Diaz-Forero, I, Kuusemets, V., Mänd, M., Liivamägi, A., Kaart, T. and Luig J. 2011.  Effects of Forest Habitats on the Local Abundance of Bumblebee Species: a Landscape-scale Study. Baltic Forestry 17(2): 235-242

main objective of our study was to analyse how different bumblebee species are influenced by the presence of forest habitats in the surrounding landscape. The local abundance of bumblebee species was studied in 22 semi-natural meadows located in Northeast Estonia. The proportion of forest cover and brushwood cover, the mean patch area of forest and the edge density of forest were calculated at four spatial scales (i.e., radii of 250 m, 500 m, 1000 m and 2000 m). In total, we found 597 individuals of bumblebees belonging to 24 species (gen. Bombus), including five species of cuckoo bumblebees (subgen. Psithyrus). Our study shows that some bumblebee species seem to have different preferences in terms of the structure of the landscape. Some species may benefit from a heterogeneous landscape with a high proportion of forest habitats (e.g., B. schrencki), whereas others seem to prefer open areas (e.g., B. veteranus). We also found that some bumblebee species that have large foraging distances (e.g., B. terrestris) seem to be negatively affected by forest, as the presence of a high quantity of forest patches in the surrounding landscape could narrow their foraging area. The joint effects of the set of landscape variables related with forests appear to be important for some bumblebee species, specially, but not only, at the largest spatial scale. Overall, our results indicate that the presence of forest is very important for bumblebees, even for some species that prefer open areas, as forest habitats and edges may offer overwintering sites and nesting places for them. In countries like Estonia, where forests are widely distributed and represent a relevant part of the landscape mosaic, this type of habitat should be preserved if conservation of biodiversity is desired. In addition, conservation efforts targeting particular species of bumblebees should consider the landscape preferences of the species under study, and these efforts should aim to maintain the habitat types that are suitable for most bumblebee species.

Key words: Bombus, forest cover, brushwood, edge density, mean patch area, landscape indices