| 1. |
- Cameron, Erin K., et al.
(author)
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Uneven global distribution of food web studies under climate change
- 2019
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In: Ecosphere. - : Wiley. - 2150-8925 .- 2150-8925. ; 10:3
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Journal article (peer-reviewed)abstract
- Trophic interactions within food webs affect species distributions, coexistence, and provision of ecosystem services but can be strongly impacted by climatic changes. Understanding these impacts is therefore essential for managing ecosystems and sustaining human well-being. Here, we conducted a global synthesis of terrestrial, marine, and freshwater studies to identify key gaps in our knowledge of climate change impacts on food webs and determine whether the areas currently studied are those most likely to be impacted by climate change. We found research suffers from a strong geographic bias, with only 3.5% of studies occurring in the tropics. Importantly, the distribution of sites sampled under projected climate changes was biased-areas with decreases or large increases in precipitation and areas with low magnitudes of temperature change were under-represented. Our results suggest that understanding of climate change impacts on food webs could be broadened by considering more than two trophic levels, responses in addition to species abundance and biomass, impacts of a wider suite of climatic variables, and tropical ecosystems. Most importantly, to enable better forecasts of biodiversity responses to dimate change, we identify critically under-represented geographic regions and climatic conditions which should be prioritized in future research.
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| 2. |
- Barrio, Isabel C., et al.
(author)
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Background invertebrate herbivory on dwarf birch (Betula glandulosa-nana complex) increases with temperature and precipitation across the tundra biome
- 2017
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In: Polar Biology. - : Springer. - 0722-4060 .- 1432-2056. ; 40:11, s. 2265-2278
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Journal article (peer-reviewed)abstract
- 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.
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| 3. |
- Barrio, Isabel C., et al.
(author)
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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)
- 2018
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In: Polar Biology. - : Springer. - 0722-4060 .- 1432-2056. ; 41:8, s. 1653-1654
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Journal article (peer-reviewed)abstract
- 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.
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| 4. |
- Beecham, Ashley H, et al.
(author)
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Analysis of immune-related loci identifies 48 new susceptibility variants for multiple sclerosis.
- 2013
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In: Nature genetics. - : Springer Science and Business Media LLC. - 1546-1718 .- 1061-4036. ; 45:11, s. 1353-60
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Journal article (peer-reviewed)abstract
- Using the ImmunoChip custom genotyping array, we analyzed 14,498 subjects with multiple sclerosis and 24,091 healthy controls for 161,311 autosomal variants and identified 135 potentially associated regions (P < 1.0 × 10(-4)). In a replication phase, we combined these data with previous genome-wide association study (GWAS) data from an independent 14,802 subjects with multiple sclerosis and 26,703 healthy controls. In these 80,094 individuals of European ancestry, we identified 48 new susceptibility variants (P < 5.0 × 10(-8)), 3 of which we found after conditioning on previously identified variants. Thus, there are now 110 established multiple sclerosis risk variants at 103 discrete loci outside of the major histocompatibility complex. With high-resolution Bayesian fine mapping, we identified five regions where one variant accounted for more than 50% of the posterior probability of association. This study enhances the catalog of multiple sclerosis risk variants and illustrates the value of fine mapping in the resolution of GWAS signals.
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| 5. |
- Blume-Werry, Gesche, et al.
(author)
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Proportion of fine roots, but not plant biomass allocation below ground, increases with elevation in arctic tundra
- 2018
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In: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 29:2, s. 226-235
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Journal article (peer-reviewed)abstract
- 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.
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| 6. |
- Bokhorst, Stef Frederik, et al.
(author)
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Contrasting responses of springtails and mites to elevation and vegetation type in the sub-Arctic
- 2018
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In: Pedobiologia. - : Elsevier. - 0031-4056 .- 1873-1511. ; 67, s. 57-64
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Journal article (peer-reviewed)abstract
- Climate change is affecting the species composition and functioning of Arctic and sub-Arctic plant and soil communities. Here we studied patterns in soil microarthropod (springtails and mites) communities across a gradient of increasing elevation that spanned 450 m, across which mean temperature declined by approximately 2.5 degrees C, in sub-Arctic Sweden. Across this gradient we characterized microarthropod communities in each of two types of vegetation, i.e., heath and meadow, to determine whether their responses to declining temperature differed with vegetation type. Mite abundance declined with increasing elevation, while springtail abundance showed the opposite response. Springtail communities were dominated by larger species at higher elevation. Mite abundance was unaffected by vegetation type, while springtail abundance was 53% higher in the heath than meadow vegetation across the gradient. Springtails but not mites responded differently to elevation in heath and meadow vegetation; hemi-edaphic species dominated in the heath at higher elevation while epiedaphic species dominated in the meadow. Our results suggest that sub-Arctic mite and springtail communities will likely respond in contrasting ways to changes in vegetation and soil properties resulting from climate warming.
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| 7. |
- Classen, Aimee T., et al.
(author)
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Direct and indirect effects of climate change on soil microbial and soil microbial-plant interactions : What lies ahead?
- 2015
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In: Ecosphere. - 2150-8925 .- 2150-8925. ; 6:8
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Journal article (peer-reviewed)abstract
- Global change is altering species distributions and thus interactions among organisms. Organisms live in concert with thousands of other species, some beneficial, some pathogenic, some which have little to no effect in complex communities. Since natural communities are composed of organisms with very different life history traits and dispersal ability it is unlikely they will all respond to climatic change in a similar way. Disjuncts in plant-pollinator and plant-herbivore interactions under global change have been relatively well described, but plant-soil microorganism and soil microbe-microbe relationships have received less attention. Since soil microorganisms regulate nutrient transformations, provide plants with nutrients, allow co-existence among neighbors, and control plant populations, changes in soil microorganism-plant interactions could have significant ramifications for plant community composition and ecosystem function. In this paper we explore how climatic change affects soil microbes and soil microbe-plant interactions directly and indirectly, discuss what we see as emerging and exciting questions and areas for future research, and discuss what ramifications changes in these interactions may have on the composition and function of ecosystems.
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| 8. |
- De Long, Jonathan, et al.
(author)
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Effects of elevation and nitrogen and phosphorus fertilization on plant defence compounds in subarctic tundra heath vegetation
- 2016
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In: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 30:2, s. 314-325
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Journal article (peer-reviewed)abstract
- Plant chemical and structural defence compounds are well known to impact upon herbivory of fresh leaves and influence decomposition rates after leaf senescence. A number of theories predict that alleviating nutrient limitation and reducing other environmental stressors will result in decreased production of plant chemical defences. In this study, we measured plant defence properties [total polyphenols (TP), condensed tannins (CT) and lignin concentrations, and protein complexation capacity (PCC)] in both fresh and senesced plant leaves in a fully factorial N and P fertilization experiment set-up at each of three elevations along an elevational gradient in Swedish subarctic tundra heath vegetation. Further, we performed a decomposition of variance analysis on community-weighted averages (CWAs) of plant defence properties to determine the relative contributions of interspecific and intraspecific variation to the total variation observed in response to elevation and nutrient addition. We hypothesized that N fertilization would reduce plant defence properties and that this reduction would be greater at higher elevations, while the effects of P fertilization would have no effect at any elevation. At the community level, N addition reduced CT and PCC in both fresh and senesced leaves and TP in senesced leaves, while P addition had few effects, broadly in line with our hypothesis. The effects of N addition frequently varied with elevation, but in contrast to our hypothesis, the said effects were strongest at the lowest elevations. The effects of N addition and the interactive effect of N with elevation were primarily driven by intraspecific, rather than interspecific, variation. Our findings suggest that as temperatures warm and N availability increases due to global climate change, secondary metabolites in subarctic heath vegetation will decline particularly within species. Our results highlight the need to consider the effects of both nutrient availability and temperature, and their interaction, in driving subarctic plant defence.
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| 9. |
- Lindén, Elin, et al.
(author)
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Circum-Arctic distribution of chemical anti-herbivore compounds suggests biome-wide trade-off in defence strategies in Arctic shrubs
- 2022
-
In: Ecography. - : John Wiley & Sons. - 0906-7590 .- 1600-0587. ; :11
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Journal article (peer-reviewed)abstract
- 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.
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| 10. |
- Lindén, Elin, 1989-
(author)
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Circumpolar impacts of herbivores on Arctic tundra vegetation
- 2022
-
Doctoral thesis (other academic/artistic)abstract
- 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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| 11. |
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| 12. |
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| 13. |
- Mayor, Jordan, et al.
(author)
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Elevation alters ecosystem properties across temperate treelines globally
- 2017
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In: Nature. - : NATURE PUBLISHING GROUP. - 0028-0836 .- 1476-4687. ; 542:7639, s. 91-95
-
Journal article (peer-reviewed)abstract
- Temperature is a primary driver of the distribution of biodiversity as well as of ecosystem boundaries(1,2). Declining temperature with increasing elevation in montane systems has long been recognized as a major factor shaping plant community biodiversity, metabolic processes, and ecosystem dynamics(3,4). Elevational gradients, as thermoclines, also enable prediction of long-term ecological responses to climate warming(5-7). One of the most striking manifestations of increasing elevation is the abrupt transitions from forest to treeless alpine tundra(8). However, whether there are globally consistent above-and belowground responses to these transitions remains an open question(4). To disentangle the direct and indirect effects of temperature on ecosystem properties, here we evaluate replicate treeline ecotones in seven temperate regions of the world. We find that declining temperatures with increasing elevation did not affect tree leaf nutrient concentrations, but did reduce ground-layer community-weighted plant nitrogen, leading to the strong stoichiometric convergence of ground-layer plant community nitrogen to phosphorus ratios across all regions. Further, elevation-driven changes in plant nutrients were associated with changes in soil organic matter content and quality (carbon to nitrogen ratios) and microbial properties. Combined, our identification of direct and indirect temperature controls over plant communities and soil properties in seven contrasting regions suggests that future warming may disrupt the functional properties of montane ecosystems, particularly where plant community reorganization outpaces treeline advance.
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| 14. |
- Metcalfe, Daniel B., et al.
(author)
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Patchy field sampling biases understanding of climate change impacts across the Arctic
- 2018
-
In: Nature Ecology and Evolution. - : Springer Science and Business Media LLC. - 2397-334X. ; 2:9, s. 1443-1448
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Journal article (peer-reviewed)abstract
- Effective societal responses to rapid climate change in the Arctic rely on an accurate representation of region-specific ecosystem properties and processes. However, this is limited by the scarcity and patchy distribution of field measurements. Here, we use a comprehensive, geo-referenced database of primary field measurements in 1,840 published studies across the Arctic to identify statistically significant spatial biases in field sampling and study citation across this globally important region. We find that 31% of all study citations are derived from sites located within 50 km of just two research sites: Toolik Lake in the USA and Abisko in Sweden. Furthermore, relatively colder, more rapidly warming and sparsely vegetated sites are under-sampled and under-recognized in terms of citations, particularly among microbiology-related studies. The poorly sampled and cited areas, mainly in the Canadian high-Arctic archipelago and the Arctic coastline of Russia, constitute a large fraction of the Arctic ice-free land area. Our results suggest that the current pattern of sampling and citation may bias the scientific consensuses that underpin attempts to accurately predict and effectively mitigate climate change in the region. Further work is required to increase both the quality and quantity of sampling, and incorporate existing literature from poorly cited areas to generate a more representative picture of Arctic climate change and its environmental impacts.
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| 15. |
- Prager, Case M., et al.
(author)
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Integrating natural gradients, experiments, and statistical modeling in a distributed network experiment : An example from the WaRM Network
- 2022
-
In: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 12:10
-
Journal article (peer-reviewed)abstract
- A growing body of work examines the direct and indirect effects of climate change on ecosystems, typically by using manipulative experiments at a single site or performing meta-analyses across many independent experiments. However, results from single-site studies tend to have limited generality. Although meta-analytic approaches can help overcome this by exploring trends across sites, the inherent limitations in combining disparate datasets from independent approaches remain a major challenge. In this paper, we present a globally distributed experimental network that can be used to disentangle the direct and indirect effects of climate change. We discuss how natural gradients, experimental approaches, and statistical techniques can be combined to best inform predictions about responses to climate change, and we present a globally distributed experiment that utilizes natural environmental gradients to better understand long-term community and ecosystem responses to environmental change. The warming and (species) removal in mountains (WaRM) network employs experimental warming and plant species removals at high- and low-elevation sites in a factorial design to examine the combined and relative effects of climatic warming and the loss of dominant species on community structure and ecosystem function, both above- and belowground. The experimental design of the network allows for increasingly common statistical approaches to further elucidate the direct and indirect effects of warming. We argue that combining ecological observations and experiments along gradients is a powerful approach to make stronger predictions of how ecosystems will function in a warming world as species are lost, or gained, in local communities.
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| 16. |
- Sundqvist, Maja K., et al.
(author)
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Chemical properties of plant litter in response to elevation : subarctic vegetation challenges phenolic allocation theories
- 2012
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In: Functional Ecology. - : John Wiley & Sons. - 0269-8463 .- 1365-2435. ; 26:5, s. 1090-1099
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Journal article (peer-reviewed)abstract
- Several theories predict that increasing stress (e.g. decreasing nutrient availability or decreasing temperature) should result in higher amounts of plant phenolic compounds both at the interspecific and intraspecific levels. Further, several theories predict that plant phenolics are major drivers of plantsoil feedbacks whereby they influence litter decomposition rates and the return of nutrients to plants. We investigated the potential influence of shifts in abiotic factors on litter phenolic properties using an elevational gradient in northern Sweden, for which temperature and soil fertility decline with increasing elevation. The system consists of two vegetation types: heath, (associated with low soil fertility) and meadow (associated with higher fertility), which occur across the entire gradient. We hypothesized that total phenolics, tannins and protein complexation capacity (PCC) of leaf litter would increase with elevation within and among plant species. We further hypothesized that at the whole-plot level (using community-weighted averages), these properties would be higher in heath than meadow, and that phenolic properties for meadow vegetation would show stronger responses to elevation than for heath. We measured phenolic properties in leaf litter for 13 species from both vegetation types across an established elevational gradient (500-1000m) in Swedish subarctic tundra. Contrary to our hypotheses, different species showed highly contrasting responses in their phenolic characteristics to elevation. At the across-species level, total phenolic content in litter decreased with elevation. At the whole-plot level, tannin concentrations were higher for the heath than for the meadow, whereas total phenolics and PCC did not differ. However, consistent with our hypothesis, our results showed that phenolic properties were more responsive to elevation for the meadow compared to the heath, as a consequence of greater species turnover for the meadow. Our results are inconsistent with theories predicting higher plant phenolic concentrations with increasing environmental stress or decreasing nutrient availability. They also provide evidence that across abiotic gradients in the subarctic tundra, there are large shifts in litter phenolic properties (including those that are able to complex protein) and highlight that the direction and strength of such shifts may differ greatly among vegetation types.
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| 17. |
- Sundqvist, Maja K., et al.
(author)
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Contrasting nitrogen and phosphorus dynamics across an elevational gradient for subarctic tundra heath and meadow vegetation
- 2014
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In: Plant and Soil. - : Springer Netherlands. - 0032-079X .- 1573-5036. ; 383:1-2, s. 387-399
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Journal article (peer-reviewed)abstract
- This study explores soil nutrient cycling processes and microbial properties for two contrasting vegetation types along an elevational gradient in subarctic tundra to improve our understanding of how temperature influences nutrient availability in an ecosystem predicted to be sensitive to global warming. We measured total amino acid (Amino-N), mineral nitrogen (N) and phosphorus (P) concentrations, in situ net N and P mineralization, net Amino-N consumption, and microbial biomass C, N and P in both heath and meadow soils across an elevational gradient near Abisko, Sweden. For the meadow, NH4 (+) concentrations and net N mineralization were highest at high elevations and microbial properties showed variable responses; these variables were largely unresponsive to elevation for the heath. Amino-N concentrations sometimes showed a tendency to increase with elevation and net Amino-N consumption was often unresponsive to elevation. Overall, PO4-P concentrations decreased with elevation and net P immobilization mostly occurred at lower elevations; these effects were strongest for the heath. Our results reveal that elevation-associated changes in temperature can have contrasting effects on the cycling of N and P in subarctic soils, and that the strength and direction of these effects depend strongly on dominant vegetation type.
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| 18. |
- Sundqvist, Maja K., et al.
(author)
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Establishment of boreal forest species in alpine dwarf-shrub heath in subarctic Sweden
- 2008
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In: Plant Ecology & Diversity. - : Informa UK Limited. - 1755-0874 .- 1755-1668. ; 1:1, s. 67-75
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Journal article (peer-reviewed)abstract
- Background: Saplings of mountain birch ( Betula pubescens ssp. czerepanovii) have established in pockets of dwarf-shrub heath approximately 250 m above the treeline in the Latnjavagge Valley, northern Sweden. Aim: We examined if the establishment of these mountain birch outposts was related to favourable local microclimate, and if birch establishment has affected the surrounding vegetation, changing it from dwarf-shrub heath to more akin to birch forest floor. Methods: Daily mean and mean maximum temperatures were compared for two sites in the dwarf-shrub heath ( 990 m a. s. l., few birch saplings; 1060 m a. s. l., numerous birch saplings) between January 2005 and June 2006. The cover-abundance of vascular plants was estimated in sample plots in dwarf-shrub heath with mountain birch, dwarf-shrub heath without mountain birch, in heath between the upper limit of closed mountain birch forest and the treeline, and in closed mountain birch forest. Species composition and diversity were statistically compared. The presence in the dwarf-shrub heath of boreal montane species other than birch was also noted. Results: The higher elevation site, containing a higher density of birch, had a significantly higher growing season temperature than the lower elevation site. There was a significant difference in plant community composition between the alpine heath plots containing mountain birch saplings and plots without mountain birch, alpine heath with birch being more similar to the plots of the treeline ecotone and the birch forest than to alpine heath without birch. No significant difference in species diversity among plots in dwarf-shrub heath was found and species diversity increased with altitude. A number of montane species were observed in the dwarf-shrub heath, however, their distribution was not associated with that of the mountain birch. Conclusions: This study provides evidence for favourable microclimate being a key driver for the establishment of mountain birch above the treeline. In addition, the results imply that the composition of the dwarf-shrub heath changes after the establishment of mountain birch to a plant community whose composition points towards a birch forest.
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| 19. |
- Sundqvist, Maja K., et al.
(author)
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Experimental evidence of the long-term effects of reindeer on Arctic vegetation greenness and species richness at a larger landscape scale
- 2019
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In: Journal of Ecology. - : Wiley-Blackwell. - 0022-0477 .- 1365-2745. ; 107:6, s. 2724-2736
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Journal article (peer-reviewed)abstract
- Large herbivores influence plant community structure and ecosystem processes in many ecosystems. In large parts of the Arctic, reindeer (or caribou) are the only large herbivores present. Recent studies show that reindeer have the potential to mitigate recent warming‐induced shrub encroachment in the Arctic and the associated greening of high‐latitude ecosystems. This will potentially have large scale consequences for ecosystem productivity and carbon cycling.To date, information on variation in the interactions between reindeer and plants across Arctic landscapes has been scarce. We utilized a network of experimental sites across a latitudinal gradient in the Scandinavian mountains where reindeer have been excluded from 59 study plots for at least 15 years. We used this study system to test the effect of long‐term exclusion of reindeer on the abundance of major plant functional groups, the greenness indexes Leaf Area Index (LAI) and Normalized Difference Vegetation Index (NDVI), soil mineral nitrogen (N) and phosphorous (P), and species richness, and to determine whether the effect of reindeer exclusion is dependent on reindeer density, productivity, soil fertility or climate.We found that NDVI and LAI, lichen and deciduous shrub abundances were largely reduced while soil mineral N was enhanced by reindeer. The direction and amplitude of other plant functional group responses to reindeer exclusion differed between forest and tundra as well as shrub‐ and herbaceous‐dominated vegetation. Higher reindeer densities were related to decreased plant species richness in low‐productive sites and to increased species richness in productive sites.The relative reduction in LAI and associated absolute reductions of deciduous shrubs in response to reindeer were positively related to reindeer density, while the relative reduction in NDVI was not. Further, relative reductions in LAI and NDVI in response to reindeer were unrelated to climate and soil fertility.Synthesis. Our results provide long‐term experimental evidence highlighting the role of reindeer density in regulating plant species richness, global climate change induced greenness patterns and shrub encroachment at regional scales in the Arctic. These findings emphasize the need to consider reindeer in models predicting vegetation patterns and changes in high‐latitude ecosystems.
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| 20. |
- Sundqvist, Maja K., et al.
(author)
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Interactive effects of vegetation type and elevation on aboveground and belowground properties in a subarctic tundra
- 2011
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In: Oikos. - Copenhagen : Munksgaard. - 0030-1299 .- 1600-0706. ; 120:1, s. 128-142
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Journal article (peer-reviewed)abstract
- An improved knowledge of how contrasting types of plant communities and their associated soil biota differ in their responses to climatic variables is important for better understanding the future impacts of climate change on terrestrial ecosystems. Elevational gradients serve as powerful study systems for answering questions on how ecological processes can be affected by changes in temperature and associated climatic variables. In this study, we evaluated how plant and soil microbial communities, and abiotic soil properties, change with increasing elevation in subarctic tundra in northern Sweden, for each of two dominant but highly contrasting vegetation types, namely heath (dominated by woody dwarf shrubs) and meadow (dominated by herbaceous species). To achieve this, we measured plant community characteristics, microbial community properties and several soil abiotic properties for both vegetation types across an elevation gradient of 500 to 1000 m. We found that the two vegetation types differed not only in several above- and belowground properties, but also in how these properties responded to elevation, pointing to important interactive effects between vegetation type and elevation. Specifically, for the heath, available soil nitrogen and phosphorus decreased with elevation whereas fungal dominance increased, while for the meadow, idiosyncratic responses to elevation for these variables were found. These differences in belowground responses to elevation among vegetation types were linked to shifts in the species and functional group composition of the vegetation. Our results highlight that these two dominant vegetation types in subarctic tundra differ greatly not only in fundamental aboveground and belowground properties, but also in how these properties respond to elevation and are therefore likely to be influenced by temperature. As such they highlight that vegetation type, and the soil abiotic properties that determine this, may serve as powerful determinants of how both aboveground and belowground properties respond to strong environmental gradients.
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| 21. |
- Sundqvist, Maja K., et al.
(author)
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Plant and microbial responses to nitrogen and phosphorus addition across an elevational gradient in subarctic tundra
- 2014
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In: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 95:7, s. 1819-1835
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Journal article (peer-reviewed)abstract
- Temperature and nutrients are major limiting factors in subarctic tundra. Experimental manipulation of nutrient availability along elevational gradients (and thus temperature) can improve our understanding of ecological responses to climate change. However, no study to date has explored impacts of nutrient addition along a tundra elevational gradient, or across contrasting vegetation types along any elevational gradient. We set up a full factorial nitrogen (N) and phosphorus (P) fertilization experiment in each of two vegetation types (heath and meadow) at 500 m, 800 m, and 1000 m elevation in northern Swedish tundra. We predicted that plant and microbial communities in heath or at lower elevations would be more responsive to N addition while communities in meadow or at higher elevations would be more responsive to P addition, and that fertilizer effects would vary more with elevation for the heath than for the meadow. Although our results provided little support for these predictions, the relationship between nutrient limitation and elevation differed between vegetation types. Most plant and microbial properties were responsive to N and/or P fertilization, but responses often varied with elevation and/or vegetation type. For instance, vegetation density significantly increased with N + P fertilization relative to the other fertilizer treatments, and this increase was greatest at the lowest elevation for the heath but at the highest elevation for the meadow. Arbuscular mycorrhizae decreased with P fertilization at 500 m for the meadow, but with all fertilizer treatments in both vegetation types at 800 m. Fungal to bacterial ratios were enhanced by N + P fertilization for the two highest elevations in the meadow only. Additionally, microbial responses to fertilization were primarily direct rather than indirect via plant responses, pointing to a decoupled response of plant and microbial communities to nutrient addition and elevation. Because our study shows how two community types differ in their responses to fertilization and elevation, and because the temperature range across this gradient is similar to 3 degrees C, our study is informative about how nutrient limitation in tundra may be influenced by temperature shifts that are comparable to those expected under climate change during this century.
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| 22. |
- Sundqvist, Maja K., et al.
(author)
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Within- and across-species responses of plant traits and litter decomposition to elevation across contrasting vegetation types in subarctic tundra
- 2011
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In: PLOS ONE. - : Plos one. - 1932-6203. ; 6:10, s. e27056-
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Journal article (peer-reviewed)abstract
- Elevational gradients are increasingly recognized as a valuable tool for understanding how community and ecosystem properties respond to climatic factors, but little is known about how plant traits and their effects on ecosystem processes respond to elevation. We studied the response of plant leaf and litter traits, and litter decomposability across a gradient of elevation, and thus temperature, in subarctic tundra in northern Sweden for each of two contrasting vegetation types, heath and meadow, dominated by dwarf shrubs and herbaceous plants respectively. This was done at each of three levels; across species, within individual species, and the plant community using a community weighted average approach. Several leaf and litter traits shifted with increasing elevation in a manner consistent with greater conservation of nutrients at all three levels, and the most consistent response was an increase in tissue N to P ratio. However, litter decomposition was less directly responsive to elevation because the leaf and litter traits which were most responsive to elevation were not necessarily those responsible for driving decomposition. At the community level, the response to elevation of foliar and litter traits, and decomposability, varied greatly among the two vegetation types, highlighting the importance of vegetation type in determining ecological responses to climatic factors such as temperature. Finally our results highlight how understanding the responses of leaf and litter characteristics of functionally distinct vegetation types, and the processes that they drive, to temperature helps provide insights about how future climate change could affect tundra ecosystems.
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| 23. |
- Veen, Ciska, et al.
(author)
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Coordinated responses of soil communities to elevation in three subarctic vegetation types
- 2017
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In: Oikos. - : WILEY. - 0030-1299 .- 1600-0706. ; 126:11, s. 1586-1599
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Journal article (peer-reviewed)abstract
- Global warming has begun to have a major impact on the species composition and functioning of plant and soil communities. However, long-term community and ecosystem responses to increased temperature are still poorly understood. In this study, we used a well-established elevational gradient in northern Sweden to elucidate how plant, microbial and nematode communities shift with elevation and associated changes in temperature in three highly contrasting vegetation types (i.e. heath, meadow and Salix vegetation). We found that responses of both the abundance and composition of microbial and nematode communities to elevation differed greatly among the vegetation types. Within vegetation types, changes with elevation of plant, microbial and nematode communities were mostly linked at fine levels of taxonomic resolution, but this pattern disappeared when coarser functional group levels were considered. Further, nematode communities shifted towards more conservative nutrient cycling strategies with increasing elevation in heath and meadow vegetation. Conversely, in Salix vegetation microbial communities with conservative strategies were most pronounced at the mid-elevation. These results provide limited support for increasing conservative nutrient cycling strategies at higher elevation (i.e. with a harsher climate). Our findings indicate that climate-induced changes in plant community composition may greatly modify or counteract the impact of climate change on soil communities. Therefore, to better understand and predict ecosystem responses to climate change, it will be crucial to consider vegetation type and its specific interactions with soil communities.
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| 24. |
- Veen, Geertje F., et al.
(author)
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Environmental factors and traits that drive plant litter decomposition do not determine home-field advantage effects
- 2015
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In: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 29:7, s. 981-991
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Journal article (peer-reviewed)abstract
- The home-field advantage' (HFA) hypothesis predicts that plant litter ecomposed faster than expected underneath the plant from which it riginates (home') than underneath other plants (away'), because ecomposer communities are specialized to break down litter from the lants they associate with. However, empirical evidence shows that the ccurrence of HFA is highly variable, and the reasons for this are ittle understood. In our study, we progress our understanding by nvestigating whether HFA is stronger for more recalcitrant litter pes nd under colder conditions and how soil properties and plant nctional raits affect the magnitude and direction of HFA. In subarctic tundra orthern Sweden, we set up a reciprocal transplant litter decomposition xperiment along an elevational gradient where three highly contrasting egetation types (heath, meadow and Salix) occur at all elevations, and here temperature decreases strongly with elevation. In this study, we sed a litter bag approach where litters from each elevationxvegetation ype combination were decomposed in all combinations of levationxvegetation type. We also measured community-level plant unctional traits, such as leaf and litter nutrient content. We etermined soil biotic and abiotic properties, such as microbial omass nd soil nutrient content, in soil cores collected for each levationxvegetation type combination. We found that mass loss creased ith plant and litter nutrient content and with soil temperature. In ontrast, the occurrence of HFA was limited in our study system, and s agnitude and direction could not be explained by vegetation type, levation, plant traits or soil properties, despite these factors erving as powerful drivers of litter mass loss in our study. We onclude that although vegetation type and climate are major drivers of itter mass loss, they do not emerge as important determinants of HFA. herefore, while rapid shifts in plant community composition or emperature due to global change are likely to influence litter mass oss directly by altering environmental conditions, plant trait spectra nd litter quality, indirect effects of global change resulting from ecoupling of specialist interactions between litter and decomposer ommunities appear to be of less importance.
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| 25. |
- Vincent, Andrea G., et al.
(author)
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Bioavailable Soil Phosphorus Decreases with Increasing Elevation in a Subarctic Tundra Landscape
- 2014
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In: PLOS ONE. - : PLOS one. - 1932-6203. ; 9:3, s. e92942-
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Journal article (peer-reviewed)abstract
- Phosphorus (P) is an important macronutrient in arctic and subarctic tundra and its bioavailability is regulated by the mineralization of organic P. Temperature is likely to be an important control on P bioavailability, although effects may differ across contrasting plant communities with different soil properties. We used an elevational gradient in northern Sweden that included both heath and meadow vegetation types at all elevations to study the effects of temperature, soil P sorption capacity and oxalate-extractable aluminium (Al-ox) and iron (Fe-ox) on the concentration of different soil P fractions. We hypothesized that the concentration of labile P fractions would decrease with increasing elevation (and thus declining temperature), but would be lower in meadow than in heath, given that N to P ratios in meadow foliage are higher. As expected, labile P in the form of Resin-P declined sharply with elevation for both vegetation types. Meadow soils did not have lower concentrations of Resin-P than heath soils, but they did have 2-fold and 1.5-fold higher concentrations of NaOH-extractable organic P and Residual P, respectively. Further, meadow soils had 3-fold higher concentrations of Al-ox + Feox and a 20% higher P sorption index than did heath soils. Additionally, Resin-P expressed as a proportion of total soil P for the meadow was on average half that in the heath. Declining Resin-P concentrations with elevation were best explained by an associated 2.5-3.0 degrees C decline in temperature. In contrast, the lower P availability in meadow relative to heath soils may be associated with impaired organic P mineralization, as indicated by a higher accumulation of organic P and P sorption capacity. Our results indicate that predicted temperature increases in the arctic over the next century may influence P availability and biogeochemistry, with consequences for key ecosystem processes limited by P, such as primary productivity.
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