| 1. |
- Björn, Lars Olof, et al.
(författare)
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Effects of ozone depletion and increased ultraviolet-B radiation on northern vegetation
- 1999
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Ingår i: Polar Research. - : Norwegian Polar Institute. - 0800-0395 .- 1751-8369. ; 18:2, s. 331-337
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Tidskriftsartikel (refereegranskat)abstract
- The stratospheric ozone layer has been depleted at high and mid-latitudes as a consequence of man's pollution of the atmosphere, and this results in increasing ultraviolet-B radiation at ground level. We investigate the effects of further radiation increases on plants and ecosystems by irradiating natural sub-Arctic and Arctic vegetation with artificial W-B radiation in field experiments extending over several years. Our experimental sites are located at Abisko, in northern Sweden (68 degrees N), and Adventdalen, on the island of Spitsbergen (78 degrees N). Additional UV-B induced interspecific differences in plant response in terms of reduced (or, in one case, increased) growth, changed morphology and changed pigment content. In some cases effects seem to be accumulated from one year to another. Plant litter decomposition is retarded. We are also studying how UV-B enhancement may affect the interaction between species. In some experiments we combine UV-B enhancement with changes in other factors: carbon dioxide concentration, water availability, and temperature. In some cases the effect of radiation enhancement is modified, or even reversed, by such changes. Over a four year period we did not find any significant radiation induced change in species composition, but based on the effects on individual plant species, such changes can be expected to take place over a longer time.
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| 2. |
- Björn, Lars Olof, et al.
(författare)
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The problem of ozone depletion in northern Europe
- 1998
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Ingår i: Ambio: a Journal of Human Environment. - 0044-7447. ; 27:4, s. 275-279
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Tidskriftsartikel (refereegranskat)abstract
- Ozone in the atmosphere, mainly in the stratosphere, absorbs most of the ultraviolet-B (wavelength 280-315 nm) radiation from the sun, which can destroy DNA and other biologically important molecules and, thereby, damage living organisms. Due to the pollution of the atmosphere by humans, the ozone layer is presently being depleted, more rapidly at higher latitudes than at lower, and more rapidly over Scandinavia than over most geographical regions at corresponding latitudes. Ultraviolet-B radiation is generally more intense in mountain regions than at sea level. We have experiments in progress in which we simulate the effects of further ozone depletion on terrestrial ecosystems (mountain heaths, bogs, tundra) by irradiating them with artificial ultraviolet-B radiation. Effects on the growth of dwarf-shrubs and mosses and on plant litter decomposition are described.
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| 3. |
- Johanson, U, et al.
(författare)
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The effects of an enhanced UV-B radiation on a sub-arctic heath ecosystem
- 1995
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Ingår i: Ambio: a Journal of Human Environment. - 0044-7447. ; 24:2, s. 106-112
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Tidskriftsartikel (refereegranskat)abstract
- To investigate the effects of increased UV-B radiation on a natural subarctic ecosystem a field irradiation experiment was established at Abisko, northern Sweden. The vegetation in the plots consists of a dwarf shrub layer with mosses and lichens beneath. Many response variables of the vegetation and soil are measured in these plots, e.g. photosynthesis, growth, phenology, changes in species composition and decomposition. This paper describes the methods used and some initial results. Decomposition was imparied by enhanced UV-B radiation. UV-B directly affected decomposition processes and also affected them indirectly by altering the tissue chemistry of leaves. The annual growth of the dwarf shrubs was lower under enhanced UV-B. This was more pronounced in evergreen than in deciduous species. Leaf thickness of the dwarf shrubs was changed by UV-B. The leaves of the evergreen Vaccinium vitis-idaea grew thicker, while those of the two deciduous species V. myrtillus and V. uliginosum grew thinner. In the moss Hylocomium splendens, the phenological development was accelerated under enhanced UV-B radiation. Its growth (number of primary branches, length and dry weight) also increased.
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| 4. |
- Johanson, U, et al.
(författare)
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The Effects of Enhanced UV-B Radiation on the Growth of Dwarf Shrubs in a Subarctic Heathland
- 1995
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Ingår i: Functional Ecology. - 1365-2435. ; 9:5, s. 713-719
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Tidskriftsartikel (refereegranskat)abstract
- In a field irradiation experiment UV-B radiation was enhanced to simulate 15% ozone depletion under clear sky conditions in northern Sweden. This was accomplished by using UV-B fluorescent lamps mounted on metal frames raised over a naturally growing plant community. 2. The study area consisted of a dwarf shrub heath mainly composed of the four species Vaccinium vitis-idaea, V. myrtillus, V. uliginosum and Empetrum hermaphroditum. The absolute annual stem growth, relative stem growth and absolute leaf growth were recorded for different years. 3. The relative growth was significantly reduced by UV-B enhancement in the two evergreen species V. vitis-idaea (27% after 2 years of enhanced UV-B) and E. hermaphroditum (14% after 1 year and 33% after 2 years). The two deciduous species also showed a tendency for decreased relative growth under enhanced UV-B, but this effect was not statistically significant. 4. The leaf thickness of V. vitis-idaea increased both during 1992 (9%) and 1993 (4%). In contrast, the two deciduous species V. myrtillus and V. uliginosum developed thinner leaves under enhanced UV-B both during 1992 (4% for V. myrtillus, 6% for V. uliginosum) and 1993 (9% for V. myrtillus, 10% for V. uliginosum).
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| 5. |
- Sonesson, M, et al.
(författare)
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Short-term effects of enhanced UV-B and CO2 on lichens at different latitudes
- 1995
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Ingår i: Lichenologist. - 0024-2829. ; 27:6, s. 547-557
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Tidskriftsartikel (refereegranskat)abstract
- Interaction effects of UV-B and CO2 on three lichens species, Cladonia arbusculo, Cetraria islandica and Stereocaulon paschale, from two latitudinal sites, 68N and 56N, were studied in a laboratory experiment. The response of the plants was recorded by measuring their chlorophyll fluorescence. All species had a similar response to enhanced UV-B depending on the latitude from which the population came and the time of the season when they were sampled. Overall, there was a significant increase in photosystem II yield (as measured by a fluorescence technique) due to UV-B and no separate effect due to enhanced CO2, although there was a significant interaction between CO2 and UV-B. The increase due to UV-B was at the low CO2 level. There were also significant differences in response due to latitude. The results contradict our hypotheses that negative effects of UV-B would be larger in the North than in the South and that a negative response should be especially large during the early season.
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| 6. |
- Taulavuori, E, et al.
(författare)
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Long-term exposure to enhanced ultraviolet-B radiation in the sub-arctic does not cause oxidative stress in Vaccinium myrtillus
- 1998
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Ingår i: New Phytologist. - : Wiley. - 1469-8137 .- 0028-646X. ; 140:4, s. 691-697
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work was to assess whether or not oxidative stress had developed in a dwarf shrub bilberry (Vaccinium myrtillus L.) under long-term exposure to enhanced levels of ultraviolet-B (u.v.-B) radiation. The bilberry plants were exposed to increased u.v.-B representing a 15 stratospheric ozone depletion for seven full growing seasons (19911997) at Abisko, Swedish Lapland (68N). The oxidative stress was assessed on leaves and stems by analysing ascorbate and glutathione concentrations, and activities of the closely related enzymes ascorbate peroxidase (EC 1.11.1.11) and glutathione reductase (EC 1.6.4.2). The affects of autumnal leaf senescence and stem cold hardening on these variables were also considered. The results showed that the treatment caused scarcely any response in the studied variables, indicating that u.v.-B flux representing a 15 ozone depletion under clear sky conditions is not sufficient to cause oxidative stress in the bilberry. It is suggested that no strain was evoked since adaptation was possible under such u.v.-B increases. The studied variables did, however, respond significantly to leaf senescence and especially to stem cold hardening.
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