Population characteristics of cephalolichen Lobaria pulmonaria (L.) Hoffm. at the northern limit of its range (Northwest Russia, Republic of Karelia)

The populations of Lobaria pulmonaria and their characteristics were studied at the northern limit of its range in the Republic of Karelia (Northwest Russia). The study was carried out in northernmost boreal zone on 8 permanent 100 x 100 m sample plots with last disturbance 180-270 years ago. It was found that in the north of the region, the number of substrate units on which lichen grows decreases with an increase of the time since last disturbance from 25 to 11 per ha. In the ontogenetic spectrum (excluding juvenile and immature thalli), virginal thalli prevailed. The proportion of generative thalli in forests in the mid-succession stages (mixed spruce-birch forests) was 2%, and they were absent at later stages (in preclimax spruce forests). In the studied forests, the main substrate of Lobaria pulmonaria was the trunks of living Populus tremula and Salix caprea. With an increase in the diameter and area of the trunk of Populus tremula, the number of thalli increased, and their average area decreased. An important role for Lobaria pulmonaria was played by the individual characteristics of the tree trunk, such as the height above ground, exposure, angle of inclination. The optimal conditions for the growth and development of this species were formed on the aspen trunks. Due to the collecting shape of crown and its wide radius, a large amount of precipitation flowed down the trunk during rain. Moreover, due to the wide and dense crown, the trunks were wet longer than other tree species. Comparison of the obtained data with similar studies done in the subzone of the middle taiga showed that at the limit of the range, the number of substrate units colonized by Lobaria pulmonaria and the number of thalli was smaller than in the south of Karelia. The share of generative thalli in the ontogenetic spectrum of species populations in forest communities of the north taiga subzone was 3 times smaller than in the middle taiga forests.