A Demographic Imbalance of Tree Populations in Białowieża Forest (NE Poland): Implications for Biodiversity and Forest Management

Forests, both natural and managed, provide a critical habitat to a significant part of a global diversity. Among many different groups of forest biota, trees occupy a special position. They act as foundation species that create conditions upon which the existence of virtually all other forest organisms depends, either directly or indirectly. To permanently play this role, trees must be demographically stable, i.e., their populations should be distinguished by the balanced, size-dependent proportions of individuals representing different developmental stages (from seedlings and saplings to mature and old trees). In this study, we examine the extent to which this condition is met in Białowieża Forest in northeastern Poland, an important biodiversity hotspot in Central Europe. Comparison of species-specific, equilibrium vs. actual size distributions revealed that almost half of all trees growing in Białowieża Forest represented "inappropriate", i.e. occurring in excess compared to the balanced model, species and/or diameter ranges. The amount of deficits was also large (around 30% of the current tree number), concerning primarily the smallest trees. To restore demographic balance of key tree species and thus, to enhance conservation of local biodiversity, we recommend targeted, active management strategies, including gradual removal of trees from surplus diameter ranges and assisted regeneration of species with the greatest deficiencies in small diameter classes.