| 1. |
- Callaghan, Terry V., et al.
(författare)
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Ecosystem change and stability over multiple decades in the Swedish subarctic : complex processes and multiple drivers
- 2013
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Ingår i: Philosophical Transactions of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8436 .- 1471-2970. ; 368:1624
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Tidskriftsartikel (refereegranskat)abstract
- The subarctic environment of northernmost Sweden has changed over the past century, particularly elements of climate and cryosphere. This paper presents a unique geo-referenced record of environmental and ecosystem observations from the area since 1913. Abiotic changes have been substantial. Vegetation changes include not only increases in growth and range extension but also counterintuitive decreases, and stability: all three possible responses. Changes in species composition within the major plant communities have ranged between almost no changes to almost a 50 per cent increase in the number of species. Changes in plant species abundance also vary with particularly large increases in trees and shrubs (up to 600%). There has been an increase in abundance of aspen and large changes in other plant communities responding to wetland area increases resulting from permafrost thaw. Populations of herbivores have responded to varying management practices and climate regimes, particularly changing snow conditions. While it is difficult to generalize and scale-up the site-specific changes in ecosystems, this very site-specificity, combined with projections of change, is of immediate relevance to local stakeholders who need to adapt to new opportunities and to respond to challenges. Furthermore, the relatively small area and its unique datasets are a microcosm of the complexity of Arctic landscapes in transition that remains to be documented.
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| 2. |
- Comont, David, et al.
(författare)
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Exploring latitudinal variation in UV radiation and climate : impacts on a model grass system
- 2011
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Ingår i: Abstracts of the 1st Annual Meeting of COST Action FA0906 UV4growth. - Szeged : Biological Research Center of the Hungarian Academy of Sciences. - 9789635086061 ; , s. 14-14
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Konferensbidrag (refereegranskat)abstract
- Perennial ryegrass (Lolium perenne) seedlings were grown at 14 European locations across a latitudinal gradient spanning 37 to 68°N. Seedlings planted in nutrient enriched vermiculite were grown outdoors over five weeks between the 29th June and the 3rd August 2010. At each location there were three treatments – open, filtered with cellulose acetate (UV transparent) and filtered with Mylar (UV opaque). Plants were regularly watered and outdoor climatic conditions were monitored at nearby meteorological stations. The aim of the experiment was to assess the significance of ambient UV radiation to L.perenne, both at each location and across the gradient in terms of aboveground biomass, tiller number, and the level of UV protective plant pigments. Material was further screened using metabolite fingerprinting (FT-IR spectroscopy) to assess local, regional and latitudinal variation in total plant chemistry. Data presented will explore and interpret the complex variations in growth and chemistry looking at local responses and the latitudinal gradient explored.
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| 3. |
- Comont, David, et al.
(författare)
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UV responses of Lolium perenne raised along a latitudinal gradient across Europe : a filtration study
- 2012
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Ingår i: Physiologia Plantarum. - : Wiley-Blackwell. - 0031-9317 .- 1399-3054. ; 145, s. 604-618
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Tidskriftsartikel (refereegranskat)abstract
- Lolium perenne (cv. AberDart) was grown at 14 locations along a latitudinal gradient across Europe (37–68◦N) to study the impact of ultraviolet radiation (UV) and climate on aboveground growth and foliar UV-B absorbing compounds. At each location, plants were grown outdoors for 5 weeks in a replicated UV-B filtration experiment consisting of open, UV-B transparent (cellulose diacetate) and UV-B opaque (polyester) environments. Fourier transform-infrared spectroscopy was used to compare plantmetabolite profiles in relation to treatment and location. UV radiation and climatic parameters were determined for each location from online sources and the data were assessed using a combination of ANOVA and multiple regression analyses. Most of the variation in growth between the locations was attributable to the combination of climatic parameters, with minimum temperature identified as an important growth constraint. However, no single environmental parameter could consistently account for the variability in plant growth. Concentrations of foliar UV-B absorbing compounds showed a positive trend with solar UV across the latitudinal gradient; however, this relationship was not consistent in all treatments. The most striking experimental outcome from this study was the effect of presence or absence of filtration frames onUV-absorbing compounds. Overall, the study demonstrates the value of an European approach in studying the impacts of natural UV across a large latitudinal gradient. We have shown the feasibility of coordinated UV filtration at multiple sites but have also highlighted the need for open controls and careful interpretation of plant responses.
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| 4. |
- Cornelissen, Johannes H C, et al.
(författare)
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Global negative vegetation feedback to climate warming responses of leaf litter decomposition rates in cold biomes
- 2007
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 10:7, s. 619-627
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Tidskriftsartikel (refereegranskat)abstract
- Whether climate change will turn cold biomes from large long-term carbon sinks into sources is hotly debated because of the great potential for ecosystem-mediated feedbacks to global climate. Critical are the direction, magnitude and generality of climate responses of plant litter decomposition. Here, we present the first quantitative analysis of the major climate-change-related drivers of litter decomposition rates in cold northern biomes worldwide.Leaf litters collected from the predominant species in 33 global change manipulation experiments in circum-arctic-alpine ecosystems were incubated simultaneously in two contrasting arctic life zones. We demonstrate that longer-term, large-scale changes to leaf litter decomposition will be driven primarily by both direct warming effects and concomitant shifts in plant growth form composition, with a much smaller role for changes in litter quality within species. Specifically, the ongoing warming-induced expansion of shrubs with recalcitrant leaf litter across cold biomes would constitute a negative feedback to global warming. Depending on the strength of other (previously reported) positive feedbacks of shrub expansion on soil carbon turnover, this may partly counteract direct warming enhancement of litter decomposition.
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| 5. |
- Moody, Sandra A., et al.
(författare)
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The direct effects of UV-B radiation on Betula pubescens litter decomposing at four European field sites
- 2001
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Ingår i: Plant Ecology. - 1573-5052. ; 154:1-2, s. 27-36
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Tidskriftsartikel (refereegranskat)abstract
- A co-ordinated series of field experiments were conducted to consider the effects of elevated UV-B radiation applied directly to decomposing plant litter. Betula pubescens was decomposed under ambient and elevated UV-B (simulating a 15% ozone depletion) using outdoor irradiation facilities at Adventdalen, Norway (78° N), Abisko, Sweden (68° N), Amsterdam, The Netherlands (52° N,) and Patras, Greece (38° N). There was no significant effect of treatment on mass loss for samples collected after 2, 12 and 14 months decomposition at Amsterdam, or after 4 months decomposition at Adventdalen. Significant reductions in the mass loss of litter decomposing under elevated UV-B compared to ambient were found at the other 2 sites. The only effect of treatment on litter chemistry during decomposition was a significant reduction in the N concentration of material at Abisko and a significant increase in C:N at Patras for litter decomposing under elevated UV-B. Significant differences were found in the structure of the fungal community decomposing litter in Sweden, the only site to be tested. These data, and the few published studies of the response of decomposition to UV-B incident on litter suggest that, in the ecosystems and climates that have been studied, such direct effects are typically confined to the initial stages of decomposition, and are rather small in magnitude.
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| 6. |
- Rozema, Jelte, et al.
(författare)
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Stratospheric ozone depletion: High arctic tundra plant growth on Svalbard is not affected by enhanced UV-B after 7 years of UV-B supplementation in the field
- 2006
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Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1573-5052 .- 1385-0237. ; 182:1-2, s. 121-135
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Tidskriftsartikel (refereegranskat)abstract
- The response of tundra plants to enhanced UV-B radiation simulating 15 and 30% ozone depletion was studied at two high arctic sites (Isdammen and Adventdalen, 78 degrees N, Svalbard).The set-up of the UV-B supplementation systems is described, consisting of large and small UV lamp arrays, installed in 1996 and 2002. After 7 years of exposure to enhanced UV-B radiation, plant cover, density, morphological (leaf fresh and dry weight, leaf thickness, leaf area, reproductive and ecophysiological parameters leaf UV-B absorbance, leaf phenolic content, leaf water content) were not affected by enhanced UV-B radiation. DNA damage in the leaves was not increased with enhanced UV-B in Salix polaris and Cassiope tetragona. DNA damage in Salix polaris leaves was higher than in leaves of C. tetragona. The length of male gametophyte moss plants of Polytrichum hyperboreum was reduced with elevated UV-B as well as the number of Pedicularis hirsuta plants per plot, but the inflorescence length of Bistorta vivipara was not significantly affected. We discuss the possible causes of tolerance of tundra plants to UV-B (absence of response to enhanced UV-B) in terms of methodology (supplementation versus exclusion), ecophysiological adaptations to UV-B and the biogeographical history of polar plants.
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| 7. |
- Solheim, Bjørn, et al.
(författare)
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The nitrogen fixation potential of arctic cryptogram species is influenced by enhanced UV-B radiation
- 2002
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 1432-1939 .- 0029-8549. ; 133:1, s. 90-93
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Tidskriftsartikel (refereegranskat)abstract
- Abstract. Effects of enhanced UV-B (representing a 15% ozone depletion) on cyanobacterial nitrogen fixation were measured at a high arctic site (Adventdalen, 79°N, Svalbard) and a subarctic site (Abisko, 68°N, Sweden). Nitrogen fixation potential (acetylene reduction) by cyanobacteria associated with the moss Sanionia uncinata in vegetation exposed to experimentally enhanced levels of UV-B for 3 and 4 years in the high arctic in Adventdalen was reduced by 50% compared to controls after 3 years. No reduction in nitrogen fixation potential was observed in cyanobacteria associated with the moss Hylocomium splendens when previously exposed to enhanced UV-B in Abisko for a 7-year period. However, in the same experiment a 50% increase in summer precipitation stimulated nitrogen fixation potential by up to 6-fold above the natural precipitation treatments both in cyanobacteria associated with vegetation exposed to natural and enhanced UV-B radiation. In contrast to the lack of UV effect on moss-associated nitrogen fixation at the subarctic site, nitrogen fixation potential by the dominant lichen species Peltigera aphthosa was reduced by 50% when measured after 8 years exposure to elevated UV-B treatment. Evidence from these studies highlights the importance of UV-B radiation for cyanobacterial nitrogen fixation in the Arctic and future impact on nitrogen availability in such plant communities.
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