| 1. |
- Hasselquist, Eliza Maher, et al.
(författare)
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Microsite differentiation among conifer species during seedling establishment at alpine treeline
- 2006
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Ingår i: Ecoscience. - : Presses de L`Université Laval. - 1195-6860. ; 13:3, s. 334-341
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Tidskriftsartikel (refereegranskat)abstract
- Tree establishment is a potentially important factor affecting tree populations in alpine-treeline ecotones. Patterns of seedling establishment of Abies lasiocarpa, Pinus albicaulis, and Picea engelmannii were evaluated relative to neighbouring trees and herbs over two years and three treelines of the Rocky Mountains, USA. The greatest mortality rates were observed in seedlings that had just emerged from seed and were in their first year of growth and in seedlings that had the least amount of cover provided by trees or other landscape features that block exposure to the sky. Although herb cover promoted survivorship in microsites that were not near trees, no seedlings were detected at or above the upper limit of the treeline ecotone. Microsite tree cover was greatest for A. lasiocarpa and least for P. albicaulis seedlings, which matches predictions based on their relative photosynthetic tolerances to the bright sunlight and frequent frost that occur in exposed microsites. Interspecific differences in seedling requirements for neighbouring plant cover likely contribute to the apparent coexistence and possible interdependency of these conifers along a continuum of colonization and succession within treelines.
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| 2. |
- Karlsson, P. Staffan, et al.
(författare)
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Relationships between fruit production and branching in monocarpic shoot modules of Rhododendron lapponicum
- 2006
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Ingår i: Ecoscience. - : Informa UK Limited. - 1195-6860. ; 13:3, s. 396-403
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Tidskriftsartikel (refereegranskat)abstract
- Rhododendron lapponicum is an ericaceous clonal dwarf shrub in which vegetative growth largely coincides with the formation of flowers and fruits. We used a flower-removal experiment and a descriptive data set to look for relationships and potential trade-offs between vegetative growth, i.e., branching, and fruit production in two contrasting subarctic populations (growing at low and high altitude). The two sites are similar in most respects and differ mainly in that the higher site has lower temperatures and a shorter growing season. We predicted that trade-offs between branching and fruit production would be less marked in a high-altitude population because at lower temperatures reproductive activities could be less resource dependent. At lower altitudes, where temperatures are higher, there would be competition for nutrients between fruiting and branching; hence, a trade-off between these two activities would be more obvious. In both populations about 80% of all new shoot modules were produced by reproductive shoot modules. We found evidence for a [linear] trade-off in the experimental study only, whereas the descriptive data set did not show any consistent indications of trade-offs between branch and fruit production. The high-altitude population showed several characteristics indicating that this population gave priority to vegetative growth over sexual reproduction. The data we present is a typical example of a case where co-variation in size and resource economy among modules masks potential trade-off patterns.
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| 3. |
- Niva, Mikael, et al.
(författare)
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Effects of light and water availability on shoot dynamics of the stoloniferous Linnaea borealis
- 2006
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Ingår i: Ecoscience. - : Informa UK Limited. - 1195-6860. ; 13:3, s. 318-323
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Tidskriftsartikel (refereegranskat)abstract
- Many stoloniferous plant species have the ability to exploit resource-rich patches via plastic growth responses. The most efficient responses are shortened spacers and increased branching frequency. Here we experimentally investigate the ability of the stoloniferous plant Linnaea borealis to respond to patches of increased light intensity and reduced water availability in natural systems. The significance of contrasts between patches was also investigated. A three-level factorial design was used, with light, water availability, and site as the factors. Increased light intensity was achieved through mowing of the surrounding vegetation, and reduced water availability was achieved by placing wooden ledges under the stolons. The treatments were applied at three subarctic sites that differ in light conditions. Branching frequency, number of new meristems, average internode length, leaf area, and dry weight production were studied 14 months after the manipulations. Increased light intensity increased branching frequencies; the strongest effects were obtained at the site with a closed canopy. Average intemode length decreased 19% in response to increased light intensity. Root:shoot ratios decreased under increased light intensity and reduced water availability. A reduction in water availability alone did not affect any other investigated traits. We conclude that ramets of L. borealis are able to respond efficiently to small-scale variations in light intensity in natural systems, an ability of great importance for the performance of a prostrate species on shady forest floors.
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| 4. |
- Angelstam, Per, et al.
(författare)
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Gap analysis as a basis for strategic spatial planning of green infrastructure: a case study in the Ukrainian Carpathians
- 2017
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Ingår i: Écoscience. - : Informa UK Limited. - 1195-6860 .- 2376-7626. ; 24, s. 41-58
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Tidskriftsartikel (refereegranskat)abstract
- Increased demand for natural resources and economic transition threaten natural and biocultural capital and thus ecosystem services for human well-being. We applied an evidence-based approach to strategic planning of functional green infrastructure in a European biodiversity hotspot: the Ukrainian Carpathian Mountains. We (1) described how potential natural vegetation types have been transformed, (2) applied evidence-based critical thresholds for each potential natural vegetation land cover, (3) measured how much of the potential natural vegetation land covers are protected, and (4) estimated the area of cultural landscapes that emerged. While only 2% of lowland land cover types were left, 55% of mountain forests and 94% of alpine land covers remained. Many mountain forests were transformed to valuable cultural landscapes. Beech and oak forests covered 42% of the study area but at low levels of protection (< 5%). The highest protection level (12-17%) was in mixed beech-fir-spruce and in spruce forests. However, taking connectivity into account, only alpine land covers formed a functional habitat network. More areas need to be protected and planned to build a functional green infrastructure. Traditional village systems with biocultural values need support. We discuss how strategic analyses can encourage collaborative spatial planning and international development cooperation.
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| 5. |
- Asplund, Johan, et al.
(författare)
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Simulated nitrogen deposition influences gastropod grazing in lichens
- 2010
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Ingår i: Ecoscience. - : Informa UK Limited. - 1195-6860. ; 17:1, s. 83-89
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Tidskriftsartikel (refereegranskat)abstract
- Lichens are often important photosynthetic organisms in oligotrophic environments where high-quality fodder plants are rare. A strong herbivore defence and/or low nutritional quality allows the accumulation of a high lichen biomass in such areas. However, it is not known how N deposition influences lichen palatability. This study analyzes possible changes in gastropod grazing preference after 3 months simulated N deposition on 3 foliose (Lobaria scrobiculata, Platismatia glauca, and Xanthoria aureola) and 1 pendulous lichen species (Alectoria sarmentosa). Lichens were daily irrigated in the field with rainwater containing 1.625 mM NH4NO3 from June to September, equivalent to a deposition of 50 kg N·ha-1·y-1. Irrigations applied at night, morning, or noon simulated different C-gain regimes. Afterwards in the lab, we offered 2 common lichen-feeding gastropods the choice between N-fertilized thalli and control thalli irrigated with artificial rainwater. The gastropods clearly preferred the unfertilized thalli of the 3 foliose species. For the pendulous A. sarmentosa, the gastropods preferred N-enriched thalli (irrigated at night) to controls. In conclusion, N-enrichment changes the palatability of lichens in species-specific ways.
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| 6. |
- Brodin, Anders, et al.
(författare)
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Optimal energy allocation and behaviour in female raptorial birds during the nestling period
- 2003
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Ingår i: Écoscience. - : University Laval. - 1195-6860. ; 10:2, s. 140-150
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Tidskriftsartikel (refereegranskat)abstract
- In many raptors and owls the male is the main provider of food in the early phase of the nestling period while the female incubates the eggs and broods the young. In the nestling period the female often helps the male to feed the young, but the factors affecting whether and when she leaves the brood to hunt have not been investigated in detail. We present a dynamic state variable model that analyses female behaviour and fat storage dynamics over the nestling period. The results show that in the first half of the nestling period the female faces a conflict between the need to brood the young and the need to hunt to provision them with food. This conflict arises because the energy needs of the young peak early in the nestling period, at a time when they still cannot thermoregulate and therefore need brooding from the female. The most critical period is the second nestling week, when both female and nestling fat reserves will decrease to low levels. Large female fat reserves in the early nestling period provide a solution to this conflict and are essential for successful breeding. Stochasticity in male provisioning is thus not needed to explain why females should be fat when the eggs hatch. Under normal circumstances, the female broods during the first two weeks and leaves the young only if hunting is absolutely necessary. After the second week the energy requirements are relaxed, and whether the female assists the male in hunting or not depends on factors such as male hunting success, environmental stochasticity, and energy requirements of the young. Our model provides a framework for empirical investigations on female behaviour during breeding in raptors, owls, and other birds with marked division of labour.
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| 7. |
- Bruun, Hans Henrik, et al.
(författare)
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Recruitment advantage of large seeds is greater in shaded habitats
- 2008
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Ingår i: Écoscience. - : Informa UK Limited. - 1195-6860 .- 2376-7626. ; 15:4, s. 498-507
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Tidskriftsartikel (refereegranskat)abstract
- Large seeds are assumed to have higher probability of successful recruitment than small seeds. This is because larger seeds give rise to larger seedlings and larger seedlings better withstand environmental hazards like deep shade and drought. Biotic and abiotic limitations to seedling growth and survival, and conversely availability of safe sites for recruitment, vary along environmental gradients and between habitat types. Thus, the value to plant species of possessing large seeds may differ between plant communities. We analyzed the relationship between seed mass and per-seed recruitment success (seedlings established per number of seeds produced) along an environmental gradient from open grassland to closed-canopy forest using data collected by Uuno Perttula in southern Finland in 1934. We found that larger seeds have greater recruitment success relative to smaller seeds in all investigated communities. However, the recruitment success of large seeds relative to small seeds strongly increased from grassland and open forest to closed-canopy forest. Of the measured environmental variables, canopy closure most strongly explained this increase. This indicates a strong direct effect of deep shade on seedling survival in natural plant communities. Additional explanatory power was associated with soil moisture. Litter cover, moss cover, and soil pH did not contribute to explaining the variation in relative recruitment success of larger seeds. Thus, the advantage of large seeds in recruitment success is pronounced in deeply shaded forest but may be insignificant in open vegetation.
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| 8. |
- Chiari, Stefano, et al.
(författare)
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Habitat of an endangered saproxylic beetle, Osmoderma eremita, in Mediterranean woodlands
- 2012
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Ingår i: Écoscience. - : Informa UK Limited. - 1195-6860 .- 2376-7626. ; 19, s. 299-307
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Tidskriftsartikel (refereegranskat)abstract
- The habitat of Osmoderma eremita, a European endangered beetle species restricted to tree cavities, was examined in central Italy, at the southernmost limit of its distributional range. The occurrence of adults, larvae, and fragments was investigated in 170 and 151 living hollow trees by pitfall trapping and sampling of wood mould (i.e., loose material) in the hollow, respectively. Overall, O. eremita was present in 22% of the trees, which belonged to 4 different tree species (Ostrya carpinifolia, Quercus suber, Acer obtusatum, and Quercus pubescens). The frequency of presence was higher in cavities with more than 4 L of wood mould, in cavities with dry or half-moist wood mould rather than wet wood mould, and with wood mould with low soil contamination. A comparison with northern regions indicated that the warmer macro-climatic conditions in the south make the species independent of a warm microclimate. As most of the hollow trees contain only a small amount of wood mould (<4 L), the habitat quality is generally poorer than in oak pastures studied in northern Europe.
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| 9. |
- Dahlberg, Anders, et al.
(författare)
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Effects of ecological continuity on species richness and composition in forests and woodlands: A review
- 2014
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Ingår i: Écoscience. - : Informa UK Limited. - 1195-6860 .- 2376-7626. ; 21, s. 34-45
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Forskningsöversikt (refereegranskat)abstract
- Forests and woodlands with a long, uninterrupted presence (continuity) are often associated with high biodiversity and many habitat specialist species. But the mechanisms by which, and the scales in time and space at which, populations are dependent on continuity remain debated. We examine the spatial and temporal scales at which occurrences of plants, fungi, and invertebrates are affected by continuity and consider whether they are restricted by time for colonization (continuity per se) or by habitat formation times. We give improved definitions of landscape and local levels of continuity anti evaluate the empirical literature with respect to these. By critically examining the reported effects of continuity on the occurrence of species in forests and woodlands, we explore the mechanisms behind the patterns at local and landscape scales. We conclude that many species are dispersal-limited in the current fragmented landscapes and occur mainly in landscapes with surplus continuity, meaning that the availability of habitats was greater in the past than it is currently. Our review indicates that local continuity per se is important at least for many forest herbs and for certain species of epiphytic lichens, insects, and land snails, but to a lesser extent for fungi. Several studies show that landscape-level continuity affects the current occurrence of species, in particular for vascular plants, but also for particular lichen, bryophyte, and invertebrate species. For continuity-dependent species, a successful conservation strategy should include both extending the period of habitat duration in relict patches and promoting habitat formation in the immediate surroundings of potential source patches. Conservation strategies need to acknowledge the continuity dependence of many species. Research on how to shorten habitat formation times by forest restoration is an urgent priority.
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| 10. |
- Forsum, A., et al.
(författare)
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Nitrogen uptake by Hylocomium splendens during snowmelt in a boreal forest
- 2008
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Ingår i: Ecoscience. - : Informa UK Limited. - 1195-6860. ; 15:3, s. 315-319
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Tidskriftsartikel (refereegranskat)abstract
- In most boreal regions snow composes a large portion of the annual precipitation. Although many boreal forest floor bryophytes depend largely on precipitation for their nitrogen (N) supply, bryophyte uptake of snow N little explored. We studied chemical forms of plant-accessible N in snowmelt, as well as the temporal dynamics of their release. In conjuction we performed a N uptake experiment using the common boreal bryophyte Hylocomium splendens. the results demonstrated that the snowmelt N pool was dominated by NO3 (86%), followed by NH4+ (11%) and amino acid N (3%), in total providing ca 0.3 kg N.ha(-1) to the forest floor vegetation. Hylocomium splendens was able to access both inorganic and organic N-15 labelled N forms (NO3-, NH4+, and glycine) applied in situ to the snow covering the moss prior to snowmelt. Across all the N forms H. splendens took up ca 24% of the snow-deposited N. Nitrate uptake exceeded that of glycine, while NH4+ uptake was intermediate, reflecting the ambient distribution of the snowmelt N pool between plant-accessible N forms.
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