Natural vegetation of acidophilous oak forest and Scots pine, Douglas fir and beech plantations in the Dabrowa Krzymowska nature reserve (Piaskowa Forest)

Dabrowa Krzymowska nature reserve contains one of the best preserved fragments of an acidophilous oak forest Calamagrostio-Quercetum in Europe, as well as Scots pine, Douglas fir and beech plantations located in the same habitat. The analysis of plant communities showed that the flora of all the compared surfaces belong to the species typical for acidophilous oak forests. Natural and artificial forests clearly differed from each other in quantitative and qualitative composition of plant communities. Among the cultivated species, the pine turned out to affect natural plant communities to the lowest extent. On the other hand, the beech exerted the strongest effect upon local communities, limiting other species by shadowing. The analysis of environmental factors using indicator values [Ellenberg et al. 1992] showed that light availability was the factor shaping species composition and abundances. No decrease of pH value was observed in the plantations of coniferous trees. The quality and thickness of leaf litter was likely an important factor determining the species composition and abundances of forest undergrowth. A thick layer of plant litter limits the growth of mosses, tuft plants and plants with small seeds, but, on the other hand, stimulates the development of stolonous plants. Agrotechnical works, preceding the creation of plantations of coniferous trees, damage forest undergrowth. Thus, a recolonization of habitats takes place in new plantations. Therefore, the undergrowth of the studied forests of III-IV age class is dominated by species with lightweight propagates, whereas species reproducing vegetatively are uncommon. The conducted analyses do not explain fully the effects of all the above-mentioned factors. However, they emphasize the need to, revise current opinions on the impact of forest management on biodiversity. The recommended activities,. aiming at forest renaturalization, may be ineffective, or even exert an adverse effect on plant diversity, thus being negative from the point of view of environmental protection. The present results are also important for the assessment of economic effectiveness of the cultivation of particular species in poor forest habitats.