| 1. |
- Hedenas, Henrik, et al.
(författare)
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Changes Versus Homeostasis in Alpine and Sub-Alpine Vegetation Over Three Decades in the Sub-Arctic
- 2012
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Ingår i: Ambio. - : Springer Verlag (Germany). - 0044-7447 .- 1654-7209. ; 41, s. 187-196
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Tidskriftsartikel (refereegranskat)abstract
- Plant species distributions are expected to shift and diversity is expected to decline as a result of global climate change, particularly in the Arctic where climate warming is amplified. We have recorded the changes in richness and abundance of vascular plants at Abisko, sub-Arctic Sweden, by re-sampling five studies consisting of seven datasets; one in the mountain birch forest and six at open sites. The oldest study was initiated in 1977–1979 and the latest in 1992. Total species number increased at all sites except for the birch forest site where richness decreased. We found no general pattern in how composition of vascular plants has changed over time. Three species, Calamagrostis lapponica, Carex vaginata and Salix reticulata, showed an overall increase in cover/frequency, while two Equisetum taxa decreased. Instead, we showed that the magnitude and direction of changes in species richness and composition differ among sites.
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| 2. |
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| 3. |
- Carlsson, Bengt Å., et al.
(författare)
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Alpine and subalpine vegetation
- 1999
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Ingår i: Swedish plant geography. - Uppsala : Svenska växtgeografiska sällskapet. - 9172100842 ; , s. 75-89
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Bokkapitel (refereegranskat)
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| 4. |
- Hedenås, Henrik, et al.
(författare)
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Changes Versus Homeostasis in Alpine and Sub-Alpine Vegetation Over Three Decades in the Sub-Arctic
- 2012
-
Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 41:Suppl 3, s. 187-196
-
Tidskriftsartikel (refereegranskat)abstract
- Plant species distributions are expected to shift and diversity is expected to decline as a result of global climate change, particularly in the Arctic where climate warming is amplified. We have recorded the changes in richness and abundance of vascular plants at Abisko, sub-Arctic Sweden, by re-sampling five studies consisting of seven datasets; one in the mountain birch forest and six at open sites. The oldest study was initiated in 1977-1979 and the latest in 1992. Total species number increased at all sites except for the birch forest site where richness decreased. We found no general pattern in how composition of vascular plants has changed over time. Three species, Calamagrostis lapponica, Carex vaginata and Salix reticulata, showed an overall increase in cover/frequency, while two Equisetum taxa decreased. Instead, we showed that the magnitude and direction of changes in species richness and composition differ among sites.
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| 5. |
- Hytteborn, Håkan, et al.
(författare)
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Spatial heterogeneity ensures long-term stability in vegetation and Fritillaria meleagris flowering in Uppsala Kungsäng, a semi-natural meadow
- 2023
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 18:3
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Tidskriftsartikel (refereegranskat)abstract
- Semi-natural grasslands are becoming increasingly rare, and their vegetation may be affected by environmental changes and altered management. At Kungsängen Nature Reserve, a wet to mesic semi-natural meadow near Uppsala, Sweden, we analysed long-term changes in the vegetation using data from 1940, 1982, 1995 and 2016. We also analysed the spatial and temporal dynamics in the Fritillaria meleagris population based on countings of flowering individuals in 1938, 1981–1988 and 2016–2021. Between 1940 and 1982 the wet part of the meadow became wetter, which led to an increased cover of Carex acuta and pushed the main area of flowering of F. meleagris up towards the mesic part. Annual variation in the flowering propensity of F. meleagris (in May) was affected by temperature and precipitation in the phenological phases of growth and bud initiation (June in the previous year), shoot development (September in the previous year) and initiation of flowering (March–April). However, the response to weather was in opposite directions in the wet and mesic parts of the meadow, and the flowering population showed large year-to-year variation but no long-term trend. Variation in management (poorly documented) led to changes in different parts of the meadow, but the overall composition of the vegetation, species richness and diversity changed little after 1982. Species richness and species composition of the meadow vegetation, and the long-term stability of the F. meleagris population are maintained by the variation in wetness, highlighting the importance of spatial heterogeneity as an insurance against biodiversity loss in semi-natural grasslands and nature reserves generally.
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| 6. |
- Sonesson, Mats, et al.
(författare)
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A comparison of the physiology, anatomy and ribosomal DNA in alpine and subalpine populations of the lichen Nephroma arcticum – the effects of an eight-year transplant experiment
- 2007
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Ingår i: The Bryologist. - 0007-2745 .- 1938-4378. ; 110:2, s. 244-253
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Tidskriftsartikel (refereegranskat)abstract
- Thalli of Nephroma arcticum were transplanted between and within a high-elevation alpine heath (1100 m) and a low-elevation subalpine mountain birch forest (380 m) in northern Swedish Lapland and harvested after eight years. Statistically significant differences (P < 0.05) were found between control samples for dark respiration rates, photon use efficiencies (apparent quantum yields) and light compensation points (all were higher in the high-altitude population). The following traits were significantly affected by transplanting: (1) epicortex thickness, (2) upper cortex thickness in the low-altitude population, (3) maximum photosynthetic rates, (4) dark respiration rates and (5) light compensation point. Of these malleable traits, all reduce the differences between the controls although there seems to be over-compensation in maximum net photosynthesis and under-compensation in dark respiration rate of the low-altitude population. Conservative traits, i.e., those that did not change significantly with transplantation were: (1) thallus thickness, (2) algal layer thickness, (3) algal cell diameter and (4) light saturation level. Small, yet significant differences in anatomy and physiology suggest that an ecotypic differentiation was established although the two internal transcribed DNA spacers ITS 1 and ITS 2 showed no corresponding variation between the populations.
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| 7. |
- Sonesson, Mats, et al.
(författare)
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Seasonal variation in concentrations of carbohydrates and lipids in two epiphytic lichens with contrasting, snow-depth related distribution on subarctic birch trees
- 2011
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Ingår i: Bryologist. - : American Bryological and Lichenological Society. - 1938-4378 .- 0007-2745. ; 114:3, s. 443-452
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Tidskriftsartikel (refereegranskat)abstract
- The lichens Parmelia olivacea and Parmeliopsis ambigua are common epiphytes in subarctic forests in Europe. They differ in abundance and vertical distribution particularly on birch trees, and these differences relate to the level and duration of the winter snow cover. Parmeliopsis ambigua is covered much of the cold season on the lower trunk whereas P. olivacea occurs well above the snow surface. Periods over 6 months under snow have no apparent effect on P. ambigua thalli while much shorter snow cover has been demonstrated to kill P. olivacea. It was hypothesized that the contrasting distributions are due to differences in growth rates and in size and quality of non-structural carbon stores in their tissues affecting their endurance to extended periods of dark respiration. To test these hypotheses, growth measurements were performed on both species and their thalli were sampled for chemical analyses. The results show that the mean annual margin extension growth of P. olivacea thalli was significantly higher than that of P. ambigua, i.e. 1.1 mm and 0.5 mm, respectively. The average non-structural carbohydrate concentration in the two species did not differ, but the annual concentration of storage lipids (triacylglycerol) in P. ambigua was four times higher than that in P. olivacea, despite a shorter growing season and lower rate of photosynthesis. The proportion of polyunsaturated fatty acids in structural (polar) lipids was high in both species, i.e. 77% in P. olivacea and 64% in P. ambigua, which appears to enable both species to withstand low ambient thallus temperatures. The higher concentration of storage lipids in P. ambigua allows survival in environments where P. olivacea would respire to death, e.g. under a prolonged snow cover. Parmeliopsis ambigua avoids competition by establishing toward the base of the tree trunk, where P. olivacea would not survive.
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| 8. |
- Svensson, Brita M., et al.
(författare)
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Changes in species abundance after seven years of elevated atmospheric CO2 and warming in a Subarctic birch forest understorey, as modified by rodent and moth outbreaks
- 2018
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Ingår i: PeerJ. - : PEERJ INC. - 2167-8359. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- A seven-year long, two-factorial experiment using elevated temperatures (5 degrees C) and CO2 (concentration doubled compared to ambient conditions) designed to test the effects of global climate change on plant community composition was set up in a Subarctic ecosystem in northernmost Sweden. Using point-frequency analyses in permanent plots, an increased abundance of the deciduous Vaccinium myrtillus, the evergreens V. vitis-idaea and Empetrum nigrum ssp. hermaphroditum and the grass Avenella flexuosa was found in plots with elevated temperatures. We also observed a possibly transient community shift in the warmed plots, from the vegetation being dominated by the deciduous V. myrtillus to the evergreen V. vitis-idaea. This happened as a combined effect of V. myrtillus being heavily grazed during two events of herbivore attack-one vole outbreak (Clethrionomys rufocanus) followed by a more severe moth (.Epirrita autumnata) outbreak that lasted for two growing seasons-producing a window of opportunity for V. vitis-idaea to utilize the extra light available as the abundance of V. myrtillus decreased, while at the same time benefitting from the increased growth in the warmed plots. Even though the effect of the herbivore attacks did not differ between treatments they may have obscured any additional treatment effects. This long-term study highlights that also the effects of stochastic herbivory events need to be accounted for when predicting future plant community changes.
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| 9. |
- Svensson, Brita M., et al.
(författare)
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Clonality in the plant community
- 2013. - 2
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Ingår i: Vegetation ecology. - : Wiley-Blackwell. - 9781444338881 ; , s. 141-163
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Bokkapitel (refereegranskat)
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| 10. |
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