| 1. |
- Andersson, Erik, et al.
(författare)
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Patterns and scale relations among urbanization measures in Stockholm, Sweden
- 2009
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Ingår i: Landscape Ecology. - : Springer Science and Business Media LLC. - 0921-2973 .- 1572-9761. ; 24, s. 1331-1339
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Tidskriftsartikel (refereegranskat)abstract
- In this study we measure urbanization based on a diverse set of 21 variables ranging from landscape indices to demographic factors such as income and land ownership using data from Stockholm, Sweden. The primary aims were to test how the variables behaved in relation to each other and if these patterns were consistent across scales. The variables were mostly identified from the literature and limited to the kind of data that was readily accessible. We used GIS to sample the variables and then principal component analyses to search for patterns among them, repeating the sampling and analysis at four different scales (250 × 250, 750 × 750, 1,250 × 1,250 and 1,750 × 1,750, all in meters). At the smallest scale most variables seemed to be roughly structured along two axes, one with landscape indices and one mainly with demographic factors but also impervious surface and coniferous forest. The other land-cover types did not align very well with these two axes. When increasing the scale this pattern was not as obvious, instead the variables separated into several smaller bundles of highly correlated variables. Some pairs or bundles of variables were correlated on all scales and thus interchangeable while other associations changed with scale. This is important to keep in mind when one chooses measures of urbanization, especially if the measures are indices based on several variables. Comparing our results with the findings from other cities, we argue that universal gradients will be difficult to find since city shape and size, as well as available information, differ greatly. We also believe that a multivariate gradient is needed if you wish not only to compare cities but also ask questions about how urbanization influences the ecological character in different parts of a city.
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| 2. |
- Berggren, Åsa
(författare)
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Effect of landscape and population variables on immune response in experimentally introduced bush-cricket populations
- 2009
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Ingår i: Landscape Ecology. - : Springer Science and Business Media LLC. - 0921-2973 .- 1572-9761. ; 24, s. 749-757
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Tidskriftsartikel (refereegranskat)abstract
- Despite the growing interest in relationships between ecological variables and individual immune function, few empirical data have been available from wild populations. In this study, I assayed the immune response from 370 wild-caught bush-crickets, Metrioptera roeseli, from 20 experimentally introduced populations, by measuring individual encapsulation responses to a surgically implanted nylon monofilament. Bush-crickets descended from populations introduced into larger habitat patches showed a greater immune response when compared to individuals from smaller habitat-area introductions. Also, there was a significant positive correlation between immune response and the amount of linear elements at the introduction site. However, there was a lack of effect of population variables (i.e., propagule size and rate of population growth) on immune response. These results suggest that large-scale environmental parameters, such as patch size and connectivity, can be important for an individual's physiological health and its ability to defend against disease-causing agents. Such effects are likely to compound the negative impacts associated with isolation of sub-populations and habitat fragmentation.
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| 3. |
- Bunce, R. G. H., et al.
(författare)
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A standardized procedure for surveillance and monitoring European habitats and provision of spatial data
- 2008
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Ingår i: Landscape Ecology. - : Springer Science and Business Media LLC. - 0921-2973 .- 1572-9761. ; 23, s. 11-25
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Tidskriftsartikel (refereegranskat)abstract
- Both science and policy require a practical, transmissible, and reproducible procedure for surveillance and monitoring of European habitats, which can produce statistics integrated at the landscape level. Over the last 30 years, landscape ecology has developed rapidly, and many studies now require spatial data on habitats. Without rigorous rules, changes from baseline records cannot be separated reliably from background noise. A procedure is described that satisfies these requirements and can provide consistent data for Europe, to support a range of policy initiatives and scientific projects. The methodology is based on classical plant life forms, used in biogeography since the nineteenth century, and on their statistical correlation with the primary environmental gradient. Further categories can therefore be identified for other continents to assist large scale comparisons and modelling. The model has been validated statistically and the recording procedure tested in the field throughout Europe. A total of 130 General Habitat Categories (GHCs) is defined. These are enhanced by recording environmental, site and management qualifiers to enable flexible database interrogation. The same categories are applied to areal, linear and point features to assist recording and subsequent interpretation at the landscape level. The distribution and change of landscape ecological parameters, such as connectivity and fragmentation, can then be derived and their significance interpreted.
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| 4. |
- Christensen, Pernilla, et al.
(författare)
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Habitat preference of Clethrionomys rufocanus in boreal Sweden
- 2006
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Ingår i: Landscape Ecology. - The Hague : SPB Academic Publ.. - 0921-2973 .- 1572-9761. ; 21:2, s. 185-194
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Tidskriftsartikel (refereegranskat)abstract
- A long-term decline of vole populations in boreal Sweden, especially of the grey-sided vole (Clethrionomysrufocanus Sund.), has been revealed by snap-trapping in 1971–2004. We identified important habitats forthe grey-sided vole by mapping the distribution of cumulated number of reproductive females in 1971–1978, prior to the major decline in the 1980s. Mean abundance of C. rufocanus was higher in the western(inland) than eastern (coastland) part of the study area. As the inland appeared to represent the most, as faras we know, pristine, abundant part of the population, we based identification of high quality habitats oninland data only. Four habitats were more important than others and yielded nearly 86% of the reproductivefemales in spring: (1) forests of dry, (2) moist and (3) wet/hydric dwarf-shrub type, in addition to (4)forest/swamp complexes rich in dwarf-shrubs. The latter three habitats were used more frequently thanexpected from their occurrence in the landscape. Still, the variation in density of reproductive femaleswithin patches of the same habitat was frequently high. This suggested that habitat composition in thesurrounding landscape, perhaps may have affected local vole density at the patch scale. Clear-cut samplingplots appeared to be low-frequently used by reproductive females, but also by males and immatures. Inconclusion, our study indicated the importance of also studying habitat at a larger scale than that of thepatch to get a deeper understanding on how habitat influences local and regional densities and populationdynamics of C. rufocanus.
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| 5. |
- Cousins, Sara A. O., et al.
(författare)
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Effects of historical and present fragmentation on plant species diversity in semi-natural grasslands in Swedish rural landscapes.
- 2007
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Ingår i: Landscape Ecology. - : Springer Science and Business Media LLC. - 0921-2973 .- 1572-9761. ; 22:5, s. 723-730
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Tidskriftsartikel (refereegranskat)abstract
- Habitat loss and fragmentation of natural and semi-natural habitats are considered as major threats to plant species richness. Recently several studies have pinpointed the need to analyse past landscape patterns to understand effects of fragmentation, as the response to landscape change may be slow in many organisms, plants in particular. We compared species richness in continuously grazed and abandoned grasslands in different commonplace rural landscapes in Sweden, and analysed effects of isolation and area in three time-steps (100 and 50 years ago and today). Old cadastral maps and aerial photographs were used to analyse past and present landscape patterns in 25 sites. Two plant diversity measures were investigated; total species richness and species density. During the last 100 years grassland area and connectivity have been reduced by about 90%. Present-day habitat area was positively related to total species richness in both habitats. There was also a relationship to habitat area 50 years ago for continuously grazed grasslands. Only present management was related to species density: continuously grazed grasslands had the highest species density. There were no relationships between grassland connectivity, present or past, and any diversity measure. We conclude that landscape history is not directly important for present-day plant diversity patterns in ordinary landscapes, although past grassland management is a prerequisite for the grassland habitats that can be found there today. It is important that studies are conducted, not only in very diverse landscapes, but also in managed landscapes in order to assess the effects of fragmentation on species.
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| 6. |
- Ecke, Frauke, et al.
(författare)
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Identification of landscape elements related to local declines of a boreal grey-sided vole population
- 2006
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Ingår i: Landscape Ecology. - : Springer Science and Business Media LLC. - 0921-2973 .- 1572-9761. ; 21:4, s. 485-497
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Tidskriftsartikel (refereegranskat)abstract
- Several studies indicate a long-term decline in numbers of different species of voles in northern Fennoscandia. In boreal Sweden, the long-term decline is most pronounced in the grey-sided vole (Clethrionomys rufocanus). Altered forest landscape structure has been suggested as a possible cause of the decline. However, habitat responses of grey-sided voles at the landscape scale have never been studied. We analyzed such responses of this species in lowland forests in Västerbotten, northern Sweden. Cumulated spring densities representing 22 local time series from 1980-1999 were obtained by a landscape sampling design and were related to the surrounding landscape structure of 2.5×2.5 km plots centred on each of the 22 1-ha trapping plots. In accordance with general knowledge on local habitat preferences of grey-sided voles, our study supported the importance of habitat variables such as boulder fields and old-growth pine forest at the landscape scale. Densities were negatively related to clear cuts. Habitat associations were primarily those of landscape structure related to habitat fragmentation, distance between habitat patches and patch interspersion rather than habitat patch type quantity. Local densities of the grey-sided vole were positively and exponentially correlated with spatial contiguity (measured with the fragmentation index) of old-growth pine forest, indicating critical forest fragmentation thresholds. Our results indicate that altered land use might be involved in the long-term decline of the grey-sided vole in managed forest areas of Fennoscandia. We propose two further approaches to reveal and test responses of this species to changes in landscape structure.
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| 7. |
- Gillson, Lindsey, et al.
(författare)
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Holocene palaeo-invasions : the link between pattern,process and scale in invasion ecology?
- 2008
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Ingår i: Landscape Ecology. - : Springer Science and Business Media LLC. - 0921-2973 .- 1572-9761. ; 23:7, s. 757-769
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Tidskriftsartikel (refereegranskat)abstract
- Invasion ecology has made rapid progress in recent years through synergies with landscape ecology, niche theory, evolutionary ecology and the ecology of climate change. The palaeo-record of Holocene invasions provides a rich but presently underexploited resource in exploring the pattern and process of invasions through time. In this paper, examples from the palaeo-literature are used to illustrate the spread of species through time and space, also revealing how interactions between invader and invaded communities change over the course of an invasion. The main issues addressed are adaptation and plant migration, ecological and evolutionary interactions through time, disturbance history and the landscape ecology of invasive spread. We consider invasions as a continuous variable, which may be influenced by different environmental or ecological variables at different stages of the invasion process, and we use palaeoecological examples to describe how ecological interactions change over the course of an invasion. Finally, the use of palaeoecological information to inform the management of invasions for biodiversity conservation is discussed.
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| 8. |
- Hörnfeldt, Birger, et al.
(författare)
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Long-term decline and local extinction of Clethrionomys rufocanus in boreal Sweden
- 2006
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Ingår i: Landscape Ecology. - The Hague : SPB Academic Publ.. - 0921-2973 .- 1572-9761. ; 21, s. 1135-1150
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Tidskriftsartikel (refereegranskat)abstract
- Over the past three decades in boreal Sweden, there has been a long-term decline of cyclic sympatric voles,leading to local extinctions of the most affected species, the grey-sided vole (Clethrionomys rufocanus). Wemonitored this decline by snap-trapping on 58 permanent plots spread over 100 km2 in spring and fall from fall1971–2003. The reason for the decline is largely unknown, although a common major factor is likely to beinvolved in the decline of C. rufocanus and of the coexisting voles.However, here we deal with the reasonabilityof one complementary hypothesis, the habitat fragmentation hypothesis, which assumes that part of thedecline of C. rufocanus is caused by habitat (forest) destruction. There was considerable local variation in thedecline among the 58 1-ha sampling plots, with respect to both density and timing of the decline; however, alldeclines ended up with local extinction almost without exception. Local declines were not associated withhabitat destruction by clear-cutting within sampling-plots, as declines started about equally often before asafter clear-cutting, which suggested that habitat destruction outside sampling plots could be involved. In amultiple regression analysis, local habitat preference (LHP; expressed as a ratio of observed to expectednumber of voles trapped per habitat) together with two habitat variables in the surrounding (2.5 · 2.5 km2)landscape matrix explained56%of the variation among local cumulated densities of C. rufocanus and hence oflocal time-series.LHPwas positively correlated and explained31%of the variation, while connectivity amongclear-cuts was negatively correlated and proximity among xeric-mesic mires was positively correlated andexplained additional 16% and 9%, respectively. Even if the overall decline cannot be connected to local clearcuttingon sampling-plots, clear-cutting and hence habitat fragmentation/destruction in the surroundinglandscapes potentially influenced grey-sided vole numbers negatively.
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| 9. |
- Lundberg, Jakob, et al.
(författare)
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Linkages beyond borders : targeting spatial processes in fragmented urban landscapes
- 2008
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Ingår i: Landscape Ecology. - : Springer Science and Business Media LLC. - 0921-2973 .- 1572-9761. ; 23:6, s. 717-726
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Tidskriftsartikel (refereegranskat)abstract
- Management of ecosystems often focuses on specific species chosen for their habitat demand, public appeal, or levels of threat. We propose a complementary framework for choosing focal species, the mobile link concept, which allows managers to focus on spatial processes and deal with multi-scale ecological dynamics. Spatial processes are important for three reasons: maintenance, re-organization, and restoration of ecological values. We illustrate the framework with a case study of the Eurasian Jay, a mobile link species of importance for the oak forest regeneration in the Stockholm National Urban Park, Sweden, and its surroundings. The case study concludes with a conceptual model for how the framework can be applied in management. The model is based on a review of published data complemented with a seed predation experiment and mapping of Jay territories to reduce the risk of applying non-urban site-specific information in an urban setting. Our case study shows that the mobile link approach has several advantages: (1) Reducing the vulnerability of ecological functions to disturbances and fluctuations in resources allocated to management, (2) Reducing management costs by maintaining natural processes, and (3) Maintaining gene flow and genetic diversity at a landscape level. We argue that management that includes mobile link organisms is an important step towards the prevention of ecosystem degradation and biodiversity loss in increasingly fragmented landscapes. Identifying and managing mobile links is a way to align management with the ecologically relevant scales in any landscape.
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| 10. |
- Olofsson, Johan, et al.
(författare)
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Effects of mammalian herbivores on revegetation of disturbed areas in different locations in the forest-tundra ecotone in northern Fennoscandia
- 2005
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Ingår i: Landscape Ecology. - : Springer Science and Business Media LLC. - 0921-2973 .- 1572-9761. ; 20, s. 351-359
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Tidskriftsartikel (refereegranskat)abstract
- Herbivores influence the structure of plant communities in arctic-alpine ecosystems. However, little is known of the effect of herbivores on plant colonisation following disturbance, and on its variability depending on the identity of herbivores and the characteristics of the habitats. To quantify the role of large and small vertebrate herbivores, we established exclosures of two different mesh sizes around disturbed subplots in forest and nearby tundra habitats in four contrasting locations in the forest-tundra ecotone in northernmost Sweden and Norway. The study revealed that herbivores influenced the abundance but not the species composition of regenerating vegetation. Gaps were colonised by the dominant species in the surrounding vegetation. The only exception to this expectation was Empetrum nigrum, which failed to colonise gaps even though it dominated undisturbed vegetation. Significant effects of herbivory were only detected when both small and large herbivores were excluded. Herbivores decreased the abundance of three of the most common species Vaccinium myrtillus, Vaccinium vitis idaea, and Deschampsia flexuosa. The effect of herbivory on the abundance of these three species did not differ between habitats and locations. However, the composition of the regenerating vegetation differed between habitats and locations. The disturbance treatment increased the species richness on the scale of plots, habitats, and sites. However, on the scale of whole locations, all species found in disturbed areas were also found in undisturbed areas, suggesting that the natural disturbance regime in arctic landscapes is high enough to sustain colonising species.
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| 11. |
- Renöfält, Birgitta Malm, et al.
(författare)
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Spatial patterns of plant invasiveness in a riparian corridor
- 2005
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Ingår i: Landscape Ecology. - : Springer Netherlands. - 0921-2973 .- 1572-9761. ; 20:2, s. 165-176
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Tidskriftsartikel (refereegranskat)abstract
- Analysis of landscape-scale patterns of plant invasiveness can assist in interpreting spatial patterns of plant species richness. We investigated downstream variation in plant invasiveness in the riparian corridor of the free-flowing Vindel River in northern Sweden by introducing seeds of an alien species, Helianthus annuus, in 0.25 m2 plots of natural vegetation from mountain headwaters to the coast and found a significant downstream pattern with middle reaches having the highest invasiveness. We related invasiveness to species richness, both on a reach scale (200-m long stretches of riverbank encompassing the experimental plots) and on the scale of experimental plots. We found no significant correlation between plant invasiveness and species richness, neither at the reach nor at the plot scale. The number of available soil substrates shows a significant positive quadratic relationship with location along the river and substrate fineness shows a near significant negative quadratic relationship with location along the river, with middle reaches having coarser substrates. Several studies have shown that plant species richness in riparian corridors often exhibits a quadratic pattern with highest species richness in the middle reaches of a river, similar to the pattern we found for invasiveness. Although species richness per se might not be a primary factor for invasibility, the same habitat conditions as those supporting plant species richness, can help in explaining large-scale patterns of plant invasion in riparian zones.
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| 12. |
- Öckinger, Erik, et al.
(författare)
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Do corridors promote dispersal in grassland butterflies and other insects?
- 2008
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Ingår i: Landscape Ecology. - : Springer Science and Business Media LLC. - 1572-9761 .- 0921-2973. ; 23:1, s. 27-40
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Tidskriftsartikel (refereegranskat)abstract
- Ecological corridors are frequently suggested to increase connectivity in fragmented landscapes even though the empirical evidence for this is still limited. Here, we studied whether corridors, in the form of linear grass strips promote the dispersal of three grassland butterflies, using mark-recapture technique in an agricultural landscape in southern Sweden. We found no effects of the presence of corridors or of corridor length on inter-patch dispersal probabilities. Instead, dispersal probabilities appeared to be related to the quality, areas and population densities of the source and recipient patches. For two of the species, the density of captured individuals along corridors was better predicted by the corridor length than by the straight-line distance from a pasture, suggesting that short-distance movements within habitat patches result in a diffusion of individuals along corridors. A literature review revealed that only 16 published studies had explicitly studied the effect of corridors on insect movement. The context in which studies were performed appeared to affect whether corridors facilitated dispersal or not. All seven studies where the corridors consisted of open areas surrounded by forest showed positive effects, while only two out of six studies where corridors consisted of grassland surrounded by other open habitats showed positive effects of corridors. Our results clearly demonstrate that corridors do not always have positive effects on insect dispersal and that the effect seems to depend on the quality of the surrounding matrix, on the spatial scale in which the study is performed and on whether true dispersal or routine movements are considered.
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| 13. |
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