Grzyby wielkoowocnikowe stwierdzone na olszy czarnej Alnus glutinosa (L.) Gaertn. w drzewostanach olszowych wykazujących objawy zamierania

Black alder Alnus glutinosa (L.) Gaertn. is an important forest−forming species in Poland, with more than 5% participation in the species structure. It is a typical lowland species, especially in the river valleys, on the banks of the lakes and in the land depressions. It is one of the main species in the following habitats: boggy mixed broadleaved forest, alder and alder−ash forest, riparian forest and moist broadleaved forest. As a valuable admixture alder is introduced in the habitat of boggy coniferous forest and boggy broadleaved forest. Until recently black alder was considered in Poland as a species with a very low level of danger from the pests and diseases. The situation changed at the turn of the centuries, when the deterioration of the health status of the alder stands began, which led locally to the mass dieback of the trees, mainly in the stands which are over 20 years old. In the following years, the phenomenon was intensified. The largest number of such stands was recorded in 2006. The strongest deterioration of health condition of the trees was observed in five regional directorates of the State Forests: Białystok, Lublin, Torun, Wrocław and Olsztyn. The study gives information on lignicolous fungi found on black alder in 62 alder stands, which exhibited the most severe signs of the dieback. The research was conducted in 14 forest districts and in Poleski National Park (fig.). The surveys revealed the presence of 49 taxa of the lignicolous fungi (44 Basidiomycota and 5 Ascomycota). The most common species were Xanthoporia radiata, Stereum hirsutum, Daedaleopsis confragosa, Armillaria spp. as well as S. subtomentosum (tab. 2). The disease contributing to the local dieback of black alder in the stands (mainly in the Lublin Regional Directorate of the State Forests) is the root rot caused by Armillaria species. Many species of lignicolous fungi (e.g. Fomes fomentarius, Fomitopsis pinicola, Ganoderma applanatum) penetrate into previously weakened trees, causing decay of wood, which can accelerate the dying of single trees.