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  • 1. Barrio, Isabel C.
    et al.
    Lindén, Elin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    te Beest, Mariska
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Olofsson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Rocha, Adrian
    Soininen, Eeva M.
    Alatalo, Juha M.
    Andersson, Tommi
    Asmus, Ashley
    Boike, Julia
    Brathen, Kari Anne
    Bryant, John P.
    Buchwal, Agata
    Bueno, C. Guillermo
    Christie, Katherine S.
    Denisova, Yulia V.
    Egelkraut, Dagmar
    Ehrich, Dorothee
    Fishback, LeeAnn
    Forbes, Bruce C.
    Gartzia, Maite
    Grogan, Paul
    Hallinger, Martin
    Heijmans, Monique M. P. D.
    Hik, David S.
    Hofgaard, Annika
    Holmgren, Milena
    Høye, Toke T.
    Huebner, Diane C.
    Jonsdottir, Ingibjorg Svala
    Kaarlejärvi, Elina
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Department of Biology, Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium.
    Kumpula, Timo
    Lange, Cynthia Y. M. J. G.
    Lange, Jelena
    Levesque, Esther
    Limpens, Juul
    Macias-Fauria, Marc
    Myers-Smith, Isla
    van Nieukerken, Erik J.
    Normand, Signe
    Post, Eric S.
    Schmidt, Niels Martin
    Sitters, Judith
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Department of Biology, Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium.
    Skoracka, Anna
    Sokolov, Alexander
    Sokolova, Natalya
    Speed, James D. M.
    Street, Lorna E.
    Sundqvist, Maja K.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. The Center for Macroecology, Evolution and Climate, The Natural History Museum of Denmark, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark.
    Suominen, Otso
    Tananaev, Nikita
    Tremblay, Jean-Pierre
    Urbanowicz, Christine
    Uvarov, Sergey A.
    Watts, David
    Wilmking, Martin
    Wookey, Philip A.
    Zimmermann, Heike H.
    Zverev, Vitali
    Kozlov, Mikhail V.
    Publisher Correction to: Background invertebrate herbivory on dwarf birch (Betula glandulosa-nana complex) increases with temperature and precipitation across the tundra biome (vol 40, pg 2265, 2017)2018Inngår i: Polar Biology, ISSN 0722-4060, E-ISSN 1432-2056, Vol. 41, nr 8, s. 1653-1654Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The above mentioned article was originally scheduled for publication in the special issue on Ecology of Tundra Arthropods with guest editors Toke T. Hoye . Lauren E. Culler. Erroneously, the article was published in Polar Biology, Volume 40, Issue 11, November, 2017. The publisher sincerely apologizes to the guest editors and the authors for the inconvenience caused.

  • 2. Barrio, Isabel C.
    et al.
    Lindén, Elin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Te Beest, Mariska
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Olofsson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Rocha, Adrian
    Soininen, Eeva M.
    Alatalo, Juha M.
    Andersson, Tommi
    Asmus, Ashley
    Boike, Julia
    Bråthen, Kari Anne
    Bryant, John P.
    Buchwal, Agata
    Bueno, C. Guillermo
    Christie, Katherine S.
    Denisova, Yulia V.
    Egelkraut, Dagmar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Ehrich, Dorothee
    Fishback, LeeAnn
    Forbes, Bruce C.
    Gartzia, Maite
    Grogan, Paul
    Hallinger, Martin
    Heijmans, Monique M. P. D.
    Hik, David S.
    Hofgaard, Annika
    Holmgren, Milena
    Høye, Toke T.
    Huebner, Diane C.
    Jónsdóttir, Ingibjorg Svala
    Kaarlejärvi, Elina
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Department of Biology, Vrije Universiteit Brussel (VUB), Brussels, Belgium.
    Kumpula, Timo
    Lange, Cynthia Y. M. J. G.
    Lange, Jelena
    Lévesque, Esther
    Limpens, Juul
    Macias-Fauria, Marc
    Myers-Smith, Isla
    van Nieukerken, Erik J.
    Normand, Signe
    Post, Eric S.
    Schmidt, Niels Martin
    Sitters, Judith
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Department of Biology, Vrije Universiteit Brussel (VUB), Brussels, Belgium.
    Skoracka, Anna
    Sokolov, Alexander
    Sokolova, Natalya
    Speed, James D. M.
    Street, Lorna E.
    Sundqvist, Maja K.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. The Center for Macroecology, Evolution and Climate, The Natural History Museum of Denmark, University of Copenhagen, Copenhagen Ø, Denmark.
    Suominen, Otso
    Tananaev, Nikita
    Tremblay, Jean-Pierre
    Urbanowicz, Christine
    Uvarov, Sergey A.
    Watts, David
    Wilmking, Martin
    Wookey, Philip A.
    Zimmermann, Heike H.
    Zverev, Vitali
    Kozlov, Mikhail V.
    Background invertebrate herbivory on dwarf birch (Betula glandulosa-nana complex) increases with temperature and precipitation across the tundra biome2017Inngår i: Polar Biology, ISSN 0722-4060, E-ISSN 1432-2056, Vol. 40, nr 11, s. 2265-2278Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Chronic, low intensity herbivory by invertebrates, termed background herbivory, has been understudied in tundra, yet its impacts are likely to increase in a warmer Arctic. The magnitude of these changes is however hard to predict as we know little about the drivers of current levels of invertebrate herbivory in tundra. We assessed the intensity of invertebrate herbivory on a common tundra plant, the dwarf birch (Betula glandulosa-nana complex), and investigated its relationship to latitude and climate across the tundra biome. Leaf damage by defoliating, mining and gall-forming invertebrates was measured in samples collected from 192 sites at 56 locations. Our results indicate that invertebrate herbivory is nearly ubiquitous across the tundra biome but occurs at low intensity. On average, invertebrates damaged 11.2% of the leaves and removed 1.4% of total leaf area. The damage was mainly caused by external leaf feeders, and most damaged leaves were only slightly affected (12% leaf area lost). Foliar damage was consistently positively correlated with mid-summer (July) temperature and, to a lesser extent, precipitation in the year of data collection, irrespective of latitude. Our models predict that, on average, foliar losses to invertebrates on dwarf birch are likely to increase by 6-7% over the current levels with a 1 degrees C increase in summer temperatures. Our results show that invertebrate herbivory on dwarf birch is small in magnitude but given its prevalence and dependence on climatic variables, background invertebrate herbivory should be included in predictions of climate change impacts on tundra ecosystems.

  • 3.
    Blume-Werry, Gesche
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Experimental Plant Ecology, Institute of Botany and Landscape Ecology, Greifswald University, Greifswald, Germany.
    Lindén, Elin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Andresen, Lisa
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Classen, Aimée T.
    Sanders, Nathan J.
    von Oppen, Jonathan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Sundqvist, Maja K.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Center for Macroecology, Evolution and Climate, The Natural History Museum of Denmark, University of Copenhagen, Copenhagen K, Denmark.
    Proportion of fine roots, but not plant biomass allocation below ground, increases with elevation in arctic tundra2018Inngår i: Journal of Vegetation Science, ISSN 1100-9233, E-ISSN 1654-1103, Vol. 29, nr 2, s. 226-235Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Questions: Roots represent a considerable proportion of biomass, primary production and litter input in arctic tundra, and plant allocation of biomass to above- or below-ground tissue in response to climate change is a key factor in the future C balance of these ecosystems. According to optimality theory plants allocate C to the above- or below-ground structure that captures the most limiting resource. We used an elevational gradient to test this theory and as a space-for-time substitution to inform on tundra carbon allocation patterns under a shifting climate, by exploring if increasing elevation was positively related to the root:shoot ratio, as well as a larger plant allocation to adsorptive over storage roots.

    Location: Arctic tundra heath dominated by Empetrum hermaphroditum close to Abisko, Sweden.

    Methods: We measured root:shoot and fine:coarse root ratios of the plant communities along an elevational gradient by sampling above- and below-ground biomass, further separating root biomass into fine (<1 mm) and coarse roots.

    Results: Plant biomass was higher at the lower elevations, but the root:shoot ratio did not vary with elevation. Resource allocation to fine relative to coarse roots increased with elevation, resulting in a fine:coarse root ratio that more than doubled with increasing elevation.

    Conclusions: Contrary to previous works, the root:shoot ratio along this elevational gradient remained stable. However, communities along our study system were dominated by the same species at each elevation, which suggests that when changes in the root:shoot ratio occur with elevation these changes may be driven by differences in allocation patterns among species and thus turnover in plant community structure. Our results further reveal that the allocation of biomass to fine relative to coarse roots can differ between locations along an elevational gradient, even when overall above- vs below-ground biomass allocation does not. Given the functionally different roles of fine vs coarse roots this could have large implications for below-ground C cycling. Our results highlight the importance of direct effects vs indirect effects (such as changes in plant community composition and nutrient availability) of climate change for future C allocation above and below ground.

  • 4.
    Lindén, Elin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Circumpolar impacts of herbivores on Arctic tundra vegetation2022Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Arctic tundra vegetation provides many ecological services that have implications for the global climate. However, the tundra biome is currently changing in response to increasing temperatures. Herbivores may mitigate some of these responses to warming through their impact on Arctic vegetation. Understanding plant-herbivore interactions is therefore crucial to make better predictions of future Arctic vegetation changes and possible ecological consequences. Most current knowledge on plant-herbivore-interactions in the Arctic comes from local studies that do not allow for large-scale generalisations due to non-comparable methods. Also, existing large-scale studies of herbivory do not cover the tundra biome in a representative way. In this thesis, I used standardised methodology in biome-wide sampling across the Arctic tundra, to uncover how plant-herbivore interactions shape circumpolar vegetation patterns.  

    I have identified clear biogeographic patterns in plant chemical defence against herbivores that could influence the capacity of herbivores to control warming-driven increases of birch shrubs. I also found that herbivores counteract many effects of climate change on tundra vegetation by reducing vegetation greenness (NDVI), Leaf Area Index (LAI), vegetation density and shrub abundance and thereby mitigate vegetation responses to climate warming. Herbivores also increase species richness across the Arctic by supressing dominant species but not by increasing light availability. In a detailed study, I show that the effects of large and small herbivores are similar between continents although they vary with habitat type. This thesis advances our understanding of top-down control of herbivores on tundra vegetation and provides important tools to better predict future Arctic vegetation changes.

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  • 5.
    Lindén, Elin
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Gough, Laura
    Department of Biological Sciences, Towson University, MD, Towson, United States.
    Olofsson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Large and small herbivores have strong effects on tundra vegetation in Scandinavia and Alaska2021Inngår i: Ecology and Evolution, E-ISSN 2045-7758, Vol. 11, nr 17, s. 12141-12152Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Large and small mammalian herbivores are present in most vegetated areas in the Arctic and often have large impacts on plant community composition and ecosystem functioning. The relative importance of different herbivores and especially how their specific impact on the vegetation varies across the Arctic is however poorly understood. Here, we investigate how large and small herbivores influence vegetation density and plant community composition in four arctic vegetation types in Scandinavia and Alaska. We used a unique set of exclosures, excluding only large (reindeer and muskoxen) or all mammalian herbivores (also voles and lemmings) for at least 20 years. We found that mammalian herbivores in general decreased leaf area index, NDVI, and abundance of vascular plants in all four locations, even though the strength of the effect and which herbivore type caused these effects differed across locations. In three locations, herbivore presence caused contrasting plant communities, but not in the location with lowest productivity. Large herbivores had a negative effect on plant height, whereas small mammalian herbivores increased species diversity by decreasing dominance of the initially dominating plant species. Above- or belowground disturbances caused by herbivores were found to play an important role in shaping the vegetation in all locations. Synthesis: Based on these results, we conclude that both small and large mammalian herbivores influence vegetation in Scandinavia and Alaska in a similar way, some of which can mitigate effects of climate change. We also see important differences across locations, but these depend rather on local herbivore and plant community composition than large biogeographical differences among continents.

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  • 6.
    Lindén, Elin
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Sundqvist, Maja K.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    te Beest, Mariska
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Forbes, Bruce
    Björk, Robert G.
    Gough, Laura
    Grogan, Paul
    Kumpula, Timo
    Moen, Jon
    Ønvik Pedersen, Åshild
    Post, Eric
    Ravolainen, Virve
    Roininen, Heikki
    Schmidt, Niels Martin
    Suominen, Otso
    Virtanen, Risto
    van der Wal, René
    Ylänne, Henni
    Olofsson, Johan
    Large herbivores alter vegetation structure and plant community composition across the Arctic tundra biomeManuskript (preprint) (Annet vitenskapelig)
  • 7.
    Lindén, Elin
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Sundqvist, Maja K.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    te Beest, Mariska
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Olofsson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Plant species dominance but not light availability drives herbivore effects on species richness in the ArcticManuskript (preprint) (Annet vitenskapelig)
  • 8.
    Lindén, Elin
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    te Beest, Mariska
    Copernicus Instute for Sustainable Development, Utrecht University, Utrecht, the Netherlands; Centre for African Conservation Ecology, Nelson Mandela Univiversity, Port Elizabeth, South Africa.
    Aubreu, Ilka
    Moritz, Thomas
    Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Sundqvist, Maja K.
    Department of Forest Ecology and Management, Swedish University of Agricultural Science, Umeå, Sweden.
    Barrio, Isabel C.
    Boike, Julia
    Bryant, John P.
    Bråthen, Kari Anne
    Buchwal, Agata
    Bueno, C. Guillermo
    Currier, Alain
    Egelkraut, Dagmar D.
    Forbes, Bruce C.
    Hallinger, Martin
    Heijmans, Monique
    Hermanutz, Luise
    Hik, David
    Hofgaard, Annika
    Holmgren, Milena
    Huebner, Diane C.
    Høye, Toke T.
    Jónsdottir, Ingibjörg S.
    Kaarlejärvi, Elina
    Kissler, Emilie
    Kumpula, Timo
    Limpens, Juul
    Myers-Smith, Isla H.
    Normand, Signe
    Post, Eric
    Rocha, Adrian V.
    Schmidt, Niels Martin
    Skarin, Anna
    Soininen, Eeva M.
    Sokolov, Aleksandr
    Sokolova, Natalia
    Speed, James D.M.
    Street, Lorna
    Tananaev, Nikita
    Tremblay, Jean-Pierre
    Urbanowicz, Christine
    Watts, David A.
    Zimmermann, Heike
    Olofsson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Circum-Arctic distribution of chemical anti-herbivore compounds suggests biome-wide trade-off in defence strategies in Arctic shrubs2022Inngår i: Ecography, ISSN 0906-7590, E-ISSN 1600-0587, nr 11, artikkel-id e06166Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Spatial variation in plant chemical defence towards herbivores can help us understand variation in herbivore top–down control of shrubs in the Arctic and possibly also shrub responses to global warming. Less defended, non-resinous shrubs could be more influenced by herbivores than more defended, resinous shrubs. However, sparse field measurements limit our current understanding of how much of the circum-Arctic variation in defence compounds is explained by taxa or defence functional groups (resinous/non-resinous). We measured circum-Arctic chemical defence and leaf digestibility in resinous (Betula glandulosa, B. nana ssp. exilis) and non-resinous (B. nana ssp. nana, B. pumila) shrub birches to see how they vary among and within taxa and functional groups. Using liquid chromatography–mass spectrometry (LC–MS) metabolomic analyses and in vitro leaf digestibility via incubation in cattle rumen fluid, we analysed defence composition and leaf digestibility in 128 samples from 44 tundra locations.

    We found biogeographical patterns in anti-herbivore defence where mean leaf triterpene concentrations and twig resin gland density were greater in resinous taxa and mean concentrations of condensing tannins were greater in non-resinous taxa. This indicates a biome-wide trade-off between triterpene- or tannin-dominated defences. However, we also found variations in chemical defence composition and resin gland density both within and among functional groups (resinous/non-resinous) and taxa, suggesting these categorisations only partly predict chemical herbivore defence. Complex tannins were the only defence compounds negatively related to in vitro digestibility, identifying this previously neglected tannin group as having a potential key role in birch anti-herbivore defence.

    We conclude that circum-Arctic variation in birch anti-herbivore defence can be partly derived from biogeographical distributions of birch taxa, although our detailed mapping of plant defence provides more information on this variation and can be used for better predictions of herbivore effects on Arctic vegetation.

    Fulltekst (pdf)
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  • 9.
    Ramirez, Juan Ignacio
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Sundqvist, Maja
    Department of Earth Sciences, University of Gothenburg, Gothenburg, Sweden.
    Lindén, Elin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Björk, Robert G.
    Gothenburg Global Biodiversity Centre, Gothenburg, Sweden; Arctic Centre, University of Lapland, Rovaniemi, Finland.
    Forbes, Bruce C.
    Kevo Subarctic Research Institute, Biodiversity Unit, University of Turku, Turku, Finland.
    Suominen, Otso
    The Biological Museum, Lund University, Lund, Sweden.
    Tyler, Torbjörn
    Ecology & Genetics, University of Oulu, Oulu, Finland.
    Virtanen, Risto
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Olofsson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Reindeer grazing reduces climate-driven vegetation changes and shifts trophic interactions in the Fennoscandian tundra2024Inngår i: Oikos, ISSN 0030-1299, E-ISSN 1600-0706Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Herbivores drive shifts in plant species composition by interacting with vegetation through defoliation, trampling and nutrient addition: urine and faeces. As herbivore effects on vegetation accumulate over time, they might spillover to other trophic levels, but how and when this happens is poorly understood. Since it is methodologically demanding to measure biodiversity across spatial gradients, an alternative approach is to assess it through biodiversity indices of vascular plants. We employed the Index of biodiversity relevance developed for Swedish flora which provides an estimated number of organisms associated with a plant species, allowing the quantification of trophic community size. Values from this index were coupled with vegetation data from a network of 96 fenced and paired grazed plots across Fennoscandia. We analysed the role herbivory has on plant richness and diversity, and on the number of organisms that interact with the vegetation according to the index values. We also explored how herbivores influence the competitive effects of tall shrubs on other plants since the dominance of a vegetation type links directly to biodiversity. Plant diversity had no clear response to grazing. Overall vegetation and the vegetation subgroups herbs and non-fruit shrubs had higher biodiversity index values in fenced plots, indicating a higher number of plant–host interactions. Herb cover was negatively related to shrubs in both treatments but with a faster decline in the absence of herbivores. This study highlights the importance of maintaining herbivore populations in the Arctic to conserve the vegetation structure and biodiversity of the tundra. This method of coupling biodiversity indexes with vegetation data provides complementary information to the plant diversity, especially when methodological or time constraints prevent complete field inventories.

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  • 10.
    Sundqvist, Maja K.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Department of Earth Sciences, University of Gothenburg, Gothenburg, Sweden; Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden; The Center for Macroecology, Evolution and Climate, The Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark.
    Sanders, Nathan J.
    Dorrepaal, Ellen
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Lindén, Elin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Metcalfe, Daniel B.
    Newman, Gregory S.
    Olofsson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Wardle, David A.
    Classen, Aimee T.
    Responses of tundra plant community carbon flux to experimental warming, dominant species removal and elevation2020Inngår i: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 34, nr 7, s. 1497-1506Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Rising temperatures can influence ecosystem processes both directly and indirectly, through effects on plant species and communities. An improved understanding of direct versus indirect effects of warming on ecosystem processes is needed for robust predictions of the impacts of climate change on terrestrial ecosystem carbon (C) dynamics.To explore potential direct and indirect effects of warming on C dynamics in arctic tundra heath, we established a warming (open top chambers) and dominant plant species (Empetrum hermaphroditum Hagerup) removal experiment at a high and low elevation site. We measured the individual and interactive effects of warming, dominant species removal and elevation on plant species cover, the normalized difference vegetation index (NDVI), leaf area index (LAI), temperature, soil moisture and instantaneous net ecosystem CO2 exchange.We hypothesized that ecosystems would be stronger CO2 sinks at the low elevation site, and that warming and species removal would weaken the CO2 sink because warming should increase ecosystem respiration (ER) and species removal should reduce gross primary productivity (GPP). Furthermore, we hypothesized that warming and species removal would have the greatest impact on processes at the high elevation where site temperature should be most limiting and dominant species may buffer the overall community to environmental stress more compared to the low elevation site where plants are more likely to compete with the dominant species.The instantaneous CO2 flux, which reflected a weak CO2 sink, was similar at both elevations. Neither experimental warming nor dominant species removal significantly changed GPP or instantaneous net ecosystem CO2 exchange even though species removal significantly reduced ER, NDVI and LAI.Our results show that even the loss of dominant plant species may not result in significant landscape‐scale responses of net ecosystem CO2 exchange to warming. They also show that NDVI and LAI may be limited in their ability to predict changes in GPP in these tundra heaths systems. Our study highlights the need for more detailed vegetation analyses and ground‐truthed measurements in order to accurately predict direct and indirect impacts of climatic change on ecosystem C dynamics.

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