| 1. |
- Arft, M, et al.
(author)
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Responses of tundra plants to experimental warming : Meta-analysis of the international tundra experiment
- 1999
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In: Ecological Monographs. - 0012-9615 .- 1557-7015. ; 69:4, s. 491-511
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Journal article (peer-reviewed)abstract
- The International Tundra Experiment (ITEX) is a collaborative, multisite experiment using a common temperature manipulation to examine variability in species response across climatic and geographic gradients of tundra ecosystems. ITEX was designed specifically to examine variability in arctic and alpine species response to increased temperature. We compiled from one to four years of experimental data from 13 different ITEX sites and used meta-analysis to analyze responses of plant phenology, growth, and reproduction to experimental warming. Results indicate that key phenological events such as leaf bud burst and flowering occurred earlier in warmed plots throughout the study period; however, there was little impact on growth cessation at the end of the season. Quantitative measures of vegetative growth were greatest in warmed plots in the early years of the experiment, whereas reproductive effort and success increased in later years. A shift away from vegetative growth and toward reproductive effort and success in the fourth treatment year suggests a shift from the initial response to a secondary response. The change in vegetative response may be due to depletion of stored plant reserves, whereas the lag in reproductive response may be due to the formation of flower buds one to several seasons prior to flowering. Both vegetative and reproductive responses varied among life-forms; herbaceous forms had stronger and more consistent vegetative growth responses than did woody forms. The greater responsiveness of the herbaceous forms may be attributed to their more flexible morphology and to their relatively greater proportion of stored plant reserves. Finally, warmer, low arctic sites produced the strongest growth responses, but colder sites produced a greater reproductive response. Greater resource investment in vegetative growth may be a conservative strategy in the Low Arctic, where there is more competition for light, nutrients, or water, and there may be little opportunity for successful germination or seedling development. In contrast, in the High Arctic, heavy investment in producing seed under a higher temperature scenario may provide an opportunity for species to colonize patches of unvegetated ground. The observed differential response to warming suggests that the primary forces driving the response vary across climatic zones, functional groups, and through time.
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| 2. |
- Jonsdottir, Ingibjörg S., et al.
(author)
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Large scale differentiation and population dynamics in tundra plants and vegetation
- 1999
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In: Ambio: a Journal of Human Environment. - 0044-7447. ; 28:3, s. 230-238
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Journal article (peer-reviewed)abstract
- The inclusion of the botanical projects in the Swedish-Russian Tundra Ecology -94 expedition provided new information on the ecology of tundra plants. The vegetation patterns on different scales were documented, and interpreted as the result of a complex interaction with environmental factors. The distribution of fruticose lichens was studied, and it was shown that these lichens rely on different modes of asexual reproduction for their dispersal. Extreme old genet ages were demonstrated for species of Carex and there were similar strong indications for lichens. Populations of Carex were genetically diverse in spite of old ages and often low levels of flowering. Large differences between sites in flowering and vegetative ramet production (vegetative reproduction) in Carex reflected a asynchronous between-year population fluctuation, which was related to cyclic lemming populations and climate. Important gaps in our knowledge of the ecology of tundra plants are pointed out, some of which will hopefully be resolved during the tundra expedition, Tundra Northwest 1999.
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| 3. |
- Jonsdottir, I.S., et al.
(author)
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Measuring growth rates in bryophytes and lichens
- 1997
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In: Summary document of 8th Annual ITEX Workshop. Royal Holloway Institute for Environmental Research, 19-22 April, 1997.
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Conference paper (other academic/artistic)
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| 4. |
- Jonsson, B O, et al.
(author)
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Clonal diversity and allozyme variation in populations of the arctic sedge Carex bigelowii (Cyperaceae).
- 1996
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In: Journal of Ecology. - 1365-2745. ; 84:3, s. 449-459
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Journal article (peer-reviewed)abstract
- 1 A study of allozyme variation in vegetatively propagating populations of the rhizomatous sedge Carex bigelowii, revealed high levels of clonal diversity (genet diversity) within populations. The structure of allelic variation within the populations suggests that sexual reproduction has played a significant role in these C. bigelowii populations, despite present lack of seedling recruitment. The study was carried out in moss-heath communities on Icelandic lava-fields. Two adjacent populations were studied at one site, while a third population was studied at a second site, 35 km away from the first two populations. 2 The number of genets detected in each population, among 85-88 analysed ramets, ranged from 41 to 55 (minimum estimate). Samples were taken every 4 m along transects in the populations. Ramets with the same allozyme genotype were often spatially aggregated. No seedlings have been observed in the populations during five years of demographic studies. 3 All the populations studied showed a diploid expression of allozymes and high levels of allelic variation, with on average 491.77 alleles per locus (A) and an allelic diversity (HS) of 0.167. Similar levels of within-population variability are found in many wind-pollinated and outcrossing plant species. 4 The difference between observed and expected heterozygosity was small in all populations, suggesting high levels of outbreeding. 5 Comparisons with other Carex taxa show that the levels of and structuring of allozyme diversity in C. bigelowii is similar to that in other outbreeding species (usually rhizomatous), and much higher than in inbreeding species (which are usually caespitose). 6 Only 5the total allelic diversity was explained by differences between the two study sites (G ST = 0.055), suggesting extensive recent or historic gene-flow.
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| 5. |
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| 6. |
- Magnadóttir, B, et al.
(author)
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Optimisation of ELISA used to measure total serum IgM and antibody activity in different groups of cod.
- 1998
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In: in Barnes, A.C., Davidson, G. A., Hiney, M. P., McIntosh, D. (eds.) Fish Disease Research. - : Fisheries Research Services, Aberdeen. ; , s. 105-
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Book chapter (other academic/artistic)
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