The contribution of open spaces to the maintenance of hoverfly (Diptera, Syrphidae) biodiversity in Irish plantation forests

We used hoverflies as an indicator group to assess the role of open spaces in maintaining biodiversity within plantation forests. We set out to investigate the factors correlated with hoverfly biodiversity in open spaces in plantation forests, and to make recommendations for planning and management of open spaces in plantation forests to enhance biodiversity. The majority (nearly 80%) of the species we recorded are associated with open space habitats rather than closed-canopy forest. The species richness of the fauna associated with large open spaces was slightly, but significantly, higher in unplanted glades compared to forest roads. The species richness of the open space fauna was positively correlated with forest road width but did not show any relationship with overall amounts of open space. Species with larvae feeding on the foliage of trees and shrubs were associated with the presence of broad-leaved woody vegetation. Species with larvae developing in surface water habitats were associated with wet habitat features. Planning and management for hoverfly biodiversity in Irish conifer plantations should focus on the open space component, and should encourage broad-leaved trees and shrubs and wet habitat features. Wide forest roads or unplanted glades should be included to allow the maintenance of well-developed open space habitat in mature spruce forests.