| 1. |
- Järemo, Johannes, et al.
(författare)
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Flee or fight uncertainty : Plant strategies in relation to anticipated damage
- 1999
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 2:6, s. 361-366
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Tidskriftsartikel (refereegranskat)abstract
- In order to cope with damage, plants have evolved a number of strategies. We incorporate two of those strategies, compensatory regrowth and escaping damage in time, into a mathematical model in an attempt to outline under what circumstances one or the other of these phenotypic traits will evolve. Escaping damage in time is accomplished by flowering and setting seeds at a point of time when the risk of damage is low, whereas a compensatory capacity is made possible by activating a proportion of meristems that are left dormant. Our analysis suggests that damage that is predictable in time will favour phenotypes that flower late in the season and that have a good compensatory capacity. As damage becomes less predictable in time, a strategy that implies flowering as early as possible in the season and with no compensatory capacity at all, becomes advantageous.
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| 2. |
- Lundberg, Per, et al.
(författare)
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Spatial population dynamics and the design of marine reserves
- 1999
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 2:3, s. 129-134
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Tidskriftsartikel (refereegranskat)abstract
- The failure of many fisheries world-wide, and the concern about marine biodiversity, has sparked a growing interest in the spatial aspects of harvested populations. If a population conforms to the Ideal Free Distribution and that one of the habitats is set aside as a reserve free from harvesting, the design of reserves may be problematic. If a substantial proportion of the unharvested population is to be preserved, then the reserve area must be unrealistically large, or have a much higher expected fitness than the unprotected area. Interestingly, the optimal harvest rate will be unaffected by both the size of the reserve and the quality of it relative to the harvested area. Even if the Ideal Free Distribution model is extended to include simple age-structure and "spillover" of recruits from the reserve, these conclusions largely remain intact. In a model that also includes spillover, the habitat quality of the reserve may also affect the catch.
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| 3. |
- Ripa, Jörgen, et al.
(författare)
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Linear analysis solves two puzzles in population dynamics : the route to extinction and extinction in coloured environments
- 1999
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 2:4, s. 219-222
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we give simple explanations to two unsolved puzzles that have emerged in recent theoretical studies in population dynamics. First, the tendency of some model populations to go extinct from high population densities, and second, the positive effect of autocorrelated environments on extinction risks for some model populations. Both phenomena are given general explanations by simple, linear, stochastic models. We emphasize the predictive and explanatory power of such models.
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| 4. |
- Saikkonen, Kari, et al.
(författare)
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Defoliation and mycorrhizal symbiosis: a functional balance between carbon sources and below-ground sinks
- 1999
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 2:1, s. 19-26
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Tidskriftsartikel (refereegranskat)abstract
- Herbivory is generally assumed to negatively influence mycorrhizal fungi because of reduced photosynthate to support mycorrhizae following defoliation. We examined effects of 60% and 100% defoliation (excluding current year needles) on tree growth and ectomycorrhizal associations of 10±15 year old Scots pines (Pinus sylvestris). Over 98% of short roots were colonized by mycorrhizal fungi, and contrary to expectation, defoliation did not decrease the proportion of living fungi in fine roots. Furthermore, defoliation did not alter the ratios of produced needle biomass to the biomass of fine roots or living fungi in fine roots. The composition of mycorrhizal morphotypes was changed, however, which suggests competition among different mycorrhizal growth forms owing to their carbon demands. We propose that these outcomes are a consequence of a functional balance between carbon sources in plant foliage and below-ground sinks, i.e. growing roots and mycorrhizal associates.
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