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  • 1. Arp, Hans Peter H.
    et al.
    Lundstedt, Staffan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Josefsson, Sarah
    Cornelissen, Gerard
    Enell, Anja
    Allard, Ann-Sofie
    Kleja, Dan Berggren
    Native Oxy-PAHs, N-PACs, and PAHs in historically contaminated soils from Sweden, Belgium, and France: their soil-porewater partitioning behavior, bioaccumulation in Enchytraeus crypticus, and bioavailability2014Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 48, nr 19, s. 11187-11195Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Soil quality standards are based on partitioning and toxicity data for laboratory-spiked reference soils, instead of real world, historically contaminated soils, which would be more representative. Here 21 diverse historically contaminated soils from Sweden, Belgium, and France were obtained, and the soil-porewater partitioning along with the bioaccumulation in exposed worms (Enchytraeus crypticus) of native polycyclic aromatic compounds (PACs) were quantified. The native PACs investigated were polycyclic aromatic hydrocarbons (PAHs) and, for the first time to be included in such a study, oxygenated-PAHs (oxy-PAHs) and nitrogen containing heterocyclic PACs (N-PACs). The passive sampler polyoxymethylene (POM) was used to measure the equilibrium freely dissolved porewater concentration, C-pw, of all PACs. The obtained organic carbon normalized partitioning coefficients, K-TOC, show that sorption of these native PACs is much stronger than observed in laboratory-spiked soils (typically by factors 10 to 100), which has been reported previously for PAHs but here for the first time for oxy-PAHs and N-PACs. A recently developed K-TOC model for historically contaminated sediments predicted the 597 unique, native K-TOC values in this study within a factor 30 for 100% of the data and a factor 3 for 58% of the data, without calibration. This model assumes that TOC in pyrogenic-impacted areas sorbs similarly to coal tar, rather than octanol as typically assumed. Black carbon (BC) inclusive partitioning models exhibited substantially poorer performance. Regarding bioaccumulation, C-pw combined with liposome-water partition coefficients corresponded better with measured worm lipid concentrations, C-lipid (within a factor 10 for 85% of all PACs and soils), than C-pw combined with octanol-water partition coefficients (within a factor 10 for 76% of all PACs and soils). E. crypticus mortality and reproducibility were also quantified. No enhanced mortality was observed in the 21 historically contaminated soils despite expectations from PAH spiked reference soils. Worm reproducibility weakly correlated to C-lipid of PACs, though the contributing influence of metal concentrations and soil texture could not be taken into account. The good agreement of POM-derived C-pw with independent soil and lipid partitioning models further supports that soil risk assessments would improve by accounting for bioavailability. Strategies for including bioavailability in soil risk assessment are presented.

  • 2.
    Bandau, Franziska
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Importance of tannins for responses of aspen to anthropogenic nitrogen enrichment2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Boreala skogar är ofta mycket kväve (N) begränsade. Men mänskliga aktiviteter leder till ökad N tillförsel i dessa ekosystem, både genom depostition av N från atmosfären och skogsgödsling. N-tillförsel i boreala skogar kan främja netto primärproduktionen men även leda till ökade skador från naturliga fiender (herbivorer och patogener) samt skiftningar i växtartsammansättning. Genetisk mångfald har föreslagits som en viktig mekanism för att främja en växtarts stabilitet inom samhällen som upplever miljöförändringar. Inom varje växtpopulation kan specifika egenskaper (t.ex. tillväxt och försvar) varierar kraftigt mellan individer och en större variation i egenskaper kan öka chanserna för att åtminstone några individer från en population överlever ifall miljöförhållandena förändras. En aspekt av växtkemi som i hög grad kan variera mellan olika genotyper (GT) är bladens kondenserade tanniner (KT). Dessa sekundära metaboliter har föreslagits påverka växtens prestationsförmåga på många sätt, t.ex. genom att påverka tillväxt, interaktioner mellan växter och herbivorer eller patogener och genom att påverka förna nedbrytning, och följaktligen återbördandet av näringsämnen till kretsloppet. För att undersöka hur genotypiska variation i KT produktion kan påverka de effekter som antopogent N kan ha på växtens prestationsförmåga och förna nedbrytning, utförde jag en serie experiment. Jag studerade olika asp (Populus tremula) GT med olika förmåga att producera KT (låg- och hög-tannin producenter). Växterna odlades i tre olika N förhållanden, som representerade ambient N nivå (+0 kg ha-1), atmosfärisk N deposition = låg nivå (+15 kg ha-1), och skogsgödsling = hög nivå (150 kg ha‑1). Dessa GT etablerades i en fält-liknande miljö där naturliga fiender uteslutits och i ett fält där naturliga fiender var närvarande. I mina första två studierna undersökte jag vävnadskemi och växternas prestationsförmåga i de båda miljöerna. Jag observerade att KT nivåerna sjönk till följd av N‑tillsats i den fiende-fria miljön (studie I), men ökade med N-tillsats ifall fiender var närvarande (studie II). Dessa motsatta reaktioner på N-tillsats kan förklaras av skillnader i N-tillgång mellan de två odlingsplatserna eller genom ökad KT produktion som respons på angrepp. Skador orsakade av herbivorer och patogener ökade generellt till följd av N‑tillsats och var högre i låg-tannin än i hög‑tannin producerande GT oavsett N‑förhållande. Tillväxten hos växter från högtannin GT begränsades i ambient- och låg N-tillsats förhållanden, troligen på grund av att avvägning mellan tillväxt och försvar förskjutits emot försvar. Den begränsade tillväxten i hög-tannin växter minskade om stora mängder N tillsattes (studie I och II) och om antalet fiender var tillräckligt högt så att nyttan av försvaret kunde uppväga kostnaderna för försvarsproduktionen (studie II). Trots dessa generella respons hos låg- och hög-tannin GT till följd av N‑tillsats observerade jag även ett antal individuella respons hos GT som i vissa fall var orelaterade till växters förmåga att producera KT. I studie III undersöktes genuttrycksnivåer och fenolinnehåll i blad från växter som odladats i en miljö där naturliga fiender exkluderats. Denna studie visade att fenylpropanoidsyntesvägen (FPV) regleras genom kontroll av många av de undersökta FPV-generna. Dessutom var FPV genuttryck högre i hög-tannin GT än i låg-tannin GT, särskilt vid ambient N. Vid låg N-tillsats minskade genuttrycket av FPV-gener i både låg- och hög-tannin producenter, medan hög N-tillgång ledde till att gener i början och slutet av FPV uppreglerades och till att skillnaderna mellan tannin grupperna försvann. Dessutom visade studien att de separata fenol-poolerna ofta var okorrelerade med varandra och att fenol-poolerna bara till viss del var korrelerade med KT produktion och FPV-genutryck. I studie IV undersökte jag nedbrytningshastigheten för förnan från fältodlade aspar. Jag upptäckte att N-tillsats generellt minskade viktförlusten men att det fanns en betydande genetisk variation mellan GT och att dessa även var olika mottagliga för tillsatt N. Studie IV visade vidare att KT endast hade en svag effekt på nedbrytning och att andra egenskaper såsom specifik bladyta och lignin:N ratio kunde bättre förklara den genotypiska skillnaden i viktförlust. Dessutom orsakade N‑tillsats en förskjutning av vilka egenskaper som mest påverkade förnans nedbrytningshastighet. Sammanfattningsvis visar mina studier på vikten av genetisk mångfald för att främja växtartens stabilitet i miljöer som upplever antropogena förändringar.

  • 3. Baskaran, Preetisri
    et al.
    Ekblad, Alf
    Soucémarianadin, Laure N.
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik. CNRS, Laboratoire de Géologie de l’ENS, Ecole Normale Supérieure, Paris, France.
    Hyvönen, Riitta
    Schleucher, Jürgen
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Lindahl, Björn D.
    Nitrogen dynamics of decomposing Scots pine needle litter depends on colonizing fungal species2019Ingår i: FEMS Microbiology Ecology, ISSN 0168-6496, E-ISSN 1574-6941, Vol. 95, nr 6, artikel-id fiz059Artikel i tidskrift (Refereegranskat)
    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 C-13 CP/MAS NMR spectroscopy and nitrogen dynamics was assessed by the addition of a N-15 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.

  • 4.
    Blume-Werry, Gesche
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Jansson, Roland
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Milbau, Ann
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Department of Biodiversity and Natural Environment, Research Institute for Nature and Forest INBO, Kliniekstraat 25,1070 Brussels, Belgium.
    Root phenology unresponsive to earlier snowmelt despite advanced above-ground phenology in two subarctic plant communities2017Ingår i: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 31, nr 7, s. 1493-1502Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    1. Earlier snowmelt at high latitudes advances above-ground plant phenology, thereby affecting water, nutrient and carbon cycles. Despite the key role of fine roots in these ecosystem processes, phenological responses to earlier snowmelt have never been assessed below-ground. 2. We experimentally advanced snowmelt in two contrasting plant community types (heath and meadow) in northern Sweden and measured above- and below-ground phenology (leaf-out, flowering and fine root growth). We expected earlier snowmelt to advance both above- and below-ground phenology, and shrub-dominated heath to be more responsive than meadow. 3. Snow melted on average 9 days earlier in the manipulated plots than in controls, and soil temperatures were on average 0.9 degrees C higher during the snowmelt period of 3 weeks. This resulted in small advances in above-ground phenology, but contrary to our expectations, root phenology was unresponsive, with root growth generally starting before leaf-out. These responses to the snowmelt treatment were similar in both plant community types, despite strong differences in dominating plant functional types and root properties, such as root length and turnover. 4. The lack of a response in root phenology, despite warmer soil temperatures and above-ground phenological advances, adds evidence that above-ground plant responses might not be directly translated to below-ground plant responses, and that our understanding of factors driving below-ground phenology is still limited, although of major importance for water, nutrient and carbon cycling.

  • 5. Bokhorst, Stef
    et al.
    Veen, G. F. (Ciska)
    Sundqvist, Maja K.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE901-83 Umeå, Sweden; Center for Macroecology, Evolution and Climate, Natural History Museum of Denmark, University of Copenhagen, Sølvgade 83S, DK-1307 Copenhagen K, Denmark.
    De Long, Jonathan R.
    Kardol, Paul
    Wardlea, David A.
    Contrasting responses of springtails and mites to elevation and vegetation type in the sub-Arctic2018Ingår i: Pedobiologia, ISSN 0031-4056, E-ISSN 1873-1511, Vol. 67, s. 57-64Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Climate change is affecting the species composition and functioning of Arctic and sub-Arctic plant and soil communities. Here we studied patterns in soil microarthropod (springtails and mites) communities across a gradient of increasing elevation that spanned 450 m, across which mean temperature declined by approximately 2.5 degrees C, in sub-Arctic Sweden. Across this gradient we characterized microarthropod communities in each of two types of vegetation, i.e., heath and meadow, to determine whether their responses to declining temperature differed with vegetation type. Mite abundance declined with increasing elevation, while springtail abundance showed the opposite response. Springtail communities were dominated by larger species at higher elevation. Mite abundance was unaffected by vegetation type, while springtail abundance was 53% higher in the heath than meadow vegetation across the gradient. Springtails but not mites responded differently to elevation in heath and meadow vegetation; hemi-edaphic species dominated in the heath at higher elevation while epiedaphic species dominated in the meadow. Our results suggest that sub-Arctic mite and springtail communities will likely respond in contrasting ways to changes in vegetation and soil properties resulting from climate warming.

  • 6. Bonner, Mark T. L.
    et al.
    Castro, David
    Schneider, Andreas N.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Sundstrom, Gorel
    Hurry, Vaughan
    Street, Nathaniel R.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Nasholm, Torgny
    Why does nitrogen addition to forest soils inhibit decomposition?2019Ingår i: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 137, artikel-id 107570Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Enrichment of forest soils with inorganic nitrogen (N) tends to inhibit oxidative enzyme expression by microbes and reduces plant litter and soil organic matter decomposition rates. Without further explanation than is currently presented in the scientific literature, we argue that upregulation of oxidative enzymes seems a more competitive response to prolonged N enrichment at high rates than the observed downregulation. Thus, as it stands, observed responses are inconsistent with predicted responses. In this article, we present a hypothesis that resolves this conflict. We suggest that high rates of N addition alter the competitive balance between enzymatic lignin mineralisation and non-enzymatic lignin oxidation. Using metatransciptomics and chemical assays to examine boreal forest soils, we found that N addition suppressed peroxidase activity, but not iron reduction activity (involved in non-enzymatic lignin oxidation). Our hypothesis seems positioned as a parsimonious and empirically consistent working model that warrants further testing.

  • 7.
    Buckland, Philip I
    et al.
    Umeå universitet, Humanistiska fakulteten, Arkeologi och samiska studier.
    Johan, Olofsson
    Umeå universitet, Humanistiska fakulteten, Arkeologi och samiska studier.
    Engelmark, Roger
    Umeå universitet, Humanistiska fakulteten, Arkeologi och samiska studier.
    SEAD: Strategic Environmental Archaeology Database, planning report2006Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This document lays out a strategy for the development of SEAD – A Strategic Environmental Archaeology Database, which will facilitate the digitisation and accessibility augmentation of MAL’s existing data from nearly thirty years of work in the fields of archaeology and environmental science. SEAD will also provide a framework for the entry of data from all future research and consultancy work at MAL, and allow guest researchers and external partners to contribute to, and work with the same data. The planned system will be implemented at both local and internet levels, and be designed with an aim towards broadening its scope with external partners in the future. SEAD will be made available online in order to increase the ease of access to environmental archaeology data and encourage an expansion of both the discipline and Sweden’s role in it. This is inline with current EU strategies on enhancing research infrastructure, and providing a greater insight into human-environment interactions for long term planning.

  • 8. De Long, Jonathan R.
    et al.
    Laudon, Hjalmar
    Blume-Werry, Gesche
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Kardol, Paul
    Nematode community resistant to deep soil frost in boreal forest soils2016Ingår i: Pedobiologia, ISSN 0031-4056, E-ISSN 1873-1511, Vol. 59, nr 5-6, s. 243-251Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    As global climate change advances, shifts in winter precipitation are becoming more common in high latitude ecosystems, resulting in less insulating snow cover and deeper soil frost. Long-term alterations to soil frost can impact on ecosystem processes such as decomposition, microbial activity and vegetation dynamics. In this study we utilized the longest running, well-characterized soil frost manipulation experiment in a boreal forest. We measured nematode family composition and feeding group abundances at four different soil layer depths from plots that had been subjected to deep soil frost for one and 11 years. The overall abundance of nematodes and the different feeding groups were unaffected by deep soil frost. However, a higher Maturity Index was weakly associated with deep soil frost (indicative of lower nutrient enrichment and more persister nematode (i.e., K-strategist) families), likely due to the loss of nutrients and reduced inputs from inhibited decomposition. Multivariate and regression analyses showed that most nematode families were weakly associated with dominant understory plant species and strongly associated with soil organic matter (SOM). This is probably the result of higher resource availability in the control plots, which is favorable to the nematode community. These results indicate that the nematode community was more strongly driven by the long-term indirect effects of deep soil frost on SOM as opposed to the direct effects. Our findings highlight that the indirect effects of altered winter precipitation and soil frost patterns may be more important than direct winter climate effects. Further, such indirect effects on SOM and the plant community that may affect the nematode community can only be seen in long-term experiments. Finally, given the critical role nematodes play in soil food webs and carbon and nutrient cycling, our results demonstrate the necessity of considering the response of nematodes to global climate change in boreal forest soils. 

  • 9.
    Erhagen, Björn
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Swedish Univ Agr Sci SLU, Dept Forest Ecol & Management, S-90183 Umeå, Sweden.
    Ilstedt, Ulrik
    Nilsson, Mats B.
    Temperature sensitivity of heterotrophic soil CO2 production increases with increasing carbon substrate uptake rate2015Ingår i: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 80, s. 45-52Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Temperature profoundly affects saprotrophic respiration rates, and carbon quality theory predicts that the rates' temperature Sensitivity should increase as the quality of the carbon source declines. However, reported relationships between saprotrophic respiration responses to temperature and carbon quality vary widely. Some of this variability may arise from confounding effects related to both substrate quality and substrate availability. The importance of these variables, as well as substrate diffusion and uptake rates, for the temperature sensitivity of saprotrophic respiration has been validated theoretically, but not empirically demonstrated. Thus, we tested effects of varying substrate uptake rates on the temperature sensitivity of organic carbon degradation. For this purpose we created a model system using the organic layer (O-horizon), of a boreal forest soil, specifically to test effects of varying monomer uptake and release rates. The addition of both monomers and polymers generally increased the temperature sensitivity of saprotrophic respiration. In response to added monomers, there was a linear increase in the temperature sensitivity of both substrate-induced respiration and the specific growth rate with increasing rate of substrate uptake as indicated by the CO2 production at 14 degrees C. Both of these responses diverge from those predicted by the carbon quality theory, but they provide the first empirical evidence consistent with model predictions demonstrating increased temperature sensitivity with increased uptake rate of carbon monomers over the cell membrane. These results may explain why organic material of higher carbon quality induces higher temperature responses than lower carbon quality compounds, without contradicting carbon quality theory. 

  • 10. Ferro-Vazquez, C.
    et al.
    Novoa-Munoz, J. C.
    Costa-Casais, M.
    Klaminder, Jonatan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Martinez-Cortizas, A.
    Metal and organic matter immobilization in temperate podzols: a high resolution study2014Ingår i: Geoderma, ISSN 0016-7061, E-ISSN 1872-6259, Vol. 217, s. 225-234Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Aluminium and Fe fractions were obtained in samples from two temperate podzols by selective extraction with NaOH (Al-n, Fe-n), Na-dithionite-citrate (Al-d, Fe-d), acid NH4-oxalate (Al-o, Fe-o) and Na-pyrophosphate (Al-p, Fe-p) following the traditional fractionation procedures, and also by the use of the chlorides of K (Al-K), La (Al-La) and Cu (Al-cu) as non-buffered extractants for Al. Carbon content was also determined in the Na-pyrophosphate extract (C-p). Soil sampling was done at high-resolution to allow a more detailed characterization of the vertical processes than the traditional sampling by whole soil horizons. Results showed that Al-p and Fe-p make a large proportion of the Alo and Fe-o meaning that organoaluminic complexes dominated in the "active" metal pool instead of inorganic compounds. The degree of metal saturation of soil organic matter (estimated by the (Al-p Fe-p)/C-p molar ratios) increases with depth, especially in the uppermost samples of spodic horizons (Bhs1) where it increases up to 0.1. Aluminium dominates in the adsorption positions of the organic matter in the spodic horizon (Fe-p/Al-p ratios <0.5), except in the Bhs1 horizon (ratios > 1), indicating that the immobilization of Fe containing complexes occurs 10-15 cm above that of Al The highly stable Al-OM complexes accounted on average for 60% of the organoaluminic associations (>70% in the Bhs horizons). The moderately stable complexes predominate in A horizons (57-77% in ACB1 and 37-48% in ACB2) and the largest proportions of low stability complexes were found in the uppermost samples of the spodic horizons (Bhs1) of both soils (9-21%), together with the highest Fep contents and a decrease in pH values. From a stepwise multiple regression model it is suggested that pH is the main variable accounting for the stability of Al-OM compounds together with C and organically bound Fe contents. It is suggested that the illuviation of unsaturated organic acids lower the pH in upper spodic horizons, leading to the complexation of metals from formerly precipitated organometallic complexes and/or leading to their redissolution, enabling their migration to deeper soil layers. Iron complexes would be less soluble at soil pH, resulting in a differentiation of an upper Fe-rich Bhs1 horizon and a lower Bhs2 Al-rich horizon. The depth variation in C accumulation was found to be related to the proportion of highly stable Al-OM fraction.

  • 11. George, T. S.
    et al.
    Giles, C. D.
    Menezes-Blackburn, D.
    Condron, L. M.
    Gama-Rodrigues, A. C.
    Jaisi, D.
    Lang, F.
    Neal, A. L.
    Stutter, M. , I
    Almeida, D. S.
    Bol, R.
    Cabugao, K. G.
    Celi, L.
    Cotner, J. B.
    Feng, G.
    Goll, D. S.
    Hallama, M.
    Krueger, J.
    Plassard, C.
    Rosling, A.
    Darch, T.
    Fraser, T.
    Giesler, Reiner
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Richardson, A. E.
    Tamburini, F.
    Shand, C. A.
    Lumsdon, D. G.
    Zhang, H.
    Blackwell, M. S. A.
    Wearing, C.
    Mezeli, M. M.
    Almas, A. R.
    Audette, Y.
    Bertrand, I
    Beyhaut, E.
    Boitt, G.
    Bradshaw, N.
    Brearley, C. A.
    Bruulsema, T. W.
    Ciais, P.
    Cozzolino, V
    Duran, P. C.
    Mora, M. L.
    de Menezes, A. B.
    Dodd, R. J.
    Dunfield, K.
    Engl, C.
    Frazao, J. J.
    Garland, G.
    Jimenez, J. L. Gonzalez
    Graca, J.
    Granger, S. J.
    Harrison, A. F.
    Heuck, C.
    Hou, E. Q.
    Johnes, P. J.
    Kaiser, K.
    Kjaer, H. A.
    Klumpp, E.
    Lamb, A. L.
    Macintosh, K. A.
    Mackay, E. B.
    McGrath, J.
    McIntyre, C.
    McLaren, T.
    Meszaros, E.
    Missong, A.
    Mooshammer, M.
    Negron, C. P.
    Nelson, L. A.
    Pfahler, V
    Poblete-Grant, P.
    Randall, M.
    Seguel, A.
    Seth, K.
    Smith, A. C.
    Smits, M. M.
    Sobarzo, J. A.
    Spohn, M.
    Tawaraya, K.
    Tibbett, M.
    Voroney, P.
    Wallander, H.
    Wang, L.
    Wasaki, J.
    Haygarth, P. M.
    Organic phosphorus in the terrestrial environment: a perspective on the state of the art and future priorities2018Ingår i: Plant and Soil, ISSN 0032-079X, E-ISSN 1573-5036, Vol. 427, nr 1-2, s. 191-208Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background: The dynamics of phosphorus (P) in the environment is important for regulating nutrient cycles in natural and managed ecosystems and an integral part in assessing biological resilience against environmental change. Organic P (P-o) compounds play key roles in biological and ecosystems function in the terrestrial environment being critical to cell function, growth and reproduction.

    Scope: We asked a group of experts to consider the global issues associated with P-o in the terrestrial environment, methodological strengths and weaknesses, benefits to be gained from understanding the P-o cycle, and to set priorities for P-o research.

    Conclusions: We identified seven key opportunities for P-o research including: the need for integrated, quality controlled and functionally based methodologies; assessment of stoichiometry with other elements in organic matter; understanding the dynamics of P-o in natural and managed systems; the role of microorganisms in controlling P-o cycles; the implications of nanoparticles in the environment and the need for better modelling and communication of the research. Each priority is discussed and a statement of intent for the P-o research community is made that highlights there are key contributions to be made toward understanding biogeochemical cycles, dynamics and function of natural ecosystems and the management of agricultural systems.

  • 12.
    Giesler, Reiner
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Karina, E. Clemmensen
    Wardle, David A.
    Klaminder, Jonatan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Bindler, Richard
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Boreal Forests Sequester Large Amounts of Mercury over Millennial Time Scales in the Absence of Wildfire2017Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 51, nr 5, s. 2621-2627Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Alterations in fire activity due to climate change and fire suppression may have profound effects on the balance between storage and release of carbon (C) and associated volatile elements. Stored soil mercury (Hg) is known to volatilize due to wildfires and this could substantially affect the land air exchange of Hg; conversely the absence of fires and human disturbance may increase the time period over which Hg is sequestered. Here we show for a wildfire chronosequence spanning over more than 5000 years in boreal forest in northern Sweden that belowground inventories of total Hg are strongly related to soil humus C accumulation (R-2 = 0.94, p < 0.001). Our data clearly show that northern boreal forest soils have a strong sink capacity for Hg, and indicate that the sequestered Hg is bound in soil organic matter pools accumulating over millennia. Our results also suggest that more than half of the Hg stock in the sites with the longest time since fire originates from deposition predating the onset of large-scale anthropogenic emissions. This study emphasizes the importance of boreal forest humus soils for Hg storage and reveals that this pool is likely to persist over millennial time scales in the prolonged absence of fire.

  • 13. Högberg, Peter
    et al.
    Högberg, M. N.
    Göttlicher, S. G.
    Betson, N. R.
    Keel, S. G.
    Metcalfe, D. B.
    Campbell, Catherine
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Schindlbacher, A.
    Hurry, Vaughan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    Lundmark, Thomas
    Linder, Sune
    Näsholm, Torgny
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    High temporal resolution tracing of photosynthate carbon from the tree canopy to forest soil microorganisms2008Ingår i: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 177, nr 1, s. 220-228Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

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

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

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

  • 14.
    Lett, Signe
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Department of Biology, Terrestrial Ecology Section, University of Copenhagen, Øster Farimagsgade 2D, Copenhagen, DK-1353 K, Denmark.
    Michelsen, Anders
    Department of Biology, Terrestrial Ecology Section, University of Copenhagen, Øster Farimagsgade 2D, Copenhagen, DK-1353 K, Denmark.
    Seasonal variation in nitrogen fixation and effects of climate change in a subarctic heath2014Ingår i: Plant and Soil, ISSN 0032-079X, E-ISSN 1573-5036, Vol. 379, nr 1-2, s. 193-204Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nitrogen fixation associated with cryptogams is potentially very important in arctic and subarctic terrestrial ecosystems, as it is a source of new nitrogen (N) into these highly N limited systems. Moss-, lichen- and legume-associated N-2 fixation was studied with high frequency (every second week) during spring, summer, autumn and early winter to uncover the seasonal variation in input of atmospheric N-2 to a subarctic heath with an altered climate. We estimated N-2 fixation from ethylene production by acetylene reduction assay in situ in a field experiment with the treatments: long- vs. short-term summer warming using plastic tents and litter addition (simulating expansion of the birch forest). N-2 fixation activity was measured from late April to mid November and 33 % of all N-2 was fixed outside the vascular plant growing season (Jun-Aug). This substantial amount underlines the importance of N-2 fixation in the cold period. Warming increased N-2 fixation two- to fivefold during late spring. However, long-term summer warming tended to decrease N-2 fixation outside the treatment (tents present) period. Litter alone did not alter N-2 fixation but in combination with warming N-2 fixation increased, probably because N-2 fixation became phosphorus limited under higher temperatures, which was alleviated by the P supply from the litter. In subarctic heath, the current N-2 fixation period extends far beyond the vascular plant growing season. Climate warming and indirect effects such as vegetation changes affect the process of N-2 fixation in different directions and thereby complicate predictions of future N cycling.

  • 15.
    Metcalfe, Daniel B.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Microbial change in warming soils2017Ingår i: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 358, nr 6359, s. 41-42Artikel i tidskrift (Övrigt vetenskapligt)
  • 16.
    Ohlsson, Anders
    Department of Forest Ecology and Management, Swedish university of Agricultural Sciences (SLU), Skogsmarksgränd, SE-901 83 Umeå, Sweden.
    Theoretical model of the abiotic component of soil (CO2)-C-13 tracer efflux in C-13 pulse-labeling experiments on plant-soil systems2011Ingår i: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 43, nr 3, s. 675-681Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    For measurement of the time lag between photosynthesis and CO2 efflux from soil, the carbon isotope pulse-labeling technique is considered as the most suitable. However, an interference from the abiotic tracer CO2 component is identified as a key difficulty for obtaining accurate results with this technique. Guidelines on how to reduce this interference are therefore urgently needed. The flux of abiotic (CO2)-C-13 tracer into soil during the labeling stage, and its return to atmosphere during the monitoring stage was modeled numerically, and the labeling stage also analytically. The controls of the abiotic interference were investigated using these models. The amount of the abiotic tracer component and the time distribution of its rate of return to the atmosphere, were predicted by these models. The main model parameters were D-m (=the ratio between the soil (CO2)-C-13 diffusivity and the retardation factor), and the (CO2)-C-13 concentration at the soil atmosphere interface during the labeling stage (S-13), while background (CO2)-C-13 soil production parameters were unnecessary. The presented models guide the selection of experimental parameters for minimization of the abiotic interference. With parameterization for a particular case, the present numerical model provides a preliminary order-of-magnitude estimate of the abiotic component, which would indicate if this interference is of significance.

  • 17. Ouyang, Wei
    et al.
    Huang, Weijia
    Hao, Xin
    Tysklind, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Haglund, Peter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Hao, Fanghua
    Watershed soil Cd loss after long-term agricultural practice and biochar amendment under four rainfall levels2017Ingår i: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 122, s. 692-700Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Some heavy metals in farmland soil can be transported into the waterbody, affecting the water quality and sediment at the watershed outlet, which can be used to determine the historical loss pattern. Cd is a typical heavy metal leached from farmland that is related to phosphate fertilizers and carries serious environmental risk. The spatial-vertical pattern of Cd in soil and the vertical trend of Cd in the river sediment core were analyzed, which showed the migration and accumulation of Cd in the watershed. To prevent watershed Cd loss, biochar was employed, and leaching experiments were conducted to investigate the Cd loss from soil depending on the initial concentration. Four rainfall intensities, 1.25 mm/h, 2.50 mm/h, 5.00 mm/h, and 10.00 mm/h, were used to simulate typical rainfall scenarios for the study area. Biochar was prepared from corn straw after pretreatment with ammonium dihydrogen phosphate (ADP) and pyrolysis at 400 °C under anoxic conditions. To identify the effects of biochar amendment on Cd migration, the biochar was mixed with soil for 90 days at concentrations of 0%, 0.5%, 1.0%, 3.0%, and 5.0% soil by weight. The results showed that the Cd leaching load increased as the initial load and rainfall intensity increased and that eluviation caused surface Cd to diffuse to the deep soils. The biochar application caused more of the heavy metals to be immobilized in the amended soil rather than transported into the waterbody. The sorption efficiency of the biochar for Cd increased as the addition level increased to 3%, which showed better performance than the 5% addition level under some initial concentration and rainfall conditions. The research indicated that biochar is a potential material to prevent diffuse heavy metal pollution and that a lower addition makes the application more feasible.

  • 18. Pu, Xiao
    et al.
    Cheng, Hongguang
    Tysklind, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Xie, Jing
    Lu, Lu
    Yang, Shengtian
    Indications of soil properties on dissolved organic carbon variability following a successive land use conversion2018Ingår i: Ecological Engineering: The Journal of Ecotechnology, ISSN 0925-8574, E-ISSN 1872-6992, Vol. 117, s. 115-119Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In seasonal freeze-thaw zones of NE China, the policy-oriented land management has caused successive land use conversions of native woodland, dry cropland and paddy field for food security. Controls of soil property factors on soil dissolved organic carbon (DOC) dynamics might vary with deforestation. This study aimed to test performance of soil properties interpreting DOC variability along soil profile following a vegetation succession of native forest, rainfed crops (maize-soybean rotations) and paddy rice in an observation area of the Sanjiang Plain. The linear mixed effects model evaluated relative importance of soil properties with comparisons of adjusting and not adjusting for random effects of land use and soil depth as subject variables. The modeling results revealed presence of consistent soil property factors indicating DOC dynamics before and after deforestation. When excluding interferences of land uses and soil layers, interpretations of soil properties were weakened. Soil moisture and bulk density predominantly accounted for DOC variability across land uses, presenting greater estimated effects (0.69 and -0.64, respectively) over those of total nitrogen, soil organic carbon and hydrolyzable nitrogen (0.49, 0.44 and 0.31, respectively). But no soil property factor indicated DOC variability with soil depth. Further research is needed to understand why indications of soil moisture and bulk density on DOC dynamics would differ between horizontal and vertical.

  • 19.
    Pu, Xiao
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. College of Resource, Environment and Tourism, Capital Normal University, Beijing, China ; State Key Laboratory of Remote Sensing Science, School of Geography, Beijing Normal University, Beijing, China.
    Cheng, Hongguang
    Tysklind, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Yang, Shengtian
    Lin, Chunye
    Lu, Lu
    Xie, Jing
    Responses of soil carbon and nitrogen to successive land use conversion in seasonally frozen zones2015Ingår i: Plant and Soil, ISSN 0032-079X, E-ISSN 1573-5036, Vol. 387, nr 1-2, s. 117-130Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Policy-oriented successive land use conversion intensively occurred in seasonally frozen zones of China during the past five decades. However, responses of soil carbon (C) and nitrogen (N) to land use conversion under cold temperate climates are not fully understood. The objective was to characterize C and N variations following a succession of forest, dryland and paddy. Soil cores were collected for 6 layers with a 10 cm increment from three adjacent chronosequences to determine concentrations of soil organic carbon (SOC), total nitrogen (TN), dissolved organic carbon (DOC) and alkaline hydrolysable nitrogen (HN). Analysis of variance with multivariate general linear model was operated on data sets. Significant losses of SOC and TN storages subject to land use conversion were merely confined within 0 - 10 cm layer, decreasing by 16 % and 38 % for forest to dryland and by 23 % and 43 % for forest to paddy, respectively. Cultivation also influenced SOC and TN stocks at 20 - 40 cm depth for dryland and 20 - 60 cm depth for paddy with increases by 38 Mg C ha(-1) and 2.8 Mg N ha(-1) for forest to dryland, and by 56 Mg C ha(-1) and 4.1 Mg N ha(-1) for forest to paddy, respectively. Successive land use conversion from forest to cropland affected C and N levels in deeper layers, demonstrating the high potentials of subsoil in sequestrating C and N. The extents of cultivation-induced SOC and TN redistribution along soil profile varied among different agricultural systems. DOC and HN changes interpreted SOC and TN changes with land use, presenting high involvements of soluble compartments in SOC and TN variations. The net variation in SOC/TN ratio effectively indicated C and N changes when dryland was converted to paddy.

  • 20. Puissant, Jeremy
    et al.
    Jassey, Vincent E. J.
    Mills, Robert T. E.
    Robroek, Bjorn J. M.
    Gavazov, Konstantin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. École Polytechnique Fédérale de Lausanne EPFL, School of Architecture, Civil and Environmental Engineering, Laboratory of Ecological Systems, Station 2, 1015, Lausanne, Switzerland; Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Site Lausanne, Station 2, 1015, Lausanne, Switzerland.
    De Danieli, Sebastien
    Spiegelberger, Thomas
    Griffiths, Robert
    Buttler, Alexandre
    Brun, Jean-Jacques
    Cecillon, Lauric
    Seasonality alters drivers of soil enzyme activity in subalpine grassland soil undergoing climate change2018Ingår i: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 124, s. 266-274Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In mountain ecosystems with marked seasonality, climate change can affect various processes in soils, potentially modifying long-term key soil services via change in soil organic carbon (C) storage. Based on a four-year soil transplantation experiment in Swiss subalpine grasslands, we investigated how imposed climate warming and reduced precipitation modified the drivers of soil carbon enzyme potential activities across winter and summer seasons. Specifically, we used structural equation models (SEMs) to identify biotic (microbial community structure, abundance and activity) and abiotic (quantity and quality of organic matter resources) drivers of soil C-enzymes (hydrolase and oxidase) in two seasons under two different climate scenarios. We found contrasting impacts of the climate manipulation on the drivers of C-enzymes between winter and summer. In winter, no direct effect of climate manipulation (reduced rainfall and warming) on enzyme activity was observed. Yet, climate indirectly down-regulated enzyme activity through a decrease in the availability of water extractable organic carbon (WEOC) labile resources. During summer, reduced soil moisture induced by the climate manipulation directly reduced soil microbial biomass, which led to a decrease in C-enzyme activity. In general, across both seasons, neither microbial community structure, nor organic matter quality were strong determinants of enzymatic activity. In particular organic matter recalcitrance (aromaticity) was not found as a general driver of either hydrolase or oxidase C-enzyme potential activities, though we did observe higher C enzyme activities led to an increase of particulate organic matter recalcitrance in the summer season. Overall, our results highlight the seasonality of climate change effects on soil organic matter enzymatic decomposition, providing a comprehensive picture of seasonal potential cause and effect relationships governing C mineralization in subalpine grasslands.

  • 21. Segura, Javier H.
    et al.
    Nilsson, Mats B.
    Schleucher, Jürgen
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Haei, Mahsa
    Sparrman, Tobias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Székely, Anna
    Bertilsson, Stefan
    Öquist, Mats G.
    Microbial utilization of simple carbon substrates in boreal peat soils at low temperatures2019Ingår i: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 135, s. 438-448Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Boreal peatlands are key high-latitude ecosystem types and act as a carbon (C) sink storing an estimated 25% of the world's soil C. These environments are currently seeing the most substantial changing climate, especially during the winter. CO2 emissions during the winter can correspond to 80% of the growing season's net CO2 assimilation. Yet, our conceptual understanding of the controls on microbial metabolic activity in peat soils at temperatures ≤0 °C is poor. We used stable isotope probing of peat samples and tracked the fate of 13C-glucose using 13C-NMR. We show that microorganisms in frozen boreal peat soils utilize monomeric C-substrates to sustain both catabolic and anabolic metabolism at temperatures down to −5 °C. The 13C-substrate was transformed into 13C–CO2, different metabolites, and incorporated into membrane phospholipid fatty acids. The 16S rRNA-based community analyses revealed the activity at −3 °C changes the composition of the bacterial community over relevant timescales. Below 0 °C, small temperature changes have strong effects on process rates and small differences in winter soil temperature may affect C dynamics of northern peatlands. Understanding biological processes at low and below zero temperatures are central for the overall functioning of these systems representing one of the world's major soil C pools.

  • 22.
    Soucemarianadin, Laure N.
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Erhagen, Björn
    Nilsson, Mats B.
    Öquist, Mats G.
    Immerzeel, Peter
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Schleucher, Jürgen
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Two dimensional NMR spectroscopy for molecular characterization of soil organic matter: Application to boreal soils and litter2017Ingår i: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 113, s. 184-195Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Organic soils in boreal ecosystems and peatlands represent a huge global carbon pool and their composition strongly affects soil properties. Nevertheless, the characterization of soil organic matter (SOM) molecular composition, which is essential for elucidating soil carbon processes and turnover, is not easily achieved, and further advances in the area are greatly needed. Two dimensional (2D) liquid state H-1-C-13 nuclear magnetic resonance (NMR) spectroscopy has been used on dimethyl sulfoxide (DMSO) extracts of SOM to achieve molecular level characterization, with signals from many identifiable molecular groups observable. Here we show that a simple and fast sample preparation allows acquisition of 2D H-1-C-13 NMR spectra from extracts of plant litter and organic layers in boreal ecosystems, with fast data acquisition. Our 2D NMR spectra revealed several differences in the DMSO extracts of different tree litter samples, O-horizons of forest soil, peat-forming moss (Sphagnum) and peat. The results mirror established differences between OM in soils and litter of different forest ecosystems (e.g. between deciduous and coniferous litter) but also provide indications for research to untangle previously conflicting results (e.g. cutin degradation in soil or carbohydrate degradation in peat). Thus, combination of 2D NMR methods can greatly improve analysis of litter composition and SOM composition, thereby facilitating the elucidation of their roles in biogeochemical and ecological processes that are critical for foreseeing feedback mechanisms for SOM turnover as a result of global environmental change.

  • 23.
    Su, Xiaolei
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Key Laboratory of Eco-Environments in Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources in Three Gorges Reservoir Region, School of Life Sciences, Southwest University, Beibei, Chongqing 400715, PR China.
    Nilsson, Christer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Pilotto, Francesca
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Liu, Songping
    Shi, Shaohua
    Zeng, Bo
    Soil erosion and deposition in the new shorelines of the Three Gorges Reservoir2017Ingår i: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 599, s. 1485-1492Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    During the last few decades, the construction of storage reservoirs worldwide has led to the formation of many new shorelines in former upland areas. After the formation of such shorelines, a dynamic phase of soil erosion and deposition follows. We explored the factors regulating soil dynatitics in the shorelines of the Three Gorges Reservoir (TGR) on the Yangtze River in China. We selected four study sites on the main stem and three on the tributaries in the upstream parts of the reservoir, and evaluated whether the sites close to the backwater tail (the point at which the river meets the reservoir) had more soil deposition than the sites far from the backwater tail. We also tested whether soil erosion differed between the main stem and the tributaries and across shorelines. We found that soil deposition in the new shorelines was higher close to the backwater tail and decreased downstream. Soil erosion was higher in the main stem than in the tributaries and higher at lower compared to higher shoreline altitudes. In the tributaries, erosion did not differ between higher and lower shoreline levels. Erosion increased with increasing fetch length, inundation duration and distance from the backwater tail, and decreased with increasing soil particle fineness. Our results provide a basis for identifying shorelines in need of restorative or protective measures.

  • 24.
    Sundqvist, Maja K.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Department of Forest Ecology and Management, SLU, Umeå, Sweden.
    Wardle, David A.
    Department of Forest Ecology and Management, SLU, Umeå, Sweden.
    Vincent, Andrea
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Giesler, Reiner
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Contrasting nitrogen and phosphorus dynamics across an elevational gradient for subarctic tundra heath and meadow vegetation2014Ingår i: Plant and Soil, ISSN 0032-079X, E-ISSN 1573-5036, Vol. 383, nr 1-2, s. 387-399Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study explores soil nutrient cycling processes and microbial properties for two contrasting vegetation types along an elevational gradient in subarctic tundra to improve our understanding of how temperature influences nutrient availability in an ecosystem predicted to be sensitive to global warming. We measured total amino acid (Amino-N), mineral nitrogen (N) and phosphorus (P) concentrations, in situ net N and P mineralization, net Amino-N consumption, and microbial biomass C, N and P in both heath and meadow soils across an elevational gradient near Abisko, Sweden. For the meadow, NH4 (+) concentrations and net N mineralization were highest at high elevations and microbial properties showed variable responses; these variables were largely unresponsive to elevation for the heath. Amino-N concentrations sometimes showed a tendency to increase with elevation and net Amino-N consumption was often unresponsive to elevation. Overall, PO4-P concentrations decreased with elevation and net P immobilization mostly occurred at lower elevations; these effects were strongest for the heath. Our results reveal that elevation-associated changes in temperature can have contrasting effects on the cycling of N and P in subarctic soils, and that the strength and direction of these effects depend strongly on dominant vegetation type.

  • 25. Sánchez-Osorio, José Luis
    et al.
    Macías-Zamora, José Vinicio
    Ramírez-Álvarez, Nancy
    Bidleman, Terry F.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Organochlorine pesticides in residential soils and sediments within two main agricultural areas of northwest Mexico: concentrations, enantiomer compositions and potential sources2017Ingår i: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 173, s. 275-287Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The agricultural Mexicali and Yaqui valleys (MV, YV) in northwest Mexico were heavily treated with organochlorine pesticides in the past. Residential soils and agricultural drain sediments were sampled in 2008–2009 and analyzed for DDTs (o,p′- and p,p′- isomers of DDE, DDD and DDT); hexachlorocyclohexanes (α-, β-, γ- and δ-HCH) and chlordanes (trans-chlordane, cis-chlordane, heptachlor and heptachlor exo-epoxide). Geometric means (GMs) (ng g−1 dry weight) were: MV soils (n = 27) ΣDDT 22, ΣHCH 0.80, ΣCHL 0.88; YV soils (n = 25) ΣDDT 5.0, ΣHCH 0.23, ΣCHL 0.67; MV sediments (n = 3) ΣDDT 5.0, ΣHCH 0.23, ΣCHL 0.53; YV sediments (n = 8) ΣDDT 2.6, ΣHCH 0.12, ΣCHL 0.090. GMs were significantly higher (p &lt; 0.05) in MV than YV soils for ΣDDT and ΣHCH, but not for ΣCHL. Comparison to worldwide regulatory guideline values (RGVs) for residential soils showed all compounds below mean or GM RGVs, but above the lowest RGV in some cases. Low p,p′-DDT/(p,p′-DDT + p,p′-DDE) in most soils indicated aged residues. Lack of p,p′-DDT metabolism might account for its dominance in a few soils. HCH isomer profiles suggested aged technical HCH in the YV, and technical HCH + lindane in the MV. Heptachlor dominated the ΣCHL, probably from application of technical heptachlor as well as chlordane. Chiral compounds were nonracemic in soils and sediments and indicated enantioselective microbial degradation of (+)α-HCH, (−)trans-chlordane, (−)cis-chlordane and (+)o,p′-DDT. Depletion of (+)o,p′-DDT in soils may account for similar enantiomer signatures previously reported in air of northwest Mexico.

  • 26. Terhivuo, J.
    et al.
    Halmepuro, A.-M.
    Saura, Anssi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Clonal diversity and morphometry in the parthenogenetic earthworm Eiseniella tetraedra (Sav.) as affected by habitat characteristics including radioactive pollution2011Ingår i: Pedobiologia, ISSN 0031-4056, E-ISSN 1873-1511, Vol. 54, s. S11-S18Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Eiseniella tetraedra (Sav.) is a cosmopolitan earthworm reproducing by obligate parthenogenesis. Here, we examined whether habitat characteristics affected the clone pool diversities and morphometric variability of the stenotopic riparian species E. tetraedra along a west-east transect from the Scandinavian mountains to lowland habitats of the Swedish east coast through Finland and to Russia (the Komi Republic) near the Ural Mountains. The transect comprised a geographical distance that cuts through the maritime to continental climatological zones within the boreal forest belt. It terminated in the Komi Republic, thus adding habitat (soil) characteristics to the factor of radioactive pollution. We found that mountain brooks in Sweden hosted the lowest numbers of clones, but in the lowland samples the clone pool diversities decreased in general from Sweden through Finland and Russia, i.e. from west to east. Nevertheless, high levels of clonal variability were observed within the countries, so that even monomorphic pools were found. However, no clones were shared between the countries. The fresh body weights and posterior body lengths of adult earthworms decreased from west to east. The numbers of posterior segments did not, however, differ between the countries, clue to decreased segment size. The location of the clitellum, tubercula pubertatis and male pores showed no clear-cut morphometric clines along the W-E gradient, but the tubercula pubertatis and male pores were more clearly demarcated in adults of the Russian material than in those from the West. Eiseniella adults from the Swedish mountains carried spermatophores considerably more often than those from the other localities. E. tetraedra from localities with radioactive pollution in Russia (the Komi Republic) showed no clear-cut clone pool diversities in comparison to the clone pools of the other sites within the area. Monomorphic clone pools were recorded in localities with low as well as high levels of long-term ionizing radiation and exposure to heavy metals. We found no morphological malformations, such as dislocations of characters, in comparison to individuals from sites with lower levels of environmental radiation.

  • 27. Terhivuo, Juhani
    et al.
    Saura, Anssi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Clone distribution of the earthworm Eiseniella tetraedra (Sav.) (Oligochaeta: Lumbricidae) across an altitudinal gradient on subarctic mountains of NW Europe2008Ingår i: Pedobiologia, ISSN 0031-4056, E-ISSN 1873-1511, Vol. 51, nr 5-6, s. 375-384Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In earlier studies, we have shown that clone diversity of the parthenogenetic earthworm Eiseniella tetraedra increases from the upper reaches of rivers in northern Sweden towards their mouths. Now we survey brooks in the Scandes Mountains in the watershed between Sweden and Norway where major rivers originate. Using starch get enzyme electrophoresis, we found 37 clones in a total catch of 379 individuals from six mountains. The most abundant clone made up 48.3% of the individuals collected. It was present on most mountains and was found at different elevations. In comparison with other clones it may represent a general-purpose genotype adapted to environmental conditions ranging from alpine through to subalpine to boreal habitats in the mountains. Diversity of clone assemblages decreased with increasing elevation. On four mountains, one to two clones were found at higher elevations. Passive downstream dispersal of E. tetraedra propagules from wider areas of the mountains was responsible for the more diverse clone pools in the tower reaches of the brooks (i.e., "small rivers behave like large ones"). Two clone groups, which deviated from the norm clone in their number of enzyme variants, were evenly distributed among different elevations. Therefore, we could not correlate genotype differences (i.e., adaptation of clones to mountain elevations). Clone pool similarities among the mountains were tow on average (range 0-58%) but in a cluster of four mountains, similarities varied from 46% to 58%. Clone pool similarities between different elevations of the same mountain ranged from 27% to 83%. One mountain brook was sampled over 3 years to assess clone turnover. Only the norm clone was found in upstream habitats but it and three other clones were recorded downstream in at least 2 years. Ten clones were found once in the latter habitat as well.

  • 28. Ushio, Masayuki
    et al.
    Makoto, Kobayashi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Klaminder, Jonatan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Nakano, Shin-ichi
    CARD-FISH analysis of prokaryotic community composition and abundance along small-scale vegetation gradients in a dry arctic tundra ecosystem2013Ingår i: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 64, s. 147-154Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The size and composition of soil microbial communities have important influences on terrestrial ecosystem processes such as soil decomposition. However, compared with studies of aboveground plant communities, there are relatively few studies on belowground microbial communities and their interactions with aboveground vegetations in the arctic region. In this study, we conducted the first investigation of the abundance and composition of prokaryotic communities along small-scale vegetation gradients (ca. 1-3 m) in a dry arctic tundra ecosystem in Northern Sweden using fluorescent in situ hybridization (FISH) coupled with catalyzed reporter deposition (CARD). The number of prokaryotic cells increased with increasing vegetation cover along vegetation gradients, mainly as a function of increased amounts of soil carbon and moisture. Eubacteria and Archaea constituted approximately 59.7% and 33.4% of DAPI-positive cells, respectively. Among the analyzed bacterial phyla and sub-phyla, Acidobacteria and alpha-proteobacteria were the most dominant groups, constituting approximately 13.5% and 10.7% of DAPI-positive cells, respectively. Interestingly, the soil prokaryotic community composition was relatively unaffected by the dramatic changes in the aboveground vegetation community. Multivariate analyses suggested that the prokaryotic community composition depended on soil pH rather than on aboveground vegetation. Surface plants are weak predictors of the composition of the soil microbial community in the studied soil system and the size of the community is constrained by carbon and water availability. In addition, our study demonstrated that CARD-FISH, which is still a rarely-used technique in soil ecology, is effective for quantifying soil microbes.

    (C) 2013 Elsevier Ltd. All rights reserved.

  • 29. Öquist, Mats G.
    et al.
    Erhagen, Björn
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Department of Forest Ecology & Management, Swedish University of Agricultural Sciences (SLU), Umeå, Sweden.
    Haei, Mahsa
    Sparrman, Tobias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Ilstedt, Ulrik
    Schleucher, Jürgen
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Nilsson, Mats B.
    The effect of temperature and substrate quality on the carbon use efficiency of saprotrophic decomposition2017Ingår i: Plant and Soil, ISSN 0032-079X, E-ISSN 1573-5036, Vol. 414, nr 1, s. 113-125Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background and aims: Mineralization of soil organic matter (SOM) constitutes a major carbon flux to the atmosphere. The carbon use efficiency (CUE) of the saprotrophic microorganisms mineralizing SOM is integral for soil carbon dynamics. Here we investigate how the CUE is affected by temperature, metabolic conditions, and the molecular complexity of the substrate.

    Methods: We incubated O-horizon soil samples (with either 13C–glucose or 13C–cellulose) from a boreal coniferous forest at 4, 9, 14, and 19 °C, and calculated CUEs based on the amount of 13C–CO2and 13C–labelled microbial biomass produced. The effects of substrate, temperature, and metabolic conditions (representing unlimited substrate supply and substrate limitation) on CUE were evaluated.

    Results: CUE from metabolizing glucose was higher as compared to cellulose. A slight decrease in CUE with increasing temperature was observed in glucose amended samples (but only in the range 9–19 °C), but not in cellulose amended samples. CUE differed significantly with metabolic conditions, i.e. CUE was higher during unlimited growth conditions as compared to conditions with substrate limitation.

    Conclusions: We conclude that it is integral to account for both differences in CUE during different metabolic phases, as well as complexity of substrate, when interpreting temperature dependence on CUE in incubation studies.

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