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  • 1.
    Andrén, O.
    et al.
    Departments of Ecology and Environmental Research, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Schnürer, Johan
    Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Barley straw decomposition with varied levels of microbial grazing by Folsomia fimetaria (L.) (Collembola, Isotomidae)1985In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 68, no 1, p. 57-62Article in journal (Refereed)
    Abstract [en]

    Folsomia fimetaria (L.) were added (0, 5, 10, 20 animals) to 0.100 g barley straw which had been inoculated 10 days (244 h) earlier with a natural soil microflora. Respiration (CO2 evolution) was monitored continuously. Mass loss, fungal standing crop (total and FDA-active), bacterial and protozoan biomass were estimated 42 days (1,000 h) after microbial inoculation. The degree of surface cover by hyphae was surveyed at regular intervals. No significant differences (P>0.05) were found in respiration, mass loss or microbial biomass, but the density of surface hyphae were reduced by addition of Collembola. Fungal production was low, less than 5% of the estimated microbial production, and could not account for all collembolan growth during incubation. F. fimetaria appeared to consume mainly bacteria and protozoa, and had little impact on carbon mineralization.

  • 2.
    Baskaran, Preetisri
    et al.
    Swedish University of Agricultural Sciences, Department of Ecology, Uppsala, Sweden.
    Ekblad, Alf
    Örebro University, School of Science and Technology.
    Soucémarianadin, Laure N.
    CNRS, Laboratoire de Géologie de l'ENS, Ecole Normale Supérieure, Paris, France; Umeå University, Department of Medical Biochemistry and Biophysics, Umeå, Sweden.
    Hyvönen, Riitta
    Swedish University of Agricultural Sciences, Department of Ecology, Uppsala, Sweden.
    Schleucher, Jürgen
    Umeå University, Department of Medical Biochemistry and Biophysics, Umeå, Sweden.
    Lindahl, Björn D.
    Swedish University of Agricultural Sciences, Department of Soil and Environment, Uppsala, Sweden.
    Nitrogen dynamics of decomposing Scots pine needle litter depends on colonizing fungal species2019In: FEMS Microbiology Ecology, ISSN 0168-6496, E-ISSN 1574-6941, Vol. 95, no 6, article id fiz059Article in journal (Refereed)
    Abstract [en]

    In boreal ecosystems plant production is often limited by low availability of nitrogen. Nitrogen retention in below-ground organic pools plays an important role in restricting recirculation to plants and thereby hampers forest production. Saprotrophic fungi are commonly assigned to different decomposer strategies, but how these relate to nitrogen cycling remains to be understood. Decomposition of Scots pine needle litter was studied in axenic microcosms with the ligninolytic litter decomposing basidiomycete Gymnopus androsaceus or the stress tolerant ascomycete Chalara longipes. Changes in chemical composition were followed by 13C CP/MAS NMR spectroscopy and nitrogen dynamics was assessed by the addition of a 15N tracer. Decomposition by C. longipes resulted in nitrogen retention in non-hydrolysable organic matter, enriched in aromatic and alkylic compounds, whereas the ligninolytic G. androsaceus was able to access this pool, counteracting nitrogen retention. Our observations suggest that differences in decomposing strategies between fungal species play an important role in regulating nitrogen retention and release during litter decomposition, implying that fungal community composition may impact nitrogen cycling at the ecosystem level.

  • 3.
    Boström, Björn
    et al.
    Örebro University, Department of Natural Sciences.
    Comstedt, Daniel
    Örebro University, Department of Natural Sciences.
    Ekblad, Alf
    Örebro University, Department of Natural Sciences.
    Can isotopic fractionation during respiration explain the 13C-enriched sporocarps of ectomycorrhizal and saprotrophic fungi?2008In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 177, no 4, p. 1012-1019Article in journal (Refereed)
    Abstract [en]

    • The mechanism behind the 13C enrichment of fungi relative to plant materials is unclear and constrains the use of stable isotopes in studies of the carbon cycle in soils.

    • Here, we examined whether isotopic fractionation during respiration contributes to this pattern by comparing δ13C signatures of respired CO2, sporocarps and their associated plant materials, from 16 species of ectomycorrhizal or saprotrophic fungi collected in a Norway spruce forest.

    • The isotopic composition of respired CO2 and sporocarps was positively correlated. The differences in δ13C between CO2 and sporocarps were generally small, < ±1‰ in nine out of 16 species, and the average shift for all investigated species was 0.04‰. However, when fungal groups were analysed separately, three out of six species of ectomycorrhizal basidiomycetes respired 13C-enriched CO2 (up to 1.6‰), whereas three out of five species of polypores respired 13C-depleted CO2 (up to 1.7‰; P < 0.05). The CO2 and sporocarps were always 13C-enriched compared with wood, litter or roots.

    • Loss of 13C-depleted CO2 may have enriched some species in 13C. However, that the CO2 was consistently 13C-enriched compared with plant materials implies that other processes must be found to explain the consistent 13C-enrichment of fungal biomass compared with plant materials.

  • 4.
    Dawes, Melissa A.
    et al.
    Mountain Ecosystems, WSL Institute for Snow and Avalanche Research-SLF, Davos Dorf, Switzerland .
    Hagedorn, Frank
    Forest Soils and Biogeochemistry, Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Birmensdorf, Switzerland .
    Handa, Ira Tanya
    Université du Québec à Montréal (UQÀM), Montreal, Canada .
    Streit, Kathrin
    Paul Scherrer Institute, Villigen, Switzerland .
    Ekblad, Alf
    Örebro University, School of Science and Technology.
    Rixen, Christian
    Mountain Ecosystems, WSL Institute for Snow and Avalanche Research-SLF, Davos Dorf, Switzerland .
    Körner, Christian
    University of Basel, Basel, Switzerland .
    Hättenschwiler, Stephan
    Centre d’Ecologie Fonctionnelle et Evolutive (CEFE), Montpellier, France.
    An alpine treeline in a carbon dioxide-rich world: synthesis of a nine-year free-air carbon dioxide enrichment study2013In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 171, no 3, p. 623-637Article in journal (Refereed)
    Abstract [en]

    We evaluated the impacts of elevated CO2 in a treeline ecosystem in the Swiss Alps in a 9-year free-air CO2 enrichment (FACE) study. We present new data and synthesize plant and soil results from the entire experimental period. Light-saturated photosynthesis (A max) of ca. 35-year-old Larix decidua and Pinus uncinata was stimulated by elevated CO2 throughout the experiment. Slight down-regulation of photosynthesis in Pinus was consistent with starch accumulation in needle tissue. Above-ground growth responses differed between tree species, with a 33 % mean annual stimulation in Larix but no response in Pinus. Species-specific CO2 responses also occurred for abundant dwarf shrub species in the understorey, where Vaccinium myrtillus showed a sustained shoot growth enhancement (+11 %) that was not apparent for Vaccinium gaultherioides or Empetrum hermaphroditum. Below ground, CO2 enrichment did not stimulate fine root or mycorrhizal mycelium growth, but increased CO2 effluxes from the soil (+24 %) indicated that enhanced C assimilation was partially offset by greater respiratory losses. The dissolved organic C (DOC) concentration in soil solutions was consistently higher under elevated CO2 (+14 %), suggesting accelerated soil organic matter turnover. CO2 enrichment hardly affected the C–N balance in plants and soil, with unaltered soil total or mineral N concentrations and little impact on plant leaf N concentration or the stable N isotope ratio. Sustained differences in plant species growth responses suggest future shifts in species composition with atmospheric change. Consistently increased C fixation, soil respiration and DOC production over 9 years of CO2 enrichment provide clear evidence for accelerated C cycling with no apparent consequences on the N cycle in this treeline ecosystem.

  • 5.
    Ekblad, Alf
    et al.
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    Högberg, Peter
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    Analysis of delta C-13 of CO2 distinguishes between microbial respiration of added C-4-sucrose and other soil respiration in a C-3-ecosystem2000In: Plant and Soil, ISSN 0032-079X, E-ISSN 1573-5036, Vol. 219, no 1-2, p. 197-209Article in journal (Refereed)
    Abstract [en]

    The main aim of this study was to test various hypotheses regarding the changes in δ13C of emitted CO2 that follow the addition of C4-sucrose to the soil of a C3-ecosystem. It forms part of an experimental series designed to assess whether or not the contributions from C3-respiration (root and microbial) and C4-respiration (microbial) to total soil respiration can be calculated from such changes. A series of five experiments, three on sieved (root-free) mor-layer material, and two in the field with intact mor-layer (and consequently with active roots), were performed. Both in the experiments on sieved mor-layer and the field experiments, we found a C4-sucrose-induced increase in C3-respiration that accounted for between 30% and 40% of the respiration increase 1 h after sucrose addition. When the course of C3-, C4- and total respiration was followed in sieved material over four days following addition of C4-sucrose, the initially increased respiration of C3-C was transient, passing within less than 24 h. In a separate pot experiment, neither ectomycorrhizal Pinus sylvestrisL. roots nor non-mycorrhizal roots of this species showed respiratory changes in response to exogenous sucrose. No shift in the δ13C of the evolved CO2 after adding C3-sucrose to sieved mor-layer material was found, confirming that the sucrose-induced increase in respiration of endogenous C was not an artefact of discrimination against 13C during respiration. Furthermore, we conclude that the C4-sucrose induced transient increase in C3-respiration is most likely the result of accelerated turnover of C in the microbial biomass. Thus, neither respiration of mycorrhizal roots, nor processes discriminating against δ13C were likely sources of error in the field. The estimated δ13C of evolved soil CO2 in three field experiments lay between −25.2‰ and −23.6‰. The study shows that we can distinguish between CO2 evolved from microbial mineralisation of added C4-sucrose, and CO2 evolved from endogenous carbon sources (roots and microbial respiration).

  • 6.
    Ekblad, Alf
    et al.
    Örebro University, School of Science and Technology. Swedish University of Agricultural Sciences, Umeå, Sweden.
    Högberg, Peter
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    Natural abundance of C-13 in CO2 respired from forest soils reveals speed of link between tree photosynthesis and root respiration2001In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 127, no 3, p. 305-308Article in journal (Refereed)
    Abstract [en]

    Soil respiration from a boreal mixed coniferous forest showed large seasonal variation in natural abundance of 13C, ranging from –21.6‰ to –26.5‰. We tested if weather conditions could explain this variation in δ13C of respired CO2, and found that the air relative humidity 1–4 days before the days of CO2 sampling best explained the variation. This suggested that high δ13C values were caused by effects of air humidity on isotope fractionation during photosynthesis and that it took 1–4 days for the C from canopy photosynthesis of 20–25 m trees to become available for root/rhizosphere respiration. We calculated that these new photoassimilates could account for at least 65% of total soil respiration.

  • 7.
    Ekblad, Alf
    et al.
    Örebro University, School of Science and Technology. Swedish University of Agricultural Sciences, Umeå, Sweden.
    Nordgren, Anders
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    Is growth of soil microorganisms in boreal forests limited by carbon or nitrogen availability?2002In: Plant and Soil, ISSN 0032-079X, E-ISSN 1573-5036, Vol. 242, no 1, p. 115-122Article in journal (Refereed)
    Abstract [en]

    To study whether the biomass of soil microorganisms in a boreal Pinus sylvestris-Vaccinium vitis-idaea forest was limited by the availability of carbon or nitrogen, we applied sucrose from sugar cane, a C4 plant, to the organic mor-layer of the C3–C dominated soil. We can distinguish between microbial mineralization of the added sucrose and respiration of endogenous carbon (root and microbial) by using the C4-sucrose as a tracer, exploiting the difference in natural abundance of 13C between the added C4-sucrose (δ13C −10.8‰) and the endogenous C3–carbon (δ13C −26.6 ‰). In addition to sucrose, NH4Cl (340 kg N ha−1) was added factorially to the mor-layer. We followed the microbial activity for nine days after the treatments, by in situ sampling of CO2 evolved from the soil and mass spectrometric analyses of δ13C in the CO2. We found that microbial biomass was limited by the availability of carbon, rather than nitrogen availability, since there was a 50% increase in soil respiration in situ between 1 h and 5 days after adding the sucrose. However, no further increase was observed unless nitrogen was also added. Analyses of the δ13C ratios of the evolved CO2 showed that increases in respiration observed between 1 h and 9 days after the additions could be accounted for by an increase in mineralization of the added C4–C.

  • 8.
    Ekblad, Alf
    et al.
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    Nyberg, Gert
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    Högberg, Peter
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    C-13-discrimination during microbial respiration of added C-3-, C-4- and C-13-labelled sugars to a C-3-forest soil2002In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 131, no 2, p. 245-249Article in journal (Refereed)
    Abstract [en]

    We tested whether 13C-discrimination during microbial respiration, or during CO2 sampling in the field, can explain changes observed in the δ13C of emitted CO2 that follow the addition of C4-sucrose, as a microbial substrate, to the soil of a C3-ecosystem. We approached this problem by adding C3-glucose (δ13C=–23.4‰), C4-sucrose (–10.8‰) or 13C-labelled glucose (103.7‰) to the intact mor layer, the upper organic soil (–26.5‰, bulk soil organic matter), of a boreal Pinus sylvestris L. forest. If 13C-discrimination is significant, it should generate illusory differences in the calculated contributions from the added C and endogenous C3-C to total soil respiration, when C4-sucrose or 13C-labelled glucose is added. Further, if discrimination occurs, we should also be able to detect a shift in the δ13C of respired CO2 after the addition of C3-glucose. The addition of the three sugar solutions gave similar increases in soil respiration (up to a doubling 1 h after the additions), while the addition of water gave no increase in respiration. There was no change in δ13C of the emitted CO2 after additions of H2O or C3-glucose. In contrast, the addition of C4-sucrose and 13C-labelled glucose gave δ13C values of evolved CO2 that were 4.5‰ and 30.3‰ higher than the pre-sugar values, respectively. The calculated respiration rates of the added carbon sources, C4-C or 13C-labelled C, were very similar. Also, we found very similar sugar-induced increases in respiration of endogenous C3-C in the plots supplied with C4-sucrose and 13C-labelled glucose, accounting for about 50% of the total increase in respiration 1 h after addition. Our results confirm that any microbial 13C-discrimination during respiration is minor.

  • 9.
    Elmarghani, Ebraheem [Ibrahim] Daabag
    et al.
    Örebro University, School of Science and Technology.
    Poonlapthawee, Sirirat
    Örebro University, School of Science and Technology.
    Olsson, Per-Erik
    Örebro University, School of Science and Technology.
    Jass, Jana
    Örebro University, School of Science and Technology.
    Antibiotic resistance in fecal indicator bacteria in Hjälmaren lake systemManuscript (preprint) (Other academic)
    Abstract [en]

    Background: Increasing levels of multi-antibiotic resistant bacteria are ound in the environment, causing serious concerns for treatment of infectious diseases. his increase is believed to be due to release of antibiotic resistant bacteria and election pressure resulting from pharmaceuticals in the environment.

    Objectives: We evaluated the presence of multi-antibiotic resistant fecal ndicator bacteria from the surface waters of a recipient river and lake downstream of he wastewater treatment plant (WWTP) in Sweden.

    Methods: Surface waters from Svartån river and Hjälmaren lake in Sweden were ampled in 2010 and 2011. The waters were analyzed for fecal indicator bacteria Escherichia coli, enterococci) by membrane filtration and selective agar plating. E. coli nd enterococci were evaluated by Etest for resistance to tetracycline, chloramphenicol, alidixic acid, trimethoprim-sulfamethoxazole, ciprofloxacin, cefotaxime, ceftazidime, eropenem, imipenem, ampicillin, vancomycin, gentamycin and streptomycin.

    Results: The highest concentration of E. coli and enterococci were found in vartån river at Naturens Hus closest site downstream of the WWTP. Tetracycline resistance as the most prominent in both fecal indicator bacteria. Over the two years, there was 42% (13/31) and 24% (7/29) multi-antibiotic resistant (≥2 antibiotics) E. coli and nterococci, respectively. Furthermore, we identified one ESBL and one AmpC hyperproducing . coli in 2010 and vancomycin (vanA) resistant E. faecium in 2011.

    Conclusions: The presence, of multi-antibiotic resistant strains of fecal ndicator organisms in regions considered predominantly clean, is of great concern. While t currently may not be a major threat in the region, it is demonstrating the accelerating incidence and spread of antibiotic resistance worldwide.

  • 10.
    Elmarghani, Ebraheem M.
    Örebro University, School of Science and Technology.
    Enterococcal distribution and responses toenvironmental waters2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The release of antibiotics and pharmaceuticals into environmental waters contribute to the increasing risk of antibiotic resistant bacteria. The spread of antibiotic resistant bacteria in the environment increases the health risks to the community. Enterococci are fecal indicator bacteria (FIB) in aquatic environments for determining water quality. In order to study enterococcal distribution and their response to environmental waters, we first screened for fecal indicator bacteria and their antibiotic resistance. Samples were collected from different locations of inland waters near Örebro city, Sweden at 4 time points during 2010 and 2011. Waters were filtered and the bacteria were cultured on selective media. We observed that the distribution of fecal indicator bacteria was higher at Svartån at Naturens Hus (≤705 CFU/100 ml for enterococci and ≤5867 CFU/100 for E. coli) near the effluent of the wastewater treatment plant (WWTP) than other locations tested. The eastern side of Hjälmaren lake, Storhjälmaren, had the lowest number of FIB (0 CFU/100 ml for enterococci and ≤2 CFU/100 ml for E.coli). Isolated E. coli, E. faecalis and E. faecium were evaluated for antibiotic resistance. We observed that ≤18% of E. coli environmental isolates and 12% of E. faecium and E. feacalis isolates were resistant to antibiotics during 2010 and 2011. Fifteen percent of these were multi antibiotic resistant (MAR) enterococci in 2010 and 31% in 2011. Tetracycline resistance was the most widespread antibiotic resistance found in FIB insolates. Extended spectrum β-lactamase expressing E. coli strains were found to also be MAR. Vancomycin and imipenem resistance was found in E. faecium isolate. Our results suggest that WWTP contributes to the distribution of FIB and antibiotic resistance. Secondly we aimed to evaluate the cellular responses of human and bacterial cells in environmental waters. We found that the pro-inflammatory response (IL-1β and TNF-α) of THP-1 cell was significantly higher in Svartån at Naturens Hus downstream of WWTP than the other locations. Based on this we evaluated E. feacalis responses to the same water. There were no statistical significant changes in gene response found in E. feacalis isolates, suggesting that environmental waters contain unidentified substances can effect on human cells responses but not bacteria. In this report we conclude that transferring of MAR strains in the environmental waters were increased annually in enterococci and E. feacalis did not initiate a response to the unknown substances that are present in river. 

    List of papers
    1. Antibiotic resistance in fecal indicator bacteria in Hjälmaren lake system
    Open this publication in new window or tab >>Antibiotic resistance in fecal indicator bacteria in Hjälmaren lake system
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Background: Increasing levels of multi-antibiotic resistant bacteria are ound in the environment, causing serious concerns for treatment of infectious diseases. his increase is believed to be due to release of antibiotic resistant bacteria and election pressure resulting from pharmaceuticals in the environment.

    Objectives: We evaluated the presence of multi-antibiotic resistant fecal ndicator bacteria from the surface waters of a recipient river and lake downstream of he wastewater treatment plant (WWTP) in Sweden.

    Methods: Surface waters from Svartån river and Hjälmaren lake in Sweden were ampled in 2010 and 2011. The waters were analyzed for fecal indicator bacteria Escherichia coli, enterococci) by membrane filtration and selective agar plating. E. coli nd enterococci were evaluated by Etest for resistance to tetracycline, chloramphenicol, alidixic acid, trimethoprim-sulfamethoxazole, ciprofloxacin, cefotaxime, ceftazidime, eropenem, imipenem, ampicillin, vancomycin, gentamycin and streptomycin.

    Results: The highest concentration of E. coli and enterococci were found in vartån river at Naturens Hus closest site downstream of the WWTP. Tetracycline resistance as the most prominent in both fecal indicator bacteria. Over the two years, there was 42% (13/31) and 24% (7/29) multi-antibiotic resistant (≥2 antibiotics) E. coli and nterococci, respectively. Furthermore, we identified one ESBL and one AmpC hyperproducing . coli in 2010 and vancomycin (vanA) resistant E. faecium in 2011.

    Conclusions: The presence, of multi-antibiotic resistant strains of fecal ndicator organisms in regions considered predominantly clean, is of great concern. While t currently may not be a major threat in the region, it is demonstrating the accelerating incidence and spread of antibiotic resistance worldwide.

    National Category
    Ecology Microbiology
    Research subject
    Microbiology; Enviromental Science
    Identifiers
    urn:nbn:se:oru:diva-28742 (URN)
    Available from: 2013-04-22 Created: 2013-04-22 Last updated: 2017-10-17Bibliographically approved
    2. The impact of environmental waters on cellular response in human and bacterial cells
    Open this publication in new window or tab >>The impact of environmental waters on cellular response in human and bacterial cells
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    The escalating frequency of pharmaceutical and antibiotic use contributes to the increasing amounts of these substances being released into the environment. While wastewater treatment plants (WWTP) effectively remove substantial amounts of contaminating substances, some are persistent and are released into the environment. It is not possible to identify all of the potentially bioactive substances released into the environment, therefore it is more rational to explore the biological effects of the waters to determine prospective health hazards. The present study evaluates the cellular response of human and bacterial cells (Enterococcus faecalis) to environmental waters upstream anddownstream of the WWTP near the  city of Örebro, Sweden. Water samples werecollected from 4 sites during May 2011. These included a site upstream in Svartån at Tekniska Kvarn, downstream at Naturens Hus near the WWTP, in the recipient Hjälmaren lake and in Ånnaboda lake (control site). THP-1 monocytes exhibited a significant increase in secretion of pro-inflammatory cytokines TNF-α and IL-β when treated with waters from Svartån at Naturens Hus, justdownstream of the WWTP outlet. Water from this site was thereafter tested using an environmental E. faecalis isolate and the stress response, virulence and antibiotic gene expression was evaluated by qPCR. There was no statistically significant effect observed on the selected genes in E. faecalis when treated with the environmental waters compared to MQ water. Thus the waters contained substances that influence inflammatory response in human cells in vitro but did not affect fecal indicator enterococci.

    National Category
    Ecology Microbiology
    Research subject
    Enviromental Science; Microbiology
    Identifiers
    urn:nbn:se:oru:diva-28789 (URN)
    Available from: 2013-04-24 Created: 2013-04-24 Last updated: 2017-10-17Bibliographically approved
  • 11.
    Elmarghani, Ibrahim [Ebraheem]
    et al.
    Örebro University, School of Science and Technology.
    Elmarghani, Ahmed
    Biotechnology research center Tripoli, Libya PO Box 3310.
    Olsson, Per-Erik
    Örebro University, School of Science and Technology.
    Jass, Jana
    Örebro University, School of Science and Technology.
    The impact of environmental waters on cellular response in human and bacterial cellsManuscript (preprint) (Other academic)
    Abstract [en]

    The escalating frequency of pharmaceutical and antibiotic use contributes to the increasing amounts of these substances being released into the environment. While wastewater treatment plants (WWTP) effectively remove substantial amounts of contaminating substances, some are persistent and are released into the environment. It is not possible to identify all of the potentially bioactive substances released into the environment, therefore it is more rational to explore the biological effects of the waters to determine prospective health hazards. The present study evaluates the cellular response of human and bacterial cells (Enterococcus faecalis) to environmental waters upstream anddownstream of the WWTP near the  city of Örebro, Sweden. Water samples werecollected from 4 sites during May 2011. These included a site upstream in Svartån at Tekniska Kvarn, downstream at Naturens Hus near the WWTP, in the recipient Hjälmaren lake and in Ånnaboda lake (control site). THP-1 monocytes exhibited a significant increase in secretion of pro-inflammatory cytokines TNF-α and IL-β when treated with waters from Svartån at Naturens Hus, justdownstream of the WWTP outlet. Water from this site was thereafter tested using an environmental E. faecalis isolate and the stress response, virulence and antibiotic gene expression was evaluated by qPCR. There was no statistically significant effect observed on the selected genes in E. faecalis when treated with the environmental waters compared to MQ water. Thus the waters contained substances that influence inflammatory response in human cells in vitro but did not affect fecal indicator enterococci.

  • 12.
    Franklin, Oskar
    et al.
    Swedish University of Agricultural Sciences, Uppsala, Sweden .
    Högberg, Peter
    Swedish University of Agricultural Sciences, Umeå, Sweden .
    Ekblad, Alf
    Örebro University, School of Science and Technology.
    Ågren, Göran I
    Swedish University of Agricultural Sciences, Uppsala, Sweden .
    Pine forest floor carbon accumulation in response to N and PK additions: Bomb C-14 modelling and respiration studies2003In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 6, no 7, p. 644-658Article in journal (Refereed)
    Abstract [en]

    The addition of nitrogen via deposition alters the carbon balance of temperate forest ecosystems by affecting both production and decomposition rates. The effects of 20 years of nitrogen (N) and phosphorus and potassium (PK) additions were studied in a 40-year-old pine stand in northern Sweden. Carbon fluxes of the forest floor were reconstructed using a combination of data on soil 14C, tree growth, and litter decomposition. N-only additions caused an increase in needle litterfall, whereas both N and PK additions reduced long-term decomposition rates. Soil respiration measurements showed a 40% reduction in soil respiration for treated compared to control plots. The average age of forest floor carbon was 17 years. Predictions of future soil carbon storage indicate an increase of around 100% in the next 100 years for the N plots and 200% for the NPK plots. As much as 70% of the increase in soil carbon was attributed to the decreased decomposition rate, whereas only 20% was attributable to increased litter production. A reduction in decomposition was observed at a rate of N addition of 30 kg C ha−1 y−1, which is not an uncommon rate of N deposition in central Europe. A model based on the continuous-quality decomposition theory was applied to interpret decomposer and substrate parameters. The most likely explanations for the decreased decomposition rate were a fertilizer-induced increase in decomposer efficiency (production-to-assimilation ratio), a more rapid rate of decrease in litter quality, and a decrease in decomposer basic growth rate.

  • 13.
    Högberg, Peter
    et al.
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    Ekblad, Alf
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    Substrate-induced respiration measured in situ in a C-3-plant ecosystem using additions of C-4-sucrose1996In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 28, no 9, p. 1131-1138Article in journal (Refereed)
    Abstract [en]

    We added sucrose derived from sugar cane, a tropical C4-plant, to the soil of a temperate C3-forest plant system. The combined measurement of CO2 respiration rate and 13C natural abundance of CO2 enabled a distinction to be made between C3- and C4-respiration, which offered new possibilities to analyze basal respiration and substrate-induced respiration (SIR) in the field. In tests in the laboratory, through-flow systems were used, while in the field the stationary gas phase under soil covers was sampled. Results from the laboratory and in the field were similar with an average SIR response of 2.2 (range 1.7–2.7) times the basal respiration. The change in δ13C after addition of C4-surcrose was less than expected from the increase in respiration rate. Calculations showed that there was an increased efflux of C3-carbon after the C4-sucrose addition. We describe mathematical models, by which we calculated the various source effects contributing to the measured response. The method has numerous advantages, e.g. it uses naturally labelled inexpensive non-hazardous compounds and measurements are non-destructive to the studied system.

  • 14.
    Högberg, Peter
    et al.
    Department of Forest Ecology, SLU, Umeå, Sweden.
    Ekblad, Alf
    Örebro University, School of Science and Technology.
    Nordgren, Anders
    Department of Forest Ecology, SLU, Umeå, Sweden.
    Plamboeck, Agneta H.
    Swedish Defence Research Agency Division of NBC-Defence, Umeå, Sweden.
    Ohlsson, Anders
    Department of Forest Ecology, SLU, Umeå, Sweden.
    Bhupinderpal-Singh, Singh
    Department of Forest Ecology, SLU, Umeå, Sweden.
    Högberg, Mona
    Department of Forest Ecology, SLU, Umeå, Sweden.
    Factors determining the 13C abundance of soil-respired CO2 in Boreal forests2005In: Stable isotopes and biosphere-atmosphere interactions: processes and biological controls / [ed] Lawrence B. Flanagan, James R. Ehleringer, Diane E. Pataki, Elsevier, 2005, p. 47-68Chapter in book (Refereed)
    Abstract [en]

    Analysis of the isotopic composition of the CO2 respired from soils may reveal information about the important component of the ecosystem C balance. This is crucial, since a large terrestrial sink for atmospheric CO2 has been located in the northern hemisphere, and the vast boreal forests may be largely responsible. At the same time, boreal and arctic ecosystems have large amounts of C stored in the soil, and could potentially become a source of CO2 in a warmer climate promoting more rapid decomposition of soil organic matter. Furthermore, the northern hemisphere has complex dynamics in terms of annual fluctuations in both the concentration of CO2 in the atmosphere and its δl3C. It is of utmost importance to understand the causes of this variability, since it interferes with the partitioning between the ocean and the terrestrial contributions in global models. This chapter aims to provide an update on the reviews by Flanagan and Ehleringer and Ehleringer et al. on the causation of the δ13C of the soil CO2 efflux and, in doing this, focuses on the boreal forests.

  • 15.
    Högberg, Peter
    et al.
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    Högberg, Mona N
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    Quist, Maud E
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    Ekblad, Alf
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    Näsholm, Torgny
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    Nitrogen isotope fractionation during nitrogen uptake by ectomycorrhizal and non-mycorrhizal Pinus sylvestris1999In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 142, no 3, p. 569-576Article in journal (Refereed)
    Abstract [en]

    An experiment was performed to find out whether ectomycorrhizal (ECM) fungi alter the nitrogen (N) isotope composition, δ15N, of N during the transport of N from the soil through the fungus into the plant. Non- mycorrhizal seedlings of Pinus sylvestris were compared with seedlings inoculated with either of three ECM fungi, Paxillus involutus, Suillus bovinus and S. variegatus. Plants were raised in sand in pots supplied with a nutrient solution with N given as either NH4+ or NO3. Fractionation against 15N was observed with both N sources; it decreased with increasing plant N uptake, and was larger when NH4+ was the source. At high ratios of Nuptake/Nsupplied there was no (NO3), or little (NH4+), fractionation. There seemed to be no difference in fractionation between ECM and non-mycorrhizal plants, but fungal rhizomorphs were sometimes enriched in 15N (up to 5‰ at most) relative to plant material; they were also enriched relative to the N source. However, this enrichment of the fungal material was calculated to cause only a marginal decrease (−0.1‰ in P. involutus) in δ15N of the N passing from the substrate through the fungus to the host, which is explained by the small size of the fungal N pool relative to the total N of the plant, i.e. the high efficiency of transfer. We conclude that the relatively high 15N abundance observed in ECM fungal species should be a function of fungal physiology in the ECM symbiosis, rather than a reflection of the isotopic signature of the N source(s) used. This experiment also shows that the δ15N of plant N is a good approximation of δ15N of the available N source(s), provided that N is limiting growth.

  • 16.
    Johansson, Veronika A.
    et al.
    Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden.
    Mikusinska, Ania
    Örebro University, School of Science and Technology.
    Ekblad, Alf
    Örebro University, School of Science and Technology.
    Eriksson, Ove
    Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden.
    Partial mycoheterotrophy in Pyroleae: nitrogen and carbon stable isotope signatures during development from seedling to adult2015In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 177, no 1, p. 203-211Article in journal (Refereed)
    Abstract [en]

    Mycoheterotrophic plants (MHP) are divided into non-photosynthesizing full MHP and green-leaved partial or initial MHP. We investigated 13C and 15N isotope enrichment in five putatively partial MHP species in the tribe Pyroleae (Ericaceae): Chimaphila umbellata, Moneses uniflora, Orthilia secunda, Pyrola chlorantha and Pyrola minor, sampled from forest sites on Öland, Sweden. For M. uniflora and P. chlorantha, we investigated isotope signatures of subterranean seedlings (which are mycoheterotrophic), to examine how the use of seedlings instead of full MHP species (Hypopitys monotropa) as reference species affects the assessment of partial mycoheterotrophy. Our main findings were as follows: (1) All investigated Pyroleae species were enriched in 15N compared to autotrophic reference plants. (2) significant fungal-derived C among the Pyroleae species was found for O. secunda and P. chlorantha. For the remaining species of C. umbellata, M. uniflora and P. minor, isotope signatures suggested adult autotrophy. (3) C and N gains, calculated using seedlings as a full MHP reference, yielded qualitatively similar results as when using H. monotropa as a reference. However, the estimated differences in C and N gains became larger when using seedlings as an MHP reference. (4) A previously unknown interspecific variation in isotope signature occurs during early ontogeny, from seed production to developing seedlings. Our findings suggest that there is a variation among Pyroleae species concerning partial mycoheterotrophy in adults. Adult autotrophy may be most common in Pyroleae species, and these species may not be as dependent on fungal-derived nutrients as some green orchids.

  • 17.
    Klapwijk, M. J.
    et al.
    Swedish University of Agricultural Sciences, Department of Ecology, Uppsala, Sweden.
    Boberg, J.
    Swedish University of Agricultural Sciences, Department of Forest Mycology and Pathology, Uppsala, Sweden.
    Bergh, J.
    Linnaeus University, Department of Forestry and Wood Technology, Växsjö, Sweden.
    Bishop, K.
    Swedish University of Agricultural Sciences, Department of Aquatic Resources and Assessment, Uppsala, Sweden.
    Björkman, C.
    Swedish University of Agricultural Sciences, Department of Ecology, Uppsala, Sweden.
    Ellison, D.
    Ellison Consulting, Baar, Switzerland; Swedish University of Agricultural Sciences, Department of Forest Resource Management, Umeå, Sweden.
    Felton, A.
    Swedish University of Agricultural Sciences, Southern Swedish Forest Research Centre, Alnarp, Sweden.
    Lidskog, Rolf
    Örebro University, School of Humanities, Education and Social Sciences.
    Lundmark, T.
    Swedish University of Agricultural Sciences, Department of Forest Ecology and Management, Umeå, Sweden.
    Keskitalo, E. C. H.
    Umeå University, Department of Geography and Economic History, Umeå, Sweden.
    Sonesson, J.
    Skogforsk, Uppsala, Sweden.
    Nordin, A.
    Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology, Umeå, Sweden.
    Nordström, E. -M
    Swedish University of Agricultural Sciences, Department of Forest Resource Management, Umeå, Sweden.
    Stenlid, J.
    Swedish University of Agricultural Sciences, Department of Forest Mycology and Pathology, Uppsala, Sweden.
    Mårald, E.
    Umeå University, Department of Historical, Philosophical and Religious Studies, Umeå, Sweden.
    Capturing complexity: Forests, decision-making and climate change mitigation action2018In: Global Environmental Change, ISSN 0959-3780, E-ISSN 1872-9495, Vol. 52, p. 238-247Article in journal (Refereed)
    Abstract [en]

    Managed forests can play an important role in climate change mitigation due to their capacity to sequester carbon. However, it has proven difficult to harness their full potential for climate change mitigation. Managed forests are often referred to as socio-ecological systems as the human dimension is an integral part of the system. When attempting to change systems that are influenced by factors such as collective knowledge, social organization, understanding of the situation and values represented in society, initial intentions often shift due to the complexity of political, social and scientific interactions. Currently, the scientific literature is dispersed over the different factors related to the socio-ecological system. To examine the level of dispersion and to obtain a holistic view, we review climate change mitigation in the context of Swedish forest research. We introduce a heuristic framework to understand decision-making connected to climate change mitigation. We apply our framework to two themes which span different dimensions in the socio-ecological system: carbon accounting and bioenergy. A key finding in the literature was the perception that current uncertainties regarding the reliability of different methods of carbon accounting inhibits international agreement on the use of forests for climate change mitigation. This feeds into a strategic obstacle affecting the willingness of individual countries to implement forest-related carbon emission reduction policies. Decisions on the utilization of forests for bioenergy are impeded by a lack of knowledge regarding the resultant biophysical and social consequences. This interacts negatively with the development of institutional incentives regarding the production of bioenergy using forest products. Normative disagreement about acceptable forest use further affects these scientific discussions and therefore is an over-arching influence on decision-making. With our framework, we capture this complexity and make obstacles to decision-making more transparent to enable their more effective resolution. We have identified the main research areas concerned with the use of managed forest in climate change mitigation and the obstacles that are connected to decision making.

  • 18.
    Kyaschenko, Julia
    et al.
    Department of Soil and Environment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Ovaskainen, Otso
    Organismal and Evolutionary Biology Research Programme, University of Helsinki, Finland; Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology, Trondheim, Norway.
    Ekblad, Alf
    Örebro University, School of Science and Technology.
    Hagenbo, Andreas
    Department of Forest Mycology and Plant Pathology, Uppsala BioCenter, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Karltun, Erik
    Department of Soil and Environment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Clemmensen, Karina E.
    Department of Forest Mycology and Plant Pathology, Uppsala BioCenter, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Lindahl, Björn D.
    Department of Soil and Environment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Soil fertility in boreal forest relates to root-driven nitrogen retention and carbon sequestration in the mor layer2019In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 221, no 3, p. 1492-1502Article in journal (Refereed)
    Abstract [en]

    Boreal forest soils retain significant amounts of carbon (C) and nitrogen (N) in purely organic layers, but the regulation of organic matter turnover and the relative importance of leaf litter and root‐derived inputs are not well understood.

    We combined bomb 14C dating of organic matter with stable isotope profiling for Bayesian parameterization of an organic matter sequestration model. C and N dynamics were assessed across annual depth layers (cohorts), together representing 256 yr of organic matter accumulation. Results were related to ecosystem fertility (soil inorganic N, pH and litter C : N).

    Root‐derived C was estimated to decompose two to 10 times more slowly than leaf litter, but more rapidly in fertile plots. The amounts of C and N per cohort declined during the initial 20 yr of decomposition, but, in older material, the amount of N per cohort increased, indicating N retention driven by root‐derived C.

    The dynamics of root‐derived inputs were more important than leaf litter dynamics in regulating the variation in organic matter accumulation along a forest fertility gradient. N retention in the rooting zone combined with impeded mining for N in less fertile ecosystems provides evidence for a positive feedback between ecosystem fertility and organic matter turnover.

  • 19.
    Ladd, Brenton
    et al.
    Facultad de Ciencias Ambientales, Universidad Científica del Sur, Lima, Peru; Earth and Environmental Sciences, Evolution and Ecology Research Centre, School of Biological, University of New South Wales, Sydney, Australia.
    Peri, Pablo L.
    Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Estación Experimental Agropecuaria (EEA), National Agricultural Technology Institute (INTA), Rio Gallegos, Argentina.
    Pepper, David A.
    Earth and Environmental Sciences, School of Biological, University of New South Wales, Sydney, Australia.
    Silva, Lucas C. R.
    Department of Land, Air and Water Resources, University of California, Davis, USA.
    Sheil, Douglas
    School of Environmental Science and Management, Southern Cross University, Lismore, Australia; Center for International Forestry Research (CIFOR), Bogor, Indonesia; Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, Ås, Norway.
    Bonser, Stephen P.
    Earth and Environmental Sciences, Evolution and Ecology Research Centre, School of Biological, University of New South Wales, Sydney, Australia.
    Laffan, Shawn W.
    Earth and Environmental Sciences, School of Biological, University of New South Wales, Sydney, Australia.
    Amelung, Wulf
    Soil Science and Soil Ecology, Institute of Crop Science and Resource Conservation (INRES), University of Bonn, Bonn, Germany.
    Ekblad, Alf
    Örebro University, School of Science and Technology.
    Eliasson, Peter
    Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden.
    Bahamonde, Hector
    Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Estación Experimental Agropecuaria (EEA), National Agricultural Technology Institute (INTA), Rio Gallegos, Argentina.
    Duarte-Guardia, Sandra
    acultad de Ciencias Ambientales, Universidad Cienifica del Sur, Lima, Peru.
    Bird, Michael
    Department of Ecology, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden; Centre for Tropical Environmental and Sustainability Science, School of Earth and Environmental Sciences, James Cook University, Cairns, Australia .
    Carbon isotopic signatures of soil organic matter correlate with leaf area index across woody biomes2014In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 102, no 6, p. 1606-1611Article in journal (Refereed)
    Abstract [en]

    Leaf area index (LAI), a measure of canopy density, is a key variable for modelling and understanding primary productivity, and also water use and energy exchange in forest ecosystems. However, LAI varies considerably with phenology and disturbance patterns, so alternative approaches to quantifying stand-level processes should be considered. The carbon isotope composition of soil organic matter (C-13(SOM)) provides a time-integrated, productivity-weighted measure of physiological and stand-level processes, reflecting biomass deposition from seasonal to decadal time scales.

    Our primary aim was to explore how well LAI correlates with C-13(SOM) across biomes.

    Using a global data set spanning large environmental gradients in tropical, temperate and boreal forest and woodland, we assess the strength of the correlation between LAI and C-13(SOM); we also assess climatic variables derived from the WorldClim database.

    We found that LAI was strongly correlated with C-13(SOM), but was also correlated with Mean Temperature of the Wettest Quarter, Mean Precipitation of Warmest Quarter and Annual Solar Radiation across and within biomes.

    Synthesis. Our results demonstrate that C-13(SOM) values can provide spatially explicit estimates of leaf area index (LAI) and could therefore serve as a surrogate for productivity and water use. While C-13(SOM) has traditionally been used to reconstruct the relative abundance of C-3 versus C-4 species, the results of this study demonstrate that within stable C-3- or C-4-dominated biomes, C-13(SOM) can provide additional insights. The fact that LAI is strongly correlated to C-13(SOM) may allow for a more nuanced interpretation of ecosystem properties of palaeoecosystems based on palaeosol C-13 values.

  • 20.
    Lundberg, Peter
    et al.
    Linköping University, Linköping, Sweden.
    Ekblad, Alf
    Örebro University, School of Science and Technology. Swedish University of Agricultural Sciences, Umeå, Sweden.
    Nilsson, Mats
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    C-13 NMR spectroscopy studies of forest soil microbial activity: glucose uptake and fatty acid biosynthesis2001In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 33, no 4-5, p. 621-632Article in journal (Refereed)
    Abstract [en]

    The intimate association of soil microorganisms with the soil matrix complicates analysis of their metabolism, since thorough separation of intact cells from the matrix is very difficult using standard protocols. Thus, in the study reported here, in situ glucose decomposition and metabolism in humus from a coniferous forest soil was monitored and evaluated using ‘solution state’ 13C NMR, which can be used in a non-invasive manner. [U-13C] glucose was added at a concentration of 1.73 mmol C g−1 dry organic matter, which is known to allow maximal substrate induced respiration (SIR), and the microbial metabolism of the added C was followed over a period of 28 days. The data showed that ∼50% of the added glucose was consumed within three days, coinciding with the appearance of label in CH3, –CH2– and –CH=CH– groups, and in glycerol-carbons, suggesting that olefinic triacylglycerols were being formed, probably located in oil droplets. During days two to three, around 40% of the consumed glucose C was allocated into solid state components, about 40% was respired and about 20% was found as triglycerols. The triacylglycerol signal reached a maximum after 13 days, but subsequently declined by 60%, as the triacylglycerols were apparently consumed, by day 28 of the incubation. Our results indicate there was an initial formation of structural microbial C (solid state carbon) followed by formation of storage lipid C, which subsequently decreased, probably because it was used to provide the organisms with energy when the external energy source (i.e. the glucose) was depleted. The formation of unsaturated triacylglycerols, typical storage metabolites of eucaryotes, suggests that fungi were the most active organisms in the glucose degradation.

  • 21.
    Magnusson, Magnus
    et al.
    Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Bergsten, Arvid
    Stockholm Resilience Center, Stockholm University, Stockholm, Sweden.
    Ecke, Frauke
    Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences, Umeå, Sweden; Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Bodin, Örjan
    Stockholm Resilience Center, Stockholm University, Stockholm, Sweden.
    Bodin, Lennart
    Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
    Hörnfeldt, Birger
    Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Predicting grey-sided vole occurrence in northern Sweden at multiple spatial scales2013In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 3, no 13, p. 4365-4376Article in journal (Refereed)
    Abstract [en]

    Forestry is continually changing the habitats for many forest-dwelling species around the world. The grey-sided vole (Myodes rufocanus) has declined since the 1970s in forests of northern Sweden. Previous studies suggested that this might partly be caused by reduced focal forest patch size due to clear-cutting. Proximity and access to old pine forest and that microhabitats often contains stones have also been suggested previously but never been evaluated at multiple spatial scales. In a field study in 2010–2011 in northern Sweden, we investigated whether occurrence of grey-sided voles would be higher in (1) large focal patches of >60 years old forest, (2) in patches with high connectivity to sur- rounding patches, and (3) in patches in proximity to stone fields. We trapped animals in forest patches in two study areas (V€asterbotten and Norrbotten). At each trap station, we surveyed structural microhabitat characteristics. Land- scape-scale features were investigated using satellite-based forest data combined with geological maps. Unexpectedly, the vole was almost completely absent in Norrbotten. The trap sites in Norrbotten had a considerably lower amount of stone holes compared with sites with voles in V€asterbotten. We suggest this might help to explain the absence in Norrbotten. In V€asterbotten, the distance from forest patches with voles to stone fields was significantly shorter than from patches without voles. In addition, connectivity to surrounding patches and size of the focal forest patches was indeed related to the occurrence of grey-sided voles, with connectivity being the overall best predictor. Our results support previous findings on the importance of large forest patches, but also highlight the importance of connectivity for occurrence of grey-sided voles. The results further suggest that proximity to stone fields increase habitat quality of the forests for the vole and that the presence of stone fields enhances the voles’ ability to move between nearby forest patches through the matrix

  • 22.
    Menichetti, Lorenzo
    et al.
    Department of Soil and Environment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Ekblad, Alf
    Örebro University, School of Science and Technology.
    Kätterer, Thomas
    Department of Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Contribution of roots and amendments to soil carbon accumulation within the soil profile in a long-term field experiment in Sweden2015In: Agriculture, Ecosystems & Environment, ISSN 0167-8809, E-ISSN 1873-2305, Vol. 200, p. 79-87Article in journal (Refereed)
    Abstract [en]

    The contribution of different C inputs to organic carbon accumulation within the soil profile in the Ultuna long-term continuous soil organic matter experiment, established in 1956, was determined. Until 1999, C3-crops were grown at the site, but since then maize (C4) has been the only crop. The effect of a total of 10 different inorganic nitrogen and organic amendment treatments (4 Mg C ha−1 yr−1) on SOC in topsoil and subsoil after 53 years was evaluated and the contribution from maize roots to SOC after 10 years of cultivation was estimated.

    Soil organic carbon (SOC) and δ13C signature were measured down to 50 cm depth. The C content in the topsoil (0–20 cm depth) was 1.5% at the start of the experiment. After 53 years of treatments, the average topsoil C content varied between 0.9 and 3.8% of soil dry weight, with the open fallow having the lowest and the peat amended the highest value. Nitrogen seemed to promote C accumulation in the topsoil treatment effects were smaller below 20 cm depth and only two of the amendments (peat and sewage sludge) significantly affected SOC content down to 35 cm depth. Despite this, penetrometer measurements showed significant treatment differences of compaction below 41 cm depth, and although we could not explain these differences this presented some evidence of an initial treatment-induced subsoil differentiation. Ten years of maize growth affected the δ13C of SOC down to 22.5 cm depth, where it varied between −25.16 and −26.33(‰), and an isotopic mass balance calculation suggested that maize C accounted for 4–8% of total SOC in the topsoil. Until less than 2500 years ago the site was a post-glacial sea floor and the 14C data suggest that marine sediment C still dominates the SOC in deeper soil layers. Overall, the results suggest that 53 years of treatments has caused dramatic changes on the stored C in the topsoil in several of the treatments, while the changes in the subsoil is much less dramatic and a small C accumulation in the upper subsoil was found in two of the treatments.

    The contribution from roots to SOC accumulation was generally equal to or greater than the contribution from amendments. The retention coefficient of root-derived C in the topsoil was on average 0.30 ± 0.09, which is higher than usually reported in the literature for plant residues but confirms previous findings for the same experiment using another approach. This strengthens the conclusion that root-derived SOC contributed more to SOC than above-ground crop residues.

  • 23.
    Menichetti, Lorenzo
    et al.
    Department of Soil and Environment, Swedish University of Agricultural Sciences, Uppsala, Sweden .
    Houot, Sabine
    INRA, UMR Environnement et Grandes Cultures Thiverval-Grignon, Plaisir, France.
    Van Oort, Folkert
    Unit of Physico-Chemistry and Ecotoxicology of Soils from Contaminated Agrosystems, INRA Centre de Recherche de Versailles-Grignon, Versailles, France.
    Kätterer, Thomas
    Department of Ecology, Sveriges lantbruksuniversitet, Uppsala, Sweden.
    Christensen, Bent T.
    Department of Agroecology, Aarhus Universitet, Århus, Denmark.
    Chenu, Claire C.
    AgroParisTech Thiverval Grignon, Plaisir, France.
    Barré, Pierre
    Laboratoire de Géologie, Ecole Normale Superieure, Paris, France.
    Vasilyeva, Nadezda A.
    AgroParisTech,, Thiverval Grignon, France.
    Ekblad, Alf
    Örebro University, School of Science and Technology.
    Increase in soil stable carbon isotope ratio relates to loss of organic carbon: results from five long-term bare fallow experiments2015In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 177, no 3, p. 811-821Article in journal (Refereed)
    Abstract [en]

    Changes in the 12C/13C ratio (expressed as δ13C) of soil organic C (SOC) has been observed over long time scales and with depth in soil profiles. The changes are ascribed to the different reaction kinetics of 12C and 13C isotopes and the different isotopic composition of various SOC pool components. However, experimental verification of the subtle isotopic shifts associated with SOC turnover under field conditions is scarce. We determined δ13C and SOC in soil sampled during 1929–2009 in the Ap-horizon of five European long-term bare fallow experiments kept without C inputs for 27–80 years and covering a latitudinal range of 11°. The bare fallow soils lost 33–65 % of their initial SOC content and showed a mean annual δ13C increase of 0.008–0.024 ‰. The 13C enrichment could be related empirically to SOC losses by a Rayleigh distillation equation. A more complex mechanistic relationship was also examined. The overall estimate of the fractionation coefficient (ε) was −1.2 ± 0.3 ‰. This coefficient represents an important input to studies of long-term SOC dynamics in agricultural soils that are based on variations in 13C natural abundance. The variance of ε may be ascribed to site characteristics not disclosed in our study, but the very similar kinetics measured across our five experimental sites suggest that overall site-specific factors (including climate) had a marginal influence and that it may be possible to isolate a general mechanism causing the enrichment, although pre-fallow land use may have some impact on isotope abundance and fractionation.

  • 24.
    Nilsson, Christer
    et al.
    Umeå University, Umeå, Sweden.
    Ekblad, Alf
    Umeå University, Umeå, Sweden.
    Dynesius, Mats
    Umeå University, Umeå, Sweden.
    Backe, Susanne
    Umeå University, Umeå, Sweden.
    Gardfjell, Maria
    Umeå University, Umeå, Sweden.
    Carlberg, Björn
    Umeå University, Umeå, Sweden.
    Hellqvist, Sven
    Umeå University, Umeå, Sweden.
    Jansson, Roland
    Umeå University, Umeå, Sweden.
    A Comparison of Species Richness and Traits of Riparian Plants between a Main River Channel and Its Tributaries1994In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 82, no 2, p. 281-295Article in journal (Refereed)
    Abstract [en]

    Summary

    1 We examined differences in species richness and frequencies of vascular plants in the riverbank vegetation between the main channel of the Vindel River system and seven of its tributaries which spanned the same biogeographic range.

    2 Species richness per site was higher in the main channel than in the tributaries, both as a whole and for many species groups. The proportions of woody plants (phanerophytes and chamaephytes), geophytes, and natural species were higher in the tributaries, while the proportions of hemicryptophytes, ruderals, and short-floating species (i.e. species unable to float > 1 day) were higher in the main channel. Both types of river had species that were more than twice as frequent there than in the other category.

    3 The main channel had a high species richness at intermediate altitudes whereas the tributaries had least species at intermediate altitudes. Except for the highest altitudes, the tributaries also had a generally lower mean species richness than the main channel.

    4 Stepwise multiple regression analyses using 15 predictor variables explained stat- istically up to 85% of the floristic variation in the river system. Mean annual discharge and number of substrates explained most of the variation in five equations each, while peat cover explained most of the variation in four equations, and altitude and silt cover in one equation each. Mean annual discharge, peat cover and silt cover differed between the main channel and the tributaries and could therefore be responsible for the observed difference.

  • 25.
    Nilsson, Christer
    et al.
    Umeå University, Umeå, Sweden.
    Ekblad, Alf
    Umeå University, Umeå, Sweden.
    Gardfjell, Maria
    Umeå University, Umeå, Sweden.
    Carlberg, Björn
    Umeå University, Umeå, Sweden.
    Long-term effects of river regulation on river margin vegetation1991In: Journal of Applied Ecology, ISSN 0021-8901, E-ISSN 1365-2664, Vol. 28, no 3, p. 963-987Article in journal (Refereed)
  • 26.
    Nyberg, Gert
    et al.
    Swedish University of Agricultural Sciences, Umeå.
    Ekblad, Alf
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    Buresh, Roland J
    International Centre for Research in Agroforestry , Nairobi, Kenya .
    Högberg, Peter
    Swedish University of Agricultural Sciences, Umeå.
    Respiration from C-3 plant green manure added to a C-4 plant carbon dominated soil2000In: Plant and Soil, ISSN 0032-079X, E-ISSN 1573-5036, Vol. 218, no 1-2, p. 83-89Article in journal (Refereed)
    Abstract [en]

    Application of tree leaves (C3 plants) on maize (Zea mays L.) (C4 plant) fields is an agroforestry management technology to restore or maintain soil fertility. The rate at which the tree leaves decompose is crucial for the nutrient supply to the crop. We studied the in situ decomposition of Sesbania sesban (L.) Merr. leaves or C3 sugar for 4 – 8 days after application to a maize field in Kenya. By using the difference of around 10‰ in natural abundance of 13C between the endogenous soil C (mainly C4) and the applied C (C3), we could calculate the contributions of the two C sources to soil respiration. The δ13C value of the basal respiration was from –15.9 to –16.7‰. The microbial response to the additions of leaves and sugar to this tropical soil was immediate. Application of sesbania leaves gave an initial peak in respiration rates that lasted from one to less than 6 days, after which it levelled off and remained about 2 – 3 times higher (230–270 mg C m-2 h-1) than the control respiration rates throughout the rest of the experiment (5 – 8 days). In the sugar treatment, there was no initial peak in respiration rate. The respiration rate was 170 mg C m-2 h-1 after 4 days. At the end of the experiments, after 4–8 days, as much as 14–17% of the added C had been respired and about 60% of the total respiration was from the added sesbania leaves or C3 sugar. This non-destructive method allows repeated measurements of the actual rate of C mineralisation and facilitates decomposition studies with high temporal resolution in the field.

  • 27.
    Nyberg, Gert
    et al.
    Swedish University of Agricultural Sciences, Umeå.
    Ekblad, Alf
    Swedish University of Agricultural Sciences, Umeå, Sweden.
    Buresh, Roland J
    International Centre for Research in Agroforestry, Nairobi, Kenya, .
    Högberg, Peter
    Swedish University of Agricultural Sciences, Umeå.
    Short-term patterns of carbon and nitrogen mineralisation in a fallow field amended with green manures from agroforestry trees2002In: Biology and Fertility of Soils, ISSN 0178-2762, E-ISSN 1432-0789, Vol. 36, no 1, p. 18-25Article in journal (Refereed)
    Abstract [en]

    The mineralisation of green manure from agroforestry trees was monitored with the objective to compare the temporal dynamics of mineralisation of litter from different species. Green manures from five agroforestry tree species were used on a fallow field during the long rainy season of 1997 (March–August) and from two species in the following short rainy season (September–January) in western Kenya. Different methods, i.e. measurements of isotopic ratios of C in respired CO2 and of soil organic matter (SOM) fractions, soil inorganic N and mass loss from litterbags, were used in the field to study decomposition and C and N mineralisation. Soil respiration, with the separation of added C from old soil C by using the isotopic ratio of 13C/12C in the respired CO2, correlated well with extractable NH4 + in the soil. Mineralisation was high and very rapid from residues of Sesbania sesban of high quality [e.g. low ratio of (polyphenol+lignin)/N] and low and slow from low quality residues of Grevillea robusta. Ten days after application, 37% and 8% of the added C had been respired from Sesbania and Grevillea, respectively. Apparently, as much as 70–90% of the added C was respired in 40 days from high quality green manure. Weight losses of around 80%, from high quality residues in litterbags, also indicate substantial C losses and that a build-up of SOM is unlikely. For immediate effects on soil fertility, application of high quality green manure may, however, be a viable management option. To achieve synchrony with crop demand, caution is needed in management as large amounts of N are mineralised within a few days after application.

  • 28.
    Poonlapthawee, Sirirat
    Örebro University, School of Science and Technology.
    Gene expression and antibiotic resistance in Escherichia coli from Swedish inland waters2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Extensive use of antibiotics both from human-medicine and veterinary sources are believed to provide selective pressure on bacteria that leads to an increase in antibiotic resistance in environmental waters. Contamination of antibiotic resistant microbes will raise human health risks. Escherichia coli are Gram negative bacilli that belong to the coliform group. E. coli are used as fecal indicators organism (FIO) to determine microbial contamination and water quality. We aimed to investigate the prevalence of antibiotic resistant bacteria in Swedish inland waters and determine the response of uropathogenic E. coli to the environmental waters. Samples were collected in different locations near Örebro Sweden at 4 different time points during 2010-2011. Waters were filtered and FIO were isolated using selective medium. The highest numbers of FIO were detected for both E. coli and enterococci in the river Svartån near the effluent from the wastewater treatment plant (WWTP). Over the two years, 42% and 24% of the antibiotic resistant strains were multi-drug resistant (MDR) E. coli and enterococci, respectively. In addition, 15% of MDR E. coli were extended spectrum beta-lactamase producing and AmpC overproducing strains. A vancomycin resistant E. faecium was also identified. Tetracycline resistance was the most common in FIO isolates. Our study suggests that WWTP distributed FIO and antibiotic resistant bacteria. In a second study we analyzed for the presence of various pharmaceutical residues from lake Mälaren in Västerås Sweden. Some pharmaceutical compounds were present at detectable levels but were removed by the drinking water treatment plant. Quantitative PCR was performed to investigate the effects on genes focused on antibiotic resistance, virulence factors and stress response. Forty one-gene array was developed and tested using tetracycline treatment or environmental water. No significant difference was found when compared to controls in the gene expression profile of bacteria grown in medium prepared with sub-MIC of tetracycline or environmental waters. We concluded that the pharmaceutical levels detected did not exert any significant effects on the E. coli strain tested. From this study, we conclude that MDR bacteria may actually persist in environmental waters in what is considered as a clean urban region. Pharmaceutical pollutants in the inland water did not exert a significant effect on the E. coli, suggesting that MDR strains are released in the effluent of the WWTP rather than induced through selective pressure by the pharmaceuticals contamination.

    List of papers
    1. Antibiotic resistance in fecal indicator bacteria in Hjälmaren lake system
    Open this publication in new window or tab >>Antibiotic resistance in fecal indicator bacteria in Hjälmaren lake system
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Background: Increasing levels of multi-antibiotic resistant bacteria are ound in the environment, causing serious concerns for treatment of infectious diseases. his increase is believed to be due to release of antibiotic resistant bacteria and election pressure resulting from pharmaceuticals in the environment.

    Objectives: We evaluated the presence of multi-antibiotic resistant fecal ndicator bacteria from the surface waters of a recipient river and lake downstream of he wastewater treatment plant (WWTP) in Sweden.

    Methods: Surface waters from Svartån river and Hjälmaren lake in Sweden were ampled in 2010 and 2011. The waters were analyzed for fecal indicator bacteria Escherichia coli, enterococci) by membrane filtration and selective agar plating. E. coli nd enterococci were evaluated by Etest for resistance to tetracycline, chloramphenicol, alidixic acid, trimethoprim-sulfamethoxazole, ciprofloxacin, cefotaxime, ceftazidime, eropenem, imipenem, ampicillin, vancomycin, gentamycin and streptomycin.

    Results: The highest concentration of E. coli and enterococci were found in vartån river at Naturens Hus closest site downstream of the WWTP. Tetracycline resistance as the most prominent in both fecal indicator bacteria. Over the two years, there was 42% (13/31) and 24% (7/29) multi-antibiotic resistant (≥2 antibiotics) E. coli and nterococci, respectively. Furthermore, we identified one ESBL and one AmpC hyperproducing . coli in 2010 and vancomycin (vanA) resistant E. faecium in 2011.

    Conclusions: The presence, of multi-antibiotic resistant strains of fecal ndicator organisms in regions considered predominantly clean, is of great concern. While t currently may not be a major threat in the region, it is demonstrating the accelerating incidence and spread of antibiotic resistance worldwide.

    National Category
    Ecology Microbiology
    Research subject
    Microbiology; Enviromental Science
    Identifiers
    urn:nbn:se:oru:diva-28742 (URN)
    Available from: 2013-04-22 Created: 2013-04-22 Last updated: 2017-10-17Bibliographically approved
    2. Gene expression in Escherichia coli CFT073 grown in sub-MIC tetracycline and environmental waters
    Open this publication in new window or tab >>Gene expression in Escherichia coli CFT073 grown in sub-MIC tetracycline and environmental waters
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    We examined the prevalence of fecal indicator bacteria (coliform E. coli and enterococci) for water quality (World Health Organization, 2011, European Enviroment Agency, 2012) and antibiotic resistant E. coli in lake Mälaren from surface water in Björnö Island at Vinterviken bay and in untreated incoming water to Mälarenergi, drinking water treatment plant (DWTP) in Västerås, Sweden. Our studies have demonstrated that the water quality of environmental water was ‘excellent‘ in both surface water at Bjornö in Vinterviken bay and in the untreated incoming water to the DWTP. However, one multi-antibiotic resistant and one antibiotic resistant strain were isolated from the surface waters. Hence antibiotic resistant strains can persist even in low population of fecal bacterial contamination in the waters. Pharmaceutical compounds in the environment are believed to provide a selective pressure for the development of antibiotic resistance in bacteria (Tenover, 2006, Alekshun and Levy, 2007, Mazumdar et al., 2006). Our study demonstrated that pharmaceutical compounds persisted in lake waters with detectable concentrations as others have shown (Godfrey et al., 2007, Loos et al., 2009). Caffeine, naproxen, hydrochlorothiazide, metoprolol and tramadol were present at detectable levels. To study the effect of contaminants on microorganisms, qPCR method was chosen due to its rapid, sensitive and quantitative analyses of gene expression. Thus a qPCR array was designed, to determine the effect of environmental waters on E. coli isolates. Specific genes that were responsible for antibiotic resistance, virulence factors and stress responses were selected. E. coli CFT073 was treated with either sub-MIC levels (0.1 μg/ml) of tetracycline in LB medium or incoming untreated waters to DWTP in LB medium and compared to controls. Gene expression was determined using qPCR. No significant difference in gene response was observed after treatment with sub-MIC of tetracycline or environmental waters. Pharmaceutical compounds which contaminated the water did not appear to exert a significant gene response in the pathogenic E. coli. Pharmaceutical contamination in the water can promote human and animal health risks however the effect of long-term exposure is yet unknown (European Environment Agency, 2011, Wennmalm and Gunnarsson, 2005, Triebskorn et al., 2007). The antibiotic resistant strains likely originated from the WWTP rather than the selective pressure due to pharmaceutical pollutants in the water. 

    National Category
    Biological Sciences
    Research subject
    Biology
    Identifiers
    urn:nbn:se:oru:diva-28743 (URN)
    Available from: 2013-04-22 Created: 2013-04-22 Last updated: 2017-10-17Bibliographically approved
  • 29.
    Schnürer, Anna
    et al.
    Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Schnürer, Johan
    Department of Microbiology, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden.
    Fungal survival during anaerobic digestion of organic household waste2006In: Waste Management, ISSN 0956-053X, E-ISSN 1879-2456, Vol. 26, no 11, p. 1205-1211Article in journal (Refereed)
    Abstract [en]

    Anaerobic digestion of organic waste yields energy rich biogas and retains nutrients (N, P, K, S, etc.) in a stabilised residue. For the residue to be used as a soil fertiliser, it must be free from pollutants and harmful microorganisms. Fungal survival during sanitation and anaerobic treatment of source-separated organic household waste and during aerobic storage of the residue obtained was investigated. Decimal reduction times were determined for inoculated fungi (Aspergillus flavus and Aspergillus fumigatus, Penicillium roqueforti, Rhizomucor pusillus, Thermoascus crustaceus and Thermomyces lanuginosus). Several different fungal species were found after waste sanitation treatment (70 degrees C, 1 h), with Aspergillus species dominating in non-inoculated waste. Anaerobic waste degradation decreased the diversity of fungal species for processes run at both 37 and 55 degrees C, but not total fungal colony forming units. Fungi surviving the mesophilic anaerobic digestion were mainly thermotolerant Talaromyces and Paecilomyces species. T crustaceus and T lanuginosus were the only inoculated fungi to survive the thermophilic anaerobic degradation process. Aerobic storage of both types of anaerobic residues for one month significantly decreased fungal counts.

  • 30.
    Schnürer, Johan
    et al.
    Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Clarholm, Marianne
    Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Boström, Sven
    Department of Zoology, University of Stockholm, Stockholm, Sweden.
    Rosswall, Thomas
    Department of Water in Environment and Society, University of Linköping, Linköping, Sweden.
    Effects of moisture on soil microorganisms and nematodes: A field experiment1986In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 12, no 2, p. 217-230Article in journal (Refereed)
    Abstract [en]

    The effects of soil moisture changes on bacteria, fungi, protozoa, and nematodes and changes in oxygen consumption were studied in a field experiment. In one plot the soil was drip-irrigated daily for 10 days, while an adjacent plot experienced one rainfall and was then allowed to dry out. Oxygen consumption was the parameter measured which responded most rapidly to changes in soil moisture content. Lengths of fluorescein diacetate-active hyphae paralleled oxygen consumption in both plots. Total hyphal length was not affected by one rainfall but increased from 700 mg-1 dry weight soil to more than 1,600 m in less than 10 days in the irrigated plot. In the rain plot, bacterial numbers doubled within 3 days and declined during the following period of drought. In the irrigated plot, numbers increased by 50% and then remained constant over the duration of the study. Only small changes in protozoan numbers were observed, with the exception of the last sampling date in the irrigated plot when large numbers of naked amoebae were recorded 2 days after a large natural rainfall. Nematode numbers, especially obligate root feeders, increased in both treatments. The increases were caused by decoiling rather than growth. The results indicate that fungal respiration was dominating, while bacteria, lacking a suitable source of energy, were less active, except for the first days.

  • 31.
    Zhao, Tao
    et al.
    Department of Forest Mycology and Plant Pathology, The Swedish University of Agricultural Sciences, Uppsala, Sweden .
    Kandasamy, Dineshkumar
    Max Planck Institute for Chemical Ecology, Jena, Germany.
    Krokene, Paal
    Norwegian Institute of Bioeconomy Research, Ås, Norway.
    Chen, Jingyuan
    Max Planck Institute for Chemical Ecology, Jena, Germany.
    Gershenzon, Jonathan
    Max Planck Institute for Chemical Ecology, Jena, Germany.
    Hammerbacher, Almuth
    Department of Zoology and Entomology, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, South Africa.
    Fungal associates of the tree-killing bark beetle, Ips typographus, vary in virulence, ability to degrade conifer phenolics and influence bark beetle tunning behavior2019In: Fungal ecology, ISSN 1754-5048, E-ISSN 1878-0083, Vol. 38, p. 71-79Article in journal (Refereed)
    Abstract [en]

    The bark beetle Ips typographus carries numerous fungi that could be assisting the beetle in colonizing live Norway spruce (Picea abies) trees. Phenolic defenses in spruce phloem are degraded by the beetle's major tree-killing fungus Endoconidiophora polonica, but it is unknown if other beetle associates can also catabolize these compounds. We compared the ability of five fungi commonly associated with I. typographus to degrade phenolic compounds in Norway spruce phloem. Grosmannia penicillata and Grosmannia europhioides were able to degrade stilbenes and flavonoids faster than E. polonica and grow on minimal growth medium with spruce bark constituents as the only nutrients. Furthermore, beetles avoided medium amended with phenolics but marginally preferred medium colonized by fungi. Taken together our results show that different bark beetle-associated fungi have complementary roles in degrading host metabolites and thus might improve this insect's persistence in well defended host tissues.

1 - 31 of 31
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