The comparison of population structure and distribution of thalli Evernia prunastri (L.) Ach. along the trunk of Tilia cordata in a shaded floodplain lime-tree forest for 2008–2017

The research was carried out in shaded flooded lime-tree forest on the territory of the Mari El Republic. Population density, ontogenetic structure of populations and thalli vitality of E. prunastri were explored on 19 marked trees of heart-leaved linden on different tree trunk heights (0–0,5 m, 0,5–1 m, 1–1,5 m, 1,5–2 m) and on different expositions (north, east, south, west). For the period from 2008 to 2017 an increase in the population density of E. prunastri was founded. These differences appear at the trunk height of 1,5–2 m. Thalli were not founded at the height of 0–0,5 m. No changes in the distribution of thalli by exposure in different years were revealed. The most of E. prunastri thalli grow on the northern exposure. In 2017 in the population the specimens share of v₁, v₂ and g₂v of ontogenetic states increases and the specimens share of g₁v decreases. The average vitality of E. prunastri thalli decreases, the deterioration of vitality is more pronounced among individuals in g₁v-ss ontogenetic states. An increase in the population density, a decrease in the size of the E. prunastri thalli and Hypogymnia physodes, a «rejuvenation» of the ontogenetic structure of the E. prunastri thalli were shown earlier for the illuminated floodplain lime forest. Similar processes in different environmental conditions and in different species indicate regular changes in the populations of epiphytic lichens, which can be caused by climate warming.