Forest management alters alpha-, beta-, and gamma diversity of saproxylic flies (Brachycera) in the Hyrcanian forests, Iran

Abstract

Forest management can cause a loss of biodiversity associated with dead wood. Today, vast areas of unmanaged temperate forests are protected forests in the Hyrcanian region in northern Iran. The Hyrcanian forest hosts large numbers of endemic species, grounding its high conservation value. However, few studies have investigated the possible impact of increasing forest management activities in these forests. We surveyed saproxylic flies in 30 managed and unmanaged plots across the entire Hyrcanian forest between 2017 and 2019 with pan traps. Overall, we collected 71 species belonging to 22 families. Forest management resulted in decreasing abundance and species richness, as well as in an altered community composition. Chloromyia speciosa (Macquart, 1834), Sargus cuprarius (Linnaeus, 1758), Pherbellia jalili Mortelmans and Kazerani, 2020, Dolichocephala sp. and Bibio sp. were bioindicators for unmanaged plots. Indicator species suggest that changes in the biodiversity of saproxylic flies where primarily linked to the management-caused loss of old-growth attributes, such as large decaying logs and fruiting bodies of wood-inhabiting fungi. Endemic species as well as rare families of saproxylic flies illustrate the importance of conserving unmanaged parts in the Hyrcanian forest.