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- Grandin, Ulf, et al.
(författare)
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Attributes of the seed bank after a century of primary succession on islands in Lake Hjalmaren, Sweden
- 1998
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Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 86:2, s. 293-303
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Tidskriftsartikel (refereegranskat)abstract
- 1 A large number of islands was created when the water table of Lake Hjälmaren, south central Sweden, was lowered between 1882 and 1886. We have complete lists of vascular plant species for 40 of these islands from 1886, 1892, 1903–04, 1927–28 and 1984–85.2 We have investigated the seed bank on nine of these islands and compared species composition at different soil depths with the species lists from the islands in 1886–1985, and with the present vegetation in the area of seed bank sampling. We have also investigated the distribution in the soil of seeds from species with different ecological attributes, including seed longevity, successional status, seed weight, seed form and species longevity.3 Seeds in soil samples were allowed to germinate over the course of two summers with an intermediate cold storage. We found 1944 seeds representing 65 taxa. The mean seed density was 84 seeds dm–2.4 The similarity between the surface soil (0–3 cm) seed bank and the vegetation at the different vegetation analyses increased from 1886 to 1993. The similarity between the present vegetation and the seed bank decreased with increasing soil depth, and the soil at 12–15 cm had no species in common with the present vegetation. Several species now absent from the vegetation were found in the seed bank.5 Deeply buried seeds came from early successional, annual species with long-term persistent and low-weight seeds, as expected from seed bank theories, but were slightly elongated, which was in contrast to theories. Spherical seeds were associated with the surface soil, as were short-lived and high-weight seeds from late successional, perennial species.
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- Piqueras, Jesús, 1961-
(författare)
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Herbivory and ramet performance in the clonal herb Trientalis europaea L.
- 1999
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Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 87:3, s. 450-460
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Tidskriftsartikel (refereegranskat)abstract
- 1 The intensity of leaf damage caused by invertebrate herbivores and grazing by vertebrates and their effects on clonal growth, survival and reproduction were examined in a population of the forest herb Trientalis europaea during 4 years. 2 Levels of herbivory were low and varied between years in the studied population. Larger ramets were exposed to a greater risk of both grazing and leaf defoliation. Ramets that suffered leaf damage in 1 year experienced an increased probability of leaf damage in succeeding years. The probability of suffering herbivore attack was independent among the ramets belonging to the same clonal fragment, suggesting that clonal propagation might operate as a risk-spreading strategy in this species. 3 Leaf damage did not affect any measure of plant performance, probably due to the low amounts of leaf area removed by invertebrate herbivores. In contrast, vertebrate grazing affected all phases of the pseudo-annual life cycle of T. europaea. Grazing prevented flowering and fruiting, increased ramet mortality during summer and decreased tuber production. Furthermore, grazed ramets produced shorter stolons and smaller tubers, which in turn had a lower winter survival and produced smaller ramets in the following growing season. The large impact of grazing was due to the consumption of the whole of the single shoot of ramets of T. europaea. Although regrowth was possible, secondary shoots were significantly smaller and assimilation was delayed. 4 Tubers originating from grazed ramets were placed shallower than tubers from ungrazed ramets. This could be due to an alteration in the growth pattern of stolons of the grazed ramets.
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- Piqueras, Jesús, 1961-
(författare)
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Infection of Trientalis europaea by the systemic smut fungus Urocystis trientalis: disease incidence, transmission and effects on performance of host ramets
- 1999
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Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 87:6, s. 995-1004
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Tidskriftsartikel (refereegranskat)abstract
- 1 The effects of fungus infection on a natural population of the pseudoannual plant Trientalis europaea were followed for 4 years. 2 The incidence of the disease was low, showed little temporal variation during the period of study and was not affected by ramet size. Disease reduced flowering, fruiting, stolon length and the number and size of daughter tubers, all of which were positively correlated with ramet size. The year–disease interaction was not significant, except for flowering, suggesting little variation in the aggressiveness of the pathogen. 3 Disease reduced survival of ramets to the end of the growing season, although the effect varied with ramet size, and decreased tuber survival both by reduction of tuber size and by reduction of the overwintering ability of tubers of a given size. 4 For two of the three annual transitions the size of the offspring ramets was affected negatively by infection in the previous year. 5 Disease transmission occurred along the stolons of only 31% of the diseased ramets. The probability of disease being shown in the following year decreased with stolon length. 6 Although disease had a detrimental effect on ramet fitness, the low level of incidence and the stability of the clone dynamics in simulation models suggest only a minor role of the disease in population regulation in this species.
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- Berg, H, et al.
(författare)
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Cleistogamy as a bet-hedging strategy in Oxalis acetosella, a perennial herb
- 1998
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Ingår i: JOURNAL OF ECOLOGY. - : BLACKWELL SCIENCE LTD. - 0022-0477. ; 86:3, s. 491-500
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- 1 Phenology and reproduction were studied in three populations of the cleistogamous herb Oxalis acetosella during three growing seasons, in order to see how the balance between chasmogamous (CH) and cleistogamous (CL) reproduction varies with temporal and
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