The effect of volcanic eruptions on the radial growth of trees in the forests of the Mari El Republic

The data ofthe long-term dynamics of radial growth for Pinus sylvestris L., Picea×fennica (Regel) Kom., Larix sibirica Ledeb. and Quercus robur L. in the forests of theof Mari El Republic (Middle Volga region, Russia) are presented. The objective of the study wasto obtain fundamental knowledge about the reactions of trees and biogeocenoses in general to the effects of various environmental factors. The research was conducted in different types of forest and vegetation conditions of Mari ElRepublic according to the traditional method in dendrochronology, which based on the wood cores, measuring the width of the annual rings of trees and subsequent mathematical processing of the initial time series: highlighting the age trend, calculating the annual growth indices and their smoothing by the method of a moving average with a lag of 7 years. The length of the dendrochronological series varied from 70 to 300 years. Was shown that the dynamics of tree growth indices in each ecotope has a clearly pronounced wave-like character, but the period of fluctuations is unstable and variedwithin large limits. All decreases in the magnitude of the growth indices were associated with a series of volcanic eruptions and explosions of Supernova and powerful solar flares that destabilized the state of the climate system of our planet. The impact of the current weather anomalies on the dynamics of tree growth was very weak and not always unambiguous. The results indicate the ambiguity of the reaction of trees in response to the same changes in external conditions, which is associated with the peculiarities of the genotypic and age structure of their cenopopulations, as well as the spatial heterogeneity of ecotopes and the entire lithosphere, which is a complex fractal-wave system of lineaments (tectonic faults, watercourses, karst voids, etc.). In this regard, in our opinion, attempts to reconstruct the dynamics of climate in the past, especially changes in temperature and precipitation, according to dendrochronological series, which reflect only information about the degree of favorable conditions for tree growth, are untenable.