Abstract
Beavers are classified as ecosystem engineers because their activities can significantly alter environmental conditions. Vegetation and landscape changes, based on a series of vegetation maps and satellite images between 1994 and 2022, were studied in a mountain valley of a protected area in the Polish part of the Eastern Carpathians. Eighteen plant communities were identified before the beavers were released, with moist and wet communities covering 76.8% of the area. After 25 years of beaver presence, the vegetation changed: fresh communities decreased from 23% to 10%, and communities with grey alder disappeared. At the same time, the moist and wet communities expanded and new ones developed. Overall, the share of these communities increased to 89% of the area, with the dominant tall herb Filipendulo-Geranietum and Menyanthes trifoliata community. A distinctive feature was an increase in vegetation patchiness with a corresponding decrease in the evenness index. Landscape analysis revealed a 9.5% increase in the length of the streambed and fluctuations in the number of beaver ponds (11-25) and migration corridors (4-20). The number of corridors increased as the availability of grey alder decreased. The total area of the ponds exceeded 2200 m(2), indicating their significant role in water retention and modifying microclimatic conditions.