Rare lichen species of the Chuvash Republic that need constant monitoring in the natural environment

The paper provides information about 13 rare lichen species of the Chuvash Republic that need constant monitoring in the natural environment (Agonimia allobata, Agonimia flabelliformis, Bryoria simplicior, Bryoria trichodes, Cetraria islandica, Cladonia stellaris, Flavoparmelia soredians, Heteredermia japonica, Inoderma byssaceum, Phaeographis dendritica, Platismatia glauca, Scytinium tenuissimum, Usnea diplotypus). A brief ecological and biological characteristic, occurrence in neighboring regions, limiting factors and measures of protection of these species are indicated for each species. 7 species of lichens are located on the border of the range or beyond (Bryoria simplicior, Bryoria trichodes, Cetraria islandica, Cladonia stellaris, Flavoparmelia soredians, Phaeographis dendritica, Platismacia glauca), 10 species are strictly confined to a certain type of habitat and substrate (Agonimia allobata, Agonimia flabelliformis, Bryoria trichodes, Bryoria simplicior, Flavoparmelia soredians, Heteredermia japonica, Inoderma byssaceum, Phaeographis dendritica, Scytinium tenuissimum, Usnea diplotypus), 7 species are decreasing in number due to a decrease in the area of old-growth forests as a result of logging, trampling and fires (Agonimia allobata, Cetraria islandica, Cladonia stellaris, Heteredermia japonica, Inoderma byssaceum, Platismatia glauca, Usnea diplotypus). Cetraria islandica disappears when the soil cover is disturbed, when collected by the population for medicinal purposes.