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  • 1. Firbank, Les G.
    et al.
    Bertora, Chiara
    Blankman, David
    Delle Vedove, Gemini
    Frenzel, Mark
    Grignani, Carlo
    Groner, Elli
    Kertész, Miklós
    Krab, Eveline J.
    Department of Ecological Science, VU University Amsterdam, Amsterdam, The Netherlands.
    Matteucci, Giorgio
    Menta, Christina
    Mueller, Carsten W.
    Stadler, Jutta
    Kunin, William E.
    Towards the co-ordination of terrestrial ecosystem protocols across European research infrastructures2017In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 7, no 11, p. 3967-3975Article in journal (Refereed)
    Abstract [en]

    The study of ecosystem processes over multiple scales of space and time is often best achieved using comparable data from multiple sites. Yet, long-term ecological observatories have often developed their own data collection protocols. Here, we address this problem by proposing a set of ecological protocols suitable for widespread adoption by the ecological community. Scientists from the European ecological research community prioritized terrestrial ecosystem parameters that could benefit from a more consistent approach to data collection within the resources available at most long-term ecological observatories. Parameters for which standard methods are in widespread use, or for which methods are evolving rapidly, were not selected. Protocols were developed by domain experts, building on existing methods where possible, and refined through a process of field testing and training. They address above-ground plant biomass; decomposition; land use and management; leaf area index; soil mesofaunal diversity; soil C and N stocks, and greenhouse gas emissions from soils. These complement existing methods to provide a complete assessment of ecological integrity. These protocols offer integrated approaches to ecological data collection that are low cost and are starting to be used across the European Long Term Ecological Research community.

  • 2. Krab, Eveline J.
    et al.
    Aerts, Rien
    Berg, Matty P.
    van Hal, Jurgen
    Keuper, Frida
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Northern peatland Collembola communities unaffected by three summers of simulated extreme precipitation2014In: Agriculture, Ecosystems & Environment. Applied Soil Ecology, ISSN 0929-1393, E-ISSN 1873-0272, Vol. 79, p. 70-76Article in journal (Refereed)
    Abstract [en]

    Extreme climate events are observed and predicted to increase in frequency and duration in high-latitudeecosystems as a result of global climate change. This includes extreme precipitation events, which maydirectly impact on belowground food webs and ecosystem functioning by their physical impacts and byaltering local soil moisture conditions.

    We assessed responses of the Collembola community in a northern Sphagnum fuscum-dominatedombrotrophic peatland to three years of experimentally increased occurrence of extreme precipitationevents. Annual summer precipitation was doubled (an increase of 200 mm) by 16 simulated extremerain events within the three months growing season, where on each occasion 12.5 mm of rain was addedwithin a few minutes. Despite this high frequency and intensity of the rain events, no shifts in Collemboladensity, relative species abundances and community weighted means of three relevant traits (moisturepreference, vertical distribution and body size) were observed. This strongly suggests that the peatlandCollembola community is unaffected by the physical impacts of extreme precipitation and the short-termvariability in moisture conditions. The lack of response is most likely reinforced by the fact that extremeprecipitation events do not seem to alter longer-term soil moisture conditions in the peat layers inhabitedby soil fauna.

    This study adds evidence to the observation that the biotic components of northern ombrotrophicpeatlands are hardly responsive to an increase in extreme summer precipitation events. Given the importance of these ecosystems for the global C balance, these findings significantly contribute to the currentknowledge of the ecological impact of future climate scenarios. (C) 2014 Elsevier B.V. All rights reserved.

  • 3.
    Krab, Eveline J
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Ecological Science, Faculty of Earth and Life Sciences, Amsterdam, The Netherlands.
    Cornelissen, Johannes H C
    Berg, Matty P
    A simple experimental set-up to disentangle the effects of altered temperature and moisture regimes on soil organisms2015In: Methods in Ecology and Evolution, ISSN 2041-210X, E-ISSN 2041-210X, Vol. 6, no 10, p. 1159-1168Article in journal (Refereed)
    Abstract [en]

    Climate manipulation experiments in the field and laboratory incubations are common methods to study the impact of climate change on soils and their biota. However, both types of methods have drawbacks either on their mechanistic interpretation or ecological relevance. We propose an experimental set-up that combines the best of both methods and can be easily obtained by modifying widely available Tullgren soil fauna extractors. This set-up creates or alters temperature and moisture gradients within intact field soil cores, after which soil biota, their activity and vertical movements can be studied. We assessed the performance and demonstrated the applicability of this set-up through a case study on Collembola response to changes in microclimatic gradients in peat bogs. Warming created a vertical temperature gradient of 14 degrees C in peat cores without varying soil moisture conditions, while at a given temperature regime, precipitation and drought treatments shifted natural soil moisture gradients to 'wetter' and 'drier', respectively. This allowed for disentangling interacting warming and moisture effects on soil fauna. In our case study, Collembola communities showed peat layer-specific responses to these climate treatments. Warming decreased Collembola density and altered community composition in the shallowest layer, whereas precipitation increase affected Collembola community composition in the deepest layer. We showed that climate change can have layer-specific effects on soil organisms that are 'hidden' by not taking microclimatic vertical gradients into account. This experimental set-up facilitates studying (multitrophic) organism responses to climate changes, with only a small adjustment of equipment that is often already present in soil ecology laboratories. Moreover, this set-up can be easily customized to study many more other research questions related to wide-ranging organisms and ecosystems.

  • 4.
    Krab, Eveline J
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Monteux, Sylvain
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Weedon, James T.
    Dorrepaal, Ellen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Plant expansion drives bacteria and collembola communities under winter climate change in frost-affected tundra2019In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 138, article id UNSP 107569Article in journal (Refereed)
    Abstract [en]

    At high latitudes, winter warming facilitates vegetation expansion into barren frost-affected soils. The interplay of changes in winter climate and plant presence may alter soil functioning via effects on decomposers. Responses of decomposer soil fauna and microorganisms to such changes likely differ from each other, since their life histories, dispersal mechanisms and microhabitats vary greatly.

    We investigated the relative impacts of short-term winter warming and increases in plant cover on bacteria and collembola community composition in cryoturbated, non-sorted circle tundra. By covering non-sorted circles with insulating gardening fibre cloth (fleeces) or using stone walls accumulating snow, we imposed two climate-change scenarios: snow accumulation increased autumn-to-late winter soil temperatures (−1 cm) by 1.4 °C, while fleeces warmed soils during that period by 1 °C and increased spring temperatures by 1.1 °C. Summer bacteria and collembola communities were sampled from within-circle locations differing in vegetation abundance and soil properties.

    Two years of winter warming had no effects on either decomposer community. Instead, their community compositions were strongly determined by sampling location: communities in barren circle centres were distinct from those in vegetated outer rims, while communities in sparsely vegetated patches of circle centres were intermediate. Diversity patterns indicate that collembola communities are tightly linked to plant presence while bacteria communities correlated with soil properties.

    Our results thus suggest that direct effects of short-term winter warming are likely to be minimal, but that vegetation encroachment on barren cryoturbated ground will affect decomposer community composition substantially. At decadal timescales, collembola community changes may follow relatively fast after warming-driven plant establishment into barren areas, whereas bacteria communities may take longer to respond. If shifts in decomposer community composition are indicative for changes in their activity, vegetation overgrowth will likely have much stronger effects on soil functioning in frost-affected tundra than short-term winter warming.

  • 5.
    Krab, Eveline J.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Soil and Environment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Roennefarth, Jonas
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Experimental Plant Ecology, Institute of Botany and Landscape Ecology, Greifswald University, Greifswald, Germany.
    Becher, Marina
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Blume-Werry, Gesche
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Experimental Plant Ecology, Institute of Botany and Landscape Ecology, Greifswald University, Greifswald, Germany.
    Keuper, Frida
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. INRA, AgroImpact UR1158, Barenton Bugny, France.
    Klaminder, Jonatan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Kreyling, Juergen
    Makoto, Kobayashi
    Milbau, Ann
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Biodiversity and Natural Environment, Research Institute for Nature and Forest - INBO, Brussels, Belgium.
    Dorrepaal, Ellen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Winter warming effects on tundra shrub performance are species-specific and dependent on spring conditions2018In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 106, no 2, p. 599-612Article in journal (Refereed)
    Abstract [en]

    Climate change-driven increases in winter temperatures positively affect conditions for shrub growth in arctic tundra by decreasing plant frost damage and stimulation of nutrient availability. However, the extent to which shrubs may benefit from these conditions may be strongly dependent on the following spring climate. Species-specific differences in phenology and spring frost sensitivity likely affect shrub growth responses to warming. Additionally, effects of changes in winter and spring climate may differ over small spatial scales, as shrub growth may be dependent on natural variation in snow cover, shrub density and cryoturbation. We investigated the effects of winter warming and altered spring climate on growing-season performance of three common and widespread shrub species in cryoturbated non-sorted circle arctic tundra. By insulating sparsely vegetated non-sorted circles and parts of the surrounding heath with additional snow or gardening fleeces, we created two climate change scenarios: snow addition increased soil temperatures in autumn and winter and delayed snowmelt timing without increasing spring temperatures, whereas fleeces increased soil temperature similarly in autumn and winter, but created warmer spring conditions without altering snowmelt timing. Winter warming affected shrub performance, but the direction and magnitude were species-specific and dependent on spring conditions. Spring warming advanced, and later snowmelt delayed canopy green-up. The fleece treatment did not affect shoot growth and biomass in any shrub species despite decreasing leaf frost damage in Empetrum nigrum. Snow addition decreased frost damage and stimulated growth of Vaccinium vitis-idaea by c. 50%, while decreasing Betula nana growth (p < .1). All of these effects were consistent the mostly barren circles and surrounding heath. Synthesis. In cryoturbated arctic tundra, growth of Vaccinium vitis-idaea may substantially increase when a thicker snow cover delays snowmelt, whereas in longer term, warmer winters and springs may favour E. nigrum instead. This may affect shrub community composition and cover, with potentially far-reaching effects on arctic ecosystem functioning via its effects on cryoturbation, carbon cycling and trophic cascading. Our results highlight the importance of disentangling effects of winter and spring climate change timing and nature, as spring conditions are a crucial factor in determining the impact of winter warming on plant performance.

  • 6.
    Lett, Signe
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Teuber, Laurenz
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Krab, Eveline
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Michelsen, Anders
    Nilsson, Marie-Charlotte
    Wardle, David
    Dorrepaal, Ellen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Mosses mediate effects of warmer and wetter conditions on tree seedlings at the alpine tree lineManuscript (preprint) (Other academic)
  • 7. Ramirez, Kelly S.
    et al.
    Knight, Christopher G.
    de Hollander, Mattias
    Brearley, Francis Q.
    Constantinides, Bede
    Cotton, Anne
    Creer, Si
    Crowther, Thomas W.
    Davison, John
    Delgado-Baquerizo, Manuel
    Dorrepaal, Ellen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Elliott, David R.
    Fox, Graeme
    Griffiths, Robert I.
    Hale, Chris
    Hartman, Kyle
    Houlden, Ashley
    Jones, David L.
    Krab, Eveline J.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Maestre, Fernando T.
    McGuire, Krista L.
    Monteux, Sylvain
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Orr, Caroline H.
    van der Putten, Wim H.
    Roberts, Ian S.
    Robinson, David A.
    Rocca, Jennifer D.
    Rowntree, Jennifer
    Schlaeppi, Klaus
    Shepherd, Matthew
    Singh, Brajesh K.
    Straathof, Angela L.
    Bhatnagar, Jennifer M.
    Thion, Cecile
    van der Heijden, Marcel G. A.
    de Vries, Franciska T.
    Detecting macroecological patterns in bacterial communities across independent studies of global soils2018In: Nature Microbiology, E-ISSN 2058-5276, Vol. 3, no 2, p. 189-196Article in journal (Refereed)
    Abstract [en]

    The emergence of high-throughput DNA sequencing methods provides unprecedented opportunities to further unravel bacterial biodiversity and its worldwide role from human health to ecosystem functioning. However, despite the abundance of sequencing studies, combining data from multiple individual studies to address macroecological questions of bacterial diversity remains methodically challenging and plagued with biases. Here, using a machine-learning approach that accounts for differences among studies and complex interactions among taxa, we merge 30 independent bacterial data sets comprising 1,998 soil samples from 21 countries. Whereas previous meta-analysis efforts have focused on bacterial diversity measures or abundances of major taxa, we show that disparate amplicon sequence data can be combined at the taxonomy-based level to assess bacterial community structure. We find that rarer taxa are more important for structuring soil communities than abundant taxa, and that these rarer taxa are better predictors of community structure than environmental factors, which are often confounded across studies. We conclude that combining data from independent studies can be used to explore bacterial community dynamics, identify potential 'indicator' taxa with an important role in structuring communities, and propose hypotheses on the factors that shape bacterial biogeography that have been overlooked in the past.

  • 8.
    Semenchuk, Philipp R.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Climate Impacts Research Centre, Umeå University, Abisko, Sweden; Department of Arctic and Marine Biology, Faculty of Biosciences Fisheries and Economics, UiT-The Arctic University of Norway, Tromsø, Norway; Division of Conservation Biology, Vegetation Ecology and Landscape Ecology, Department of Botany and Biodiversity Research, Vienna University, Vienna, Austria.
    Krab, Eveline J
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Climate Impacts Research Centre, Umeå University, Abisko, Sweden; Swedish University of Agricultural Sciences, Department of Soil and Environment, Uppsala, Sweden.
    Hedenström, Mattias
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Phillips, Carly A.
    Ancin-Murguzur, Francisco J.
    Cooper, Elisabeth J.
    Soil organic carbon depletion and degradation in surface soil after long-term non-growing season warming in High Arctic Svalbard2019In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 646, p. 158-167Article in journal (Refereed)
    Abstract [en]

    Arctic tundra active-layer soils are at risk of soil organic carbon (SOC) depletion and degradation upon global climate warming because they are in a stage of relatively early decomposition. Non-growing season (NGS) warming is particularly pronounced, and observed increases of CO2 emissions during experimentally warmed NGSs give concern for great SOC losses to the atmosphere. Here, we used snow fences in Arctic Spitsbergen dwarf shrub tundra to simulate 1.86 degrees C NGS warming for 9 consecutive years, while growing season temperatures remained unchanged. In the snow fence treatment, the 4-11 cm thick A-horizon had a 2% lower SOC concentration and a 0.48 kg Cm-2 smaller pool size than the controls, indicating SOC pool depletion. The snow fence treatment's A-horizon's alkyl/O-alkyl ratio was also significantly increased, indicating an advance of SOC degradation. The underlying 5 cm of B/C-horizon did not show these effects. Our results support the hypothesis that SOC depletion and degradation are connected to the long-term transience of observed ecosystem respiration (ER) increases upon soil warming. We suggest that the bulk of warming induced ER increases may originate from surface and not deep active layer or permafrost horizons. The observed losses of SOC might be significant for the ecosystem in question, but are in magnitude comparatively small relative to anthropogenic greenhouse gas enrichment of the atmosphere. We conclude that a positive feedback of carbon losses from surface soils of Arctic dwarf shrub tundra to anthropogenic forcing will be minor, but not negligible.

  • 9.
    Väisänen, Maria
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Arctic Research Centre at Umeå University.
    Gavazov, Konstantin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Arctic Research Centre at Umeå University.
    Krab, Eveline J
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Arctic Research Centre at Umeå University. Department of Soil and Environment, Swedish University of Agricultural Sciences, Lennart Hjelms väg 9, SE-750 07 Uppsala, Sweden.
    Dorrepaal, Ellen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Arctic Research Centre at Umeå University.
    The Legacy Effects of Winter Climate on Microbial Functioning After Snowmelt in a Subarctic Tundra2019In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 77, no 1, p. 186-190Article in journal (Refereed)
    Abstract [en]

    Warming-induced increases in microbial CO2 release in northern tundra may positively feedback to climate change. However, shifts in microbial extracellular enzyme activities (EEAs) may alter the impacts of warming over the longer term. We investigated the in situ effects of 3years of winter warming in combination with the in vitro effects of a rapid warming (6days) on microbial CO2 release and EEAs in a subarctic tundra heath after snowmelt in spring. Winter warming did not change microbial CO2 release at ambient (10 degrees C) or at rapidly increased temperatures, i.e., a warm spell (18 degrees C) but induced changes (P<0.1) in the Q(10) of microbial respiration and an oxidative EEA. Thus, although warmer winters may induce legacy effects in microbial temperature acclimation, we found no evidence for changes in potential carbon mineralization after spring thaw.

  • 10.
    Väisänen, Maria
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Arctic Centre, University of Lapland, Rovaniemi, Finland.
    Krab, Eveline J.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Dorrepaal, Ellen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Carbon dynamics at frost-patterned tundra driven by long-term vegetation change rather than by short-term non-growing season warming2017In: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 136, no 1, p. 103-117Article in journal (Refereed)
    Abstract [en]

    Frost-patterned grounds, such as mostly barren frost boils surrounded by denser vegetation, are typical habitat mosaics in tundra. Plant and microbial processes in these habitats may be susceptible to short-term warming outside the growing season, while the areal cover of barren frost boils has decreased during the past decades due to climate warming-induced shrub expansion. The relative importance of such short-term and long-term climate impacts on carbon (C) dynamics remains unknown. We measured ecosystem CO2 uptake and release (in the field), microbial respiration (in the laboratory), as well as microbial biomass N and soil extractable N in frost boils and the directly adjacent heath in late spring and late summer. These habitats had been experimentally warmed with insulating fleeces from late September until late May for three consecutive years, which allowed us to investigate the direct short-term effects of warming and longer-term, indirect climate effects via vegetation establishment into frost boils. Non-growing season warming increased C uptake at the frost boils in late spring and decreased it in late summer, while the timing and direction of responses was opposite for the heath. Experimental warming had no effects on microbial or ecosystem C release or soil N at either of the habitats. However, C cycling was manifold higher at the heath compared to the frost boils, likely because of a higher SOM stock in the soil. Short-term climate change can thus directly alter ecosystem C uptake at frost-patterned grounds but will most likely not affect microbial C release. We conclude that the C dynamics at frost-patterned grounds under a changing climate depend most strongly on the potential of vegetation to encroach into frost boils in the long-term.

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