Species deletion in Potentillo albae-Quercetum phytocoenoses reversed by the removal of Carpinus betulus

The studies were conducted in the Biaowiea primeval forest on a study area of 28,000 m², divided into two plots and 280 quadrats. In 1979, all Carpinus betulus individuals were cut off within the experimental plot (E, 7800 m²), whilst the control plot (C, 13000 m²) remained unchanged. Each plot contained a phytocoenose of Potentillo albae-Quercetum and an adjacent community of Tilio-Carpinetum.By 1983, hornbeam invasion into the oak-forest habitat within C plot had resulted in: 1) a decrease in species number by more than 10 per 100 m² on average (c.a. 30%); 2) a twofold greater deletion rate of heliophil oak-forest species than for Fagetalia and Querco-Fagetea; 3) a diminution of the area of oak-forest phytocoenose by more than 100 m² per year; 4) formation of a community with a species combination corresponding to Tilio-Carpinetum. Hornbeam removal had the opposite effect: 1) the number of species increased by more than 100%; 2) the number and frequency of oak forest species rose considerably; 3) those parts of the phytocoenose colonized previously by Carpinus betulus regenerated, and thence the area of Potentillo albae-Quercetum community increased.