1. Institute for Agricultural and Forest Environment; Polish Academy of Sciences; Bukowska 19 Poznań 60-809 Poland
2. Institute of Nature Conservation; Polish Academy of Sciences; Lower-Silesian Field Station al. A. Mickiewicza 33 31-120 Krakow Poland
3. Department of Nature Conservation; Faculty of Biological Sciences; University of Zielona Góra; Prof. Z. Szafrana 1 Zielona Góra 65-516 Poland