The decline of the Salix lapponum population and reduction of the number of its natural stands is mainly attributable to changes in water conditions in the habitat (dehydration and changes in water chemical composition) which are caused by various anthropogenic factors. Selected parameters of abiotic environment were determined in 15 chosen downy willow stations on the peat-bogs in Polesie Lubelskie Region in Poland, from May 2001 to August 2003. Based on a comparison of the abiotic conditions in the research stations, in terms of the population size of S. lapponum, the optimum values of the factors were determined (habitat hydration, acidity and electrolytic conductivity of the underground water, as well as ion content) for adequate functioning of a given species.