| 1. |
- Björkman, Anne, 1981, et al.
(författare)
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Plant functional trait change across a warming tundra biome
- 2018
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 562:7725, s. 57-62
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Tidskriftsartikel (refereegranskat)abstract
- The tundra is warming more rapidly than any other biome on Earth, and the potential ramifications are far-reaching because of global feedback effects between vegetation and climate. A better understanding of how environmental factors shape plant structure and function is crucial for predicting the consequences of environmental change for ecosystem functioning. Here we explore the biome-wide relationships between temperature, moisture and seven key plant functional traits both across space and over three decades of warming at 117 tundra locations. Spatial temperature–trait relationships were generally strong but soil moisture had a marked influence on the strength and direction of these relationships, highlighting the potentially important influence of changes in water availability on future trait shifts in tundra plant communities. Community height increased with warming across all sites over the past three decades, but other traits lagged far behind predicted rates of change. Our findings highlight the challenge of using space-for-time substitution to predict the functional consequences of future warming and suggest that functions that are tied closely to plant height will experience the most rapid change. They also reveal the strength with which environmental factors shape biotic communities at the coldest extremes of the planet and will help to improve projections of functional changes in tundra ecosystems with climate warming.
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| 2. |
- Björkman, Anne, 1981, et al.
(författare)
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Tundra Trait Team: A database of plant traits spanning the tundra biome
- 2018
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Ingår i: Global Ecology and Biogeography. - : Wiley. - 1466-822X .- 1466-8238. ; 27:12, s. 1402-1411
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Tidskriftsartikel (refereegranskat)abstract
- © 2018 The Authors Global Ecology and Biogeography Published by John Wiley & Sons Ltd Motivation: The Tundra Trait Team (TTT) database includes field-based measurements of key traits related to plant form and function at multiple sites across the tundra biome. This dataset can be used to address theoretical questions about plant strategy and trade-offs, trait–environment relationships and environmental filtering, and trait variation across spatial scales, to validate satellite data, and to inform Earth system model parameters. Main types of variable contained: The database contains 91,970 measurements of 18 plant traits. The most frequently measured traits (>1,000 observations each) include plant height, leaf area, specific leaf area, leaf fresh and dry mass, leaf dry matter content, leaf nitrogen, carbon and phosphorus content, leaf C:N and N:P, seed mass, and stem specific density. Spatial location and grain: Measurements were collected in tundra habitats in both the Northern and Southern Hemispheres, including Arctic sites in Alaska, Canada, Greenland, Fennoscandia and Siberia, alpine sites in the European Alps, Colorado Rockies, Caucasus, Ural Mountains, Pyrenees, Australian Alps, and Central Otago Mountains (New Zealand), and sub-Antarctic Marion Island. More than 99% of observations are georeferenced. Time period and grain: All data were collected between 1964 and 2018. A small number of sites have repeated trait measurements at two or more time periods. Major taxa and level of measurement: Trait measurements were made on 978 terrestrial vascular plant species growing in tundra habitats. Most observations are on individuals (86%), while the remainder represent plot or site means or maximums per species. Software format: csv file and GitHub repository with data cleaning scripts in R; contribution to TRY plant trait database (www.try-db.org) to be included in the next version release.
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| 3. |
- Brachmann, Cole, 1993, et al.
(författare)
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Herbivore-shrub interactions influence ecosystem respiration and biogenic volatile organic compound composition in the subarctic
- 2023
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Ingår i: Biogeosciences. - 1726-4170 .- 1726-4189. ; 20, s. 4069-4086
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Tidskriftsartikel (refereegranskat)abstract
- Arctic ecosystems are warming nearly 4 times faster than the global average, which is resulting in plant community shifts and subsequent changes in biogeochemical processes such as gaseous fluxes. Additionally, herbivores shape plant communities and thereby may alter the magnitude and composition of ecosystem respiration and biogenic volatile organic compound (BVOC) emissions. Here we determine the effect of large mammalian herbivores on ecosystem respiration and BVOC emissions in two southern and two northern sites in Swedish Scandes, encompassing mountain birch (LOMB) and shrub heath (LORI) communities in the south and low-herb meadow (RIGA) and shrub heath (RIRI) communities in the north. Herbivory significantly altered BVOC composition between sites and decreased ecosystem respiration at RIGA. The difference in graminoid cover was found to have a large effect on ecosystem respiration between sites as RIGA, with the highest cover, had 35 % higher emissions than the next highest-emitting site (LOMB). Additionally, LOMB had the highest emissions of terpenes, with the northern sites having significantly lower emissions. Differences between sites were primarily due to differences in exclosure effects and soil temperature and the prevalence of different shrub growth forms. Our results suggest that herbivory has a significant effect on trace gas fluxes in a productive meadow community and that differences between communities may be driven by differences in shrub composition. Copyright:
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| 4. |
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| 5. |
- Ihrfors, Jane, et al.
(författare)
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Oljerelaterade miljögiftshalter i sediment och biota efter dieselspill i Himleån
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Natten den 14 april 2022 skedde ett större dieselläckage efter en bränslestöld på fastigheten Varberg Signalen 14:1, Cylindervägen 12. Läckaget härrörde från en ovanjordscistern tillhörande Circle K. IVL Svenska Miljöinstitutet fick i uppdrag att undersöka drabbade vattenrecipienter, Himleån, Getteröns naturreservat och Farehammarsviken, med avseende på oljeföroreningsgrad och biologiskt viktiga komponenter. Uppdraget omfattade också att ge förslag på eventuella åtgärder och hur oljeutsläppet bör följas upp. Den 9–10 maj 2022 togs prover av sediment och biota på en rad platser längs Himleån, i Getteröns naturreservat och vid utloppet till Farehammarsviken. Dagvattenröret från området där olyckan skedde har sitt utlopp i ett mänskligt skapat biflöde till Himleån.I Himleån genomfördes provtagningen från utloppet ner till den punkt där ån rinner under väg 41 från strandkanten. På övriga platser längs ån provtogs sediment i åfåran med hjälp av Van Veen-huggare där detta var möjligt. Vid järnvägsbron (gränsen till naturreservatet) och vid Himleåns utlopp gjordes sedimentsprovtagningen från båt med Van Veen-huggare. Vid varje provtagningspunkt togs bilder och anteckningar för att dokumentera förhållandena på platsen. Vid fyra speciellt utvalda platser, varav en referenslokal uppströms olycksplatsen, genomfördes elfiske.Kemiska analyser av sedimentproverna visade på höga halter av alifater och PAH:er vid ett antal platser längs Himleån (provplats 2, 3 och 9) och i stora dammen inom Getteröns naturreservat (provplats 11, 14 och 16).I stora dammen var halterna höga främst i sediment från kanalen in mot den lilla dammen samt längs med stranden vid vägen. Utifrån de höga PAH-halter som påträffats i sedimenten vid dagvattenröret (provplats 2), men även med hänsyn till de förhöjda halter som påträffats vid andra provtagningsplatser i området, föreslogs uppföljande provtagning och analyser i dessa områden efter fågelsäsongen för att minimera störningarna.Resultaten från den uppföljande provtagningen skulle bidra till ett uppdaterat underlag för rekommendation om och var sanering bör utföras för att undvika eventuella biologiska effekter och vidare spridning av förorenat sediment. IVL rekommenderade också att absorptionslänsarna vid dagvattenutloppet skulle ligga kvar, åtminstone till resultaten från den uppföljande provtagningen analyserats för att kunna fånga upp lättare PAH:er.Analyser av fiskmuskel visade förhöjda halter PAH endast vid provplats 7 (Kockargården). Halterna överskred dock inte gränsvärdena för halter i fiskmuskel (HVMFS2019:25), men bör följas upp med ett senare elfiske för att utesluta följdeffekter av spill och åtgärder. Vid analyser av alger påvisades halter över referensprovet för PAH:er i samtliga prover. På tre platser (provplats 8, 10 och 16) överskreds gränsvärdet för kräftdjur och blötdjur (HVMFS 2019:25). Det saknas gränsvärden för vattenväxter.En uppföljande provtagning av gifter i sediment vid samma provplatser genomfördes av IVL 8 december 2022. Analyserna visade då för normaliserade värden inga kvarvarande detekterbara halter alifater eller PAH:er uppströms länsar vid dagvattenutloppet (provplats 2). Däremot hade halterna PAH nedströms länsar (provplats 3) ökat och översteg för floranten gränsvärde (HVMFS 2019:25).Även vid fågelskyddsområdet norr om dämmet (provplats 11) hade halterna PAH ökat och översteg för bens(g,h,i)perylen gränsvärde (HAV2018:31). IVL bedömer utifrån dessa resultat att provplats 3 efter länsar vid dagvattenutloppet bör saneras, gärna snarast innan våren tar fart. Här bör man ta kontakt med länsstyrelsen för att samråda kring lämpliga saneringsmetoder samt utarbeta en plan för efterkontroll. Analysresultat vid uppföljning av övriga provplatser föranleder inga åtgärder.
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| 6. |
- Lindwall, Frida, et al.
(författare)
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Reindeer grazing has contrasting effect on species traits in Vaccinium vitis-idaea L. and Bistorta vivipara (L.) Gray
- 2013
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Ingår i: Acta Oecologica. - 1146-609X. ; 53, s. 33-37
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Tidskriftsartikel (refereegranskat)abstract
- That reindeer grazing can have large effects on plant communities is well known, but how reindeer grazing affects plant traits and plant carbon (C) and nitrogen (N) allocation has not been studied to the same extent. This study was conducted in a sub-arctic dry heath in northern Sweden. 17-year-old reindeer exclosures were used to test whether reindeer grazing affects the C:N ratio (a plant quality index), and the δ13C and δ15N (indicators of changes in C and N dynamics) as well as the C and N content of above- and below ground parts of the evergreen dwarf shrub Vaccinium vitis-idaea L. and the perennial forb Bistorta vivipara (L.) Gray. A lower C:N ratio was found in B. vivipara compared to V. vitis-idaea suggesting a higher grazing pressure on that species. We found that grazing reduced the total C content, by 26%, and increased the δ15N, by 1‰, in the leaves of B. vivipara, while no changes were observed in V. vitis-idaea. Fine roots of B. vivipara had higher δ13C (1‰) and δ15N (2.5‰) than the leaves, while such differences were not found in V. vitis-idaea. The results also highlight the importance of analysing both above- and belowground plant parts when interpreting natural variations in δ13C and δ15N.
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| 7. |
- Sundqvist, Maja K., et al.
(författare)
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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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Ingår i: Journal of Ecology. - : Wiley-Blackwell. - 0022-0477 .- 1365-2745. ; 107:6, s. 2724-2736
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Tidskriftsartikel (refereegranskat)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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| 8. |
- Thomas, H. J. D., et al.
(författare)
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Global plant trait relationships extend to the climatic extremes of the tundra biome
- 2020
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Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- The majority of variation in six traits critical to the growth, survival and reproduction of plant species is thought to be organised along just two dimensions, corresponding to strategies of plant size and resource acquisition. However, it is unknown whether global plant trait relationships extend to climatic extremes, and if these interspecific relationships are confounded by trait variation within species. We test whether trait relationships extend to the cold extremes of life on Earth using the largest database of tundra plant traits yet compiled. We show that tundra plants demonstrate remarkably similar resource economic traits, but not size traits, compared to global distributions, and exhibit the same two dimensions of trait variation. Three quarters of trait variation occurs among species, mirroring global estimates of interspecific trait variation. Plant trait relationships are thus generalizable to the edge of global trait-space, informing prediction of plant community change in a warming world.
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| 9. |
- Thomas, H. J.D., et al.
(författare)
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Traditional plant functional groups explain variation in economic but not size-related traits across the tundra biome
- 2019
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Ingår i: Global Ecology and Biogeography. - : Wiley. - 1466-822X .- 1466-8238. ; 28:2, s. 78-95
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Tidskriftsartikel (refereegranskat)abstract
- © 2018 The Authors Global Ecology and Biogeography Published by John Wiley & Sons Ltd Aim: Plant functional groups are widely used in community ecology and earth system modelling to describe trait variation within and across plant communities. However, this approach rests on the assumption that functional groups explain a large proportion of trait variation among species. We test whether four commonly used plant functional groups represent variation in six ecologically important plant traits. Location: Tundra biome. Time period: Data collected between 1964 and 2016. Major taxa studied: 295 tundra vascular plant species. Methods: We compiled a database of six plant traits (plant height, leaf area, specific leaf area, leaf dry matter content, leaf nitrogen, seed mass) for tundra species. We examined the variation in species-level trait expression explained by four traditional functional groups (evergreen shrubs, deciduous shrubs, graminoids, forbs), and whether variation explained was dependent upon the traits included in analysis. We further compared the explanatory power and species composition of functional groups to alternative classifications generated using post hoc clustering of species-level traits. Results: Traditional functional groups explained significant differences in trait expression, particularly amongst traits associated with resource economics, which were consistent across sites and at the biome scale. However, functional groups explained 19% of overall trait variation and poorly represented differences in traits associated with plant size. Post hoc classification of species did not correspond well with traditional functional groups, and explained twice as much variation in species-level trait expression. Main conclusions: Traditional functional groups only coarsely represent variation in well-measured traits within tundra plant communities, and better explain resource economic traits than size-related traits. We recommend caution when using functional group approaches to predict tundra ecosystem change, or ecosystem functions relating to plant size, such as albedo or carbon storage. We argue that alternative classifications or direct use of specific plant traits could provide new insight into ecological prediction and modelling.
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| 10. |
- Vowles, Tage, et al.
(författare)
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Complex effects of mammalian grazing on extramatrical mycelial biomass in the Scandes forest-tundra ecotone
- 2018
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Ingår i: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 8:2, s. 1019-1030
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Tidskriftsartikel (refereegranskat)abstract
- Mycorrhizal associations are widespread in high-latitude ecosystems and are potentially of great importance for global carbon dynamics. Although large herbivores play a key part in shaping subarctic plant communities, their impact on mycorrhizal dynamics is largely unknown. We measured extramatrical mycelial (EMM) biomass during one growing season in 16-year-old herbivore exclosures and unenclosed control plots (ambient), at three mountain birch forests and two shrub heath sites, in the Scandes forest-tundra ecotone. We also used high-throughput amplicon sequencing for taxonomic identification to investigate differences in fungal species composition. At the birch forest sites, EMM biomass was significantly higher in exclosures (1.36 +/- 0.43g C/m(2)) than in ambient conditions (0.66 +/- 0.17g C/m(2)) and was positively influenced by soil thawing degree-days. At the shrub heath sites, there was no significant effect on EMM biomass (exclosures: 0.72 +/- 0.09g C/m(2); ambient plots: 1.43 +/- 0.94). However, EMM biomass was negatively related to Betula nana abundance, which was greater in exclosures, suggesting that grazing affected EMM biomass positively. We found no significant treatment effects on fungal diversity but the most abundant ectomycorrhizal lineage/cortinarius, showed a near-significant positive effect of herbivore exclusion (p=.08), indicating that herbivory also affects fungal community composition. These results suggest that herbivory can influence fungal biomass in highly context-dependent ways in subarctic ecosystems. Considering the importance of root-associated fungi for ecosystem carbon balance, these findings could have far-reaching implications.
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| 11. |
- Vowles, Tage, et al.
(författare)
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Contrasting impacts of reindeer grazing in two tundra grasslands
- 2017
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9318 .- 1748-9326. ; 12:3
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Tidskriftsartikel (refereegranskat)abstract
- Plant communities in Arctic and alpine areas are changing due to higher temperatures and longer vegetation periods and it is uncertain how this will affect plant-herbivore dynamics. For instance, relatively fast-growing, deciduous shrub species that are the most responsive to warming may also be the most targeted by herbivores such as reindeer, giving less palatable evergreen shrubs the chance to expand. Using herbivore exclosures, we have studied how two grasslands with contrasting nutrient and moisture regimes, a dry, nutrient-poor alpine grass heath and a wet, productive low herb meadow, changed between 1995 and 2012, in grazed and ungrazed conditions. At the grass heath, evergreen low shrub abundance had more than doubled, regardless of grazer treatment, whereas at the low herb meadow, evergreen shrubs had increased only outside exclosures while deciduous tall shrubs and forbs were significantly more abundant inside exclosures. Deciduous tall shrubs were also significantly taller in exclosures. These contrasting findings suggest that the impact of herbivores is to a great deal determined by their influence on competitive interactions between plant species, and therefore depends on the underlying composition of the plant community. Consequently, as the balance in these competitive interactions is shifting due to climate warming, we conclude that the potential of herbivory to influence this balance is considerable yet highly site dependent.
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| 12. |
- Vowles, Tage, et al.
(författare)
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Ecosystem responses to reindeer grazing along the Scandinavian mountain range
- 2016
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Ingår i: Book of Abstracts, Grazing in a Changing Nordic Region, 12-15 th of September, 2016, Reykjavík, Iceland. - Ås, Norway : The Nordic Genetic Resource Center.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The warming of recent years has caused a shift in plant community structure in arctic areas and one of the most obvious changes is the expansion of shrubs. However, studies have found that reindeer can influence ecosystem responses to warming and inhibit shrub expansion. In this project we have revisited grazed (ambient) and ungrazed (fenced) study plots, at the southern as well as the northern limits of the Scandes mountain range, to investigate how the vegetation had changed in response to increasing temperatures between 1995 – 2012 occurring across the Scandes. Several plant communities within the Forest-Tundra Ecotone (FTE) were studied. Furthermore, we examined the impact of reindeer grazing on the production of extramatrical mycelia (EMM) and community structure of the ectomycorrhizal fungi using ingrowth mesh bags, nitrogen cycling using PRS-probes and fluxes of greenhouse gases. At shrub and grass heaths the evergreen shrubs nearly doubled from 1995-2012, whether grazed or not. Deciduous shrubs, too, showed a significant increase over time but, contrary to the evergreen shrubs, they also showed a positive effect of reindeer exclosure. Deciduous shrub cover had increased from 11% to 19% in ambient plots and 32% in fenced plots. Reindeer grazing was also found to significantly limit the advancement of tall (over 30 cm in height) dwarf birch and willow species at the grass meadow and shrub heaths. At the mountain birch forest sites, too, evergreen shrubs showed the greatest rise, increasing on average from 20% to 47% with no effect of reindeer exclosure, while the increase in deciduous shrubs was not as large as at the heath sites. Nor was there any treatment effect. The EMM production, at the shrub heath sites in the southern mountains, was 3 times larger in ambient plots than exclosures, which could be explained by a decreased abundance and an increased carbon (C) allocation to the roots of dwarf birch (Betula nana) when reindeer are present. However, this alteration of C did not affect the CO2 flux at the site, although the CO2 flux at the most productive site, grass meadow, showed a general pattern of lower fluxes from grazed plots. We conclude that shrub expansion is occurring rapidly in the Scandes mountain range. Reindeer, however, may restrain the expanding shrub cover and affect the C allocation in plants, in turn influencing the EMM production and in the longer term, potentially, the soil C budget.
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| 13. |
- Vowles, Tage, et al.
(författare)
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Expansion of deciduous tall shrubs but not evergreen dwarf shrubs inhibited by reindeer in Scandes mountain range
- 2017
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Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 105:6, s. 1547-1561
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Tidskriftsartikel (refereegranskat)abstract
- One of the most palpable effects of warming in Arctic ecosystems is shrub expansion above the tree line. However, previous studies have found that reindeer can influence plant community responses to warming and inhibit shrubification of the tundra. We revisited grazed (ambient) and ungrazed study plots (exclosures), at the southern as well as the northern limits of the Swedish alpine region, to study long-term grazing effects and vegetation changes in response to increasing temperatures between 1995 and 2011, in two vegetation types (shrub heath and mountain birch forest). In the field layer at the shrub heath sites, evergreen dwarf shrubs had increased in cover from 26% to 49% but were unaffected by grazing. Deciduous dwarf and tall shrubs also showed significant, though smaller, increases over time. At the birch forest sites, the increase was similar for evergreen dwarf shrubs (20-48%) but deciduous tall shrubs did not show the same consistent increase over time as in the shrub heath. The cover and height of the shrub layer were significantly greater in exclosures at the shrub heath sites, but no significant treatment effects were found on species richness or diversity. July soil temperatures and growing season thawing degree days (TDD) were higher in exclosures at all but one site, and there was a significant negative correlation between mean shrub layer height and soil TDD at the shrub heath sites. Synthesis. This study shows that shrub expansion is occurring rapidly in the Scandes mountain range, both above and below the tree line. Tall, deciduous shrubs had benefitted significantly from grazing exclosure, both in terms of cover and height, which in turn lowered summer soil temperatures. However, the overriding vegetation shift across our sites was the striking increase in evergreen dwarf shrubs, which were not influenced by grazing. As the effects of an increase in evergreen dwarf shrubs and more recalcitrant plant litter may to some degree counteract some of the effects of an increase in deciduous tall shrubs, herbivore influence on shrub interactions is potentially of great importance for shaping arctic shrub expansion and its associated ecosystem effects.
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| 14. |
- Vowles, Tage, et al.
(författare)
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Implications of evergreen shrub expansion in the Arctic
- 2019
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Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 107:2, s. 650-655
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Tidskriftsartikel (refereegranskat)abstract
- © 2018 The Authors. Journal of Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society. Arctic shrub expansion is occurring across large parts of the tundra biome and its potential ecological repercussions have been widely discussed. But while the term “shrub expansion” often implicitly refers to an increase in tall, deciduous species such as birch and willow, several studies have also found a strong increase in evergreen dwarf shrubs in response to warming, a fact which has received far less attention. The effects of an evergreen dwarf shrub expansion are markedly different from the effects of an increase in taller, deciduous species. While deciduous shrubs may increase carbon (C) cycling through changes in albedo, litter input, and snow depth, the low stature of evergreen dwarf shrubs means that they are unlikely to influence snow cover. They also produce more recalcitrant litter, which reduces microbial activity. Furthermore, recent research suggests that ericoid mycorrhiza associated with evergreen shrubs may help to decelerate litter and soil organic matter turnover rates through the production of melanized hyphae that resist decomposition. Through selective browsing, herbivores may promote evergreen shrubs and facilitate C storage. Synthesis. In this mini review, we argue that basing predictions of how shrub expansion will affect tundra ecosystems on characteristics only applicable to tall deciduous shrubs hampers our understanding of the complex feedbacks related to Arctic vegetation shifts.
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| 15. |
- Vowles, Tage, et al.
(författare)
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Reindeer grazing and climate change affects vegetation structure in the Swedish mountains
- 2013
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Ingår i: Geophysical Research Abstracts. ; 15
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Konferensbidrag (refereegranskat)abstract
- There is substantial evidence indicating that arctic and alpine landscapes are undergoing distinct changes in plant community structure, presumably brought about by increasing temperatures and a prolonged snow-free season. However, recent studies have revealed that grazing by large herbivores can inhibit a climate-driven shrub expansion and plant community change. In northern Fennoscandia reindeer grazing has helped to shape the vegetation patterns since the last glacial period and is an important factor to consider in the understanding of how a changing climate will affect tundra ecosystems. This project examines the effects of reindeer grazing by revisiting fenced exclosures constructed in 1995. The exclosures were erected at four sites with different grazing intensities situated along the Scandinavian mountain range (from 61 30’ to 68 30’). At three of the four sites, three fenced and three control (ambient conditions) plots (25x25 m each) were established in alpine tundra and in mountain birch forest, respectively. In the fourth site only tundra plots were established. In 2011/12 we used the same methodology as in the original 1995 inventories to determine the species composition, canopy height, and percentage cover of the shrub, field and bottom layers in the plots. In the birch forest, the tree layer was also estimated by determining species composition, cover, height, diameter, and individual density. Our results show that on the tundra, tall shrub cover has increased at our fenced-in plots over the past 16 years, whereas in ambient plots the response varies between sites. Low shrubs, too, have increased over time, yet showing no significant treatment effect. Graminoids, on the other hand have decreased overall, but significantly more in fenced-in plots. Furthermore, the shrub canopy height has increased significantly over time with implications for albedo and snow trapping effects. Bryophyte cover was significantly larger in ambient plots than in fenced-in plots on the tundra which affects summer soil temperatures (which were consistently higher in ambient plots). A great deal of data still needs to be processed but these preliminary results indicate that vegetation composition in the Swedish mountain range is changing rapidly and that large herbivore grazing has a substantial part to play in shaping these changes.
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| 16. |
- Vowles, Tage, et al.
(författare)
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The impact of shrub browsing by mountain hare and reindeer in subarctic Sweden
- 2016
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Ingår i: Plant Ecology and Diversity. - : Informa UK Limited. - 1755-0874 .- 1755-1668. ; 9:4, s. 421-428
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Tidskriftsartikel (refereegranskat)abstract
- Background: Climate warming has been causing an increase in tall shrub cover around the Arctic, however, mammalian herbivory has been shown to inhibit shrub expansion. Though the effect of reindeer (Rangifer tarandus) and many other mammals has been widely studied in this context, the role of the mountain hare (Lepus timidus) in subarctic Scandinavia remains unknown. Aims: To quantify browsing from mountain hare and reindeer on tall shrubs in different vegetation types and to investigate differences in shrub preference between the two. Methods: In the summers of 2013 and 2014, we counted signs of browsing by hare and reindeer on tall shrub species in 31 study plots at three alpine locations in the Scandes range, Sweden. Results: Hare browsing was significantly more frequent than that by reindeer in two (dry-mesic heath and dry meadow) out of seven vegetation types studied. Reindeer browsing was significantly higher in the low herb meadow and Långfjället shrub heath. Two shrub species, Betula nana and Salix hastata, were significantly more browsed by hare, while reindeer browsing was significantly higher on S. phylicifolia and S. lapponum. Conclusions: Our results show that mountain hares can cause extensive damage to tall shrubs in the subarctic and may have a stronger impact on shrub communities than previously recognised.
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| 17. |
- Vowles, Tage, et al.
(författare)
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Vegetation Responses to Herbivory and Climate Change along the Swedish Mountains
- 2012
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Ingår i: IPY 2012 From Knowledge to Action Conference, Montreal, Canada, 22-27 April 2012.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Substantial evidence has accumulated indicating that arctic and alpine landscapes are undergoing distinct changes in plant community structure, presumably brought about by increasing temperatures and a prolonged snow-free season. However, recent studies have revealed that grazing by large herbivores can inhibit a climate-driven shrub expansion and plant community change. In northern Fennoscandia reindeer grazing has helped to shape the vegetation patterns since the last glacial period and is an important factor to consider in the understanding of how a changing climate will affect tundra ecosystems. This research project examines the effects of reindeer grazing by revisiting fenced exclosures constructed in 1995. The exclosures were erected at four sites with different grazing intensities situated along the Scandinavian mountain range (from 61°30’ to 68°30’). At three of the four sites three fenced and three control plots (25×25 m each) were established in alpine tundra and in mountain birch forest, respectively. In the forth site only alpine fences were established. Using the same methodology as in the original 1995 inventories we have determined the species composition, canopy height, and percentage cover of the shrub, field and bottom layers in the plots. In the birch forest, the tree layer was also estimated by determining species composition, cover, height, diameter, and individual density. Preliminary analyses of the coverage of field and bottom layers show that dwarf and low shrubs, most notably Empetrum nigrum, Vaccinium vitis-idaea and Calluna vulgaris, have increased substantially in coverage at our southern sites over the past 16 years, in both fenced and control plots, whereas lichens like Cladonia stellaris have decreased. Coverages of Betula nana showed clear differences between experimental and control plots, but herbivory grazing on the whole, however, seems to have had a lesser impact on the vegetation than expected. An apparent expansion of Pinus sylvestris seedlings at higher altitudes was also noted but tree inventory data is yet to be analysed. A more in-depth analysis of all data will be presented since much raw data still needs to be processed.
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