Dynamics of <i>Evernia prunastri</i> (L.) Ach. and <i>Hypogymnia physodes</i> (L.) Nyl. population structure on Tilia cordata Mill. in the flooded lime-tree forest of the Bolshaya Kokshaga river

The paper deals with perennial dynamics of the population structure of the epiphytic lichens Evernia prunastri (L.) Ach. (2008-2016) and Hypogymnia physodes (L.) Nyl. (2010-2016) with the different life forms and the ecological strategies. The research was carried out in the Mari El Republic in the flooded lime-tree forest. The authors studied the density (number of thalli on a tree) on the trunk from 0 to 1,5 meters, the size and the ontogenetic structure of population of both species of different ontogenetic states: virginile (v1, v2), potentially generative (g1v, g2v, g3v), subsenile (ss) on 17 trees of Tilia cordata. The density of E. prunastri and H. physodes population increases. These changes are more specific for E. prunastri . Thalli of E. prunastri have a bigger size than thalli of H. physodes . These differences are observed on g1v, g2v, g3v, ss thalli. The decrease of thalli size is observed for both species but the difference is more for E. prunastri . The comparison of ontogenetic spectra of populations was made according to their heterogeneity within trees. The values of the effects (the effect is the parameter of the ontogenetic spectrum of the population) decreased in 2016, which indicated a shift of the ontogenetic spectra to the left, i.e. an increase in the proportion of young thalli that can be traced in the total ontogenetic spectra of populations. At the same time, the differences between the ontogenetic spectra of the E. prunastri population are statistically significant.