Regeneration potential of stands dominated by Quercus robur L. in Vardim Islands.
Regeneration processes in riparian forests in Vardim and Malak Vardim islands, Bulgaria, were studied. Natural oak forest stands, which are dominated by Quercus robur, in the investigated region were insignificantly impacted by anthropogenic activities in the last 40-50 years. Populus alba, Ulmus laevis and Pyrus communis were the most dispersed. The introduced Amorpha fruticosa and Fraxinus americana were also dispersed in large scales. The regeneration potential of U. laevis was good and that of Q. robur to a lesser extent. The main reason for the unsatisfactory regeneration of Q. robur was due to grazing of wild animals. The establishment of regeneration cuttings in Vardim oak forests was difficult due to the introduced limiting status of the protected area. For the successful natural regeneration of Q. robur, it is recommended to make fences around solitaire and groups of fruiting trees, as well as strict protection and soil scarification. To stop the further invasion of introduced species and to increase the number of other native tree species, the following are recommended: (i) reafforestations with hybrid Euroamerican poplars and other exotic tree species should be no longer performed; (ii) clear cuttings in forests of native tree and shrub species should be prohibited; and (iii) regeneration groups of Quercus robur, Ulmus laevis, Populus alba, Populus nigra and Salix alba should be established. This could be done through natural regeneration (soil scarification, cutting of the understorey and sowing of seeds) and afforestation using Vardim reproduction materials.