Effects of forest management on bird assemblages in oak-dominated stands of the Western Carpathians – Refuges for rare species

Abstract

Forest management practices have varying impacts on biodiversity because the treatments and their outcomes do not always reflect the natural processes that maintain biodiversity. These management activities can be assessed using indicator species, among which birds are most frequently used. In 2018 we compared bird assemblages in oak (Quercus spp.)-dominated forests with admixtures of European beech (Fagus sylvatica), hereafter referred to as oak-beech forests, between managed and natural forest stands on opposite sides of the Carpathian range (south-facing in Slovakia and north-facing in Poland). The aim was to quantify and model the relationships between the quantitative parameters of bird assemblages and the main habitat parameters, as influenced by differing intensities of forest management. The point-count method with limited distance was applied to census birds (N = 100). Overall forest bird assemblages were found to be similar in respect to diversity indexes in managed and protected areas, as well as between southern and northern slopes of the Western Carpathian range, but all these types of forest differed in respect to bird species composition. However, both geographic location and management intensity, altogether with forest complexity contributed the mostly in explanation of bird diversity. The greatest differences were recorded for rare species, particularly those annexed in the Birds Directive of the European Union (mainly woodpeckers and flycatchers), as these birds were found either exclusively or in much greater numbers in nature reserves. Management intensity, forest complexity, and topography best explained the diversity of rare birds. Silvicultural systems applied in management of the Carpathian oak-beech forests, particularly the shelterwood system, seem to be sufficient for the preservation of overall bird diversity. However, decreased forest fragmentation and increased deadwood amounts are necessary measures to provide more close-to-nature stand structures, which will help support higher diversity of most bird species associated with mature forests. Because the oak-beech forests comprises only about 15% of the total forest area in the Western Carpathians, creating a network of natural or close-to-nature forest patches is recommended for the conservation of forest birds (and whole forest communities), including species annexed in the Birds Directive. Conservation priorities should be focused mainly in areas of harsh topography, where reduced wood production in these forests would have a less detrimental effect on the local forestry communities. These actions should also greatly improve the nature conservation system in the Carpathians and more generally throughout Central Europe.