Biotic stability of Scots pine growing in stands on fairly fertile soil types of the Lviv Roztochya

Abstract

In recent years in Ukraine and other European countries, there has been observed a decrease in biotic resistance and mass drying of pine stands. The ecological precondition for this drying off is global climate change and related fluctuations, primarily, of the temperature and hydrological regimes. At the same time, the tremendous ecological, economic and social importance of pine stands necessitates a thorough study of forest site conditions, particularly of phytocenotic ones. They are the most viable and have high biotic stability. The objects of research were the stands formed by forest-forming species typical for Lviv Roztochche: Scots pine, beech, oak, hornbeam with participation, as associated species, of maple, sycamore, small-leaved linden and others. The specific features of certain forest site conditions of the experimental objects are responsible for the different phytocoenotic interactions of pine with other tree species and, accordingly, its different vitality. The criteria used to determine the vitality were dielectric parameters - impedance and polarization capacity. It is found that the annual dynamics of impedance and polarization capacity correlate with the annual intensity of physiological and biochemical processes in the cambial tissues of pine. The impedance decreases sharply during the growing season (minimum values in pine trees are observed in June-July). During the period of physiological and forced rest, the impedance increases, reaching its maximum values in December. At the same time, the minimum values of polarization capacity in pine trees are observed in November, and the maximum is in February. The most significant differences between pine trees of different stands in terms of the annual dynamics of impedance and polarization capacity are observed in the periods of fixing the maximum values of these indicators. At other times of the year, these differences are usually insignificant. At the same time, the study shows that the average annual values of dielectric parameters are the most informative ones as to the vital power of pine trees. Middle-aged (55-year-old) pine trees grown after various methods of main felling (clear felling, uniform, shelterwood felling in two or three cuts, group-selection ones in three cuts) with sufficient light supply have greater vitality and, respectively, are characterized by less impedance and greater polarization capacity than parent trees. It is also established that the vitality of Scots pine trees in hornbeam-oak-pine and pine-beech stands is not steady. With age, a decrease in biotic resistance of pine trees becomes more intensive in pine-beech stands than that of hornbeam-oak-pine stands. In general, phytocoenotic interactions for Scots pine in hornbeam-oak-pine stands are more favorable than in pine-beech stands.

Keywords

• electrical indicators
• annual dynamics
• hornbeam-oak-pine and pine-beech stands