Downy willow (Salix lapponum L.) as a component of different phytocoenoses in Polesie National Park

The aim of this study was to make an evaluation of the current stands of a relict species, Salix lapponum, within the area of the Polesie National Park, to determine the population size and condition of downy willow as well as to analyse biocenotic conditions in its stands. The study, conducted in the years 2001-2003, allowed to establish that the number of S. lapponum stands had decreased significantly and that its population size in the confirmed stands in the Polesie National Park was substantially lower than 50 years ago. Salix lapponum was a component of different phytocoenoses, but its highest population size and a high degree of development were noted at the sites with the Betulo-Salicetum repentis and Thelypteridi-Phragmitetum communities. The character of the phytocoenoses in which Salix lapponum occurred in greatest numbers may evidence the wide range of tolerance of downy willow with respect to habitat conditions. There is a probability that not only the changes in its habitat conditions, which were noted over the last half-century, had a significant effect on the reduction in the number of stands and in the population size of this species. An essential problem appears to be the fact of the absence of flowering in individuals in many of the studied populations, which may result in an insufficient degree of adaptation of S. lapponum to changing habitat conditions