Ecological and cenotic features of the old-growth Pinus sibirica forests in the North-Chuya glaciation center, Russian Altai

Ecological and cenotic features of the old-growth forests of Siberian pine – Pinus sibirica Du Tour situated in the mountain-glacial basin Aktru in the North-Chuya glaciation center of the Russian Altai at the altitudes of 2160–2300 m a.s.l. were examined for the first time. These forests can be defined as virgin ones since they have never been subjected by direct human-caused disturbances throughout their existence. This makes them a valuable pattern of the undisturbed forests of the Altai. The age of the primary generation of P. sibirica forming the base of the tree layer of these forests is about 400 years; the age of some trees reaches 600 years and more. A significant floristic diversity (104 species of vascular plants) was detected in these forests. In the Aktru mountain-glacial basin, old-growth forests of P. sibirica exist in eight variants, significantly differing in the composition and structure of subordinate layers and the diversity of vascular plants, mosses, and ground lichens. We have carried out the phytoindication of the most important ecological factors at the old-growth P. sibirica forests situated on the northern, western, and eastern slopes of the valley of the Aktru River. Despite the fact, these forests are found on different types of soils (coarse-humus gleyed cryozems in the northern slope, typical soddy-podburs on the eastern one, and skeletal coarse-stony weak podburs in the western slope), all habitats are characterized by narrow ranges of moisture conditions – four grades (67.1 to 70.0) indicated series of humid-forest habitats and active soil richness – two grades (7.0 to 8.1) indicated series of mesotrophic habitats. Such environmental conditions are optimal for P. sibirica in all studied habitats. Both the great scientific significance of the examined old-growth P. sibirica forests for climatic and environmental studies and the need for their conservation, due to their rarity, undisturbed state, and significant age of the trees, are noted.