PubMedID)
Available from: 2016-10-05 Created: 2016-10-05 Last updated: 2017-11-30Bibliographically approved
Campeau, A., Wallin, M., Giesler, R., Löfgren, S., Mörth, C.-M., Schiff, S., . . . Bishop, K. (2017). Multiple sources and sinks of dissolved inorganic carbon across Swedish streams, refocusing the lens of stable C isotopes. Scientific Reports, 7, Article ID 9158.
Open this publication in new window or tab >>Multiple sources and sinks of dissolved inorganic carbon across Swedish streams, refocusing the lens of stable C isotopes
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2017 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 9158Article in journal (Refereed) Published
Abstract [en]

It is well established that stream dissolved inorganic carbon (DIC) fluxes play a central role in the global C cycle, yet the sources of stream DIC remain to a large extent unresolved. Here, we explore large-scale patterns in delta C-13-DIC from streams across Sweden to separate and further quantify the sources and sinks of stream DIC. We found that stream DIC is governed by a variety of sources and sinks including biogenic and geogenic sources, CO2 evasion, as well as in-stream processes. Although soil respiration was the main source of DIC across all streams, a geogenic DIC influence was identified in the northernmost region. All streams were affected by various degrees of atmospheric CO2 evasion, but residual variance in delta C-13-DIC also indicated a significant influence of in-stream metabolism and anaerobic processes. Due to those multiple sources and sinks, we emphasize that simply quantifying aquatic DIC fluxes will not be sufficient to characterise their role in the global C cycle.

National Category
Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-328530 (URN)10.1038/s41598-017-09049-9 (DOI)000408285200002 ()28831088 (PubMedID)
Funder
Swedish Research Council, 2012-3919Swedish Research Council, 2007-3841Swedish Research Council, 2013-5001Swedish Research Council Formas, 214-2008-202Knut and Alice Wallenberg Foundation
Available from: 2017-08-25 Created: 2017-08-25 Last updated: 2019-04-15Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-8057-1051

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