Tree Cavity Resources in Spruce-Pine Managed and Protected Stands of the Bialowieza Forest, Poland

Tree cavities are vital resources for many animals, especially birds and mammals. We aimed to determine density of cavity resources in coniferous spruce-pine (Pinus/Picea genera) stands of the Bialowieza Forest, Poland, and to correlate their presence with tree species composition, and characteristics of trees and stands (condition, DBH, basal area). We conducted studies in spruce-pine stands with no (national park), medium (seminatural reserves), and high (managed forest) management activity. We measured all trees within 50-m 50-m sample plots (eight plots in each zone) and searched for all tree cavities. The highest density of cavities was observed in the national park (12.5/ha) and the lowest in managed plots (3.0/ha). Most cavities were found in dead trees (74.4%), mainly in pines Pinus sylvestris L. The basal area of dead pines within the stand was the best predictor of cavity presence on sample plots. Our results confirm a key role of pine snags in natural coniferous stands. Forest management leads to dramatic reduction of tree cavity resources in managed stands. We suggest that the leaving or creation of pine snags is the most effective method of providing or retaining cavity resources in commercial coniferous forests in Europe.