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Browsing by Subject "paikalliset ja maisemalliset tekijät"

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  • Huttunen, Johanna (2022)
    Bumblebees are important pollinators globally and especially in Fennoscandia, yet they are declining. The amount of natural vegetation in cities is decreasing with urbanisation. Hence suitable habitats for urban bumblebees are diminishing. Brownfields can be important habitats for bumblebees in cities because they resemble natural habitats. I studied bumblebee communities in urban brownfields. My main aims were to evaluate how local and landscape scale environmental factors affect the suitability of a brownfield to be a habitat for bumblebees. I also evaluated whether certain bumblebee functional traits are filtered in the brownfields. I expected that especially local characteristics and primarily the amount of flowering plant cover and the size of a site would affect bumblebee richness and abundance. I also expected the bumblebee communities to be characterised by generalist feeders. I collected bumblebees using line tracking in 15 brownfield sites in the city of Lahti and sampled bumblebees six times during the summer of 2020. The share of ground cover types within each site was estimated, as well as the share of different habitat types within a 300 m buffer zone around the sites. The data were used to analyse which local and landscape characteristics affect bumblebee community composition, species richness, and abundance in a brownfield site. Trait analyses were used to test the relationship between bumblebee traits and environmental factors. I showed that bumblebee abundance and richness were affected by local site characteristics but not landscape-scale factors. However, community composition was associated with landscape characteristics, including forest and commercial or industrial areas. Unexpectedly, the size of a brownfield site did not affect community composition, richness, or abundance. Functional traits were filtered in brownfield sites, especially the prevalence of a short proboscis, which is linked to a generalist diet in these bees. Brownfield sites are rich in bumblebees. Brownfields are suitable habitats for bumblebees regardless of the scale of urbanisation, and even small sites can host a diversity of bumblebees. As the amount of natural habitat in urban areas is decreasing, brownfields should be considered important habitats for bumblebees and other pollinators in urban planning.