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  • 1.
    Algesten, Grete
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Sobek, Sebastian
    Bergström, Ann-Kristin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ågren, Anneli
    Tranvik, Lars J
    Jansson, Mats
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Role of lakes for organic carbon cycling in the boreal zone2004In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 10, no 1, p. 141-147Article in journal (Refereed)
    Abstract [en]

    We calculated the carbon loss (mineralization plus sedimentation) and net CO2 escape to the atmosphere for 79 536 lakes and total running water in 21 major Scandinavian catchments (size range 437–48 263 km2). Between 30% and 80% of the total organic carbon that entered the freshwater ecosystems was lost in lakes. Mineralization in lakes and subsequent CO2 emission to the atmosphere was by far the most important carbon loss process. The withdrawal capacity of lakes on the catchment scale was closely correlated to the mean residence time of surface water in the catchment, and to some extent to the annual mean temperature represented by latitude. This result implies that variation of the hydrology can be a more important determinant of CO2 emission from lakes than temperature fluctuations. Mineralization of terrestrially derived organic carbon in lakes is an important regulator of organic carbon export to the sea and may affect the net exchange of CO2 between the atmosphere and the boreal landscape.

  • 2.
    Bartholomew, David
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. School of Geography, University of Exeter, Exeter, United Kingdom; Botanic Gardens Conservation International, Richmond, United Kingdom.
    Hayward, Robin
    Biological and Environmental Sciences, University of Stirling, Stirling, United Kingdom; School of Earth and Environment, University of Leeds, Leeds, United Kingdom.
    Burslem, David F. R. P.
    School of Biological Sciences, University of Aberdeen, Aberdeen, United Kingdom.
    Bittencourt, Paulo R. L.
    School of Geography, University of Exeter, Exeter, United Kingdom.
    Chapman, Daniel
    Biological and Environmental Sciences, University of Stirling, Stirling, United Kingdom.
    Bin Suis, Mohd. Aminur Faiz
    Forest Research Centre Sepilok, Sandakan, Malaysia.
    Nilus, Reuben
    Forest Research Centre Sepilok, Sandakan, Malaysia.
    O'Brien, Michael J.
    Estación Experimental de Zonas Áridas, Consejo Superior de Investigaciones Científicas, Almería, Spain.
    Reynolds, Glen
    SE Asia Rainforest Research Partnership, Sabah, Kota Kinabalu, Malaysia.
    Rowland, Lucy
    School of Geography, University of Exeter, Exeter, United Kingdom.
    Banin, Lindsay F.
    UK Centre for Ecology & Hydrology, Edinburgh, United Kingdom.
    Dent, Daisy
    Smithsonian Tropical Research Institute, Balboa, Panama; Department of Environmental Systems Science, ETH, Zürich, Switzerland.
    Bornean tropical forests recovering from logging at risk of regeneration failure2024In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 30, no 3, article id e17209Article in journal (Refereed)
    Abstract [en]

    Active restoration through silvicultural treatments (enrichment planting, cutting climbers and liberation thinning) is considered an important intervention in logged forests. However, its ability to enhance regeneration is key for long-term recovery of logged forests, which remains poorly understood, particularly for the production and survival of seedlings in subsequent generations. To understand the long-term impacts of logging and restoration we tracked the diversity, survival and traits of seedlings that germinated immediately after a mast fruiting in North Borneo in unlogged and logged forests 30–35 years after logging. We monitored 5119 seedlings from germination for ~1.5 years across a mixed landscape of unlogged forests (ULs), naturally regenerating logged forests (NR) and actively restored logged forests via rehabilitative silvicultural treatments (AR), 15–27 years after restoration. We measured 14 leaf, root and biomass allocation traits on 399 seedlings from 15 species. Soon after fruiting, UL and AR forests had higher seedling densities than NR forest, but survival was the lowest in AR forests in the first 6 months. Community composition differed among forest types; AR and NR forests had lower species richness and lower evenness than UL forests by 5–6 months post-mast but did not differ between them. Differences in community composition altered community-weighted mean trait values across forest types, with higher root biomass allocation in NR relative to UL forest. Traits influenced mortality ~3 months post-mast, with more acquisitive traits and relative aboveground investment favoured in AR forests relative to UL forests. Our findings of reduced seedling survival and diversity suggest long time lags in post-logging recruitment, particularly for some taxa. Active restoration of logged forests recovers initial seedling production, but elevated mortality in AR forests lowers the efficacy of active restoration to enhance recruitment or diversity of seedling communities. This suggests current active restoration practices may fail to overcome barriers to regeneration in logged forests, which may drive long-term changes in future forest plant communities.

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  • 3. Berger, Stella A
    et al.
    Diehl, Sebastian
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Stibor, Herwig
    Trommer, Gabriele
    Ruhenstroth, Miriam
    Water temperature and stratification depth independently shift cardinal events during plankton spring succession2010In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 16, no 7, p. 1954-1965Article in journal (Refereed)
    Abstract [en]

    In deep temperate lakes, the beginning of the growing season is triggered by thermal stratification, which alleviates light limitation of planktonic producers in the surface layer and prevents heat loss to deeper strata. The sequence of subsequent phenological events (phytoplankton spring bloom, grazer peak, clearwater phase) results in part from coupled phytoplankton–grazer interactions. Disentangling the separate, direct effects of correlated climatic drivers (stratification-dependent underwater light climate vs. water temperature) from their indirect effects mediated through trophic feedbacks is impossible using observational field data, which challenges our understanding of global warming effects on seasonal plankton dynamics. We therefore manipulated water temperature and stratification depth independently in experimental field mesocosms containing ambient microplankton and inocula of the resident grazer Daphnia hyalina. Higher light availability in shallower surface layers accelerated primary production, warming accelerated consumption and growth of Daphnia, and both factors speeded up successional dynamics driven by trophic feedbacks. Specifically, phytoplankton peaked and decreased earlier and Daphnia populations increased and peaked earlier at both shallower stratification and higher temperature. The timing of ciliate dynamics was unrelated to both factors. Volumetric peak densities of phytoplankton, ciliates and Daphnia in the surface layer were also unaffected by temperature but declined with stratification depth in parallel with light availability. The latter relationship vanished, however, when population sizes were integrated over the entire water column. Overall our results suggest that, integrated over the entire water column of a deep lake, surface warming and shallower stratification independently speed up spring successional events, whereas the magnitudes of phytoplankton and zooplankton spring peaks are less sensitive to these factors. Therefore, accelerated dynamics under warming need not lead to a trophic mismatch (given similar grazer inocula at the time of stratification). We emphasize that entire water column dynamics must be studied to estimate global warming effects on lake ecosystems.

  • 4.
    Bergström, Ann-Kristin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Creed, Irena F.
    Department of Physical and Environmental Sciences, University of Toronto, ON, Toronto, Canada.
    Palstev, Aleksey
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    de Wit, Heleen A.
    Centre of Biogeochemistry in the Anthropocene and Department of Bioscience, University of Oslo, Oslo, Norway; Norwegian Institute for Water Research, Oslo, Norway.
    Lau, Danny C. P.
    Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Drakare, Stina
    Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Vrede, Tobias
    Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Isles, Peter D. F.
    Watershed Management Division, Vermont Department of Environmental Conservation, VT, Montpelier, United States.
    Jonsson, Anders
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Geibrink, Erik
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Kortelainen, Pirkko
    Finnish Environment Institute (SYKE), Helsinki, Finland.
    Vuorenmaa, Jussi
    Finnish Environment Institute (SYKE), Helsinki, Finland.
    Vuorio, Kristiina
    Finnish Environment Institute (SYKE), Helsinki, Finland.
    Kahilainen, Kimmo K.
    Lammi Biological Station, University of Helsinki, Helsinki, Finland.
    Hessen, Dag Olav
    Centre of Biogeochemistry in the Anthropocene and Department of Bioscience, University of Oslo, Oslo, Norway.
    Declining calcium concentration drives shifts toward smaller and less nutritious zooplankton in northern lakes2024In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 30, no 3, article id e17220Article in journal (Refereed)
    Abstract [en]

    Zooplankton community composition of northern lakes is changing due to the interactive effects of climate change and recovery from acidification, yet limited data are available to assess these changes combined. Here, we built a database using archives of temperature, water chemistry and zooplankton data from 60 Scandinavian lakes that represent broad spatial and temporal gradients in key parameters: temperature, calcium (Ca), total phosphorus (TP), total organic carbon (TOC), and pH. Using machine learning techniques, we found that Ca was the most important determinant of the relative abundance of all zooplankton groups studied, while pH was second, and TOC third in importance. Further, we found that Ca is declining in almost all lakes, and we detected a critical Ca threshold in lake water of 1.3 mg L−1, below which the relative abundance of zooplankton shifts toward dominance of Holopedium gibberum and small cladocerans at the expense of Daphnia and copepods. Our findings suggest that low Ca concentrations may shape zooplankton communities, and that current trajectories of Ca decline could promote widespread changes in pelagic food webs as zooplankton are important trophic links from phytoplankton to fish and different zooplankton species play different roles in this context.

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  • 5.
    Bergström, Ann-Kristin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Faithfull Mathisen, Carolyn
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Daniel
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Nitrogen deposition and warming  – effects on phytoplankton nutrient limitation in subarctic lakes2013In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 19, no 8, p. 2557-2568Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to predict the combined effects of enhanced nitrogen (N) deposition and warming on phytoplankton development in high latitude and mountain lakes. Consequently, we assessed, in a series of enclosureexperiments, how lake water nutrient stoichiometry and phytoplankton nutrient limitation varied over the growingseason in 11 lakes situated along an altitudinal/climate gradient with low N-deposition (<1 kg N ha1yr1) in northern subarctic Sweden. Short-term bioassay experiments with N- and P-additions revealed that phytoplankton inhigh-alpine lakes were more prone to P-limitation, and with decreasing altitude became increasingly N- andNP-colimited. Nutrient limitation was additionally most obvious in midsummer. There was also a strong positivecorrelation between phytoplankton growth and water temperature in the bioassays. Although excess nutrients wereavailable in spring and autumn, on these occasions growth was likely constrained by low water temperatures. Theseresults imply that enhanced N-deposition over the Swedish mountain areas will, with the exception of high-alpinelakes, enhance biomass and drive phytoplankton from N- to P-limitation. However, if not accompanied by warming,N-input from deposition will stimulate limited phytoplankton growth due to low water temperatures during largeparts of the growing season. Direct effects of warming, allowing increased metabolic rates and an extension of thegrowing season, seem equally crucial to synergistically enhance phytoplankton development in these lakes.

  • 6.
    Bergström, Ann-Kristin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Climate Impacts Research Centre (CIRC), Umeå University, Abisko, Sweden.
    Light and nutrient control phytoplankton biomass responses to global change in northern lakes2019In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 25, no 6, p. 2021-2029Article in journal (Refereed)
    Abstract [en]

    Global change affects terrestrial loadings of colored dissolved organic carbon (DOC) and nutrients to northern lakes. Still, little is known about how phytoplankton respond to changes in light and nutrient availability across gradients in lake DOC. In this study, we used results from whole-lake studies in northern Sweden to show that annual mean phytoplankton biomass expressed unimodal curved relationships across lake DOC gradients, peaking at threshold DOC levels of around 11 mg/L. Whole-lake single nutrient enrichment in selected lakes caused elevated biomass, with most pronounced effect at the threshold DOC level. These patterns give support to the suggested dual control by DOC on phytoplankton via nutrient (positively) and light (negatively) availability and imply that the lakes' location along the DOC axis is critical in determining to what extent phytoplankton respond to changes in DOC and/or nutrient loadings. By using data from the large Swedish Lake Monitoring Survey, we further estimated that 80% of northern Swedish lakes are below the DOC threshold, potentially experiencing increased phytoplankton biomass with browning alone, and/or combined with nutrient enrichment. The results support the previous model results on effects of browning and eutrophication on lake phytoplankton, and provide important understanding of how northern lakes may respond to future global changes.

  • 7. Bokhorst, Stef
    et al.
    Huiskes, Ad
    Aerts, Rien
    Convey, Peter
    Cooper, Elisabeth J
    Dalen, Linda
    Erschbamer, Brigitta
    Gudmundsson, Jon
    Hofgaard, Annika
    Hollister, Robert D
    Johnstone, Jill
    Jonsdottir, Ingibjorg S
    Lebouvier, Marc
    Van De Vijver, Bart
    Wahren, Carl-Henrik
    Dorrepaal, Ellen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Variable temperature effects of Open Top Chambers at polar and alpine sites explained by irradiance and snow depth2013In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 19, no 1, p. 64-74Article, review/survey (Refereed)
    Abstract [en]

    Environmental manipulation studies are integral to determining biological consequences of climate warming. Open Top Chambers (OTCs) have been widely used to assess summer warming effects on terrestrial biota, with their effects during other seasons normally being given less attention even though chambers are often deployed year-round. In addition, their effects on temperature extremes and freeze-thaw events are poorly documented. To provide robust documentation of the microclimatic influences of OTCs throughout the year, we analysed temperature data from 20 studies distributed across polar and alpine regions. The effects of OTCs on mean temperature showed a large range (-0.9 to 2.1 degrees C) throughout the year, but did not differ significantly between studies. Increases in mean monthly and diurnal temperature were strongly related (R-2 = 0.70) with irradiance, indicating that PAR can be used to predict the mean warming effect of OTCs. Deeper snow trapped in OTCs also induced higher temperatures at soil/vegetation level. OTC-induced changes in the frequency of freeze-thaw events included an increase in autumn and decreases in spring and summer. Frequency of high-temperature events in OTCs increased in spring, summer and autumn compared with non-manipulated control plots. Frequency of low-temperature events was reduced by deeper snow accumulation and higher mean temperatures. The strong interactions identified between aspects of ambient environmental conditions and effects of OTCs suggest that a detailed knowledge of snow depth, temperature and irradiance levels enables us to predict how OTCs will modify the microclimate at a particular site and season. Such predictive power allows a better mechanistic understanding of observed biotic response to experimental warming studies and for more informed design of future experiments. However, a need remains to quantify OTC effects on water availability and wind speed (affecting, for example, drying rates and water stress) in combination with microclimate measurements at organism level.

  • 8. Cazelles, Kevin
    et al.
    Bartley, Timothy
    Guzzo, Matthew M.
    Brice, Marie-Hélène
    MacDougall, Andrew S.
    Bennett, Joseph R.
    Esch, Ellen H.
    Kadoya, Taku
    Kelly, Jocelyn
    Matsuzaki, Shin-ichiro
    Nilsson, Karin A.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    McCann, Kevin S.
    Homogenization of freshwater lakes: Recent compositional shifts in fish communities are explained by gamefish movement and not climate change2019In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 25, no 12, p. 4222-4233Article in journal (Refereed)
    Abstract [en]

    Globally, lake fish communities are being subjected to a range of scale-dependent anthropogenic pressures, from climate change to eutrophication, and from overexploitation to species introductions. As a consequence, the composition of these communities is being reshuffled, in most cases leading to a surge in taxonomic similarity at the regional scale termed homogenization. The drivers of homogenization remain unclear, which may be a reflection of interactions between various environmental changes. In this study, we investigate two potential drivers of the recent changes in the composition of freshwater fish communities: recreational fishing and climate change. Our results, derived from 524 lakes of Ontario, Canada sampled in two periods (1965-1982 and 2008-2012), demonstrate that the main contributors to homogenization are the dispersal of gamefish species, most of which are large predators. Alternative explanations relating to lake habitat (e.g., area, phosphorus) or variations in climate have limited explanatory power. Our analysis suggests that human-assisted migration is the primary driver of the observed compositional shifts, homogenizing freshwater fish community among Ontario lakes and generating food webs dominated by gamefish species.

  • 9. Creed, Irena F.
    et al.
    Bergström, Ann-Kristin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Trick, Charles G.
    Grimm, Nancy B.
    Hessen, Dag O.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Kidd, Karen A.
    Kritzberg, Emma
    McKnight, Diane M.
    Freeman, Erika C.
    Senar, Oscar E.
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ask, Jenny
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Berggren, Martin
    Cherif, Mehdi
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Giesler, Reiner
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hotchkiss, Erin R.
    Kortelainen, Pirkko
    Palta, Monica M.
    Vrede, Tobias
    Weyhenmeyer, Gesa A.
    Global change-driven effects on dissolved organic matter composition: Implications for food webs of northern lakes2018In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 24, no 8, p. 3692-3714Article, review/survey (Refereed)
    Abstract [en]

    Northern ecosystems are experiencing some of the most dramatic impacts of global change on Earth. Rising temperatures, hydrological intensification, changes in atmospheric acid deposition and associated acidification recovery, and changes in vegetative cover are resulting in fundamental changes in terrestrial-aquatic biogeochemical linkages. The effects of global change are readily observed in alterations in the supply of dissolved organic matter (DOM)-the messenger between terrestrial and lake ecosystems-with potentially profound effects on the structure and function of lakes. Northern terrestrial ecosystems contain substantial stores of organic matter and filter or funnel DOM, affecting the timing and magnitude of DOM delivery to surface waters. This terrestrial DOM is processed in streams, rivers, and lakes, ultimately shifting its composition, stoichiometry, and bioavailability. Here, we explore the potential consequences of these global change-driven effects for lake food webs at northern latitudes. Notably, we provide evidence that increased allochthonous DOM supply to lakes is overwhelming increased autochthonous DOM supply that potentially results from earlier ice-out and a longer growing season. Furthermore, we assess the potential implications of this shift for the nutritional quality of autotrophs in terms of their stoichiometry, fatty acid composition, toxin production, and methylmercury concentration, and therefore, contaminant transfer through the food web. We conclude that global change in northern regions leads not only to reduced primary productivity but also to nutritionally poorer lake food webs, with discernible consequences for the trophic web to fish and humans.

  • 10. De Frenne, Pieter
    et al.
    Brunet, Jörg
    Shevtsova, Anna
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Kolb, Annette
    Graae, Bente J
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Chabrerie, Olivier
    Cousins, Sara AO
    Decocq, Guillaume
    De Schrijver, An
    Diekmann, Martin
    Gruwez, Robert
    Heinken, Thilo
    Hermy, Martin
    Nilsson, Christer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Stanton, Sharon
    Tack, Wesley
    Willaert, Justin
    Verheyen, Kris
    Temperature effects on forest herbs assessed by warmingand transplant experiments along a latitudinal gradient2011In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 17, no 10, p. 3240-3253Article in journal (Refereed)
    Abstract [en]

    Slow-colonizing forest understorey plants are probably not able to rapidly adjust their distribution range following large-scale climate change. Therefore, the acclimation potential to climate change within their actual occupied habitats will likely be key for their short- and long-term persistence. We combined transplant experiments along a latitudinal gradient with open-top chambers to assess the effects of temperature on phenology, growth and reproductive performance of multiple populations of slow-colonizing understorey plants, using the spring flowering geophytic forb Anemone nemorosa and the early summer flowering grass Milium effusum as study species. In both species, emergence time and start of flowering clearly advanced with increasing temperatures. Vegetative growth (plant height, aboveground biomass) and reproductive success (seed mass, seed germination and germinable seed output) of A. nemorosa benefited from higher temperatures. Climate warming may thus increase future competitive ability and colonization rates of this species. Apart from the effects on phenology, growth and reproductive performance of M. effusum generally decreased when transplanted southwards (e.g., plant size and number of individuals decreased towards the south) and was probably more limited by light availability in the south. Specific leaf area of both species increased when transplanted southwards, but decreased with open-top chamber installation in A. nemorosa. In general, individuals of both species transplanted at the home site performed best, suggesting local adaptation. We conclude that contrasting understorey plants may display divergent plasticity in response to changing temperatures which may alter future understorey community dynamics.

  • 11.
    Ellison, David
    et al.
    Umeå University, Faculty of Social Sciences, Department of Geography and Economic History.
    Futter, Martyn N.
    Bishop, Kevin
    On the forest cover-water yield debate: from demand- to supply-side thinking2012In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 18, no 3, p. 806-820Article, review/survey (Refereed)
    Abstract [en]

    Several major articles from the past decade and beyond conclude the impact of reforestation or afforestation on water yield is negative: additional forest cover will reduce and removing forests will raise downstream water availability. A second group of authors argue the opposite: planting additional forests should raise downstream water availability and intensify the hydrologic cycle. Obtaining supporting evidence for this second group of authors has been more difficult due to the larger scales at which the positive effects of forests on the water cycle may be seen. We argue that forest cover is inextricably linked to precipitation. Forest-driven evapotranspiration removed from a particular catchment contributes to the availability of atmospheric moisture vapor and its cross-continental transport, raising the likelihood of precipitation events and increasing water yield, in particular in continental interiors more distant from oceans. Seasonal relationships heighten the importance of this phenomenon. We review the arguments from different scales and perspectives. This clarifies the generally beneficial relationship between forest cover and the intensity of the hydrologic cycle. While evidence supports both sides of the argument trees can reduce runoff at the small catchment scale at larger scales, trees are more clearly linked to increased precipitation and water availability. Progressive deforestation, land conversion from forest to agriculture and urbanization have potentially negative consequences for global precipitation, prompting us to think of forest ecosystems as global public goods. Policy-making attempts to measure product water footprints, estimate the value of ecosystem services, promote afforestation, develop drought mitigation strategies and otherwise manage land use must consider the linkage of forests to the supply of precipitation.

  • 12.
    Erhagen, Björn
    et al.
    Department of Forest Ecology & Management, Swedish University of Agricultural Sciences (SLU), Umeå, Sweden.
    Öquist, Mats
    Department of Forest Ecology & Management, Swedish University of Agricultural Sciences (SLU), Umeå, Sweden.
    Sparrman, Tobias
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Haei, Mahsa
    Department of Forest Ecology & Management, Swedish University of Agricultural Sciences (SLU), Umeå, Sweden.
    Ilstedt, Ulrik
    Department of Forest Ecology & Management, Swedish University of Agricultural Sciences (SLU), Umeå, Sweden.
    Hedenström, Mattias
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Schleucher, Jürgen
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Nilsson, Mats B
    Department of Forest Ecology & Management, Swedish University of Agricultural Sciences (SLU), Umeå, Sweden.
    Temperature response of litter and soil organic matter decomposition is determined by chemical composition of organic material2013In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 19, no 12, p. 3858-3871Article in journal (Refereed)
    Abstract [en]

    The global soil carbon pool is approximately three times larger than the contemporary atmospheric pool, therefore even minor changes to its integrity may have major implications for atmospheric CO2 concentrations. While theory predicts that the chemical composition of organic matter should constitute a master control on the temperature response of its decomposition, this relationship has not yet been fully demonstrated. We used laboratory incubations of forest soil organic matter (SOM) and fresh litter material together with NMR spectroscopy to make this connection between organic chemical composition and temperature sensitivity of decomposition. Temperature response of decomposition in both fresh litter and SOM was directly related to the chemical composition of the constituent organic matter, explaining 90% and 70% of the variance in Q10 in litter and SOM respectively. The Q10 of litter decreased with increasing proportions of aromatic and O-aromatic compounds, and increased with increased contents of alkyl- and O-alkyl carbons. In contrast, in SOM, decomposition was affected only by carbonyl compounds. To reveal why a certain group of organic chemical compounds affected the temperature sensitivity of organic matter decomposition in litter and SOM, a more detailed characterisation of the (13) C aromatic region using Heteronuclear Single Quantum Coherence (HSQC) was conducted. The results revealed considerable differences in the aromatic region between litter and SOM. This suggests that the correlation between chemical composition of organic matter and the temperature response of decomposition differed between litter and SOM. The temperature response of soil decomposition processes can thus be described by the chemical composition of its constituent organic matter, this paves the way for improved ecosystem modelling of biosphere feedbacks under a changing climate.

  • 13. Erlandsson, Martin
    et al.
    Buffam, Ishi
    Fölster, Jens
    Laudon, Hjalmar
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Temnerud, Johan
    Weyhenmeyer, Gesa A.
    Bishop, Kevin
    Thirty-five years of synchrony in the organic matter concentrations of Swedish rivers explained by variation in flow and sulphate2008In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 14, no 5, p. 1191-1198Article in journal (Refereed)
    Abstract [en]

    Increasing concentrations of organic matter ( OM) in surface waters have been noted over large parts of the boreal/nemoral zone in Europe and North America. This has raised questions about the causes and the likelihood of further increases. A number of drivers have been proposed, including temperature, hydrology, as well as SO42 - and Cl (-) deposition. The data reported so far, however, have been insufficient to define the relative importance of different drivers in landscapes where they interact. Thirty-five years of monthly measurements of absorbance and chemical oxygen demand ( COD), two common proxies for OM, from 28 large Scandinavian catchments provide an unprecedented opportunity to resolve the importance of hypothesized drivers. For 21 of the catchments, there are 18 years of total organic carbon (TOC) measurements as well. Despite the heterogeneity of the catchments with regards to climate, size and land use, there is a high degree of synchronicity in OM across the entire region. Rivers go from widespread trends of decreasing OM to increasing trends and back again three times in the 35-year record. This synchronicity in decadal scale oscillations and long-term trends suggest a common set of dominant OM drivers in these landscapes. Here, we use regression models to test the importance of different potential drivers. We show that flow and SO42 - together can predict most of the interannual variability in OM proxies, up to 88% for absorbance, up to 78% for COD. Two other candidate drivers, air temperature and Cl (-) , add little explanatory value. Declines in anthropogenic SO42 - since the mid-1970s are thus related to the observed OM increases in Scandinavia, but, in contrast to many recent studies, flow emerges as an even more important driver of OM variability. Stabilizing SO42 - levels also mean that hydrology is likely to be the major driver of future variability and trends in OM.

  • 14. Eskelinen, Anu
    et al.
    Kaarlejarvi, Elina
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Plant Biology and Nature Management, Vrije Universiteit Brussel, Brussels, Belgium.
    Olofsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Herbivory and nutrient limitation protect warming tundra from lowland species' invasion and diversity loss2017In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 23, no 1, p. 245-255Article in journal (Refereed)
    Abstract [en]

    Herbivory and nutrient limitation can increase the resistance of temperature-limited systems to invasions under climate warming. We imported seeds of lowland species to tundra under factorial treatments of warming, fertilization, herbivore exclusion and biomass removal. We show that warming alone had little impact on lowland species, while exclusion of native herbivores and relaxation of nutrient limitation greatly benefitted them. In contrast, warming alone benefitted resident tundra species and increased species richness; however, these were canceled by negative effects of herbivore exclusion and fertilization. Dominance of lowland species was associated with low cover of tundra species and resulted in decreased species richness. Our results highlight the critical role of biotic and abiotic filters unrelated to temperature in protecting tundra under warmer climate. While scarcity of soil nutrients and native herbivores act as important agents of resistance to invasions by lowland species, they concurrently promote overall species coexistence. However, when these biotic and abiotic resistances are relaxed, invasion of lowland species can lead to decreased abundance of resident tundra species and diminished diversity.

  • 15.
    Esseen, Per-Anders
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ekström, Magnus
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics. Department of Forest Resource Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Grafström, Anton
    Department of Forest Resource Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Jonsson, Bengt Gunnar
    Department of Natural Sciences, Mid Sweden University, Sundsvall, Sweden; Department of Fish, Wildlife and Environmental Sciences, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Palmqvist, Kristin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Westerlund, Bertil
    Department of Forest Resource Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Ståhl, Göran
    Department of Forest Resource Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Multiple drivers of large-scale lichen decline in boreal forest canopies2022In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 28, no 10, p. 3293-3309Article in journal (Refereed)
    Abstract [en]

    Thin, hair-like lichens (Alectoria, Bryoria, Usnea) form conspicuous epiphyte communities across the boreal biome. These poikilohydric organisms provide important ecosystem functions and are useful indicators of global change. We analyse how environmental drivers influence changes in occurrence and length of these lichens on Norway spruce (Picea abies) over 10 years in managed forests in Sweden using data from >6000 trees. Alectoria and Usnea showed strong declines in southern-central regions, whereas Bryoria declined in northern regions. Overall, relative loss rates across the country ranged from 1.7% per year in Alectoria to 0.5% in Bryoria. These losses contrasted with increased length of Bryoria and Usnea in some regions. Occurrence trajectories (extinction, colonization, presence, absence) on remeasured trees correlated best with temperature, rain, nitrogen deposition, and stand age in multinomial logistic regression models. Our analysis strongly suggests that industrial forestry, in combination with nitrogen, is the main driver of lichen declines. Logging of forests with long continuity of tree cover, short rotation cycles, substrate limitation and low light in dense forests are harmful for lichens. Nitrogen deposition has decreased but is apparently still sufficiently high to prevent recovery. Warming correlated with occurrence trajectories of Alectoria and Bryoria, likely by altering hydration regimes and increasing respiration during autumn/winter. The large-scale lichen decline on an important host has cascading effects on biodiversity and function of boreal forest canopies. Forest management must apply a broad spectrum of methods, including uneven-aged continuous cover forestry and retention of large patches, to secure the ecosystem functions of these important canopy components under future climates. Our findings highlight interactions among drivers of lichen decline (forestry, nitrogen, climate), functional traits (dispersal, lichen colour, sensitivity to nitrogen, water storage), and population processes (extinction/colonization).

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  • 16.
    Finstad, Anders G.
    et al.
    Norwegian Institute for Nature Research, Trondheim, Norway.
    Hein, Catherine L.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Migrate or stay: terrestrial primary productivity and climate drive anadromy in Arctic char2012In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 18, no 8, p. 2487-2497Article in journal (Refereed)
    Abstract [en]

    A shift in the magnitude and timing of animal migrations is one of the most documented ecological effects of climate change. Although migrations are largely driven by spatial variation in resource gradients, few studies connect expected changes in primary production with geographic patterns in migratory behavior. Here, we link lake primary production to the occurrence of sea migrations in the partially anadromous salmonid Arctic char (Salvelinus alpinus L.). We compiled presence/absence records of anadromous char populations spanning productivity and temperature gradients along the Norwegian coast. The probability of anadromy decreased with increasing migration distance, maximum slope of the migration route and lake productivity. There was a significant interaction between lake productivity and migration distance. The negative effect of longer migration distances was more severe in lakes with higher productivity, indicating reduced relative profitability of migration with increased feeding opportunities in freshwater. Lake productivity was mainly driven by terrestrial primary production in the catchment. We predicted future distributions of anadromous char given downscaled temperature and precipitation changes projected by two different emission scenarios and global climate models (GCMs). Projected increases in temperature and precipitation in 20712100 increased terrestrial primary production and, compared to the control scenario (19611990), decreased the range of anadromous populations. The prevalence of anadromy decreased by 53% in the HadAm3H GCM with the A2 emission scenario, 61% in HadAm3H with the B2 scenario and 22% in ECHAM4 with the B2 scenario. Cross-ecosystem studies (e.g., terrestrial to freshwater) are critical for understanding ecological impacts of climate change. In this case, climate-driven increases in terrestrial primary production are expected to increase primary production in lakes and ultimately reduce the prevalence of anadromy in Arctic char populations.

  • 17. Freeman, Erika C.
    et al.
    Creed, Irena F.
    Jones, Blake
    Bergström, Ann-Kristin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Global changes may be promoting a rise in select cyanobacteria in nutrient-poor northern lakes2020In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 26, no 9, p. 4966-4987Article in journal (Refereed)
    Abstract [en]

    The interacting effects of global changes-including increased temperature, altered precipitation, reduced acidification and increased dissolved organic matter loads to lakes-are anticipated to create favourable environmental conditions for cyanobacteria in northern lakes. However, responses of cyanobacteria to these global changes are complex, if not contradictory. We hypothesized that absolute and relative biovolumes of cyanobacteria (both total and specific genera) are increasing in Swedish nutrient-poor lakes and that these increases are associated with global changes. We tested these hypotheses using data from 28 nutrient-poor Swedish lakes over 16 years (1998-2013). Increases in cyanobacteria relative biovolume were identified in 21% of the study sites, primarily in the southeastern region of Sweden, and were composed mostly of increases from three specific genera:Merismopedia,ChroococcusandDolichospermum. Taxon-specific changes were related to different environmental stressors; that is, increased surface water temperature favoured higherMerismopediarelative biovolume in low pH lakes with high nitrogen to phosphorus ratios, whereas acidification recovery was statistically related to increased relative biovolumes ofChroococcusandDolichospermum. In addition, enhanced dissolved organic matter loads were identified as potential determinants of Chroococcussuppression and Dolichospermumpromotion. Our findings highlight that specific genera of cyanobacteria benefit from different environmental changes. Our ability to predict the risk of cyanobacteria prevalence requires consideration of the environmental condition of a lake and the sensitivities of the cyanobacteria genera within the lake. Regional patterns may emerge due to spatial autocorrelations within and among lake history, rates and direction of environmental change and the niche space occupied by specific cyanobacteria.

  • 18.
    Gavazov, Konstantin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Swiss Federal Institute for Forest, Snowand Landscape Research, WSL SiteLausanne, Lausanne, Switzerland; Laboratory of Ecological Systems ECOS,School of Architecture, Civil and Environmental Engine ering ENAC, EcolePolytechnique Fédérale de Lausanne EPFL,Lausanne, Switzerland.
    Albrecht, Remy
    Buttler, Alexandre
    Dorrepaal, Ellen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Garnett, Mark H.
    Gogo, Sebastien
    Hagedorn, Frank
    Mills, Robert T. E.
    Robroek, Bjorn J. M.
    Bragazza, Luca
    Vascular plant-mediated controls on atmospheric carbon assimilation and peat carbon decomposition under climate change2018In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 24, no 9, p. 3911-3921Article in journal (Refereed)
    Abstract [en]

    Climate change can alter peatland plant community composition by promoting the growth of vascular plants. How such vegetation change affects peatland carbon dynamics remains, however, unclear. In order to assess the effect of vegetation change on carbon uptake and release, we performed a vascular plant-removal experiment in two Sphagnum-dominated peatlands that represent contrasting stages of natural vegetation succession along a climatic gradient. Periodic measurements of net ecosystem CO2 exchange revealed that vascular plants play a crucial role in assuring the potential for net carbon uptake, particularly with a warmer climate. The presence of vascular plants, however, also increased ecosystem respiration, and by using the seasonal variation of respired CO2 radiocarbon (bomb-C-14) signature we demonstrate an enhanced heterotrophic decomposition of peat carbon due to rhizosphere priming. The observed rhizosphere priming of peat carbon decomposition was matched by more advanced humification of dissolved organic matter, which remained apparent beyond the plant growing season. Our results underline the relevance of rhizosphere priming in peatlands, especially when assessing the future carbon sink function of peatlands undergoing a shift in vegetation community composition in association with climate change.

  • 19.
    Gronchi, Enzo
    et al.
    Limnological Institute, University of Konstanz, Konstanz, Germany.
    Jöhnk, Klaus D.
    CSIRO Land and Water, ACT, Canberra, Australia.
    Straile, Dietmar
    Limnological Institute, University of Konstanz, Konstanz, Germany.
    Diehl, Sebastian
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Integrated Science Lab – IceLab, Umeå University, Umeå, Sweden.
    Peeters, Frank
    Limnological Institute, University of Konstanz, Konstanz, Germany.
    Local and continental-scale controls of the onset of spring phytoplankton blooms: Conclusions from a proxy-based model2021In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 27, no 9, p. 1976-1990Article in journal (Refereed)
    Abstract [en]

    A key phenological event in the annual cycle of many pelagic ecosystems is the onset of the spring algal bloom (OAB). Descriptions of the factors controlling the OAB in temperate to polar lakes have been limited to isolated studies of single systems and conceptual models. Here we present a validated modelling approach that, for the first time, enables a quantitative prediction of the OAB and a systematic assessment of the processes controlling its timing on a continental scale. We used a weather-driven, one-dimensional lake model to simulate the seasonal dynamics of the underwater light climate in 16 lake types characterized by the factorial combination of four lake depths with four levels of water transparency. We did so at 1962 locations across Western Europe and over 31 years (1979–2009). Assuming that phytoplankton production is light-limited in winter, we identified four patterns of OAB control across lake types and climate zones. OAB timing is controlled by (i) the timing of ice-off in ice-covered clear or shallow lakes, (ii) the onset of thermal stratification in sufficiently deep and turbid lakes and (iii) the seasonal increase in incident radiation in all other lakes, except for (iv) ice-free, shallow and clear lakes in the south, where phytoplankton is not light-limited. The model predicts that OAB timing should respond to two pervasive environmental changes, global warming and browning, in opposite ways. OAB timing should be highly sensitive to warming in lakes where it is controlled by either ice-off or the onset of stratification, but resilient to warming in lakes where it is controlled by incident radiation. Conversely, OAB timing should be most sensitive to browning where it is controlled by incident radiation, but resilient to browning where it is controlled by ice-off or the onset of stratification. Available lake data are consistent with our findings.

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  • 20.
    Gundale, Michael J.
    et al.
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Axelsson, E. Petter
    Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Buness, Vincent
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Callebaut, Timon
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    DeLuca, Thomas H.
    College of Forestry, Oregon State University, OR, Corvallis, United States.
    Hupperts, Stefan F.
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Ibáñez, Theresa S.
    Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Metcalfe, Daniel B.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Nilsson, Marie-Charlotte
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Peichl, Matthias
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Spitzer, Clydecia M.
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Stangl, Zsofia R.
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Strengbom, Joachim
    Department of Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Sundqvist, Maja K.
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Wardle, David A.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Lindahl, Björn D.
    Department of Soil Science, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    The biological controls of soil carbon accumulation following wildfire and harvest in boreal forests: a review2024In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 30, no 5, article id e17276Article, review/survey (Refereed)
    Abstract [en]

    Boreal forests are frequently subjected to disturbances, including wildfire and clear-cutting. While these disturbances can cause soil carbon (C) losses, the long-term accumulation dynamics of soil C stocks during subsequent stand development is controlled by biological processes related to the balance of net primary production (NPP) and outputs via heterotrophic respiration and leaching, many of which remain poorly understood. We review the biological processes suggested to influence soil C accumulation in boreal forests. Our review indicates that median C accumulation rates following wildfire and clear-cutting are similar (0.15 and 0.20 Mg ha−1 year−1, respectively), however, variation between studies is extremely high. Further, while many individual studies show linear increases in soil C stocks through time after disturbance, there are indications that C stock recovery is fastest early to mid-succession (e.g. 15–80 years) and then slows as forests mature (e.g. >100 years). We indicate that the rapid build-up of soil C in younger stands appears not only driven by higher plant production, but also by a high rate of mycorrhizal hyphal production, and mycorrhizal suppression of saprotrophs. As stands mature, the balance between reductions in plant and mycorrhizal production, increasing plant litter recalcitrance, and ectomycorrhizal decomposers and saprotrophs have been highlighted as key controls on soil C accumulation rates. While some of these controls appear well understood (e.g. temporal patterns in NPP, changes in aboveground litter quality), many others remain research frontiers. Notably, very little data exists describing and comparing successional patterns of root production, mycorrhizal functional traits, mycorrhizal-saprotroph interactions, or C outputs via heterotrophic respiration and dissolved organic C following different disturbances. We argue that these less frequently described controls require attention, as they will be key not only for understanding ecosystem C balances, but also for representing these dynamics more accurately in soil organic C and Earth system models.

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  • 21. Gundale, Michael J.
    et al.
    From, Fredrik
    Bach, Lisbet H.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Nordin, Annika
    Anthropogenic nitrogen deposition in boreal forests has a minor impact on the global carbon cycle2014In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 20, no 1, p. 276-286Article in journal (Refereed)
    Abstract [en]

    It is proposed that increases in anthropogenic reactive nitrogen (N-r) deposition may cause temperate and boreal forests to sequester a globally significant quantity of carbon (C); however, long-term data from boreal forests describing how C sequestration responds to realistic levels of chronic N-r deposition are scarce. Using a long-term (14-year) stand-scale (0.1ha) N addition experiment (three levels: 0, 12.5, and 50kgNha(-1)yr(-1)) in the boreal zone of northern Sweden, we evaluated how chronic N additions altered N uptake and biomass of understory communities, and whether changes in understory communities explained N uptake and C sequestration by trees. We hypothesized that understory communities (i.e. mosses and shrubs) serve as important sinks for low-level N additions, with the strength of these sinks weakening as chronic N addition rates increase, due to shifts in species composition. We further hypothesized that trees would exhibit nonlinear increases in N acquisition, and subsequent C sequestration as N addition rates increased, due to a weakening understory N sink. Our data showed that understory biomass was reduced by 50% in response to the high N addition treatment, mainly due to reduced moss biomass. A N-15 labeling experiment showed that feather mosses acquired the largest fraction of applied label, with this fraction decreasing as the chronic N addition level increased. Contrary to our hypothesis, the proportion of label taken up by trees was equal (ca. 8%) across all three N addition treatments. The relationship between N addition and C sequestration in all vegetation pools combined was linear, and had a slope of 16kgCkg(-1)N. While canopy retention of N-r deposition may cause C sequestration rates to be slightly different than this estimate, our data suggest that a minor quantity of annual anthropogenic CO2 emissions are sequestered into boreal forests as a result of N-r deposition.

  • 22. Haubrock, Phillip J.
    et al.
    Pilotto, Francesca
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Innocenti, Gianna
    Cianfanelli, Simone
    Haase, Peter
    Two centuries for an almost complete community turnover from native to non-native species in a riverine ecosystem2021In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 27, no 3, p. 606-623Article in journal (Refereed)
    Abstract [en]

    Non-native species introductions affect freshwater communities by changing community compositions, functional roles, trait occurrences and ecological niche spaces. Reconstructing such changes over long periods is difficult due to limited data availability. We collected information spanning 215 years on fish and selected macroinvertebrate groups (Mollusca and Crustacea) in the inner-Florentine stretch of the Arno River (Italy) and associated water grid, to investigate temporal changes. We identified an almost complete turnover from native to non-native fish (1800: 92% native; 2015: 94% non-native species) and macroinvertebrate species (1800: 100% native; 2015: 70% non-native species). Non-native fish species were observed similar to 50 years earlier compared to macroinvertebrate species, indicating phased invasion processes. In contrast, alpha-diversity of both communities increased significantly following a linear pattern. Separate analyses of changes in alpha-diversities for native and non-native species of both fish and macroinvertebrates were nonlinear. Functional richness and divergence of fish and macroinvertebrate communities decreased non-significantly, as the loss of native species was compensated by non-native species. Introductions of non-native fish and macroinvertebrate species occurred outside the niche space of native species. Native and non-native fish species exhibited greater overlap in niche space over time (62%-68%) and non-native species eventually replaced native species. Native and non-native macroinvertebrate niches overlapped to a lesser extent (15%-30%), with non-natives occupying mostly unoccupied niche space. These temporal changes in niche spaces of both biotic groups are a direct response to the observed changes in alpha-diversity and species turnover. These changes are potentially driven by deteriorations in hydromorphology as indicated by alterations in trait modalities. Additionally, we identified that angling played a considerable role for fish introductions. Our results support previous findings that the community turnover from native to non-native species can be facilitated by, for example, deteriorating environmental conditions and that variations in communities are multifaceted requiring more indicators than single metrics.

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  • 23. Hicks Pries, Caitlin E.
    et al.
    van Logtestijn, Richard S. P.
    Schuur, Edward A. G.
    Natali, Susan M.
    Cornelissen, Johannes H. C.
    Aerts, Rien
    Dorrepaal, Ellen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Decadal warming causes a consistent and persistent shift from heterotrophic to autotrophic respiration in contrasting permafrost ecosystems2015In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 21, no 12, p. 4508-4519Article in journal (Refereed)
    Abstract [en]

    Soil carbon in permafrost ecosystems has the potential to become a major positive feedback to climate change if permafrost thaw increases heterotrophic decomposition. However, warming can also stimulate autotrophic production leading to increased ecosystem carbon storage-a negative climate change feedback. Few studies partitioning ecosystem respiration examine decadal warming effects or compare responses among ecosystems. Here, we first examined how 11 years of warming during different seasons affected autotrophic and heterotrophic respiration in a bryophyte-dominated peatland in Abisko, Sweden. We used natural abundance radiocarbon to partition ecosystem respiration into autotrophic respiration, associated with production, and heterotrophic decomposition. Summertime warming decreased the age of carbon respired by the ecosystem due to increased proportional contributions from autotrophic and young soil respiration and decreased proportional contributions from old soil. Summertime warming's large effect was due to not only warmer air temperatures during the growing season, but also to warmer deep soils year-round. Second, we compared ecosystem respiration responses between two contrasting ecosystems, the Abisko peatland and a tussock-dominated tundra in Healy, Alaska. Each ecosystem had two different timescales of warming (<5years and over a decade). Despite the Abisko peatland having greater ecosystem respiration and larger contributions from heterotrophic respiration than the Healy tundra, both systems responded consistently to short- and long-term warming with increased respiration, increased autotrophic contributions to ecosystem respiration, and increased ratios of autotrophic to heterotrophic respiration. We did not detect an increase in old soil carbon losses with warming at either site. If increased autotrophic respiration is balanced by increased primary production, as is the case in the Healy tundra, warming will not cause these ecosystems to become growing season carbon sources. Warming instead causes a persistent shift from heterotrophic to more autotrophic control of the growing season carbon cycle in these carbon-rich permafrost ecosystems.

  • 24. Hough, Moira
    et al.
    McCabe, Samantha
    Vining, S. Rose
    Pickering Pedersen, Emily
    Wilson, Rachel M.
    Lawrence, Ryan
    Chang, Kuang-Yu
    Bohrer, Gil
    Riley, William J.
    Crill, Patrick M.
    Varner, Ruth K.
    Blazewicz, Steven J.
    Dorrepaal, Ellen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Tfaily, Malak M.
    Saleska, Scott R.
    Rich, Virginia, I
    Coupling plant litter quantity to a novel metric for litter quality explains C storage changes in a thawing permafrost peatland2022In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 28, no 3, p. 950-968Article in journal (Refereed)
    Abstract [en]

    Permafrost thaw is a major potential feedback source to climate change as it can drive the increased release of greenhouse gases carbon dioxide (CO2) and methane (CH4). This carbon release from the decomposition of thawing soil organic material can be mitigated by increased net primary productivity (NPP) caused by warming, increasing atmospheric CO2, and plant community transition. However, the net effect on C storage also depends on how these plant community changes alter plant litter quantity, quality, and decomposition rates. Predicting decomposition rates based on litter quality remains challenging, but a promising new way forward is to incorporate measures of the energetic favorability to soil microbes of plant biomass decomposition. We asked how the variation in one such measure, the nominal oxidation state of carbon (NOSC), interacts with changing quantities of plant material inputs to influence the net C balance of a thawing permafrost peatland. We found: (1) Plant productivity (NPP) increased post-thaw, but instead of contributing to increased standing biomass, it increased plant biomass turnover via increased litter inputs to soil; (2) Plant litter thermodynamic favorability (NOSC) and decomposition rate both increased post-thaw, despite limited changes in bulk C:N ratios; (3) these increases caused the higher NPP to cycle more rapidly through both plants and soil, contributing to higher CO2 and CH4 fluxes from decomposition. Thus, the increased C-storage expected from higher productivity was limited and the high global warming potential of CH4 contributed a net positive warming effect. Although post-thaw peatlands are currently C sinks due to high NPP offsetting high CO2 release, this status is very sensitive to the plant community's litter input rate and quality. Integration of novel bioavailability metrics based on litter chemistry, including NOSC, into studies of ecosystem dynamics, is needed to improve the understanding of controls on arctic C stocks under continued ecosystem transition.

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  • 25.
    Huaraca Huasco, Walter
    et al.
    Environmental Change Institute, School of Geography and the Environment, University of Oxford, Oxford, United Kingdom.
    Riutta, Terhi
    Environmental Change Institute, School of Geography and the Environment, University of Oxford, Oxford, United Kingdom.
    Girardin, Cécile A. J.
    Environmental Change Institute, School of Geography and the Environment, University of Oxford, Oxford, United Kingdom.
    Hancco Pacha, Fernando
    Universidad Nacional de San Antonio Abad del Cusco, Cusco, Peru.
    Puma Vilca, Beisit L.
    Universidad Nacional de San Antonio Abad del Cusco, Cusco, Peru.
    Moore, Sam
    Environmental Change Institute, School of Geography and the Environment, University of Oxford, Oxford, United Kingdom.
    Rifai, Sami W.
    ARC Centre of Excellence for Climate Extremes, University of New South Wales, NSW, Sydney, Australia.
    del Aguila-Pasquel, Jhon
    Instituto de Investigaciones de la Amazonía Peruana (IIAP), Iquitos, Peru.
    Araujo Murakami, Alejandro
    Museo de Historia Natural Noel Kempff Mercado Universidad Autónoma Gabriel Rene Moreno, Santa Cruz, Bolivia.
    Freitag, Renata
    Programa de Pós-graduação em Ecologia e Conservação, Universidade do Estado de Mato Grosso, MT, Nova Xavantina, Brazil.
    Morel, Alexandra C.
    Department of Geography and Environmental Science, University of Dundee, Dundee, United Kingdom.
    Demissie, Sheleme
    Environment and Coffee Forest Forum, Addis Ababa, Ethiopia.
    Doughty, Christopher E.
    School of Informatics, Computing and Cyber systems, Northern Arizona University, AZ, Flagstaff, United States.
    Oliveras, Imma
    Environmental Change Institute, School of Geography and the Environment, University of Oxford, Oxford, United Kingdom.
    Galiano Cabrera, Darcy F.
    Universidad Nacional de San Antonio Abad del Cusco, Cusco, Peru.
    Durand Baca, Liliana
    Universidad Nacional Federico Villarreal de Lima, Lima, Peru.
    Farfán Amézquita, Filio
    Universidad Nacional de San Antonio Abad del Cusco, Cusco, Peru.
    Silva Espejo, Javier E.
    Departamento de Biología, Universidad de La Serena, La Serena, Chile.
    da Costa, Antonio C.L.
    Instituto de Geosciências, Universidade Federal do Pará, Belém, Brazil.
    Oblitas Mendoza, Erick
    Instituto Nacional de Pesquisas da Amazônia, Manaus, Brazil.
    Quesada, Carlos Alberto
    Instituto Nacional de Pesquisas da Amazônia, Manaus, Brazil.
    Evouna Ondo, Fidele
    Agence Nationale des Parcs Nationaux, Libreville, Gabon.
    Edzang Ndong, Josué
    Agence Nationale des Parcs Nationaux, Libreville, Gabon.
    Jeffery, Kathryn J.
    Faculty of Natural Sciences, University of Stirling, Stirling, United Kingdom.
    Mihindou, Vianet
    Ministère de la Foret, de la Mer, de l'Environnement, Chargé Du Plan Climat, Libreville, Gabon.
    White, Lee J. T.
    Ministère de la Foret, de la Mer, de l'Environnement, Chargé Du Plan Climat, Libreville, Gabon.
    N'ssi Bengone, Natacha
    Ministère de la Foret, de la Mer, de l'Environnement, Chargé Du Plan Climat, Libreville, Gabon.
    Ibrahim, Forzia
    Forestry Research Institute of Ghana, Council for Scientific and Industrial Research, University, Kumasi, Ghana.
    Addo-Danso, Shalom D.
    Forestry Research Institute of Ghana, Council for Scientific and Industrial Research, University, Kumasi, Ghana.
    Duah-Gyamfi, Akwasi
    Forestry Research Institute of Ghana, Council for Scientific and Industrial Research, University, Kumasi, Ghana.
    Djaney Djagbletey, Gloria
    Forestry Research Institute of Ghana, Council for Scientific and Industrial Research, University, Kumasi, Ghana.
    Owusu-Afriyie, Kennedy
    Forestry Research Institute of Ghana, Council for Scientific and Industrial Research, University, Kumasi, Ghana.
    Amissah, Lucy
    Forestry Research Institute of Ghana, Council for Scientific and Industrial Research, University, Kumasi, Ghana.
    Mbou, Armel T.
    Centro Euro-Mediterraneo sui Cambiamenti Climatici, Leece, Italy.
    Marthews, Toby R.
    UK Centre for Ecology & Hydrology (UKCEH), Wallingford, United Kingdom.
    Metcalfe, Daniel B.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Aragão, Luiz E. O.
    Divisão de Sensoriamento Remoto-DIDSR, Instituto Nacional de Pesquisas Espaciais, SP, São Jose dos Campos, Brazil.
    Marimon-Junior, Ben H.
    Programa de Pós-graduação em Ecologia e Conservação, Universidade do Estado de Mato Grosso, MT, Nova Xavantina, Brazil.
    Marimon, Beatriz S.
    Programa de Pós-graduação em Ecologia e Conservação, Universidade do Estado de Mato Grosso, MT, Nova Xavantina, Brazil.
    Majalap, Noreen
    Sabah Forestry Department, Forest Research Centre, Sabah, Malaysia.
    Adu-Bredu, Stephen
    Forestry Research Institute of Ghana, Council for Scientific and Industrial Research, University, Kumasi, Ghana.
    Abernethy, Katharine A.
    Faculty of Natural Sciences, University of Stirling, Stirling, United Kingdom.
    Silman, Miles
    Department of Biology, Wake Forest University, NC, Winston-Salem, United States.
    Ewers, Robert M.
    Department of Life Science, Imperial College London, Ascot, United Kingdom.
    Meir, Patrick
    Research School of Biology, Australian National University, ACT, Canberra, Australia; School of Geosciences, University of Edinburgh, Edinburgh, United Kingdom.
    Malhi, Yadvinder
    Environmental Change Institute, School of Geography and the Environment, University of Oxford, Oxford, United Kingdom.
    Fine root dynamics across pantropical rainforest ecosystems2021In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 27, no 15, p. 3657-3680Article in journal (Refereed)
    Abstract [en]

    Fine roots constitute a significant component of the net primary productivity (NPP) of forest ecosystems but are much less studied than aboveground NPP. Comparisons across sites and regions are also hampered by inconsistent methodologies, especially in tropical areas. Here, we present a novel dataset of fine root biomass, productivity, residence time, and allocation in tropical old-growth rainforest sites worldwide, measured using consistent methods, and examine how these variables are related to consistently determined soil and climatic characteristics. Our pantropical dataset spans intensive monitoring plots in lowland (wet, semi-deciduous, and deciduous) and montane tropical forests in South America, Africa, and Southeast Asia (n = 47). Large spatial variation in fine root dynamics was observed across montane and lowland forest types. In lowland forests, we found a strong positive linear relationship between fine root productivity and sand content, this relationship was even stronger when we considered the fractional allocation of total NPP to fine roots, demonstrating that understanding allocation adds explanatory power to understanding fine root productivity and total NPP. Fine root residence time was a function of multiple factors: soil sand content, soil pH, and maximum water deficit, with longest residence times in acidic, sandy, and water-stressed soils. In tropical montane forests, on the other hand, a different set of relationships prevailed, highlighting the very different nature of montane and lowland forest biomes. Root productivity was a strong positive linear function of mean annual temperature, root residence time was a strong positive function of soil nitrogen content in montane forests, and lastly decreasing soil P content increased allocation of productivity to fine roots. In contrast to the lowlands, environmental conditions were a better predictor for fine root productivity than for fractional allocation of total NPP to fine roots, suggesting that root productivity is a particularly strong driver of NPP allocation in tropical mountain regions.

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  • 26. Humborg, Christoph
    et al.
    Mörth, Carl-Magnus
    Sundblom, Marcus
    Borg, Hans
    Blenckner, Thorsten
    Giesler, Reiner
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ittekot, Venugopalan
    CO2 supersaturation along the aquatic conduit in Swedish watersheds as constrained by terrestrial respiration, aquatic respiration and weathering2010In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 16, no 7, p. 1966-1978Article in journal (Refereed)
    Abstract [en]

    We tested the hypothesis that CO2 supersaturation along the aquatic conduit over Sweden can be explained by processes other than aquatic respiration. A first generalized-additive model (GAM) analysis evaluating the relationships between single water chemistry variables and pCO2 in lakes and streams revealed that water chemistry variables typical for groundwater input, e.g., dissolved silicate (DSi) and Mg2+ had explanatory power similar to total organic carbon (TOC). Further GAM analyses on various lake size classes and stream orders corroborated the slightly higher explanatory power for DSi in lakes and Mg2+ for streams compared with TOC. Both DSi and TOC explained 22–46% of the pCO2 variability in various lake classes (0.01–>100 km2) and Mg2+ and TOC explained 11–41% of the pCO2 variability in the various stream orders. This suggests that aquatic pCO2 has a strong groundwater signature. Terrestrial respiration is a significant source of the observed supersaturation and we may assume that both terrestrial respiration and aquatic respiration contributed equally to pCO2 efflux. pCO2 and TOC concentrations decreased with lake size suggesting that the longer water residence time allow greater equilibration of CO2 with the atmosphere and in-lake mineralization of TOC. For streams, we observed a decreasing trend in pCO2 with stream orders between 3 and 6. We calculated the total CO2 efflux from all Swedish lakes and streams to be 2.58 Tg C yr−1. Our analyses also demonstrated that 0.70 Tg C yr−1 are exported to the ocean by Swedish watersheds as HCO3 and CO32− of which about 0.56 Tg C yr−1 is also a residual from terrestrial respiration and constitute a long-term sink for atmospheric CO2. Taking all dissolved inorganic carbon (DIC) fluxes along the aquatic conduit into account will lower the estimated net ecosystem C exchange (NEE) by 2.02 Tg C yr−1, which corresponds to 10% of the NEE in Sweden.

  • 27.
    James, Kelly
    et al.
    NatureScot, Perth, United Kingdom.
    Macreadie, Peter I.
    Marine Research and Innovation Centre, School of Life and Environmental Sciences, Deakin University, VIC, Burwood, Australia.
    Burdett, Heidi L.
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Davies, Ian
    Marine Scotland Science, Aberdeen, United Kingdom.
    Kamenos, Nicholas A.
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    It's time to broaden what we consider a 'blue carbon ecosystem'2024In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 30, no 5, article id e17261Article in journal (Refereed)
    Abstract [en]

    Photoautotrophic marine ecosystems can lock up organic carbon in their biomass and the associated organic sediments they trap over millennia and are thus regarded as blue carbon ecosystems. Because of the ability of marine ecosystems to lock up organic carbon for millennia, blue carbon is receiving much attention within the United Nations' 2030 Agenda for Sustainable Development as a nature-based solution (NBS) to climate change, but classically still focuses on seagrass meadows, mangrove forests, and tidal marshes. However, other coastal ecosystems could also be important for blue carbon storage, but remain largely neglected in both carbon cycling budgets and NBS strategic planning. Using a meta-analysis of 253 research publications, we identify other coastal ecosystems—including mud flats, fjords, coralline algal (rhodolith) beds, and some components or coral reef systems—with a strong capacity to act as blue carbon sinks in certain situations. Features that promote blue carbon burial within these ‘non-classical’ blue carbon ecosystems included: (1) balancing of carbon release by calcification via carbon uptake at the individual and ecosystem levels; (2) high rates of allochthonous organic carbon supply because of high particle trapping capacity; (3) high rates of carbon preservation and low remineralization rates; and (4) location in depositional environments. Some of these features are context-dependent, meaning that these ecosystems were blue carbon sinks in some locations, but not others. Therefore, we provide a universal framework that can evaluate the likelihood of a given ecosystem to behave as a blue carbon sink for a given context. Overall, this paper seeks to encourage consideration of non-classical blue carbon ecosystems within NBS strategies, allowing more complete blue carbon accounting.

  • 28. Jessen, Maria-Theresa
    et al.
    Kaarlejarvi, Elina
    Olofsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Eskelinen, Anu
    Mammalian herbivory shapes intraspecific trait responses to warmer climate and nutrient enrichment2020In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 26, no 12, p. 6742-6752Article in journal (Refereed)
    Abstract [en]

    Variation in intraspecific traits is one important mechanism that can allow plant species to respond to global changes. Understanding plant trait responses to environmental changes such as grazing patterns, nutrient enrichment and climate warming is, thus, essential for predicting the composition of future plant communities. We measured traits of eight common tundra species in a fully factorial field experiment with mammalian herbivore exclusion, fertilization, and passive warming, and assessed how trait responsiveness to the treatments was associated with abundance changes in those treatments. Herbivory exhibited the strongest impact on traits. Exclusion of herbivores increased vegetative plant height by 50% and specific leaf area (SLA) by 19%, and decreased foliar C:N by 11%; fertilization and warming also increased height and SLA but to a smaller extent. Herbivory also modulated intraspecific height, SLA and foliar C:N responses to fertilization and warming, and these interactions were species-specific. Furthermore, herbivory affected how trait change translated into relative abundance change: increased height under warming and fertilization was more positively related to abundance change inside fences than in grazed plots. Our findings highlight the key role of mammalian herbivory when assessing intraspecific trait change in tundra and its consequences for plant performance under global changes.

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  • 29.
    Johansson, Otilia
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Palmqvist, Kristin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Olofsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Nitrogen deposition drives lichen community changes through differential species responses2012In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 18, no 8, p. 2626-2635Article in journal (Refereed)
    Abstract [en]

    Nitrogen (N) deposition has increased globally over the last 150 years and further increases are predicted. Epiphytic lichens decline in abundance and diversity in areas with high N loads, and the abundance of lichens decreases along gradients of increased deposition. Thus, although N is an essential nutrient for lichens, excessive loads may be detrimental for them. However, these gradients include many correlated pollutants and the mechanisms behind the decline are thus poorly known. The aim of this study was to assess effects of N deposition, alone, on the epiphytic lichen community composition in a naturally N-poor boreal forest. For this purpose, whole spruce trees were fertilized daily with N at five levels, equivalent to 0.6, 6, 12.5, 25, and 50 kg N ha-1 yr-1, during four consecutive growing seasons (20062009), and changes in the abundance of lichens were monitored each autumn from the preceding year (2005). The studied lichen communities were highly dynamic and responded strongly to the environmental perturbation. N deposition detectably altered the direction of succession and reduced the species richness of the epiphytic lichen communities, even at the lowest fertilization application (6 kg N ha-1 yr-1). The simulated N deposition caused significant changes in the abundance of Alectoria sarmentosa, Bryoria spp., and Hypogymnia physodes, which all increased at low N loads and decreased at high loads, but with species-specific optima. The rapid decline of A. sarmentosa may have been caused by the added nitrogen reducing the stability of the lichen thalli, possibly due to increases in the photobiont: mycobiont ratio or parasitic fungal attacks. We conclude that increases in nitrogen availability, per se, could be responsible for the reductions in lichen abundance and diversity observed along deposition gradients, and those community responses may be due to physiological responses of the individual species rather than changes in competitive interactions.

  • 30.
    Kaarlejarvi, Elina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hoset, Katrine S.
    Olofsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Mammalian herbivores confer resilience of Arctic shrub-dominated ecosystems to changing climate2015In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 21, no 9, p. 3379-3388Article in journal (Refereed)
    Abstract [en]

    Climate change is resulting in a rapid expansion of shrubs in the Arctic. This expansion has been shown to be reinforced by positive feedbacks, and it could thus set the ecosystem on a trajectory toward an alternate, more productive regime. Herbivores, on the other hand, are known to counteract the effects of simultaneous climate warming on shrub biomass. However, little is known about the impact of herbivores on resilience of these ecosystems, that is, the capacity of a system to absorb disturbance and still remain in the same regime, retaining the same function, structure, and feedbacks. Here, we investigated how herbivores affect resilience of shrub-dominated systems to warming by studying the change of shrub biomass after a cessation of long-term experimental warming in a forest-tundra ecotone. As predicted, warming increased the biomass of shrubs, and in the absence of herbivores, shrub biomass in tundra continued to increase 4 years after cessation of the artificial warming, indicating that positive effects of warming on plant growth may persist even over a subsequent colder period. Herbivores contributed to the resilience of these systems by returning them back to the original low-biomass regime in both forest and tundra habitats. These results support the prediction that higher shrub biomass triggers positive feedbacks on soil processes and microclimate, which enable maintaining the rapid shrub growth even in colder climates. Furthermore, the results show that in our system, herbivores facilitate the resilience of shrub-dominated ecosystems to climate warming.

  • 31.
    Kamenos, Nicholas A.
    et al.
    School of Geographical and Earth Sciences, University of Glasgow, Glasgow, UK.
    Burdett, Heidi L.
    Aloisio, Elena
    Findlay, Helen S.
    Martin, Sophie
    Longbone, Charlotte
    Dunn, Jonathan
    Widdicombe, Stephen
    Calosi, Piero
    Coralline algal structure is more sensitive to rate, rather than the magnitude, of ocean acidification2013In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 19, no 12, p. 3621-3628Article in journal (Refereed)
    Abstract [en]

    Marine pCO2 enrichment via ocean acidification (OA), upwelling and release from carbon capture and storage (CCS) facilities is projected to have devastating impacts on marine biomineralisers and the services they provide. However, empirical studies using stable endpoint pCO2 concentrations find species exhibit variable biological and geochemical responses rather than the expected negative patterns. In addition, the carbonate chemistry of many marine systems is now being observed to be more variable than previously thought. To underpin more robust projections of future OA impacts on marine biomineralisers and their role in ecosystem service provision, we investigate coralline algal responses to realistically variable scenarios of marine pCO2 enrichment. Coralline algae are important in ecosystem function; providing habitats and nursery areas, hosting high biodiversity, stabilizing reef structures and contributing to the carbon cycle. Red coralline marine algae were exposed for 80 days to one of three pH treatments: (i) current pH (control); (ii) low pH (7.7) representing OA change; and (iii) an abrupt drop to low pH (7.7) representing the higher rates of pH change observed at natural vent systems, in areas of upwelling and during CCS releases. We demonstrate that red coralline algae respond differently to the rate and the magnitude of pH change induced by pCO2 enrichment. At low pH, coralline algae survived by increasing their calcification rates. However, when the change to low pH occurred at a fast rate we detected, using Raman spectroscopy, weaknesses in the calcite skeleton, with evidence of dissolution and molecular positional disorder. This suggests that, while coralline algae will continue to calcify, they may be structurally weakened, putting at risk the ecosystem services they provide. Notwithstanding evolutionary adaptation, the ability of coralline algae to cope with OA may thus be determined primarily by the rate, rather than magnitude, at which pCO2 enrichment occurs.

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  • 32.
    Karlsson, Jan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Jonsson, Anders
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Jansson, Mats
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Productivity of high-latitude lakes: climate effect inferred from altitude gradient2005In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 11, no 5, p. 710-715Article in journal (Refereed)
    Abstract [en]

    Climate change is predicted to be dramatic at high latitudes. Still, climate impact on high latitude lake ecosystems is poorly understood. We studied 15 subarctic lakes located in a climate gradient comprising an air temperature difference of about 6&DEG; C. We show that lake water productivity varied by one order of magnitude along the temperature gradient. This variation was mainly caused by variations in the length of the ice-free period and, more importantly, in the supply of organic carbon and inorganic nutrients, which followed differences in terrestrial vegetation cover along the gradient. The results imply that warming will have rapid effects on the productivity of high latitude lakes, by prolongation of ice-free periods. However, a more pronounced consequence will be a delayed stimulation of the productivity following upon changes of the lakes terrestrial surroundings and subsequent increasing input of elements that stimulate the production of lake biota.

  • 33. Keuper, Frida
    et al.
    Dorrepaal, Ellen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Van Bodegom, Peter M.
    Aerts, Rien
    Van Logtestijn, Richard S.P.
    Callaghan, Terry V.
    Cornelissen, Johannes H . C .
    A race for space?: How Sphagnum fuscumstabilizes vegetation composition during long-termclimate manipulations2011In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 17, no 6, p. 2162-2171Article in journal (Refereed)
    Abstract [en]

    Strong climate warming is predicted at higher latitudes this century, with potentially major consequences forproductivity and carbon sequestration. Although northern peatlands contain one-third of the world’s soil organiccarbon, little is known about the long-term responses to experimental climate change of vascular plant communities inthese Sphagnum-dominated ecosystems.We aimed to see how long-term experimental climate manipulations, relevantto different predicted future climate scenarios, affect total vascular plant abundance and species composition whenthe community is dominated by mosses. During 8 years, we investigated how the vascular plant community of aSphagnum fuscum-dominated subarctic peat bog responded to six experimental climate regimes, including factorialcombinations of summer as well as spring warming and a thicker snow cover. Vascular plant species composition inour peat bog was more stable than is typically observed in (sub)arctic experiments: neither changes in total vascularplant abundance, nor in individual species abundances, Shannon’s diversity or evenness were found in response tothe climate manipulations. For three key species (Empetrum hermaphroditum, Betula nana and S. fuscum) we alsomeasured whether the treatments had a sustained effect on plant length growth responses and how these responsesinteracted. Contrasting with the stability at the community level, both key shrubs and the peatmoss showed sustainedpositive growth responses at the plant level to the climate treatments. However, a higher percentage of mossencroachedE. hermaphroditum shoots and a lack of change in B. nana net shrub height indicated encroachment byS. fuscum, resulting in long-term stability of the vascular community composition: in a warmer world, vascular speciesof subarctic peat bogs appear to just keep pace with growing Sphagnum in their race for space. Our findings contributeto general ecological theory by demonstrating that community resistance to environmental changes does notnecessarily mean inertia in vegetation response.

  • 34.
    Keuper, Frida
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Systems Ecology, Department of Ecological Science, VU University Amsterdam, Amsterdam, The Netherlands ; UR1158 AgroImpact, INRA, Barenton-Bugny, France.
    Dorrepaal, Ellen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Systems Ecology, Department of Ecological Science, VU University Amsterdam, Amsterdam, The Netherlands.
    van Bodegom, Peter M.
    van Logtestijn, Richard
    Venhuizen, Gemma
    van Hal, Jurgen
    Aerts, Rien
    Experimentally increased nutrient availability at the permafrost thaw front selectively enhances biomass production of deep-rooting subarctic peatland species2017In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 23, no 10, p. 4257-4266Article in journal (Refereed)
    Abstract [en]

    Climate warming increases nitrogen (N) mineralization in superficial soil layers (the dominant rooting zone) of subarctic peatlands. Thawing and subsequent mineralization of permafrost increases plant-available N around the thaw-front. Because plant production in these peatlands is N-limited, such changes may substantially affect net primary production and species composition. We aimed to identify the potential impact of increased N-availability due to permafrost thawing on subarctic peatland plant production and species performance, relative to the impact of increased N-availability in superficial organic layers. Therefore, we investigated whether plant roots are present at the thaw-front (45 cm depth) and whether N-uptake (N-15-tracer) at the thaw-front occurs during maximum thaw-depth, coinciding with the end of the growing season. Moreover, we performed a unique 3-year belowground fertilization experiment with fully factorial combinations of deep-(thaw-front) and shallow-fertilization (10 cm depth) and controls. We found that certain species are present with roots at the thaw-front (Rubus chamaemorus) and have the capacity (R. chamaemorus, Eriophorum vaginatum) for N-uptake from the thaw-front between autumn and spring when aboveground tissue is largely senescent. In response to 3-year shallow-belowground fertilization (S) both shallow-(Empetrum hermaphroditum) and deep-rooting species increased aboveground biomass and N-content, but only deep-rooting species responded positively to enhanced nutrient supply at the thaw-front (D). Moreover, the effects of shallow-fertilization and thaw-front fertilization on aboveground biomass production of the deep-rooting species were similar in magnitude (S: 71%; D: 111% increase compared to control) and additive (S + D: 181% increase). Our results show that plant-available N released from thawing permafrost can form a thus far overlooked additional N-source for deep-rooting subarctic plant species and increase their biomass production beyond the already established impact of warming-driven enhanced shallow N-mineralization. This may result in shifts in plant community composition and may partially counteract the increased carbon losses from thawing permafrost.

  • 35.
    Keuper, Frida
    et al.
    Vrije Univ Amsterdam, Dept Ecol Sci, NL-1081 HV Amsterdam, Netherlands .
    van Bodegom, Peter M.
    Vrije Univ Amsterdam, Dept Ecol Sci, NL-1081 HV Amsterdam, Netherlands .
    Dorrepaal, Ellen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Weedon, James T.
    Vrije Univ Amsterdam, Dept Ecol Sci, NL-1081 HV Amsterdam, Netherlands .
    van Hal, Jurgen
    Vrije Univ Amsterdam, Dept Ecol Sci, NL-1081 HV Amsterdam, Netherlands .
    van Logtestijn, Richard S. P.
    Vrije Univ Amsterdam, Dept Ecol Sci, NL-1081 HV Amsterdam, Netherlands .
    Aerts, Rien
    Vrije Univ Amsterdam, Dept Ecol Sci, NL-1081 HV Amsterdam, Netherlands .
    A frozen feast: thawing permafrost increases plant-available nitrogen in subarctic peatlands2012In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 18, no 6, p. 1998-2007Article in journal (Refereed)
    Abstract [en]

    Many of the world's northern peatlands are underlain by rapidly thawing permafrost. Because plant production in these peatlands is often nitrogen (N)-limited, a release of N stored in permafrost may stimulate net primary production or change species composition if it is plant-available. In this study, we aimed to quantify plant-available N in thawing permafrost soils of subarctic peatlands. We compared plant-available N-pools and -fluxes in near-surface permafrost (010cm below the thawfront) to those taken from a current rooting zone layer (515cm depth) across five representative peatlands in subarctic Sweden. A range of complementary methods was used: extractions of inorganic and organic N, inorganic and organic N-release measurements at 0.5 and 11 degrees C (over 120days, relevant to different thaw-development scenarios) and a bioassay with Poa alpina test plants. All extraction methods, across all peatlands, consistently showed up to seven times more plant-available N in near-surface permafrost soil compared to the current rooting zone layer. These results were supported by the bioassay experiment, with an eightfold larger plant N-uptake from permafrost soil than from other N-sources such as current rooting zone soil or fresh litter substrates. Moreover, net mineralization rates were much higher in permafrost soils compared to soils from the current rooting zone layer (273mgNm-2 and 1348mgNm-2 per growing season for near-surface permafrost at 0.5 degrees C and 11 degrees C respectively, compared to -30mgNm-2 for current rooting zone soil at 11 degrees C). Hence, our results demonstrate that near-surface permafrost soil of subarctic peatlands can release a biologically relevant amount of plant available nitrogen, both directly upon thawing as well as over the course of a growing season through continued microbial mineralization of organically bound N. Given the nitrogen-limited nature of northern peatlands, this release may have impacts on both plant productivity and species composition.

  • 36.
    Klaus, Marcus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Seekell, David A.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Tree line advance reduces mixing and oxygen concentrations in arctic–alpine lakes through wind sheltering and organic carbon supply2021In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 27, no 18, p. 4238-4253Article in journal (Refereed)
    Abstract [en]

    Oxygen depletion in lake bottom waters has adverse impacts on ecosystem health including decreased water quality from release of nutrients and reduced substances from sediments, and the reduction of fish growth and reproduction. Depletion occurs when oxygen is consumed during decomposition of organic matter, and oxygen replenishment is limited by water column stratification. Arctic–alpine lakes are often well mixed and oxygenated, but rapid climate change in these regions is an important driver of shifts in catchment vegetation that could affect the mixing and oxygen dynamics of lakes. Here, we analyze high-resolution time series of dissolved oxygen concentration and temperature profiles in 40 Swedish arctic–alpine lakes across the tree line ecotone. The lakes stratified for 1−125 days, and during stratification, near-bottom dissolved oxygen concentrations changed by −0.20 to +0.15 mg L−1 day−1, resulting in final concentrations of 1.1−15.5 mg L−1 at the end of the longest stratification period. Structural equation modeling revealed that lakes with taller shoreline vegetation relative to lake area had higher dissolved organic carbon concentrations and oxygen consumption rates, but also lower wind speeds and longer stratification periods, and ultimately, lower near-bottom dissolved oxygen concentrations. We use an index of shoreline canopy height and lake area to predict variations among our study lakes in near-bottom dissolved oxygen concentrations at the end of the longest stratification period (R2 = 0.41). Upscaling this relationship to 8392 Swedish arctic–alpine lakes revealed that near-bottom dissolved oxygen concentrations drop below 3, 5, and 7 mg L−1 in 15%, 32%, and 53% of the lakes and that this proportion is sensitive (5%−22%, 13%−45%, and 29%−69%) to hypothetical tree line shifts observed in the past century or reconstructed for the Holocene (±200 m elevation; ±0.5° latitude). Assuming space-for-time substitution, we predict that tree line advance will decrease near-bottom dissolved oxygen concentrations in many arctic–alpine lakes.

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  • 37. Kokfelt, U
    et al.
    Rosén, Peter
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Schoning, K
    Christensen, TR
    Förster, Johannes
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Reuss, N
    Rundgren, M
    Callaghan, T
    Abisko Scientific Research Station, SE-981 07 Abisko, Sweden.
    Jonasson, C
    Abisko Scientific Research Station, SE-981 07 Abisko, Sweden.
    Hammarlund, D
    Ecosystem responses to increased precipitation and permafrost decay in subarctic Sweden inferred from peat and lake sediments2009In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 15, no 7, p. 1652-1663Article in journal (Refereed)
    Abstract [en]

    Recent accelerated decay of discontinuous permafrost at the Stordalen Mire in northern Sweden has been attributed to increased temperature and snow depth, and has caused expansion of wet minerotrophic areas leading to significant changes in carbon cycling in the mire. In order to track these changes through time and evaluate potential forcing mechanisms, this paper analyses a peat succession and a lake sediment sequence from within the mire, providing a record for the last 100 years, and compares these with monitored climate and active layer thickness data. The peat core was analysed for testate amoebae to reconstruct changes in peatland surface moisture conditions and water table fluctuations. The lake sediment core was analysed by near infrared spectroscopy to infer changes in the total organic carbon (TOC) concentration of the lake-water, and changes in δ13C and C, N and δ15N to track changes in the dissolved inorganic carbon (DIC) pool and the influence of diagenetic effects on sediment organic matter, respectively. Results showed that major shifts towards increased peat surface moisture and TOC concentration of the lake-water occurred around 1980, one to two decades earlier than a temperature driven increase in active layer thickness. Comparison with monitored temperature and precipitation from a nearby climate station indicates that this change in peat surface moisture is related to June–September (JJAS) precipitation and that the increase in lake-water TOC concentration reflects an increase in total annual precipitation. A significant depletion in 13C of sediment organic matter in the early 1980s probably reflects the effect of a single or a few consecutive years with anomalously high summer precipitation, resulting in elevated DIC content of the lake water, predominantly originating from increased export and subsequent respiration of organic carbon from the mire. Based on these results, it was not possible to link proxy data obtained on peat and lake-sediment records directly to permafrost decay. Instead our data indicate that increased precipitation and anomalously high rainfall during summers had a significant impact on the mire and the adjacent lake ecosystem. We therefore propose that effects of increased precipitation should be considered when evaluating potential forcing mechanisms of recent changes in carbon cycling in the subarctic.

  • 38. Lapierre, Jean-Francois
    et al.
    Seekell, David A.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department ofEnvironmental Sciences, University of Virginia, Charlottesville, VA, USA.
    del Giorgio, Paul A.
    Climate and landscape influence on indicators of lake carbon cycling through spatial patterns in dissolved organic carbon2015In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 21, no 12, p. 4425-4435Article in journal (Refereed)
    Abstract [en]

    Freshwater ecosystems are strongly influenced by both climate and the surrounding landscape, yet the specific pathways connecting climatic and landscape drivers to the functioning of lake ecosystems are poorly understood. Here, we hypothesize that the links that exist between spatial patterns in climate and landscape properties and the spatial variation in lake carbon (C) cycling at regional scales are at least partly mediated by the movement of terrestrial dissolved organic carbon (DOC) in the aquatic component of the landscape. We assembled a set of indicators of lake C cycling (bacterial respiration and production, chlorophyll a, production to respiration ratio, and partial pressure of CO2), DOC concentration and composition, and landscape and climate characteristics for 239 temperate and boreal lakes spanning large environmental and geographic gradients across seven regions. There were various degrees of spatial structure in climate and landscape features that were coherent with the regionally structured patterns observed in lake DOC and indicators of C cycling. These different regions aligned well, albeit nonlinearly along a mean annual temperature gradient; whereas there was a considerable statistical effect of climate and landscape properties on lake C cycling, the direct effect was small and the overall effect was almost entirely overlapping with that of DOC concentration and composition. Our results suggest that key climatic and landscape signals are conveyed to lakes in part via the movement of terrestrial DOC to lakes and that DOC acts both as a driver of lake C cycling and as a proxy for other external signals.

  • 39.
    Lau, Danny C. P.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Jonsson, Anders
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Isles, Peter D. F.
    Department of Aquatic Ecology, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland.
    Creed, Irena F.
    Department of Physical and Environmental Sciences, University of Toronto-Scarborough Campus, ON, Toronto, Canada.
    Bergström, Ann-Kristin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Lowered nutritional quality of plankton caused by global environmental changes2021In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 27, no 23, p. 6294-6306Article in journal (Refereed)
    Abstract [en]

    Global environmental changes are causing widespread nutrient depletion, declines in the ratio of dissolved inorganic nitrogen (N) to total phosphorus (DIN:TP), and increases in both water temperature and terrestrial colored dissolved organic carbon (DOC) concentration (browning) in high-latitude northern lakes. Declining lake DIN:TP, warming, and browning alter the nutrient limitation regime and biomass of phytoplankton, but how these stressors together affect the nutritional quality in terms of polyunsaturated fatty acid (PUFA) contents of the pelagic food web components remains unknown. We assessed the fatty acid compositions of seston and zooplankton in 33 lakes across south-to-north and boreal-to-subarctic gradients in Sweden. Data showed higher lake DIN:TP in the south than in the north, and that boreal lakes were warmer and browner than subarctic lakes. Lake DIN:TP strongly affected the PUFA contents—especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)—in seston, calanoids, and copepods (as a group), but not in cladocerans. The EPA+DHA contents increased by 123% in seston, 197% in calanoids, and 230% in copepods across a lake molar DIN:TP gradient from 0.17 to 14.53, indicating lower seston and copepod nutritional quality in the more N-limited lakes (those with lower DIN:TP). Water temperature affected EPA+DHA contents of zooplankton, especially cladocerans, but not seston. Cladoceran EPA+DHA contents were reduced by ca. 6% for every 1°C increase in surface water. Also, the EPA, DHA, or EPA+DHA contents of Bosmina, cyclopoids, and copepods increased in lakes with higher DOC concentrations or aromaticity. Our findings indicate that zooplankton food quality for higher consumers will decrease with warming alone (for cladocerans) or in combination with declining lake DIN:TP (for copepods), but impacts of these stressors are moderated by lake browning. Global environmental changes that drive northern lakes toward more N-limited, warmer, and browner conditions will reduce PUFA availability and nutritional quality of the pelagic food web components.

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  • 40.
    Lefebure, Robert
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Degerman, Rickard
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Larsson, Stefan
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Eriksson, Lars-Ove
    Department of Wildlife, Fish and Environmental Studies, SLU, Umeå, Sweden.
    Båmstedt, Ulf
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Impacts of elevated terrestrial nutrient loads and temperature on pelagic food-web efficiency and fish production2013In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 19, no 5, p. 1358-1372Article in journal (Other academic)
    Abstract [en]

    Both temperature and terrestrial organic matter have strong impacts on aquatic food-web dynamics and production. Temperature affects vital rates of all organisms, and terrestrial organic matter can act both as an energy source for lower trophic levels, while simultaneously reducing light availability for autotrophic production. As climate change predictions for the Baltic Sea and elsewhere suggest increases in both terrestrial matter runoff and increases in temperature, we studied the effects on pelagic food-web dynamics and food-web efficiency in a plausible future scenario with respect to these abiotic variables in a large-scale mesocosm experiment. Total basal (phytoplankton plus bacterial) production was slightly reduced when only increasing temperatures, but was otherwise similar across all other treatments. Separate increases in nutrient loads and temperature decreased the ratio of autotrophic:heterotrophic production, but the combined treatment of elevated temperature and terrestrial nutrient loads increased both fish production and food-web efficiency. CDOM: Chl a ratios strongly indicated that terrestrial and not autotrophic carbon was the main energy source in these food webs and our results also showed that zooplankton biomass was positively correlated with increased bacterial production. Concomitantly, biomass of the dominant calanoid copepod Acartia sp. increased as an effect of increased temperature. As the combined effects of increased temperature and terrestrial organic nutrient loads were required to increase zooplankton abundance and fish production, conclusions about effects of climate change on food-web dynamics and fish production must be based on realistic combinations of several abiotic factors. Moreover, our results question established notions on the net inefficiency of heterotrophic carbon transfer to the top of the food web.

  • 41. Lembrechts, Jonas J.
    et al.
    Aalto, Juha
    Ashcroft, Michael B.
    De Frenne, Pieter
    Kopecky, Martin
    Lenoir, Jonathan
    Luoto, Miska
    Maclean, Ilya M. D.
    Roupsard, Olivier
    Fuentes-Lillo, Eduardo
    Garcia, Rafael A.
    Pellissier, Loic
    Pitteloud, Camille
    Alatalo, Juha M.
    Smith, Stuart W.
    Bjork, Robert G.
    Muffler, Lena
    Backes, Amanda Ratier
    Cesarz, Simone
    Gottschall, Felix
    Okello, Joseph
    Urban, Josef
    Plichta, Roman
    Svatek, Martin
    Phartyal, Shyam S.
    Wipf, Sonja
    Eisenhauer, Nico
    Puscas, Mihai
    Turtureanu, Pavel D.
    Varlagin, Andrej
    Dimarco, Romina D.
    Jump, Alistair S.
    Randall, Krystal
    Dorrepaal, Ellen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Larson, Keith
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Walz, Josefine
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Vitale, Luca
    Svoboda, Miroslav
    Higgens, Rebecca Finger
    Halbritter, H.
    Curasi, Salvatore R.
    Klupar, Ian
    Koontz, Austin
    Pearse, William D.
    Simpson, Elizabeth
    Stemkovski, Michael
    Graae, Bente Jessen
    Sorensen, Mia Vedel
    Hoye, Toke T.
    Fernandez Calzado, M. Rosa
    Lorite, Juan
    Carbognani, Michele
    Tomaselli, Marcello
    Forte, T'ai G. W.
    Petraglia, Alessandro
    Haesen, Stef
    Somers, Ben
    Van Meerbeek, Koenraad
    Bjorkman, Mats P.
    Hylander, Kristoffer
    Merinero, Sonia
    Gharun, Mana
    Buchmann, Nina
    Dolezal, Jiri
    Matula, Radim
    Thomas, Andrew D.
    Bailey, Joseph J.
    Ghosn, Dany
    Kazakis, George
    de Pablo, Miguel A.
    Kemppinen, Julia
    Niittynen, Pekka
    Rew, Lisa
    Seipel, Tim
    Larson, Christian
    Speed, James D. M.
    Ardo, Jonas
    Cannone, Nicoletta
    Guglielmin, Mauro
    Malfasi, Francesco
    Bader, Maaike Y.
    Canessa, Rafaella
    Stanisci, Angela
    Kreyling, Juergen
    Schmeddes, Jonas
    Teuber, Laurenz
    Aschero, Valeria
    Ciliak, Marek
    Malis, Frantisek
    De Smedt, Pallieter
    Govaert, Sanne
    Meeussen, Camille
    Vangansbeke, Pieter
    Gigauri, Khatuna
    Lamprecht, Andrea
    Pauli, Harald
    Steinbauer, Klaus
    Winkler, Manuela
    Ueyama, Masahito
    Nunez, Martin A.
    Ursu, Tudor-Mihai
    Haider, Sylvia
    Wedegartner, Ronja E. M.
    Smiljanic, Marko
    Trouillier, Mario
    Wilmking, Martin
    Altman, Jan
    Bruna, Josef
    Hederova, Lucia
    Macek, Martin
    Man, Matej
    Wild, Jan
    Vittoz, Pascal
    Partel, Meelis
    Barancok, Peter
    Kanka, Robert
    Kollar, Jozef
    Palaj, Andrej
    Barros, Agustina
    Mazzolari, Ana C.
    Bauters, Marijn
    Boeckx, Pascal
    Benito Alonso, Jose-Luis
    Zong, Shengwei
    Di Cecco, Valter
    Sitkova, Zuzana
    Tielboerger, Katja
    van den Brink, Liesbeth
    Weigel, Robert
    Homeier, Juergen
    Dahlberg, C. Johan
    Medinets, Sergiy
    Medinets, Volodymyr
    De Boeck, Hans J.
    Portillo-Estrada, Miguel
    Verryckt, Lore T.
    Milbau, Ann
    Daskalova, Gergana N.
    Thomas, Haydn J. D.
    Myers-Smith, Isla H.
    Blonder, Benjamin
    Stephan, Jorg G.
    Descombes, Patrice
    Zellweger, Florian
    Frei, Esther R.
    Heinesch, Bernard
    Andrews, Christopher
    Dick, Jan
    Siebicke, Lukas
    Rocha, Adrian
    Senior, Rebecca A.
    Rixen, Christian
    Jimenez, Juan J.
    Boike, Julia
    Pauchard, Anibal
    Scholten, Thomas
    Scheffers, Brett
    Klinges, David
    Basham, Edmund W.
    Zhang, Jian
    Zhang, Zhaochen
    Geron, Charly
    Fazlioglu, Fatih
    Candan, Onur
    Sallo Bravo, Jhonatan
    Hrbacek, Filip
    Laska, Kamil
    Cremonese, Edoardo
    Haase, Peter
    Moyano, Fernando E.
    Rossi, Christian
    Nijs, Ivan
    SoilTemp: A global database of near-surface temperature2020In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 26, no 11, p. 6616-6629Article in journal (Refereed)
    Abstract [en]

    Current analyses and predictions of spatially explicit patterns and processes in ecology most often rely on climate data interpolated from standardized weather stations. This interpolated climate data represents long‐term average thermal conditions at coarse spatial resolutions only. Hence, many climate‐forcing factors that operate at fine spatiotemporal resolutions are overlooked. This is particularly important in relation to effects of observation height (e.g. vegetation, snow and soil characteristics) and in habitats varying in their exposure to radiation, moisture and wind (e.g. topography, radiative forcing or cold‐air pooling). Since organisms living close to the ground relate more strongly to these microclimatic conditions than to free‐air temperatures, microclimatic ground and near‐surface data are needed to provide realistic forecasts of the fate of such organisms under anthropogenic climate change, as well as of the functioning of the ecosystems they live in. To fill this critical gap, we highlight a call for temperature time series submissions to SoilTemp, a geospatial database initiative compiling soil and near‐surface temperature data from all over the world. Currently, this database contains time series from 7,538 temperature sensors from 51 countries across all key biomes. The database will pave the way toward an improved global understanding of microclimate and bridge the gap between the available climate data and the climate at fine spatiotemporal resolutions relevant to most organisms and ecosystem processes.

  • 42.
    Lembrechts, Jonas J.
    et al.
    Research Group PLECO (Plants and Ecosystems), University of Antwerp, Wilrijk, Belgium.
    van den Hoogen, Johan
    Department of Environmental Systems Science, Institute of Integrative Biology, ETH Zürich, Zürich, Switzerland.
    Dorrepaal, Ellen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Larson, Keith
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Sarneel, Judith M.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Walz, Josefine
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Nijs, Ivan
    Research Group PLECO (Plants and Ecosystems), University of Antwerp, Wilrijk, Belgium.
    Lenoir, Jonathan
    UMR 7058 CNRS ‘Ecologie et Dynamique des Systèmes Anthropisés’ (EDYSAN), Univ. de Picardie Jules Verne, Amiens, France.
    Global maps of soil temperature2022In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 28, no 9, p. 3110-3144Article in journal (Refereed)
    Abstract [en]

    Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km2 resolution for 0–5 and 5–15 cm soil depth. These maps were created by calculating the difference (i.e. offset) between in situ soil temperature measurements, based on time series from over 1200 1-km2 pixels (summarized from 8519 unique temperature sensors) across all the world's major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (−0.7 ± 2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications.

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  • 43. Lenoir, Jonathan
    et al.
    Graae, Bente Jessen
    Aarrestad, Per Arild
    Alsos, Inger Greve
    Armbruster, W. Scott
    Austrheim, Gunnar
    Bergendorff, Claes
    Birks, H. John B.
    Brathen, Kari Anne
    Brunet, Jorg
    Bruun, Hans Henrik
    Dahlberg, Carl Johan
    Decocq, Guillaume
    Diekmann, Martin
    Dynesius, Mats
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ejrnaes, Rasmus
    Grytnes, John-Arvid
    Hylander, Kristoffer
    Klanderud, Kari
    Luoto, Miska
    Milbau, Ann
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Moora, Mari
    Nygaard, Bettina
    Odland, Arvid
    Ravolainen, Virve Tuulia
    Reinhardt, Stefanie
    Sandvik, Sylvi Marlen
    Schei, Fride Hoistad
    Speed, James David Mervyn
    Tveraabak, Liv Unn
    Vandvik, Vigdis
    Velle, Liv Guri
    Virtanen, Risto
    Zobel, Martin
    Svenning, Jens-Christian
    Local temperatures inferred from plant communities suggest strong spatial buffering of climate warming across Northern Europe2013In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 19, no 5, p. 1470-1481Article in journal (Refereed)
    Abstract [en]

    Recent studies from mountainous areas of small spatial extent (<2500km2) suggest that fine-grained thermal variability over tens or hundreds of metres exceeds much of the climate warming expected for the coming decades. Such variability in temperature provides buffering to mitigate climate-change impacts. Is this local spatial buffering restricted to topographically complex terrains? To answer this, we here study fine-grained thermal variability across a 2500-km wide latitudinal gradient in Northern Europe encompassing a large array of topographic complexities. We first combined plant community data, Ellenberg temperature indicator values, locally measured temperatures (LmT) and globally interpolated temperatures (GiT) in a modelling framework to infer biologically relevant temperature conditions from plant assemblages within <1000-m2 units (community-inferred temperatures: CiT). We then assessed: (1) CiT range (thermal variability) within 1-km2 units; (2) the relationship between CiT range and topographically and geographically derived predictors at 1-km resolution; and (3) whether spatial turnover in CiT is greater than spatial turnover in GiT within 100-km2 units. Ellenberg temperature indicator values in combination with plant assemblages explained 4672% of variation in LmT and 9296% of variation in GiT during the growing season (June, July, August). Growing-season CiT range within 1-km2 units peaked at 6065 degrees N and increased with terrain roughness, averaging 1.97 degrees C (SD=0.84 degrees C) and 2.68 degrees C (SD=1.26 degrees C) within the flattest and roughest units respectively. Complex interactions between topography-related variables and latitude explained 35% of variation in growing-season CiT range when accounting for sampling effort and residual spatial autocorrelation. Spatial turnover in growing-season CiT within 100-km2 units was, on average, 1.8 times greater (0.32 degrees Ckm1) than spatial turnover in growing-season GiT (0.18 degrees Ckm1). We conclude that thermal variability within 1-km2 units strongly increases local spatial buffering of future climate warming across Northern Europe, even in the flattest terrains.

  • 44.
    Lett, Signe
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Biology, Terrestrial Ecology Section, University of Copenhagen, Denmark.
    Teuber, Laurenz M.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Experimental Plant Ecology, Institute for Botany and Landscape Ecology, University of Greifswald, Germany.
    Krab, Eveline J
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Soil and Environment, Swedish Agricultural University, Uppsala, Sweden.
    Michelsen, Anders
    Olofsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Nilsson, Marie-Charlotte
    Wardle, David A.
    Dorrepaal, Ellen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Mosses modify effects of warmer and wetter conditions on tree seedlings at the alpine treeline2020In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 26, no 10, p. 5754-5766Article in journal (Refereed)
    Abstract [en]

    Climate warming enables tree seedling establishment beyond the current alpine treeline, but to achieve this, seedlings have to establish within existing tundra vegetation. In tundra, mosses are a prominent feature, known to regulate soil temperature and moisture through their physical structure and associated water retention capacity. Moss presence and species identity might therefore modify the impact of increases in temperature and precipitation on tree seedling establishment at the arctic‐alpine treeline. We followed Betula pubescens and Pinus sylvestris seedling survival and growth during three growing seasons in the field. Tree seedlings were transplanted along a natural precipitation gradient at the subarctic‐alpine treeline in northern Sweden, into plots dominated by each of three common moss species and exposed to combinations of moss removal and experimental warming by open‐top chambers (OTCs). Independent of climate, the presence of feather moss, but not Sphagnum , strongly supressed survival of both tree species. Positive effects of warming and precipitation on survival and growth of B. pubescens seedlings occurred in the absence of mosses and as expected, this was partly dependent on moss species. P. sylvestris survival was greatest at high precipitation, and this effect was more pronounced in Sphagnum than in feather moss plots irrespective of whether the mosses had been removed or not. Moss presence did not reduce the effects of OTCs on soil temperature. Mosses therefore modified seedling response to climate through other mechanisms, such as altered competition or nutrient availability. We conclude that both moss presence and species identity pose a strong control on seedling establishment at the alpine treeline, and that in some cases mosses weaken climate‐change effects on seedling establishment. Changes in moss abundance and species composition therefore have the potential to hamper treeline expansion induced by climate warming.

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  • 45. Maaroufi, Nadia I
    et al.
    Nordin, Annika
    Hasselquist, Niles J
    Bach, Lisbet H
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Palmqvist, Kristin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Gundale, Michael J
    Anthropogenic nitrogen deposition enhances carbon sequestration in boreal soils2015In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 21, no 8, p. 3169-3180Article in journal (Refereed)
    Abstract [en]

    It is proposed that carbon (C) sequestration in response to reactive nitrogen (N-r) deposition in boreal forests accounts for a large portion of the terrestrial sink for anthropogenic CO2 emissions. While studies have helped clarify the magnitude by which N-r deposition enhances C sequestration by forest vegetation, there remains a paucity of long-term experimental studies evaluating how soil C pools respond. We conducted a long-term experiment, maintained since 1996, consisting of three N addition levels (0, 12.5, and 50kgNha(-1)yr(-1)) in the boreal zone of northern Sweden to understand how atmospheric N-r deposition affects soil C accumulation, soil microbial communities, and soil respiration. We hypothesized that soil C sequestration will increase, and soil microbial biomass and soil respiration will decrease, with disproportionately large changes expected compared to low levels of N addition. Our data showed that the low N addition treatment caused a non-significant increase in the organic horizon C pool of similar to 15% and a significant increase of similar to 30% in response to the high N treatment relative to the control. The relationship between C sequestration and N addition in the organic horizon was linear, with a slope of 10kgCkg(-1)N. We also found a concomitant decrease in total microbial and fungal biomasses and a similar to 11% reduction in soil respiration in response to the high N treatment. Our data complement previous data from the same study system describing aboveground C sequestration, indicating a total ecosystem sequestration rate of 26kgCkg(-1)N. These estimates are far lower than suggested by some previous modeling studies, and thus will help improve and validate current modeling efforts aimed at separating the effect of multiple global change factors on the C balance of the boreal region.

  • 46. Maaroufi, Nadia, I
    et al.
    Nordin, Annika
    Palmqvist, Kristin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hasselquist, Niles J.
    Forsmark, Benjamin
    Rosenstock, Nicholas P.
    Wallander, Håkan
    Gundale, Michael J.
    Anthropogenic nitrogen enrichment enhances soil carbon accumulation by impacting saprotrophs rather than ectomycorrhizal fungal activity2019In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 25, no 9, p. 2900-2914Article in journal (Refereed)
    Abstract [en]

    There is evidence that anthropogenic nitrogen (N) deposition enhances carbon (C) sequestration in boreal forest soils. However, it is unclear how free-living saprotrophs (bacteria and fungi, SAP) and ectomycorrhizal (EM) fungi responses to N addition impact soil C dynamics. Our aim was to investigate how SAP and EM communities are impacted by N enrichment and to estimate whether these changes influence decay of litter and humus. We conducted a long-term experiment in northern Sweden, maintained since 2004, consisting of ambient, low N additions (0, 3, 6, and 12 kg N ha(-1) year(-1)) simulating current N deposition rates in the boreal region, as well as a high N addition (50 kg N ha(-1) year(-1)). Our data showed that long-term N enrichment impeded mass loss of litter, but not of humus, and only in response to the highest N addition treatment. Furthermore, our data showed that EM fungi reduced the mass of N and P in both substrates during the incubation period compared to when only SAP organisms were present. Low N additions had no effect on microbial community structure, while the high N addition decreased fungal and bacterial biomasses and altered EM fungi and SAP community composition. Actinomycetes were the only bacterial SAP to show increased biomass in response to the highest N addition. These results provide a mechanistic understanding of how anthropogenic N enrichment can influence soil C accumulation rates and suggest that current N deposition rates in the boreal region (<= 12 kg N ha(-1) year(-1)) are likely to have a minor impact on the soil microbial community and the decomposition of humus and litter.

  • 47.
    MacDougall, Andrew S.
    et al.
    Umeå University. Department of Integrative Biology, University of Guelph, Guelph, ON, Canada.
    Caplat, Paul
    Olofsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Siewert, Matthias B.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bonner, Colin
    Esch, Ellen
    Lessard-Therrien, Malie
    Rosenzweig, Hannah
    Umeå University.
    Schäfer, Anne-Kathrin
    Umeå University.
    Raker, Pia
    Umeå University.
    Ridha, Hassan
    Umeå University.
    Bolmgren, Kjell
    Umeå University.
    Fries, Thore C. E.
    Larson, Keith
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Comparison of the distribution and phenology of Arctic Mountain plants between the early 20th and 21st centuries2021In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 27, no 20, p. 5070-5083Article in journal (Refereed)
    Abstract [en]

    Arctic plants are adapted to climatic variability, but their long-term responses to warming remain unclear. Responses may occur by range shifts, phenological adjustments in growth and reproduction, or both. Here, we compare distribution and phenology of 83 arctic and boreal mountain species, sampled identically in the early 20th (1917-1919) and 21st centuries (2017-2018) from a region of northern Sweden that has warmed significantly. We test two compensatory hypotheses to high-latitude warming-upward shifts in distribution, and earlier or extended growth and reproduction. For distribution, we show dramatic upward migration by 69% of species, averaging 6.1 m per decade, especially boreal woodland taxa whose upward expansion has reduced arctic montane habitat by 30%. Twenty percent of summit species showed distributional shifts but downward, especially moisture-associated snowbed flora. For phenology, we detected wide inter-annual variability in the onset of leafing and flowering in both eras. However, there was no detectable change in growing-season length, relating to two mechanisms. First, plot-level snow melt data starting in 1917 demonstrated that melt date, rather than vernal temperatures, better predicts plant emergence, with snow melt influenced by warmer years having greater snowfall-warmer springs did not always result in earlier emergence because snowbeds can persist longer. Second, the onset of reproductive senescence between eras was similar, even when plant emergence was earlier by a month, possibly due to intensified summer heat stress or hard-wired 'canalization' where senescence occurs regardless of summer temperature. Migrations in this system have possibly buffered arctic species against displacement by boreal expansion and warming, but ongoing temperature increases, woody plant invasion, and a potential lack of flexibility in timing of senescence may foreshadow challenges.

  • 48. Mao, Jinhua
    et al.
    Burdett, Heidi L.
    McGill, Rona A. R.
    Newton, Jason
    Gulliver, Pauline
    Kamenos, Nicholas A.
    School of Geographical and Earth Sciences, University of Glasgow, Glasgow, UK.
    Carbon burial over the last four millennia is regulated by both climatic and land use change2020In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 26, no 4, p. 2496-2504Article in journal (Refereed)
    Abstract [en]

    Carbon sequestration by sediments and vegetated marine systems contributes to atmospheric carbon drawdown, but little empirical evidence is available to help separate the effects of climate change and other anthropogenic activities on carbon burial over centennial timescales. We used marine sediment organic carbon to determine the role of historic climate variability and human habitation in carbon burial over the past 5,071 years. There was centennial-scale sensitivity of carbon supply and burial to climatic variability, with Little Ice Age cooling causing an abrupt ecosystem shift and an increase in marine carbon contributions compared to terrestrial carbon. Although land use changes during the late 1800s did not cause marked alteration in average carbon burial, they did lead to marked increases in the spatial variability of carbon burial. Thus, while carbon burial by vegetated systems is expected to increase with projected climate warming over the coming century, ecosystem restructuring caused by abrupt climate change may produce unexpected change in carbon burial whose variability is also modulated by land use change.

  • 49. McCoy, Sophie J.
    et al.
    Kamenos, Nicholas A.
    School of Geographical and Earth Science, University of Glasgow, Glasgow, UK.
    Coralline algal skeletal mineralogy affects grazer impacts2018In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 24, no 10, p. 4775-4783Article in journal (Refereed)
    Abstract [en]

    In macroalgal-dominated systems, herbivory is a major driver in controlling ecosystem structure. However, the role of altered plant-herbivore interactions and effects of changes to trophic control under global change are poorly understood. This is because both macroalgae and grazers themselves may be affected by global change, making changes in plant-herbivore interactions hard to predict. Coralline algae lay down a calcium carbonate skeleton, which serves as protection from grazing and is preserved in archival samples. Here, we compare grazing damage and intensity to coralline algae in situ over 4 decades characterized by changing seawater acidity. While grazing intensity, herbivore abundance and identity remained constant over time, grazing wound width increased together with Mg content of the skeleton and variability in its mineral organization. In one species, decreases in skeletal organization were found concurrent with deeper skeletal damage by grazers over time since the 1980s. Thus, in a future characterized by acidification, we suggest coralline algae may be more prone to grazing damage, mediated by effects of variability between individuals and species.

  • 50. McCoy, Sophie J.
    et al.
    Kamenos, Nicholas A.
    School of Geographical and Earth Science, University of Glasgow, Glasgow, Scotland.
    Chung, Peter
    Wootton, Timothy J.
    Pfister, Caterine A.
    A mineralogical record of ocean change: Decadal and centennial patterns in the California mussel2018In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 24, no 6, p. 2554-2562Article in journal (Refereed)
    Abstract [en]

    Ocean acidification, a product of increasing atmospheric carbon dioxide, may already have affected calcified organisms in the coastal zone, such as bivalves and other shellfish. Understanding species' responses to climate change requires the context of long-term dynamics. This can be particularly difficult given the longevity of many important species in contrast with the relatively rapid onset of environmental changes. Here, we present a unique archival dataset of mussel shells from a locale with recent environmental monitoring and historical climate reconstructions. We compare shell structure and composition in modern mussels, mussels from the 1970s, and mussel shells dating back to 1000-2420 years BP. Shell mineralogy has changed dramatically over the past 15 years, despite evidence for consistent mineral structure in the California mussel, Mytilus californianus, over the prior 2500 years. We present evidence for increased disorder in the calcium carbonate shells of mussels and greater variability between individuals. These changes in the last decade contrast markedly from a background of consistent shell mineralogy for centuries. Our results use an archival record of natural specimens to provide centennial-scale context for altered minerology and variability in shell features as a response to acidification stress and illustrate the utility of long-term studies and archival records in global change ecology. Increased variability between individuals is an emerging pattern in climate change responses, which may equally expose the vulnerability of organisms and the potential of populations for resilience.

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