The effects of tree age and tree species composition on bird species richness in a Central European montane forest

Abstract

AbstractLarge areas of montane forests are commercially harvested, while some other parts remain unmanaged. These conditions provide an opportunity to study the response of bird communities to forest management. Here we focused on the effects of tree species composition and tree age on bird species richness. We counted birds in two types of montane forest (beech and mixed) replicated in three age classes (managed 55-65 years, managed 85-95 years, unmanaged over 200 years) in the Vtačnik Mountains, Slovakia. Number of bird species at individual study sites (local richness) was predicted solely by the tree age and not by the forest type. Specifically, the number of species was highest in the oldest stands, while the stands of 55-65 and 85-95 years did not differ from each other. By contrast, forest type seems important for total bird species richness (number of species recorded in all study sites of a given type) with more species recorded in mixed forests than in beech forests. The local richness seems thus limited by the amount resources available at a given site, which is highest in the oldest stands irrespective to forest type, probably due to largest amount of food, dead wood or tree cavities, being particularly suitable for habitat specialists. However, larger species pool in mixed forest, enriched by birds adapted to coniferous trees, increases the total number of species observed in this type. We thus recommend to shift the harvest to the highest possible age and to include some other tree species into parts of beech monocultures.