Selected physiological processes of Betula ×oycoviensis Besser in different habitat conditions of the Ojcowska Valley (Southern Poland)

For years, the Ojców birch Betula×oycoviensis Besser. was considered an endemic species. However, it turned out that apart from southern Poland it also occurs in other European locations. Nevertheless, it is a rare taxon that is vulnerable to extinction. The experiment aimed to learn about the functioning of the photosynthetic apparatus of Ojców birch and the condition of individuals of this species occurring at two stands in the Ojców National Park with different levels of sunlight. These studies have shown that this birch is a heliophilous taxon and that not very large changes in light intensity do not cause significant environmental stress. However, they induce differences in the content of chlorophyll pigments.