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- Lundkvist, Elisabeth, 1970-, et al.
(författare)
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Diving beetle (Dytiscidae) assemblages along environmental gradients in an agricultural landscape in Southeastern Sweden
- 2001
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Ingår i: Wetlands (Wilmington, N.C.). - : Wiley. - 0277-5212 .- 1943-6246. ; 21:1, s. 48-58
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Tidskriftsartikel (refereegranskat)abstract
- We investigated diving beetle (Dytiscidae) assemblages in twelve wetlands in an agricultural landscape in southeastern Sweden. Beetles were trapped in wetlands that varied in permanence (temporary or permanent), area (25 to 4,800 m2), age (11 to >50 yr), and shading (open to wooded surroundings). Our objective was to determine if those environmental factors are important in structuring the local assemblages of diving beetles and how the combination of different types of wetlands influence the diversity of diving beetles in a landscape. Generally, species-area relationships were weak, and shaded wetlands, both permanent and temporary, of intermediate size (240-1,100 m2) had the highest richness after a rarefaction analysis. It was not possible to discern a certain type of wetland where diversity was highest (measured by index a and Shannon-Wiener's index), although, again, intermediate sized wetlands did tend to be more diverse than others. Similarities in species compositions were highest among environmentally similar wetlands, and assemblage structure differed substantially between different types of wetlands. Results of ordination (CCA) and variance partitioning revealed that permanence and degree of shading were the most important factors in structuring assemblages. Our findings imply that high diversity of the diving beetles depends on the number of wetland types represented in a landscape. It is possible to achieve high diversity in a small area by combining permanent and temporary wetlands, as well as many age and successional stages, located in wooded and open environments.
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| 2. |
- Linderholm, Hans W., 1968, et al.
(författare)
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An assessment of twentieth century tree-cover changes on a southern Swedish peatland combining dendrochronoloy and aerial photograph analysis
- 2004
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Ingår i: Wetlands. - 0277-5212. ; 24:2, s. 357-363
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Tidskriftsartikel (refereegranskat)abstract
- In the twentieth century, there have been increases in Scots pine (Pinus sylvestris) coverage on peatlands in southern Sweden. In order to assess possible links to contemporary climate change; aerial photograph analysis and dendrochronology were combined to study recent pine cover changes at Anebymossen, a raised peat bog in south central Sweden. Multi-temporal analyses of three sets of panchromatic images from 1950 to 1993 showed a 30% increase of the marginal pine forest of the raised bog during that time, where a significant increase had occurred in the eastern part. Dendrochronological analyses were performed in two parts: the eastern part and the western part where the increase in pine coverage was considerably lower. The tree-ring growth patterns disclosed that a major event, most likely drainage, had occurred at Anebymossen in 1927, affecting tree growth at both sites. The effect of the drainage, which lowers the local ground-water table and hence promotes tree growth, was growth surges with a doubling of the annual increment rates. The effect was short lived in the western part, but continuous drainage in the eastern part caused growth enhancement until the beginning of the 1980s. We suggest that rather than being caused by climate change, the increase in pine coverage on Anebymossen was initiated by the considerable drainage in 1927. Since most peatlands in southern Sweden have been affected by anthropogenic activities, we suggest that it is difficult to make climatological interpretations of tree cover changes on peatlands using only aerial photograph analyses.
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