| 1. |
- Kramshøj, Magnus, et al.
(författare)
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Volatile emissions from thawing permafrost soils are influenced by meltwater drainage conditions
- 2019
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 25:5, s. 1704-1716
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 John Wiley & Sons Ltd Vast amounts of carbon are bound in both active layer and permafrost soils in the Arctic. As a consequence of climate warming, the depth of the active layer is increasing in size and permafrost soils are thawing. We hypothesize that pulses of biogenic volatile organic compounds are released from the near-surface active layer during spring, and during late summer season from thawing permafrost, while the subsequent biogeochemical processes occurring in thawed soils also lead to emissions. Biogenic volatile organic compounds are reactive gases that have both negative and positive climate forcing impacts when introduced to the Arctic atmosphere, and the knowledge of their emission magnitude and pattern is necessary to construct reliable climate models. However, it is unclear how different ecosystems and environmental factors such as drainage conditions upon permafrost thaw affect the emission and compound composition. Here we show that incubations of frozen B horizon of the active layer and permafrost soils collected from a High Arctic heath and fen release a range of biogenic volatile organic compounds upon thaw and during subsequent incubation experiments at temperatures of 10°C and 20°C. Meltwater drainage in the fen soils increased emission rates nine times, while having no effect in the drier heath soils. Emissions generally increased with temperature, and emission profiles for the fen soils were dominated by benzenoids and alkanes, while benzenoids, ketones, and alcohols dominated in heath soils. Our results emphasize that future changes affecting the drainage conditions of the Arctic tundra will have a large influence on volatile emissions from thawing permafrost soils – particularly in wetland/fen areas.
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| 2. |
- 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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| 3. |
- 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. - : Elsevier BV. - 1146-609X .- 1873-6238. ; 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 delta C-13 and delta N-15 (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 delta N-15, by 1 parts per thousand, in the leaves of B. vivipara, while no changes were observed in V. vitis-idaea. Fine roots of B. vivipara had higher delta C-13 (1 parts per thousand) and delta N-15 (2.5 parts per thousand) 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 delta C-13 and delta N-15. (C) 2013 The Authors. Published by Elsevier Masson SAS. All rights reserved.
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| 4. |
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| 5. |
- 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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