Wieloletnie zmiany składu gatunkowego drzewostanów naturalnych w Puszczy Białowieskiej

In the paper the long term dynamics (about 40 years) of selected, the most important, natural forest stands of the Białowieża Forest were presented. The studies were carried out on 120 permanent study plots, located both in nature reserves and in the Białowieża National Park. The DBH of all the trees were measured and the number of all the individuals trees and shrubs species with the height under 1,3 m was counted. The analysis of tree species composition and their density changes was carried out, as well as their natural regeneration was analyzed. The strong expansion of hornbeam were observed (fig. 1a, b; tab.). Actually this species was predominant in forest stands, in natural regeneration and was expansive to the more oligotrophic and mezotrophic forest stands, causing their unification towards hornbeam forest. Norway spruce generally declined in abundance and became limited to oligotrophic forest communities. Significantly reduction this species were observed, especially on the mixed coniferous forest at mixed deciduous forest stands. Scots pine, oak and birch declined their share in forest stands, as well as their natural regeneration have been limited too (tab.). In the short time of the last 15 years, the strong reduction of ash share in forest stands has been observed, and the more rapid changes in all the forest stands composition as well.