Features of the Dynamics of Lichen Pine Forests under Flooding by the Rybinsk Reservoir

Abstract

The article presents the results of studying the long-term dynamics of the Darwin Nature Reserve’s forests, which turned out in altered environmental conditions due to the creation of the Rybinsk Reservoir. Multi-year reservoir influence has significantly changed the environment of coastal areas, which resulted in necessity of studying the coastal forests state. The lichen pine forest growing in the zone of direct influence of the Rybinsk Reservoir became an object of study. A geobotanical description was carried out and inventory characteristics of the woodland were determined in order to study the direction and speed of growth and development processes at the trial areas. The main focus was on the dynamics of the living ground cover as an indicator of soil and hydrological conditions and the state of the stand, undergrowth, and understorey. The connection of growth and development processes of flooded stands with climatic features of growth periods, relief features and level regime of the reservoir was found. The calculation of the effect of flooding, which characterizes the impulses of deviation of the pine stand productivity indicators, showed that in the conditions of well-defined mesorelief and deep groundwater occurrence in the low-water period, the effect was negative, and in the high-water period – positive. This value was positive for both periods on the slopes of shallow subsurface depressions. A comparative analysis of absolute increments in flooded and reference stands revealed significant differences in the nature of these changes. The average growth tends to increase under flooding, which is not typical for natural stands in ripe age. Sharp peaks of current increment rise correspond to the period with the most well-defined influence of flooding. Significant mobility and variability of the ground cover indicate the dynamism of the studied type of forest, the processes of self-regulation in lichen pine trees are so disturbed by the reservoir influence that even the formed forest type is not able to survive. From the perspective of I.S. Melekhov’s dynamic typology, the studied forest type under flooding should be considered as a type-stage on the way to the accelerated formation of a new type – green-moss pine forest. The findings confirming the provisions of the dynamic typology are important both for forest science and forestry practice, and for monitoring studies in the reserve.