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  • 1.
    Fransson Forsberg, Joel
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Quantifying changes in soil bioporosity in subarctic soils after earthworm invasions2021Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Pores provide important hotspots for chemical and biological processes in soils. Earthworm burrows affect the macropore structure and their actions may create new preferential pathways for water and gas flow within soils. This, in turn, indirectly affect plants, nutrient cycling, hydraulic conductivity, gas exchange, and soil organisms. While the effects of invasive earthworms on soil properties has been well-documented in temperate and boreal ecosystems, we know little how these organism may affect tundra soils. In this study, I assessed how the three-dimensional network of soil-macropores are affected by earthworm species (Aporrectodea sp. and Lumbricus sp). I hypothesized: i) that earthworms increase the frequency of macropores with a likely biological origin (biopores); ii) effects of biopores are dependent on tundra vegetation type (meadow or heath); and iii) the macropore network properties are altered by earthworms.  The hypotheses were tested using a common garden experiment with 48 mesocosms. The pore structure of each mesocosm was analyzed using X-ray CT tomography. I found that biopores increased in the tundra from on 0.05 ±0.01 % (mean ± standard deviation) in the control to about 0.59 ± 0.07 % in the earthworm treatments. However, in contrast to my second hypothesis, I found no vegetation dependent effect. Interestingly, I found that earthworms decreased the complexity and directionality of macropores. My findings strongly indicate that burrowing can severely impact the pore properties of previously uninhabited subarctic soils.

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  • 2.
    Gavazov, Konstantin
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Canarini, Alberto
    Centre for Microbiology and Environmental Systems Science, Division of Terrestrial Ecosystem Research, University of Vienna, Vienna, Austria.
    Jassey, Vincent E.J.
    ECOLAB, Laboratoire D'Ecologie Fonctionnelle et Environnement, Université de Toulouse, CNRS, Toulouse, France.
    Mills, Robert
    Department of Environment and Geography, University of York, York, United Kingdom.
    Richter, Andreas
    Centre for Microbiology and Environmental Systems Science, Division of Terrestrial Ecosystem Research, University of Vienna, Vienna, Austria.
    Sundqvist, Maja K.
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Väisänen, Maria
    Ecology and Genetics Research Unit, University of Oulu, Oulu, Finland; Arctic Centre, University of Lapland, Rovaniemi, Finland.
    Walker, Tom W.N.
    Department of Environmental Systems Science, ETH Zürich, Zürich, Switzerland; Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland.
    Wardle, David A.
    Asian School of the Environment, Nanyang Technological University, Singapore.
    Dorrepaal, Ellen
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Plant-microbial linkages underpin carbon sequestration in contrasting mountain tundra vegetation types2022In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 165, article id 108530Article in journal (Refereed)
    Abstract [en]

    Tundra ecosystems hold large stocks of soil organic matter (SOM), likely due to low temperatures limiting rates of microbial SOM decomposition more than those of SOM accumulation from plant primary productivity and microbial necromass inputs. Here we test the hypotheses that distinct tundra vegetation types and their carbon supply to characteristic rhizosphere microbes determine SOM cycling independent of temperature. In the subarctic Scandes, we used a three-way factorial design with paired heath and meadow vegetation at each of two elevations, and with each combination of vegetation type and elevation subjected during one growing season to either ambient light (i.e., ambient plant productivity), or 95% shading (i.e., reduced plant productivity). We assessed potential above- and belowground ecosystem linkages by uni- and multivariate analyses of variance, and structural equation modelling. We observed direct coupling between tundra vegetation type and microbial community composition and function, which underpinned the ecosystem's potential for SOM storage. Greater primary productivity at low elevation and ambient light supported higher microbial biomass and nitrogen immobilisation, with lower microbial mass-specific enzymatic activity and SOM humification. Congruently, larger SOM at lower elevation and in heath sustained fungal-dominated microbial communities, which were less substrate-limited, and invested less into enzymatic SOM mineralisation, owing to a greater carbon-use efficiency (CUE). Our results highlight the importance of tundra plant community characteristics (i.e., productivity and vegetation type), via their effects on soil microbial community size, structure and physiology, as essential drivers of SOM turnover. The here documented concerted patterns in above- and belowground ecosystem functioning is strongly supportive of using plant community characteristics as surrogates for assessing tundra carbon storage potential and its evolution under climate and vegetation changes.

  • 3.
    George, T. S.
    et al.
    James Hutton Inst, Dundee DD2 5DA, Scotland.
    Giles, C. D.
    James Hutton Inst, Dundee DD2 5DA, Scotland.
    Menezes-Blackburn, D.
    Univ Lancaster, Lancaster Environm Ctr, Lancaster LA1 4YQ, England.
    Condron, L. M.
    Lincoln Univ, Christchurch 7647, New Zealand.
    Gama-Rodrigues, A. C.
    Univ Estadual Norte Flumninense Darcy Ribeiro, UENF, Lab Solos, Av Alberto Lamego 2000, Campos Dos Goytacazes, RJ, Brazil.
    Jaisi, D.
    Univ Delaware, Plant & Soil Sci, 160 Townsend Hall, Newark, DE 19716 USA.
    Lang, F.
    Univ Freiburg, Chair Soil Ecol, Fac Environm & Nat Resources, Bertoldstr 17, D-79098 Freiburg, Germany.
    Neal, A. L.
    Rothamsted Res, Harpenden AL5 2JQ, Herts, England.
    Stutter, M. , I
    Almeida, D. S.
    Sao Paulo State Univ, UNESP, Dept Crop Sci, Coll Agr Sci, 1780 Jose Barbosa de Barros St, Botucatu, SP, Brazil.
    Bol, R.
    Forschungszentrum Julich, Inst Bio & Geosci IBG Agrosphere 3, D-52425 Julich, Germany.
    Cabugao, K. G.
    Oak Ridge Natl Lab, POB 2008, Oak Ridge, TN 37831 USA.
    Celi, L.
    Univ Turin, Soil Biogeochem, DISAFA, Largo Braccini 2, I-10095 Turin, Italy.
    Cotner, J. B.
    Univ Minnesota, 1479 Gortner Ave St Paul, Twin, MN 55108 USA.
    Feng, G.
    China Agr Univ, Beijing, Peoples R China.
    Goll, D. S.
    IPSL LSCE CEA CNRS UVSQ Saclay, Lab Sci Climat & Environm, Gif Sur Yvette, France.
    Hallama, M.
    Univ Hohenheim, Inst Soil Sci, Emil Wolff Str 27, D-70599 Stuttgart, Germany.
    Krueger, J.
    Univ Freiburg, Chair Soil Ecol, Fac Environm & Nat Resources, Bertoldstr 17, D-79098 Freiburg, Germany.
    Plassard, C.
    INRA, UMR ECO & SOLS, Montpellier, France.
    Rosling, Anna
    Uppsala universitet, Evolutionsbiologi.
    Darch, T.
    Rothamsted Res, Okehampton EX20 2SB, Devon, England.
    Fraser, T.
    Univ Reading, Sch Agr Policy & Dev, Ctr Agrienvironm Res, POB 237, Reading RG6 6AR, Berks, England.
    Giesler, R.
    Umea Univ, Dept Ecol & Environm Sci, Climate Impacts Res Ctr, S-98107 Abisko, Sweden.
    Richardson, A. E.
    CSIRO Agr & Food, Canberra, ACT, Australia.
    Tamburini, F.
    ETH, D USYS, Tannenstr 1, CH-8092 Zurich, Switzerland.
    Shand, C. A.
    James Hutton Inst, Aberdeen AB15 8QH, Scotland.
    Lumsdon, D. G.
    James Hutton Inst, Aberdeen AB15 8QH, Scotland.
    Zhang, H.
    Univ Lancaster, Lancaster Environm Ctr, Lancaster LA1 4YQ, England.
    Blackwell, M. S. A.
    Rothamsted Res, Okehampton EX20 2SB, Devon, England.
    Wearing, C.
    Univ Lancaster, Lancaster Environm Ctr, Lancaster LA1 4YQ, England.
    Mezeli, M. M.
    James Hutton Inst, Dundee DD2 5DA, Scotland.
    Almas, A. R.
    Norwegian Univ Life Sci, Dept Environm Sci, Post Box 5003, N-1432 As, Norway.
    Audette, Y.
    Univ Guelph, 50 Stone Rd East, Guelph, ON N1G 2W1, Canada.
    Bertrand, I
    INRA, UMR ECO & SOLS, Montpellier, France.
    Beyhaut, E.
    Natl Inst Agr Res Uruguay, Montevideo, Uruguay.
    Boitt, G.
    Lincoln Univ, Christchurch 7647, New Zealand.
    Bradshaw, N.
    Univ Sheffield, Dept Chem & Biol Engn, Mappin St, Sheffield S1 3JD, S Yorkshire, England.
    Brearley, C. A.
    Univ East Anglia, Sch Biol Sci, Norwich Res Pk, Norwich NR4 7TJ, Norfolk, England.
    Bruulsema, T. W.
    Int Plant Nutr Inst, 18 Maplewood Dr, Guelph, ON N1G 1L8, Canada.
    Ciais, P.
    IPSL LSCE CEA CNRS UVSQ Saclay, Lab Sci Climat & Environm, Gif Sur Yvette, France.
    Cozzolino, V
    Univ Napoli Federico II, Ctr Interdipartimentale Ric Risonanza Magnet Nucl, Via Univ 100, I-80055 Portici, Italy.
    Duran, P. C.
    Univ La Frontera, Temuco, Chile.
    Mora, M. L.
    Univ Napoli Federico II, Ctr Interdipartimentale Ric Risonanza Magnet Nucl, Via Univ 100, I-80055 Portici, Italy.
    de Menezes, A. B.
    Univ Salford, Sch Environm & Life Sci, Manchester M5 4WT, The Crescent, England.
    Dodd, R. J.
    Bangor Univ, Sch Environm Nat Resources & Geog, Bangor LL57 2UW, Gwynedd, Wales.
    Dunfield, K.
    Univ Guelph, 50 Stone Rd East, Guelph, ON N1G 2W1, Canada.
    Engl, C.
    Queens Univ Belfast, Med Biol Ctr, Sch Biol Sci, 97 Lisburn Rd, Belfast BT9 7BL, Antrim, North Ireland;Queens Univ Belfast, Med Biol Ctr, Inst Global Food Secur, 97 Lisburn Rd, Belfast BT9 7BL, Antrim, North Ireland.
    Frazao, J. J.
    Univ Sao Paulo, CENA, Ave Centenario 303, BR-13416000 Piracicaba, SP, Brazil.
    Garland, G.
    ETH, D USYS, Tannenstr 1, CH-8092 Zurich, Switzerland.
    Jimenez, J. L. Gonzalez
    Johnstown Castle Co, TEAGASC, Environm Res Ctr, Wexford, Ireland.
    Graca, J.
    Johnstown Castle Co, TEAGASC, Environm Res Ctr, Wexford, Ireland.
    Granger, S. J.
    Rothamsted Res, Okehampton EX20 2SB, Devon, England.
    Harrison, A. F.
    Ctr Ecol & Hydrol, Lib Ave, Lancaster LA1 4AP, England.
    Heuck, C.
    Univ Bayreuth, Bayreuth Ctr Ecol & Environm Res BayCEER, Dept Soil Biogeochem, Dr Hans Frisch Str 1-3, D-95448 Bayreuth, Germany.
    Hou, E. Q.
    Chinese Acad Sci, South China Bot Garden, Guangdong Prov Key Lab Appl Bot, 723 Xingke Rd, Guangzhou 510650, Guangdong, Peoples R China.
    Johnes, P. J.
    Univ Bristol, Sch Geog Sci, Univ Rd, Bristol BS8 1SS, Avon, England;Univ Bristol, Sch Chem, Univ Rd, Bristol BS8 1SS, Avon, England.
    Kaiser, K.
    Martin Luther Univ Halle Wittenberg, Soil Sci & Soil Protect, von Seckendorff Pl 3, D-06120 Halle, Saale, Germany.
    Kjaer, H. A.
    Univ Copenhagen, Ctr Ice & Climate, Niels Bohr Inst, Copenhagen, Denmark.
    Klumpp, E.
    Uppsala universitet, Evolutionsbiologi.
    Lamb, A. L.
    British Geol Survey, NERC Isotope Geosci Facil, Nottingham NG12 5GG, England.
    Macintosh, K. A.
    Queens Univ Belfast, Med Biol Ctr, Sch Biol Sci, 97 Lisburn Rd, Belfast BT9 7BL, Antrim, North Ireland;Queens Univ Belfast, Med Biol Ctr, Inst Global Food Secur, 97 Lisburn Rd, Belfast BT9 7BL, Antrim, North Ireland.
    Mackay, E. B.
    Ctr Ecol & Hydrol, Lib Ave, Lancaster LA1 4AP, England.
    McGrath, J.
    Queens Univ Belfast, Med Biol Ctr, Sch Biol Sci, 97 Lisburn Rd, Belfast BT9 7BL, Antrim, North Ireland;Queens Univ Belfast, Med Biol Ctr, Inst Global Food Secur, 97 Lisburn Rd, Belfast BT9 7BL, Antrim, North Ireland.
    McIntyre, C.
    Univ Bristol, Sch Geog Sci, Univ Rd, Bristol BS8 1SS, Avon, England;Univ Bristol, Sch Chem, Univ Rd, Bristol BS8 1SS, Avon, England.
    McLaren, T.
    ETH, D USYS, Tannenstr 1, CH-8092 Zurich, Switzerland.
    Meszaros, E.
    ETH, D USYS, Tannenstr 1, CH-8092 Zurich, Switzerland.
    Missong, A.
    Forschungszentrum Julich, Inst Bio & Geosci IBG Agrosphere 3, D-52425 Julich, Germany.
    Mooshammer, M.
    Univ Vienna, Dept Microbiol & Ecosyst Sci, Althanstr 14, A-1090 Vienna, Austria.
    Negron, C. P.
    Univ La Frontera, Temuco, Chile.
    Nelson, L. A.
    Univ Northern British Columbia, 3333 Univ Way, Prince George, BC V2N 4Z9, Canada.
    Pfahler, V
    Rothamsted Res, Okehampton EX20 2SB, Devon, England.
    Poblete-Grant, P.
    Univ La Frontera, Temuco, Chile.
    Randall, M.
    Brigham Young Univ, Provo, UT 84602 USA.
    Seguel, A.
    Univ La Frontera, Temuco, Chile.
    Seth, K.
    Lincoln Univ, Christchurch 7647, New Zealand.
    Smith, A. C.
    British Geol Survey, NERC Isotope Geosci Facil, Nottingham NG12 5GG, England.
    Smits, M. M.
    Hasselt Univ, Ctr Environm Sci, Bldg D,Agoralaan, B-3590 Diepenbeek, Belgium.
    Sobarzo, J. A.
    Univ La Frontera, Temuco, Chile.
    Spohn, M.
    Univ Bayreuth, Bayreuth Ctr Ecol & Environm Res BayCEER, Dept Soil Biogeochem, Dr Hans Frisch Str 1-3, D-95448 Bayreuth, Germany.
    Tawaraya, K.
    Yamagata Univ, Tsuruoka, Yamagata 9978555, Japan.
    Tibbett, M.
    Univ Reading, Sch Agr Policy & Dev, Ctr Agrienvironm Res, POB 237, Reading RG6 6AR, Berks, England.
    Voroney, P.
    Univ Guelph, 50 Stone Rd East, Guelph, ON N1G 2W1, Canada.
    Wallander, H.
    Lund Univ, Dept Biol, Biol Bldg Solvegatan 35, S-22362 Lund, Sweden.
    Wang, L.
    Forschungszentrum Julich, Inst Bio & Geosci IBG Agrosphere 3, D-52425 Julich, Germany.
    Wasaki, J.
    Hiroshima Univ, Grad Sch Biosphere Sci, Assessment Microbial Environm, Hiroshima, Japan.
    Haygarth, P. M.
    Univ Lancaster, Lancaster Environm Ctr, Lancaster LA1 4YQ, England.
    Organic phosphorus in the terrestrial environment: a perspective on the state of the art and future priorities2018In: Plant and Soil, ISSN 0032-079X, E-ISSN 1573-5036, Vol. 427, no 1-2, p. 191-208Article in journal (Refereed)
    Abstract [en]

    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. 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. 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.

  • 4. Jansson, Janet K.
    et al.
    Wu, Ruonan
    Soil viral diversity, ecology and climate change2023In: Nature Reviews Microbiology, ISSN 1740-1526, E-ISSN 1740-1534, Vol. 21, no 5, p. 296-311Article in journal (Refereed)
    Abstract [en]

    Soil viruses are highly abundant and have important roles in the regulation of host dynamics and soil ecology. Climate change is resulting in unprecedented changes to soil ecosystems and the life forms that reside there, including viruses. In this Review, we explore our current understanding of soil viral diversity and ecology, and we discuss how climate change (such as extended and extreme drought events or more flooding and altered precipitation patterns) is influencing soil viruses. Finally, we provide our perspective on future research needs to better understand how climate change will impact soil viral ecology.

  • 5. Jerand, Philip
    et al.
    Klaminder, Jonatan
    Linderholm, Johan
    The legacy of ecological imperialism in the Scandes: Earthworms and their implications for Arctic research2023In: Arctic, Antarctic and Alpine research, ISSN 1523-0430, E-ISSN 1938-4246, Vol. 55, no 1Article in journal (Refereed)
    Abstract [en]

    In the nineteenth century, numerous settlements were established in the alpine region of Fennoscandia (the Scandes), an area that later became a major international scene for Arctic research. Here we raise awareness of this era and show that earthworm-driven bioturbation in “pristine” soils around contemporary Arctic research infrastructure is caused by soil fauna left behind during early land use. We use soil preserved under an alpine settlement to highlight that soils were not bioturbated when the first house was built at a site where bioturbation is now widespread. A review of archived material with unique site-specific chronology constrained the onset of bioturbation to the post-1871 era. Our results suggest that small-scale land use introduced earthworms that now thrive far beyond the realms of former cultivated fields. The legacy of soil fauna from this example of “ecological imperialism” still lingers and should be considered when studying soils of the Scandes.

  • 6.
    Keen, Sara C.
    et al.
    Department of Geological Sciences, Stanford University, CA, Stanford, United States.
    Wackett, Adrian A.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Willenbring, Jane K.
    Department of Geological Sciences, Stanford University, CA, Stanford, United States.
    Yoo, Kyungsoo
    Department of Soil, Water, and Climate, University of Minnesota, MN, United States.
    Jonsson, Hanna
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Clow, Travis
    Department of Geological Sciences, Stanford University, CA, Stanford, United States.
    Klaminder, Jonatan
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Non-native species change the tune of tundra soils: novel access to soundscapes of the Arctic earthworm invasion2022In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 838, article id 155976Article in journal (Refereed)
    Abstract [en]

    Over the last decade, an increasing number of studies have used soundscapes to address diverse ecological questions. Sound represents one of the few sources of information capable of providing in situ insights into processes occurring within opaque soil matrices. To date, the use of soundscapes for soil macrofauna monitoring has been experimentally tested only in controlled laboratory environments. Here we assess the validity of laboratory predictions and explore the use of soil soundscape proxies for monitoring soil macrofauna (i.e., earthworm) activities in an outdoor context. In a common garden experiment in northern Sweden, we constructed outdoor mesocosm plots (N = 36) containing two different Arctic vegetation types (meadow and heath) and introduced earthworms to half of these plots. Earthworms substantially altered the ambient soil soundscape under both vegetation types, as measured by both traditional soundscape indices and frequency band power levels, although their acoustic impacts were expressed differently in heath versus meadow soils. While these findings support the as-of-yet untapped promise of using belowground soundscape analyses to monitor soil ecosystem health, direct acoustic emissions from earthworm activities appear to be an unlikely proxy for tracking worm activities at daily timescales. Instead, earthworms indirectly altered the soil soundscape by ‘re-engineering’ the soil matrix: an effect that was dependent on vegetation type. Our findings suggest that long-term (i.e., seasonal) earthworm activities in natural soil settings can likely be monitored indirectly via their impacts on soundscape measures and acoustic indices. Analyzing soil soundscapes may enable larger-scale monitoring of high-latitude soils and is directly applicable to the specific case of earthworm invasions within Arctic soils, which has recently been identified as a potential threat to the resilience of high-latitude ecosystems. Soil soundscapes could also offer a novel means to monitor soils and soil-plant-faunal interactions in situ across diverse pedogenic, agronomic, and ecological systems.

  • 7. Klaminder, J.
    et al.
    Krab, E. J.
    Larsbo, M.
    Jonsson, H.
    Fransson, J.
    Koestel, J.
    Holes in the tundra: Invasive earthworms alter soil structure and moisture in tundra soils2023In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 859, article id 160125Article in journal (Refereed)
    Abstract [en]

    Human introductions have resulted in earthworms establishing in the Arctic, species known to cause cascading ecosystem change. However, few quantitative outdoor experiments have been performed that describe how these soil modifying earthworms are reshaping structures in tundra soils. In this study, we used three-dimensional (3-D) X-ray images of soil cores (approximately 10 cm diameter, 20 cm height, N = 48) to assess how earthworms (Aporrectodea sp. and Lumbricus sp.) affect soil structure and macropore networks in an outdoor mesocosm experiment that lasted four summers. Effects were assessed in both shrub-dominated (heath) and herb-dominated (meadow) tundra. Earthworms almost doubled the macroporosity in meadow soils and tripled macroporosity in heath. Interestingly, the fractal dimension of macropores decreased in response to earthworm burrowing in both systems, indicating that the presence of earthworms reduced the geometric complexity in comparison to other pore-generating processes active in the tundra. Observed effects on soil structure occurred along with a dramatically reduced soil moisture content, which was observed the first winter after earthworm introduction in the meadow. Our findings suggest that predictions of future changes in vegetation and soil carbon pools in the Arctic should include major impacts on soil properties that earthworms induce.

  • 8.
    Lett, Signe
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    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 heath2014In: Plant and Soil, ISSN 0032-079X, E-ISSN 1573-5036, Vol. 379, no 1-2, p. 193-204Article in journal (Refereed)
    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.

  • 9. Lí, Jin-Tao
    et al.
    Hicks, Lettice C.
    Brangarí, Albert C.
    Tájmel, Dániel
    Cruz-Paredes, Carla
    Rousk, Johannes
    Subarctic winter warming promotes soil microbial resilience to freeze–thaw cycles and enhances the microbial carbon use efficiency2024In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 30, no 1Article in journal (Refereed)
    Abstract [en]

    Climate change is predicted to cause milder winters and thus exacerbate soil freeze?thaw perturbations in the subarctic, recasting the environmental challenges that soil microorganisms need to endure. Historical exposure to environmental stressors can facilitate the microbial resilience to new cycles of that same stress. However, whether and how such microbial memory or stress legacy can modulate microbial responses to cycles of frost remains untested. Here, we conducted an in situ field experiment in a subarctic birch forest, where winter warming resulted in a substantial increase in the number and intensity of freeze?thaw events. After one season of winter warming, which raised mean surface and soil (?8?cm) temperatures by 2.9 and 1.4°C, respectively, we investigated whether the in situ warming-induced increase in frost cycles improved soil microbial resilience to an experimental freeze?thaw perturbation. We found that the resilience of microbial growth was enhanced in the winter warmed soil, which was associated with community differences across treatments. We also found that winter warming enhanced the resilience of bacteria more than fungi. In contrast, the respiration response to freeze?thaw was not affected by a legacy of winter warming. This translated into an enhanced microbial carbon-use efficiency in the winter warming treatments, which could promote the stabilization of soil carbon during such perturbations. Together, these findings highlight the importance of climate history in shaping current and future dynamics of soil microbial functioning to perturbations associated with climate change, with important implications for understanding the potential consequences on microbial-mediated biogeochemical cycles.

  • 10. Michel, Jennifer
    et al.
    Hartley, Iain P.
    Buckeridge, Kate M.
    van Meegen, Carmen
    Broyd, Rosanne C.
    Reinelt, Laura
    Ccahuana Quispe, Adan J.
    Whitaker, Jeanette
    Preferential substrate use decreases priming effects in contrasting treeline soils2022In: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515XArticle in journal (Refereed)
    Abstract [en]

    Climate change currently manifests in upward and northward shifting treelines, which encompasses changes to the carbon (C) and nitrogen (N) composition of organic inputs to soils. Whether these changed inputs will increase or decrease microbial mineralisation of native soil organic matter remains unknown, making it difficult to estimate how treeline shifts will affect the C balance. Aiming to improve mechanistic understanding of C cycling in regions experiencing treeline shifts, we quantified priming effects in soils of high altitudes (Peruvian Andes) and high latitudes (subarctic Sweden), differentiating landcover types (boreal forest, tropical forest, tundra heath, Puna grassland) and soil horizons (organic, mineral). In a controlled laboratory incubation, soils were amended with substrates of different C:N, composed of an organic C source at a constant ratio of 30% substrate-C to microbial biomass C, combined with different levels of a nutrient solution neutral in pH. Substrate additions elicited both positive and negative priming effects in both ecosystems, independent from substrate C:N. Positive priming prevailed above the treeline in high altitudes and in mineral soils in high latitudes, where consequently climate change-induced treeline shifts and deeper rooting plants may enhance SOM-mineralisation and soil C emissions. However, such C loss may be compensated by negative priming, which dominated in the other soil types and was of larger magnitude than positive priming. In line with other studies, these results indicate a consistent mechanism linking decreased SOM-mineralisation (negative priming) to increased microbial substrate utilisation, suggesting preferential substrate use as a potential tool to support soil C storage.

  • 11. Poppeliers, Sanne W M
    et al.
    Hefting, Mariet
    Dorrepaal, Ellen
    Weedon, James T
    Functional microbial ecology in arctic soils: the need for a year-round perspective2022In: FEMS Microbiology Ecology, ISSN 0168-6496, E-ISSN 1574-6941, Vol. 98, no 12Article in journal (Refereed)
    Abstract [en]

    The microbial ecology of arctic and sub-arctic soils is an important aspect of the global carbon cycle, due to the sensitivity of the large soil carbon stocks to ongoing climate warming. These regions are characterized by strong climatic seasonality, but the emphasis of most studies on the short vegetation growing season could potentially limit our ability to predict year-round ecosystem functions. We compiled a database of studies from arctic, subarctic, and boreal environments that include sampling of microbial community and functions outside the growing season. We found that for studies comparing across seasons, in most environments, microbial biomass and community composition vary intra-annually, with the spring thaw period often identified by researchers as the most dynamic time of year. This seasonality of microbial communities will have consequences for predictions of ecosystem function under climate change if it results in: seasonality in process kinetics of microbe-mediated functions; intra-annual variation in the importance of different (a)biotic drivers; and/or potential temporal asynchrony between climate change-related perturbations and their corresponding effects. Future research should focus on (i) sampling throughout the entire year; (ii) linking these multi-season measures of microbial community composition with corresponding functional or physiological measurements to elucidate the temporal dynamics of the links between them; and (iii) identifying dominant biotic and abiotic drivers of intra-annual variation in different ecological contexts.

  • 12. Spitzer, Clydecia M.
    et al.
    Wardle, David A.
    Lindahl, Björn D.
    Sundqvist, Maja K.
    Gundale, Michael J.
    Fanin, Nicolas
    Kardol, Paul
    Root traits and soil micro-organisms as drivers of plant–soil feedbacks within the sub-arctic tundra meadow2021In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. n/a, no n/aArticle in journal (Refereed)
    Abstract [en]
    1. Plant–soil feedback (PSF) results from the influence of plants on the composition and abundance of various taxa and functional groups of soil micro-organisms, and their reciprocal effects on the plants. However, little is understood about the importance of fine root traits and root economic strategies in moderating microbial-driven PSF.
    2. We examined the relationships between PSF and 11 chemical and morphological root traits from 18 sub-arctic meadow plant species, as well as the soil microbial community composition which we characterized using phospholipid fatty acids (PLFAs) and high-throughput sequencing. We also investigated the importance of the root economics spectrum in influencing PSF, because it indicates plant below-ground economic strategies via trade-offs between resource acquisition and conservation.
    3. When we considered the entire root economics spectrum, we found that PSFs were more negative when root trait values were more acquisitive across the 18 species. In addition, PSF was more negative when values of root nitrogen content and root forks per root length were higher, and more positive when root dry matter content was higher. We additionally identified two fungal orders that were negatively related to PSF. However, we found no evidence that root traits influenced PSF through its relationship with these fungal orders.
    4. Synthesis. Our results provide evidence that for some fine root traits, the root economics spectrum and some fungal orders have an important role in influencing PSF. By investigating the roles of soil micro-organisms and fine root traits in driving PSF, this study enables us to better understand root trait–microbial linkages across species and therefore offers new insights about the mechanisms that underpin PSFs and ultimately plant community assembly.
  • 13.
    Spitzer, Clydecia Melissa
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences.
    Linking root traits and plant-soil feedbacks toenvironmental change in the sub-arctictundra2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Plant community assembly processes shape the composition and abundances of species, and encompass functional traits and resource acquisition strategy of species, biotic interactions and abiotic filtering. Hence, an understanding of these complex processes requires disentangling the effects of multiple factors influencing plant community assembly. In this thesis, I investigated fine root trait associations with soil microorganisms, the resulting feedback effects from those interactions (i.e., plant-soil feedbacks), plant-plant interactions under warming, and the effects of temperature on fine root traits of plant communities in the Swedish sub-arctic tundra.

    Here, the chemical root economics spectrum (i.e., tradeoff between acquisitive and conservative strategies) predicted the abundance of broad microbial groups, whereas individual fine root traits were associated with the relative abundances of fungal taxa. It also explained plant-soil feedback, with acquisitive trait values resulting in negative feedbacks. In addition, plant-plant interactions were altered under warming, but this was not related to resource-acquisition strategy. Further, community-level root trait responses to temperature were not necessarily related to root resource investment strategy. 

    Taken together, this thesis shows the importance of fine root traits for understanding plant community responses to global change. This has implications for plant community assembly, as well as carbon and nutrient cycling in a future warmer sub-arctic tundra.

  • 14.
    Sundqvist, Maja K.
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Wardle, David A.
    Department of Forest Ecology and Management, SLU, Umeå, Sweden.
    Vincent, Andrea
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Giesler, Reiner
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Contrasting nitrogen and phosphorus dynamics across an elevational gradient for subarctic tundra heath and meadow vegetation2014In: Plant and Soil, ISSN 0032-079X, E-ISSN 1573-5036, Vol. 383, no 1-2, p. 387-399Article in journal (Refereed)
    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.

  • 15.
    Väisänen, Maria
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Krab, Eveline J
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Monteux, Sylvain
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Teuber, Laurenz M.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Gavazov, Konstantin
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Weedon, James T.
    Keuper, Frida
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Dorrepaal, Ellen
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Meshes in mesocosms control solute and biota exchange in soils: A step towards disentangling (a)biotic impacts on the fate of thawing permafrost2020In: Agriculture, Ecosystems & Environment. Applied Soil Ecology, ISSN 0929-1393, E-ISSN 1873-0272, Vol. 151, article id UNSP 103537Article in journal (Refereed)
    Abstract [en]

    Environmental changes feedback to climate through their impact on soil functions such as carbon (C) and nutrient sequestration. Abiotic conditions and the interactions between above- and belowground biota drive soil responses to environmental change but these (a)biotic interactions are challenging to study. Nonetheless, better understanding of these interactions would improve predictions of future soil functioning and the soil-climate feedback and, in this context, permafrost soils are of particular interest due to their vast soil C-stores. We need new tools to isolate abiotic (microclimate, chemistry) and biotic (roots, fauna, microorganisms) components and to identify their respective roles in soil processes. We developed a new experimental setup, in which we mimic thermokarst (permafrost thaw-induced soil subsidence) by fitting thawed permafrost and vegetated active layer sods side by side into mesocosms deployed in a subarctic tundra over two growing seasons. In each mesocosm, the two sods were separated from each other by barriers with different mesh sizes to allow varying degrees of physical connection and, consequently, (a)biotic exchange between active layer and permafrost. We demonstrate that our mesh-approach succeeded in controlling 1) lateral exchange of solutes between the two soil types, 2) colonization of permafrost by microbes but not by soil fauna, and 3) ingrowth of roots into permafrost. In particular, experimental thermokarst induced a similar to 60% decline in permafrost nitrogen (N) content, a shift in soil bacteria and a rapid buildup of root biomass (+33.2 g roots m(-2) soil). This indicates that cascading plant-soil-microbe linkages are at the heart of biogeochemical cycling in thermokarst events. We propose that this novel setup can be used to explore the effects of (a)biotic ecosystem components on focal biogeochemical processes in permafrost soils and beyond.

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