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  • 1.
    Ecke, Frauke
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Christensen, Pernilla
    Department of Forest Resource Management and Geomatics, Swedish University of Agricultural Sciences, Umeå.
    Rentz, Ralf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Nilsson, Mats
    Department of Forest Resource Management and Geomatics, Swedish University of Agricultural Sciences, Umeå.
    Sandström, Per
    Department of Forest Resource Management and Geomatics, Swedish University of Agricultural Sciences, Umeå.
    Hörnfeldt, Birger
    Department of Forest Resource Management and Geomatics, Swedish University of Agricultural Sciences, Umeå.
    Landscape structure and the long-term decline of cyclic grey-sided voles in Fennoscandia2010Inngår i: Landscape Ecology, ISSN 0921-2973, E-ISSN 1572-9761, Vol. 25, nr 4, s. 551-560Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Changes in forest landscape structure have been suggested as a likely contributing factor behind the long-term decline in the numbers of cyclic grey-sided voles (Clethrionomys rufocanus) in northern Fennoscandian lowland regions in contrast to mountain regions due to the absence of forest management in the mountains. This study, for the first time, formally explored landscape structure in 29 lowland (LF) and 14 mountain forest (MF) landscapes (each 2.5 × 2.5 km) in northern Sweden, and related the results to the cumulated spring trapping index of the grey-sided vole in 2002-2006. The grey-sided vole showed striking contrasts in dynamics close in space and time. The MF landscapes were characterized by larger patches and less fragmentation of preferred forest types. The grey-sided vole was trapped in all of 14 analyzed MF landscapes but only in three out of 29 of the LF landscapes. MF and LF landscapes with grey-sided vole occurrence were characterized by similar focal forest patch size (mean 357 ha, minimum 82 ha and mean 360 ha, minimum 79 ha, respectively). In contrast, these MF compared to the LF landscapes were characterized by larger patches of preferred forest types and less fragmented preferred forest types and by a lower proportion of clear-cut areas. The present results suggest that landscape structure is important for the abundance of grey-sided voles in both regions. However, in the mountains the change from more or less seasonal dynamics to high-amplitude cycles between the mid 1990s and 2000s cannot be explained by changes in landscape structure.

  • 2.
    Ecke, Frauke
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Christensen, Pernilla
    Department of Ecology and Environmental Science, Umeå University.
    Sandström, Per
    Department of Forest Resource Management and Geomatics, Swedish University of Agricultural Sciences, Umeå.
    Hörnfeldt, Birger
    Department of Ecology and Environmental Science, Umeå University.
    Identification of landscape elements related to local declines of a boreal grey-sided vole population2006Inngår i: Landscape Ecology, ISSN 0921-2973, E-ISSN 1572-9761, Vol. 21, nr 4, s. 485-497Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 3.
    Hörnfeldt, Birger
    et al.
    Umeå universitet.
    Christensen, Pernilla
    Umeå universitet.
    Sandström, Per
    SLU, Umeå.
    Ecke, Frauke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Long-term decline and local extinction of Clethrionomys rufocanus in boreal Sweden2006Inngår i: Landscape Ecology, ISSN 0921-2973, E-ISSN 1572-9761, Vol. 21, nr 7, s. 1135-1150Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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). We monitored this decline by snap-trapping on 58 permanent plots spread over 100 km2 in spring and fall from fall 1971-2003. The reason for the decline is largely unknown, although a common major factor is likely to be involved in the decline of C. rufocanus and of the coexisting voles. However, here we deal with the reasonability of one complementary hypothesis, the habitat fragmentation hypothesis, which assumes that part of the decline of C. rufocanus is caused by habitat (forest) destruction. There was considerable local variation in the decline among the 58 1-ha sampling plots, with respect to both density and timing of the decline; however, all declines ended up with local extinction almost without exception. Local declines were not associated with habitat destruction by clear-cutting within sampling-plots, as declines started about equally often before as after clear-cutting, which suggested that habitat destruction outside sampling plots could be involved. In a multiple regression analysis, local habitat preference (LHP; expressed as a ratio of observed to expected number of voles trapped per habitat) together with two habitat variables in the surrounding (2.5×2.5 km2) landscape matrix explained 56% of the variation among local cumulated densities of C. rufocanus and hence of local time-series. LHP was positively correlated and explained 31% of the variation, while connectivity among clear-cuts was negatively correlated and proximity among xeric-mesic mires was positively correlated and explained additional 16% and 9%, respectively. Even if the overall decline cannot be connected to local clear-cutting on sampling-plots, clear-cutting and hence habitat fragmentation/destruction in the surrounding landscapes potentially influenced grey-sided vole numbers negatively.

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