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  • 1
    Electronic Resource
    Electronic Resource
    Relative susceptibility of Salix clones to chrysomelid beetles: evidence from the Stott willow collection at Ness (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Forest pathology 28 (1998), S. 0 
    Details
    ISSN: 1439-0329
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Willow species and hybrids growing in the Stott willow collection at Ness, UK, differed markedly in their susceptibility to leaf damage by insects, predominantly chrysomelid beetles, with the rank order of susceptibility remaining relatively constant over 2 years. Some species displayed a wide range of variation in susceptibility amongst clones; others very little. The range of susceptibilities of hybrids tended to mirror those of the parent species, with the hybrid usually sustaining leaf damage levels intermediate between those of the parents. Leaf damage in most species was higher on the lower leaf surface up to mid-season, beyond which leaf perforation damage became prevalent. Damage levels did not appear related to leaf toughness. Apparent levels of leaf damage were lower in October versus July/August samples across nearly all species. Heavy leaf damage in one year did not appear to induce the production of leaves that were more resistant to insect attack in the following year.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1439-0329.1998.tb01182.x
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  • 2
    Electronic Resource
    Electronic Resource
    Climatic severity and the response to temperature elevation of Arctic aphids (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Global change biology 1 (1995), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: 〈list xml:id="l1" style="custom"〉1 Theory suggests that any given rise in temperature resulting from climate change will have its greatest effect on high Arctic ecosystems where growing seasons are short and temperatures low.2 A small temperature rise, similar to that predicted for the middle of the next century, has profound effects on a population of the high Arctic, Dryas-feeding aphid Acyrthosiphon svalbardicum on Spitsbergen (Strathdee et al. 1993a).3 Here comparative experiments on a closely related Dryas-feeding species, A. brevicorne, at two contrasting sub-Arctic sites are described. Together with the results from Spitsbergen these sites represent two colder sites (high Arctic and upland sub-Arctic) and one warmer site (lowland sub-Arctic).4 Differential responses in aphid population density and overwintering egg production to temperature elevation support the hypothesis that the ecological effects are greatest at sites with the most severe climates; however, there is no similar gradient in advancement of host plant phenology with warming.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2486.1995.tb00003.x
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  • 3
    Electronic Resource
    Electronic Resource
    Hydrology, water availability and tundra ecosystem function in a changing climate: the need for a closer integration of ideas? (1999)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 5 (1999), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Hydrologists and ecologists studying tundra ecosystems have worked largely independently, with little cross-fertilization between disciplines. Their disciplines are, however, inextricably linked by a need to understand the dynamics and significance of the common substance water, in its liquid, solid and gaseous state within tundra environments. The impacts of predicted long-term changes in climate have particularly important consequences for the functioning of tundra systems and there is a pressing need to initiate studies that integrate hydrological and ecological methodologies and concepts. Our paper attempts to summarize existing information on the role of water within tundra ecosystems, to emphasize the fundamental links between the biotic and the physico/chemical environments and to suggest how a closer integration of ideas might be achieved. Given the breadth of the subject matter the paper is intended to be illustrative rather than comprehensive. The paper examines the physical impacts of water in its various states on the tundra environment, emphasizing in particular the causes of spatial variation in water availability to living organisms. The significance of water is discussed for a range of organism groups, including plants, invertebrates and microorganisms and its pivotal role in ecosystem function and disturbance stressed. The need to develop integrated hydological/ecological models for tundra systems on different spatial scales is emphasized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.1999.00229.x
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of photoperiod and raised winter temperatures on egg development and timing of oviposition in the willow psyllid Cacopsylla moscovita (1996)
    Springer
    Entomologia experimentalis et applicata 78 (1996), S. 143-147 
    Details
    ISSN: 1570-7458
    Keywords: diapause ; insect-plant interactions ; phenology ; Salix repens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nymphal development of Cacopsylla moscovita (And.) (Homoptera: Psylloidea) takes place only on female catkins of Salix repens L. and close phenological synchrony is crucial because development times of catkins and nymphs are similar. Eggs are laid on catkins as soon as they develop and close synchrony between oviposition and budburst maximizes time available for nymphal development. Sampling adult C. moscovita in the field revealed little synchrony between egg development and budburst, with over 60% of females containing mature eggs four weeks before catkins first appeared. In the laboratory, egg development was influenced by both temperature and photoperiod. At 10°C, egg development occurred approximately one month earlier than at 5°C and two weeks earlier than in the field. Adult survival in the laboratory was substantially reduced at increased temperature, with only 20% of adults surviving longer than two weeks at 10°C, compared with over 95% at 5°C. Body condition (weight corrected for size) of males and females decreased significantly in the field over winter. However, body condition of females levelled off before budburst, coincident with egg development implying that females had resumed feeding. We discuss our results in relation to regulation of phenological synchrony between oviposition and catkin appearance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00187510
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  • 5
    Electronic Resource
    Electronic Resource
    Simulated climate change: the interaction between vegetation type and microhabitat temperatures at Ny Ålesund, Svalbard (1993)
    Springer
    Polar biology 13 (1993), S. 67-70 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Small polythene tents were used to simulate the effects of climate warming on two contrasting vegetation types (polar semi-desert and tundra heath) at Ny Ålesund, Spitzbergen, Svalbard. Temperature microclimates are compared within and without tents and between sites with contrasting vegetation types. Summer temperatures were increased by about 5°C in the vegetation mat and by about 2°C in the soil at 3 cm depth. Cumulative day degrees above zero were enhanced by around 35% in the vegetation and by around 9% in the soil. Soil temperatures were greatly influenced by the nature of the overlying vegetation, which at one of the sites appeared to act as an efficient thermal insulator, preventing heat conductance into the soil from above and enhancing thermal contact between the upper soil layer and the cooling permafrost below. The significance of the observed temperature differences for the ecology of the plants and invertebrates is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236585
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  • 6
    Electronic Resource
    Electronic Resource
    Feeding studies on Onychiurus arcticus (Tullberg) (Collembola: Onychiuridae) on West Spitsbergen (1994)
    Springer
    Polar biology 14 (1994), S. 17-19 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The feeding biology of the arctic collembolan Onychiurus arcticus (Tullberg) is described from West Spitsbergen, based on a combination of gut content analyses for field collected and microcosm-living animals, together with laboratory feeding trials. There was wide variation in the food items consumed by individual animals, reflecting the wide choice available in the environment. Most animals fed predominantly on living and dead bryophytes, detritus and to a lesser extent algal cells. Laboratory trials showed that O. arcticus feeds as a herbivore on a range of bryophyte species. The presence of dense aggregations below bird cliffs and elsewhere may reflect the distribution of particularly favourable microenvironments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00240267
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  • 7
    Electronic Resource
    Electronic Resource
    Energy flow and organic matter decomposition in an abandoned beaver pond ecosystem (1975)
    Springer
    Oecologia 21 (1975), S. 131-139 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A beaver pond can be considered an open ecosystem with a number of energy inputs and outputs. The net difference between input and output represents the accumulation of energy within the system. During 1973 input-output parameters were measured independently for one spring fed pond (surface area 736 m2) in the Kananaskis Valley, Alberta, Canada. The yearly energy budged indicated that allochthonous energy inputs into the pond were much greater than autochthonous inputs. Of the total yearly energy input 18% was exported, 26% was respired and 56% accumulated in the sediments. This percentage utilization for respiration was low when compared with similar data from the literature for live aquatic ecosystems elsewhere. However the actual annual mean sediment respiration rate of 8.4 ml m-1 hr-1 compared favourably with the figure of 6.1 ml m-2 hr-1 predicted from Hargrave's 1969 respiration equation for benthic communities. This situation suggests that the allochthonous input, while dominant, is highly refractive and rapidly becomes locked up in the sediments. The high photosynthesis-respiration ratio of 0.81 together with the results of earlier litter bag experiments (Hodkinson, 1975) support this conclusion. Thus the beaver pond is a highly accretive heterotrophic ecosystem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00345556
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of temperature elevation on a field population of Acyrthosiphon svalbardicum (Hemiptera: Aphididae) on Spitsbergen (1993)
    Springer
    Oecologia 96 (1993), S. 457-465 
    Details
    ISSN: 1432-1939
    Keywords: Aphid ; Arctic ; Climate change ; Life-cycle ; Thermal budget
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A manipulation experiment was carried out on a field population of the aphid Acyrthosiphon svalbardicum near Ny Ålesund, on the high arctic island of Spitsbergen, using cloches to raise temperature. An average rise in temperature of 2.8 deg. C over the summer season markedly advanced the phenology of both the host plant Dryas octopetala and the aphid. Advanced aphid phenology, with concomitant increases in reproductive output and survival, and successful completion of the life-cycle led to an eleven-fold increase in the number of overwintering eggs. Thermal budget requirements in day degrees above 0°C were calculated for key life-cycle stages of the aphid. Temperature data from Ny Ålesund over the past 23 years were used to calculate thermal budgets for the field site over the same period and these were compared with the requirements of the aphid. Each estimated thermal budget was then adjusted to simulate the effect of a +2, +4, and −2deg. C change in average temperature on aphid performance. This retrospective analysis (i) confirms that the life-cycle of A. svalbardicum is well suited to exploit higher summer temperatures, (ii) indicates that the annual success of local populations are sensitive to small changes in temperature and (iii) suggests that the aphid is living at the limits of its thermal range at Ny Ålesund based on its summer thermal budget requirements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00320502
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of experimental temperature elevation on high-arctic soil microarthropod populations (1996)
    Springer
    Polar biology 16 (1996), S. 147-153 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  An experiment was conducted to measure the effects of summer warming on the total population densities of soil-dwelling microarthropods in the high Arctic and to compare these results with those from natural between-year and between-site variations. Small polythene tents were used to elevate summer temperatures over 3 years on polar semi-desert and tundra heath in West Spitsbergen, Svalbard, Norway. Soil cores were taken at regular intervals from tented and untented (control) plots and heat extracted for mites (Acarina: Oribatida) and springtails (Collembola). Species present were similar at both sites, but at the start of the experiment total springtail populations were greater at the polar semi-desert whilst oribatid mite densities were equal at both sites. No significant effect of temperature elevation on oribatid mite populations emerged, even after 3 years. By contrast, springtail numbers were significantly lower on tented versus control plots at the polar semi-desert at the end of year 3, but not so at the tundra heath. Collembola numbers declined at both sites during the warm dry midsummers of 1992/1993 and this was most marked at the better drained polar semi-desert site. Over the equivalent period total oribatid mite populations, while relatively more stable, increased significantly at the polar semi-desert as a result of an increase in the number of juveniles. Results are interpreted in the context of the ecophysiological adaptations of oribatid mites and springtails to soil temperature and moisture. The resulting survival characteristics are considered in relation to the temperature and moisture characteristics of the two sites. The experiment demonstrated that year to year variation in climate, interacting with physical differences between sites, produced an equal or greater effect on microarthropod numbers at any one site than the 8–10% increase in “heat availability” (day degrees above zero) resulting from the summer tent treatment. The limitations of the use of tents to elevate soil temperatures are discussed. Comparisons are made with microarthropod population data from other polar and alpine sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050039
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  • 10
    Electronic Resource
    Electronic Resource
    Effects of experimental temperature elevation on high-arctic soil microarthropod populations (1996)
    Springer
    Polar biology 16 (1996), S. 147-153 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An experiment was conducted to measure the effects of summer warming on the total population densities of soil-dwelling microarthropods in the high Arctic and to compare these results with those from natural between-year and between-site variations. Small polythene tents were used to elevate summer temperatures over 3 years on polar semi-desert and tundra heath in West Spitsbergen, Svalbard, Norway. Soil cores were taken at regular intervals from tented and untented (control) plots and heat extracted for mites (Acarina: Oribatida) and springtails (Collembola). Species present were similar at both sites, but at the start of the experiment total springtail populations were greater at the polar semi-desert whilst oribatid mite densities were equal at both sites. No significant effect of temperature elevation on oribatid mite populations emerged, even after 3 years. By contrast, springtail numbers were significantly lower on tented versus control plots at the polar semi-desert at the end of year 3, but not so at the tundra heath. Collembola numbers declined at both sites during the warm dry midsummers of 1992/1993 and this was most marked at the better drained polar semi-desert site. Over the equivalent period total oribatid mite populations, while relatively more stable, increased significantly at the polar semi-desert as a result of an increase in the number of juveniles. Results are interpreted in the context of the ecophysiological adaptations of oribatid mites and springtails to soil temperature and moisture. The resulting survival characteristics are considered in relation to the temperature and moisture characteristics of the two sites. The experiment demonstrated that year to year variation in climate, interacting with physical differences between sites, produced an equal or greater effect on microarthropod numbers at any one site than the 8–10% increase in “heat availability” (day degrees above zero) resulting from the summer tent treatment. The limitations of the use of tents to elevate soil temperatures are discussed. Comparisons are made with microarthropod population data from other polar and alpine sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02390435
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