Ecological and substrate characteristics of epilithic group of lichens in the conditions of the North-West of Russia
The aim of this work is to study the environmental and substrate features of the formation of epilithic lichen cover on quartz-bearing rocks of different chemical composition: on granites (acidic rocks), shungites (carbon-containing acidic rocks), basalts (basic rocks), dolerites (ultrabasic rocks) in rocky forest communities and coastal ecosystems of the North-West of Russia. This paper summarizes the results of 20-year study of species composition and structure of epilithic lichen cover in these ecosystems within the Murmansk region, the Arkhangelsk region and the Republic of Karelia. Geobotanical, floristic approaches were used as field methods. Data processing was done by one-way regression analysis and multivariate methods using MS Excel.In the conditions of sea coasts and fresh water shore zones epilithic lichen cover is formed between the water line and the vegetation of the indigenous seashore. The leading factors in the formation of the epilithic lichen cover are the dynamics of the water body (according of multivariate analysis, the greatest load on the parameter “distance from the water line” - 0.95-0.86) as well as the structure of the rocky substrate (load on this factor is 0.96-0.56). From the water line, the number of lichen species and the average total projective cover on the plots increase significantly (p < 0.05). In forest ecosystems, the limiting factor for epilithic lichens is the light intensity. The light intensity depends on the surface exposure, the angle of inclination, and the microtopographic characteristics of the substrate (chips, graininess, depression), as well as on the type of plant community that forms the macroconditions for lichen cover. The pattern of light distribution on the surface of the substrate depending on its angle of inclination (r2 = 0.4-0.8; p≤ 0.05) is shown. It was found that in the studied ecosystems on these types of substrates the formation of lichen cover depends on a complex of abiotic and biotic factors. Within the group of investigated substrates, no strong species relations to the chemical parameters of the substrates were revealed.