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- Baskin, CC, et al.
(author)
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Seed dormancy-breaking and germination requirements of Drosera anglica, an insectivorous species of the Northern Hemisphere
- 2001
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In: Acta Oecologica. - 1146-609X .- 1873-6238. ; 22:1
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Journal article (peer-reviewed)abstract
- Seeds of Drosera anglica collected in Sweden were dormant at maturity in late summer, and dormancy break occurred during cold stratification. Stratified seeds required light for germination, but light had to be given after temperatures were high enough to be favorable for germination. Seeds stratified in darkness at 5/1 ░C and incubated in light at 12/12 h daily temperature regimes of 15/6, 20/10 and 25/15 ░C germinated slower and to a significantly lower percentage at each temperature regime than those stratified in light and incubated in light. Length of the stratification period required before seeds would germinate to high percentages depended on (1) whether seeds were in light or in darkness during stratification and during the subsequent incubation period, and (2) the temperature regime during incubation. Seeds collected in 1999 germinated to 4, 24 and 92 % in light at 15/6, 20/10 and 25/15 ░C, respectively, after 2 weeks of stratification in light. Seeds stratified in light for 18 weeks and incubated in light at 15/6, 20/10 and 25/15 ░C germinated to 87, 95 and 100 %, respectively, while those stratified in darkness for 18 weeks and incubated in light germinated to 6, 82 and 91 %, respectively. Seeds collected from the same site in 1998 and 1999, stratified in light at 5/1 ░C and incubated in light at 15/6 ░C germinated to 22 and 87 %, respectively, indicating year-to-year variation in degree of dormancy. As dormancy break occurred, the minimum temperature for germination decreased. Thus, seed dormancy is broken in nature by cold stratification during winter, and by spring, seeds are capable of germinating at low habitat temperatures, if they are exposed to light. ⌐ 2001 ╔ditions scientifiques et mΘdicales Elsevier SAS.
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- Bergfur, J, et al.
(author)
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Phenological changes within a growth season in two semi-natural pastures in southern Sweden
- 2004
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In: Annales Botanici Fennici. - 0003-3847 .- 1797-2442. ; 41:1, s. 15-25
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Journal article (peer-reviewed)abstract
- Phenological changes within a growth season were investigated in two grazed, semi-natural grasslands in southern Sweden. On four occasions during the growth season, two independent observers recorded plant frequency and percentage cover. The vegetation data sets were analysed with ordination methods. The temporal changes were highly significant, but accounted for only a small part of the total variation in the data. Most species had early maxima, regarding both cover and frequency. There were differences in temporal pattern between the two grasslands. In a xeric area, the vegetation underwent a major change sometime in August, between survey-visit three and four. In a mesic area, the vegetation changed throughout the study period but least so during August. Therefore, phenological changes can be manifested in different ways, even within the same geographic region. Species-wise ordination scores highlighted those species whose records might be most affected by phenological patterns, information which is valuable when evaluating data collected in Scandinavian grasslands.
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- Bergstedt, Johan, et al.
(author)
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The impact of logging intensity on field-layer vegetation in Swedish boreal forests
- 2001
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In: Forest Ecology and Management. - 0378-1127. ; 154:1-2, s. 105-115
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Journal article (peer-reviewed)abstract
- The relationship between logging intensity and changes in ground cover vegetation was studied in 16 species and groups of species recorded at 10- or 11-year intervals in mature conifer-dominated forests. The 789 plots located in northern and central Sweden had been surveyed by the National Forest Inventory and the National Survey of Forest Soil and Vegetation. Thirty-seven percent of the plots had been subjected to a thinning or clear-cutting between the inventories. A principal components analysis showed that, of the variables considered, logging intensity had the highest explanatory power regarding change in ground cover vegetation between the inventories (the other variables were sum of temperatures, age of stand, timber volume, percentage Pinus sylvestris and site productivity). A multivariate direct gradient analysis technique (Redundancy analysis) showed that the logging intensity significantly affected the change in cover. This analysis also ranked the species in their responsiveness to logging. Epilobium angustifolium, narrow-leaved grasses and broad-leaved grasses, increased most with logging intensity. The response was not linear and only detectable at high logging intensities (>80%). In contrast, Vaccinium myrtillus seemed to decrease linearly with increased logging intensity. There was several years time-lag in the response to logging of E. angustifolium, V. myrtillus and narrow-leaved grasses. Several species and groups of species seemed unaffected by the logging. In sample plots unaffected by logging the cover of most species decreased.
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