| 1. |
- Alatalo, Juha, 1966-, et al.
(författare)
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Effect of Altitude on the Sex-Ratio in Populations of Silene Acaulis (Caryophyllaceae) : Effect of Altitude on the Sex-Ratio in Populations of Silene Acaulis (Caryophyllaceae)
- 1995
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Ingår i: Nordic Journal of Botany. - 0107-055X .- 1756-1051. ; 15:3, s. 251-256
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Tidskriftsartikel (refereegranskat)abstract
- Predicted increase of female frequencies in gynodioecious Silene acaulis was tested along an altitude gradient in northern Sweden. Average female frequencies for the four sites increased with altitude from 42% to 59% within a short geographical distance. This follows the outcrossing hypothesis, that female frequencies should be positively correlated with selfing rates of hermaphrodites in populations. More adverse environmental conditions should favour gynodioecy in areas where reproduction to a greater part relies on vegetative reproduction or selfing. Further, a significant difference in corolla width was found between females and the larger hermaphrodites, but not between sites. Cushion size and the number of flowers per cushion decreased with altitude.
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| 2. |
- Alatalo, Juha, 1966-
(författare)
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Gender lability in trioecious Silene acaulis (Caryophyllaceae)
- 1997
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Ingår i: Nordic Journal of Botany. - : Wiley. - 0107-055X .- 1756-1051. ; 17:2, s. 181-183
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Tidskriftsartikel (refereegranskat)abstract
- Gender expression of individual cushions of Silene acaulis was shown to vary between years. Fifteen of thirty-nine (= 38%) cushions monitored changed gender expression between 1993 and 1995. Cushions dominated by female flowers were shown to be more stable in gender expression than cushions dominated by male or hermaphrodite flowers.
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| 3. |
- Alatalo, Juha, 1966-, et al.
(författare)
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Response to simulated climatic change in an alpine and subarctic pollen-risk strategist, Silene acaulis
- 1997
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Ingår i: Global Change Biology. - : Wiley. - 1365-2486 .- 1354-1013. ; 3, s. 74-79
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to test if early no overing species respond with increased seed production to climate warming as is predicted for late-flowering seed-risk strategists. Experimental climate warming of about 3 degrees C was applied to two populations of the cushion-forming plant Silene acaulis (L.) Jacq. The experiment was run at one subarctic site and one alpine site for 2 years and 1 year, respectively, using open-top chambers (OTC). The 2-year temperature enhancement at the subarctic site had a marked effect on the flowering phenology. Cushions inside the OTC started flowering substantially earlier than control cushions. Both the male and female phases developed faster in the OTCs, and maturation of capsules occurred earlier. The cushions also responded positively in reproductive terms and produced more mature seeds and had a higher seed/ovule ratio. After 1 year temperature enhancement at the alpine site there was a weak trend for earlier flowering, but there was no significant difference in seed production or seed/ovule ratio.
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| 4. |
- Arft, M, et al.
(författare)
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Responses of tundra plants to experimental warming : Meta-analysis of the international tundra experiment
- 1999
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Ingår i: Ecological Monographs. - 0012-9615 .- 1557-7015. ; 69:4, s. 491-511
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Tidskriftsartikel (refereegranskat)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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| 5. |
- Molau, U, et al.
(författare)
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Responses of subarctic-alpine plant communities to simulated environmental change : Biodiversity of bryophytes, lichens, and vascular plants
- 1998
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Ingår i: Ambio. - 0044-7447 .- 1654-7209. ; 27:4, s. 322-329
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Tidskriftsartikel (refereegranskat)abstract
- The predicted changes in climate over the next 50 years are expected to be most pronounced in arctic and subarctic regions. In the present study, we examine the responses of a subarctic-alpine rich meadow and poor heath community to factorial manipulations of temperature and nutrient treatments. Specifically, we address response to the treatments in terms of biodiversity and relative cover of the bryophyte, lichen and vascular plant communities. We point out that the responses differ among mosses, lichens, vascular plants, and communities, and this will probably cause shifts in the dominance of both bottom layer and canopy layer species. It is important to note that the decrease in cover and species number of the bottom layer mainly occurred due to a decline in mosses; in contrast, lichen cover increased in all treatments in both communities. Climate change may thus cause a shift in the bottom layer from being dominated by mosses, to become dominated by lichens.
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