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Heather WoodDoktorand

Forskningsprojekt

Publikationer

I urval från Stockholms universitets publikationsdatabas

  • European Union tree density limits do not reflect bat diversity in wood-pastures

    2017. Heather Wood, Regina Lindborg, Simon Jakobsson. Biological Conservation 210, 60-71

    Artikel

    The European Union's Common Agricultural Policy (CAP) recommends subsidies are only granted for wood-pastures with < 100 trees/ha. This guidance exists despite these habitats being among the most biodiverse in boreal Europe and currently under threat due to land conversion. Bats are important bio-indicators of agricultural landscapes, but bat diversity has not explicitly been studied in relation to this policy. We investigate how bat activity, foraging, species richness and functional groups are affected in twenty-six wood-pastures along a gradient of tree density, from open to dense. In parallel, open fields and deciduous forests were sampled and the effect of the surrounding landscape configuration was explored. Our results show a consistent increase in total bat activity, foraging activity and species richness within wood-pastures along the tree density gradient. We find optimal tree densities within wood-pastures are higher than values reported in previous studies, and suggest thresholds might depend on the landscape context. Shrub density was a strong predictor of total bat activity and foraging; whilst structural variation of tree size in wood-pastures was most strongly correlated with species richness. We show that wood-pastures are an important habitat and in comparison to forests they contribute to higher bat species richness and activity levels. Interestingly, higher activity levels of forest feeding specialists were observed in wood-pastures compared to forests. At the landscape level, amount of water in the landscape was the strongest predictor of bat activity whilst deciduous forest mostly influenced foraging activity. This study demonstrates that tree density within wood-pastures is not a limiting factor of bat activity and foraging and that other habitat and landscape parameters are important. Thereby focusing solely on tree density limits will not help to promote the ecological requirements for bats. Instead we suggest that a results based approach to CAP payments would be preferable.

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  • HistMapR

    2017. Alistair G. Auffret (et al.). Methods in Ecology and Evolution 8 (11), 1453-1457

    Artikel

    Habitat destruction and degradation represent serious threats to biodiversity, and quantification of land-use change over time is important for understanding the consequences of these changes to organisms and ecosystem service provision. Comparing land use between maps from different time periods allows estimation of the magnitude of habitat change in an area. However, digitizing historical maps manually is time-consuming and analyses of change are usually carried out at small spatial extents or at low resolutions. HistMapR contains a number of functions that can be used to semi-automatically digitize historical land use according to a map's colours, as defined by the RGB bands of the raster image. We test the method on different historical land-use map series and compare results to manual digitizations. Digitization is fast, and agreement with manually digitized maps of around 80-90% meets common targets for image classification. We hope that the ability to quickly classify large areas of historical land use will promote the inclusion of land-use change into analyses of biodiversity, species distributions and ecosystem services.

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  • Contrasting multi-taxa functional diversity patterns along vegetation structure gradients of woody pastures

    2020. Simon Jakobsson (et al.). Biodiversity and Conservation 29, 3551-3572

    Artikel

    Woody pastures represent keystone habitats for biodiversity in agricultural landscapes, contributing to increased resource availability, landscape heterogeneity and structural variability. High taxonomic diversity is closely linked to vegetation structure in woody pastures, but examining functional characteristics of species assemblages can shed more light on the ecological mechanisms driving divergent responses to habitat characteristics and help guide good management practices. To this end, we use a multi-taxa approach to investigate how plant, bat and bird taxonomic and functional diversity are affected by pasture tree and shrub density, structural complexity and proximate forest cover in southern Sweden. In particular, we use a trait exclusion approach to estimate the sensitivity of diversity-environment relationships to specific traits. We found little congruence between corresponding diversity metrics across taxa. Bird species richness responded stronger to environmental variables than functional diversity metrics, whereas the functional response to the environment was stronger than the taxonomic response among plants and bats. While increasing tree densities increased the taxonomic diversity of all three taxa, a simultaneous functional response was only evident for plants. Contrasting measures of vegetation structure affected different aspects of functional diversity across taxa, driven by different traits. For plants and birds, traits linked to resource use contributed particularly to the functional response, whereas body mass had stronger influence on bat functional diversity metrics. Multi-taxa functional approaches are essential to understand the effects of woody pasture structural attributes on biodiversity, and ultimately inform management guidelines to preserve the biological values in woody pastures.

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  • How do African elephants utilize the landscape during wet season? A habitat connectivity analysis for Sioma Ngwezi landscape in Zambia

    2021. Doubt Chibeya (et al.). Ecology and Evolution 11 (21), 14916-14931

    Artikel
    1. The influence of environmental factors on the distribution and persistence of African elephants (Loxodonta africana) is pertinent to policy makers and managers to formulate balanced plans for different land-use types.
    2. The study focuses on movement of elephants and how they utilize foraging areas in Sioma Ngwezi landscape in Zambia by answering the following questions: (1) Which environmental variables and land-cover class predict the movement of elephants during the wet season in Sioma Ngwezi landscape? (2) What is the wet season suitable habitat for elephants in Sioma Ngwezi landscape? (3) What are the major wet season movement corridors for elephants in Sioma Ngwezi landscape?
    3. We used GPS telemetry data from the collared elephants to assess habitat connectivity. Maximum entropy (MaxEnt) and linkage mapper were the tools used to predict habitat suitability, movement corridors, and barriers in the landscape during the wet season.
    4. The study identified elevation, land cover, and NDVI as the most important environmental predictors that modify the dispersal of elephants in the landscape during the wet season. Additionally, a total of 36 potential wet season corridors were identified connecting 15 core areas mainly used for foraging and protection from poachers in the landscape. Of these, 24 corridors were highly utilized and are suggested as priority corridors for elephant movement in the landscape.
    5. The identified wet season habitats and functional corridors may help to combat elephant poaching by patrolling areas with high relative probability of elephant presence. The findings may also help abate human–elephant conflict such as crop-raiding by managing identified corridors that run into agriculture zones in the game management area.
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