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  • 1
    Electronic Resource
    Electronic Resource
    Contrasting strategies for UV-B screening in sub-Arctic dwarf shrubs (2003)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 26 (2003), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The content and distribution of UV-absorbing phenolic compounds was investigated in leaves of three species of Vaccinium co-existing at a site in north Sweden. Vaccinium myrtillus L., Vaccinium vitis-idaea L., and Vaccinium uliginosum L. exhibit markedly different strategies, in terms of localization and content of leaf phenolics and in their responses to UV-B enhancement. Plants were exposed to either ambient radiation or to enhancement of UV-B corresponding to 15% (clear sky) depletion of stratospheric ozone for approximately 10 years prior to commencement of this study. Vaccinium myrtillus contained the highest concentration of methanol-extractable UV-B-absorbing compounds, which was elevated in plants exposed to enhanced UV-B. Fluorescence and confocal laser scanning microscopy showed that these compounds were distributed throughout the leaf, and were particularly concentrated in chlorophyll-containing cells. In V. vitis-idaea, most phenolic compounds were cell wall-bound and concentrated in the walls of the epidermis; this pool increased in response to UV-B enhancement. It is suggested that these two plants represent extreme forms of two divergent strategies for UV-B screening, the different responses possibly being related to leaf longevity in the two species. The response of V. uliginosum was intermediate between the other two, with high concentrations of cell wall-bound phenolics in the epidermis but with this pool decreasing, and the methanol-soluble pool tending to increase, after exposure to enhanced UV-B. One explanation for this response is that this plant is deciduous, like V. myrtillus, but has leaves that are structurally similar to those of V. vitis-idaea.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2003.01029.x
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  • 2
    Electronic Resource
    Electronic Resource
    Responses of bracken to increased temperature and nitrogen availability (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Global change biology 2 (1996), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: In 1993 a project was set up at Upper Teesdale to investigate some of the effects of predicted increased temperatures and increased nutrient availability resulting from increased litter decomposition rates, and atmospheric deposition of nitrogen, on the interaction between bracken and heather, two species which cover large areas globally. 32 2 × 2 m plots were laid out on a hillside on, and just below, the interface between the two species. Half of the plots were placed on pure bracken, and the other half on the boundary. Within each vegetation type half of the plots were covered with open-topped polythene tents to simulate climate warming, while the other plots remained open. The second treatment consisted of additional fertilizer at 50 kg N ha−1 y−1 simulating increased decomposition rates at higher temperatures and increased atmospheric nitrogen deposition. The two treatments and their controls were combined in a 2 × 2 factorial design, with two replicates in each of two blocks.Results obtained in the first two summers indicated that fronds emerged earlier in spring and senesced later in autumn inside the tents, effectively lengthening the growing season. Fronds were taller when growing in warmer conditions, and carried more pinnae. In addition, the frond density was higher inside the tents, and together these effects contributed to greatly enhanced vigour of bracken in some of the conditions predicted by General Circulation Models. It seems likely that bracken will be more competitive, and have the potential to further encroach into heather dominated areas under these conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2486.1996.tb00049.x
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of experimentally imposed climate scenarios on flowering phenology and flower production of subarctic bog species (2004)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 10 (2004), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Climate scenarios for high-latitude areas predict not only increased summer temperatures, but also larger variation in snowfall and winter temperatures. By using open-top chambers, we experimentally manipulated both summer temperatures and winter and spring snow accumulations and temperatures independently in a blanket bog in subarctic Sweden, yielding six climate scenarios. We studied the effects of these scenarios on flowering phenology and flower production of Andromeda polifolia (woody evergreen) and Rubus chamaemorus (perennial herb) during 2 years. The second year of our study (2002) was characterized by unusually high spring and early summer temperatures.Our winter manipulations led to consistent increases in winter snow cover. As a result, average and minimum air and soil temperatures in the high snow cover treatments were higher than in the winter ambient treatments, whereas temperature fluctuations were smaller. Spring warming resulted in higher average, minimum, and maximum soil temperatures. Summer warming led to higher air and soil temperatures in mid-summer (June–July), but not in late summer (August–September).The unusually high temperatures in 2002 advanced the median flowering date by 2 weeks for both species in all treatments. Superimposed on this effect, we found that for both Andromeda and Rubus, all our climate treatments (except summer warming for Rubus) advanced flowering by 1–4 days. The total flower production of both species showed a more or less similar response: flower production in the warm year 2002 exceeded that in 2001 by far. However, in both species flower production was only stimulated by the spring-warming treatments.Our results show that the reproductive ecology of both species is very responsive to climate change but this response is very dependent on specific climate events, especially those that occur in winter and spring. This suggests that high-latitude climate change experiments should focus more on winter and spring events than has been the case so far.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2486.2004.00815.x
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  • 4
    Electronic Resource
    Electronic Resource
    Long-term ecosystem level experiments at Toolik Lake, Alaska, and at Abisko, Northern Sweden: generalizations and differences in ecosystem and plant type responses to global change (2004)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 10 (2004), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Long-term ecosystem-level experiments, in which the environment is manipulated in a controlled manner, are important tools to predict the responses of ecosystem functioning and composition to future global change. We present the results of a meta-analysis performed on the results of long-term ecosystem-level experiments near Toolik Lake, Alaska, and Abisko, Sweden. We quantified aboveground biomass responses of different arctic and subarctic ecosystems to experimental fertilization, warming and shading. We not only analysed the general patterns but also the differences in responsiveness between sites and regions. Aboveground plant biomass showed a broad similarity of responses in both locations, and also showed some important differences. In both locations, aboveground plant biomass, particularly the biomass of deciduous and graminoid plants, responded most strongly to nutrient addition. The biomass of mosses and lichens decreased in both locations as the biomass of vascular plants increased. An important difference between the two regions was the smaller positive aboveground biomass response of deciduous shrubs in Abisko as compared with Toolik Lake. Whereas in Toolik Lake Betula nana increased its dominance and replaced many of the other plant types, in Abisko all vascular plant types increased in abundance without major shifts in relative abundance. The differences between the responses of the dominant vegetation types of the Toolik Lake region, i.e. tussock tundra systems, and that of the Abisko region, i.e. heath systems, may have important implications for ecosystem development under expected patterns of global change. However, there were also large site-specific differences within each region. Several potential mechanistic explanations for the differences between sites and regions are discussed. The response patterns show the need for analyses of joint data sets from many regions and sites, in order to uncover common responses to changes in climate across large arctic regions from regional or local responses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2486.2003.00719.x
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  • 5
    Electronic Resource
    Electronic Resource
    Surface morphology, leaf and cuticle thickness of four dwarf shrubs from a sub-Arctic heath following long-term exposure to enhanced levels of UV-B (2003)
    Oxford, UK : Munksgaard International Publishers
    Physiologia plantarum 117 (2003), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In 1991 a field experiment was established in subarctic heathland at Abisko (68°35′N, 18°82′E), northern Sweden, to investigate the effects of enhanced UV-B (280–315 nm) radiation, simulating 15% ozone depletion, on plants in their natural environment. Leaves of the four dominant dwarf shrubs, the deciduous Vaccinium myrtillus L. and V. uliginosum L. and the evergreen V. vitis-idaea L. and Empetrum hermaphroditum Hagerup were examined after 7 years of UV-B treatment. SEM and ESEM were used to visualize surface features and to determine trichome density. Multiphoton laser scanning microscopy showed that UV-B absorbing compounds were localized in the trichomes of all species. Trichomes varied in size, number and distribution between the species. Enhanced UV-B reduced adaxial trichome density significantly (by approximately 25%) in only one species, V. uliginosum. This effect could be of importance for the UV-B absorbing potential of the adaxial epidermis of V. uliginosum. Epicuticular wax structures were found only on the abaxial surface of V. uliginosum and were unaffected by enhanced UV-B. The cuticular surfaces of all other species were smooth and featureless. Leaf thickness, adaxial and abaxial cuticle thickness varied between the species although there was no apparent effect of enhanced UV-B. It is concluded that long-term enhancement of UV-B has an effect on adaxial trichome density in V. uliginosum, but that there is no general effect on leaf morphology of the other species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2003.00006.x
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  • 6
    Electronic Resource
    Electronic Resource
    Primary productivity and the prospects for biofuels in the United Kingdom (1983)
    Springer
    International journal of biometeorology 27 (1983), S. 197-218 
    Details
    ISSN: 1432-1254
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract Estimates of land use and plant productivity are combined to predict total annual primary production in the UK as 252 million tonnes dry matter (10.5 t ha−1yr−1). Annual above ground production is predicted to be 165 Mt (6.9 t ha−1yr−1). Within these totals, intensive agriculture contributes 60%, productive woodland 8%, natural vegetation 26% and urban vegetation 5%. However, only 25% of total plant production is cropped by man and animals, and most of this is subsequently discarded as wastes and residues. 2112 PJ of organic material is available for fuel without reducing food or fibre production, but since much of this could not be economically collected, 859 PJ is calculated as a more realistic biofuel contribution by the year 2000. After deducting 50% conversion losses, this could save P1 billion (1979 prices) in oil imports. Short rotation energy plantations, forest residues, coppice woodlands, animal and crop wastes, industrial and domestic wastes, catch crops, natural vegetation and urban vegetation all have immediate or short term potential as biofuel sources. Sensitive planning is required to reduce environmental impact, but in some cases more diverse wildlife habitats may be created.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02184236
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  • 7
    Electronic Resource
    Electronic Resource
    Environmental constraints on the growth, photosynthesis and reproductive development of Dryas octopetala at a high Arctic polar semi-desert, Svalbard (1995)
    Springer
    Oecologia 102 (1995), S. 478-489 
    Details
    ISSN: 1432-1939
    Keywords: Arctic ; Climate change ; Dryas octopetala ; L. ssp. octopetala ; Clonal growth ; Reproductive output
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Opportunities exist in high Arctic polar semidesert communities for colonisation of unvegetated ground by long-lived clonal plants such as Dryas octopetala. This can be achieved by lateral spread of vegetative ramets, or by sexual reproduction and seedling recruitment. The objectives of this study were (1) to determine whether these two means of proliferation show differential sensitivity to contrasting components of the abiotic environment (temperature, soil nutrient and water availability) and (2) to evaluate the potential for D. octopetala to respond to climate change by an increase in cover and biomass in polar semi-desert communities. Factorial environmental manipulations of growing season temperature, soil nutrient and water status were conducted over 3 years at a polar semi-desert community in Svalbard, Norway (78°56.12′N, 11°50.4′E) and both clonal and sexual reproductive performance, together with instantaneous net photosynthesis (Pn), were recorded during the third season (1993). D. octopetala capitalised rapidly on an amelioration in the availability of inorganic nutrients (N, P and K) by an expansion in leaf area and biomass supported by increased Pn per unit leaf weight, and by apparent luxury uptake of nutrients (particularly P). Several facets of sexual reproductive development and seed viability were markedly improved by elevated temperatures or soil nutrient availability. Thus although D. octopetala is a long-lived clonal plant, with many traits characteristic of stress resistance syndrome, it showed considerable phenotypic plasticity in response to environmental manipulations. The results support the hypothesis that clonal growth confers survival potential during unfavourable years, together with the ability to capitalise on nutrient flushes and recycle nutrients internally. Continued investment in sexual reproduction ensures that seed setting is successful during favourable years, even if these occur infrequently. Cimate warming in the high Arctic could thus result in changes in the cover, biomass and the relative significance of clonal versus sexual proliferation of D. octopetala (and thus the genetic diversity of the population) but the long-term responses will probably be constrained by lack of available nutrients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00341360
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  • 8
    Electronic Resource
    Electronic Resource
    Leaf carbon isotope discrimination and vegetative responses of Dryas octopetala to temperature and water manipulations in a High Arctic polar semi-desert, Svalbard (1993)
    Springer
    Oecologia 95 (1993), S. 463-469 
    Details
    ISSN: 1432-1939
    Keywords: Arctic physiological ecology ; Carbon isotope discrimination ; Climate change ; Water-use efficiency ; Polar semi-desert
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Integrative ecophysiological and vegetative responses of Dryas octopetala were measured in response to field perturbations of temperature, precipitation and their interactions in a polar semi-desert in Svalbard, Norway (79°N, 12°E). Leaf carbon isotope discrimination (Δ), total leaf nitrogen concentration and leaf development were determined for photosynthetic leaves collected during the last week of August 1991, after one season of manipulations. Individual leaf weight and the total mass of leaf tissue were significantly lower when water was added, irrespective of temperature regime. Leaf carbon isotope discrimination and estimated long-term c i/c avalues (the ratio of CO2 concentration in leaf intercellular spaces to that in the atmosphere) were significantly higher under all three field manipulation treatments, and Δ was significantly reduced when Dryas was grown under drought conditions in a related greenhouse study. Nitrogen concentrations of plants from the field experiment were significantly lower under warmed conditions regardless of water regime. Our results indicate that changes in environmental conditions in high arctic settings will result in alterations of Dryas leaf gas exchange, as expressed by increases in carbon isotope discrimination, which may be accompanied by shifts in leaf nitrogen content and leaf biomass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317428
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  • 9
    Electronic Resource
    Electronic Resource
    Fungal hyphal length in litter ofDryas octopetala in a high-Arctic polar semi-desert, Svalbard (1996)
    Springer
    Polar biology 16 (1996), S. 71-74 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mean fungal hyphal length was estimated in the surface horizons of a lithosol underDryas octopetala in a polar semi-desert ecosystem at Ny-Ålesund, Svalbard (78°56′N, 11°50′E). This site is the most northerly from which such values have been collected and provides the only record from polar semi-desert sites in the Eurasian high Arctic. Although mean (+SE) fungal hyphal length was the lowest recorded in surface horizons of northern tundra (23±1 mg−1), it was of he same order as results from a Canadian high-Arctic soil and Antarctic soils of high pH and low moisture and organic matter content, with little vegetation cover.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01876831
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  • 10
    Electronic Resource
    Electronic Resource
    Fungal hyphal length in litter ofDryas octopetala in a high-Arctic polar semi-desert, Svalbard (1996)
    Springer
    Polar biology 16 (1996), S. 71-74 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mean fungal hyphal length was estimated in the surface horizons of a lithosol underDryas octopetala in a polar semi-desert ecosystem at Ny-Ålesund, Svalbard (78°56′N, 11°50′E). This site is the most northerly from which such values have been collected and provides the only record from polar semi-desert sites in the Eurasian high Arctic. Although mean (± SE) fungal hyphal length was the lowest recorded in surface horizons of northern tundra (23±1 mg−1), it was of the same order as results from a Canadian high-Arctic soil and Antarctic soils of high pH and low moisture and organic matter content, with little vegetation cover.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02388737
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