Climate change accounts for some specific threats, such as windfalls, snow breakages, fires, outbreaks of diseases and pests. It also brings about certain negative consequences for forestry, namely changes in the productivity and sustainability of planted forests. A number of Ukrainian scientists came to the conclusion that climate change will lead to the displacement of species habitats and borders of forest areas. Tendencies to the change of the prevailing tree species, stand structure, growth dynamics and forest stability will arise on the forest phytocenoses level. Therefore, it is important to study the growth of beech stands and how climate change affects them.
The aim of the study was to analyse the influence of climate indices on the radial increment formation features of the middle-aged pure beech stands growing in the upper basin of the river Latorytsya, as well as to describe synergistic effects of the main climate indices (precipitation, air temperature, moisture deficit and air humidity) on the radial increment of the beech stands during the growing season.
Materials and Methods
The objects of the study were the middle-aged pure stands that grow in the optimum for beech ecological conditions on the slopes of the southern and north-eastern exposure. We used Presler borer to take core on each sample area in the group of 10 trees at a height of 1.3 m. For each group 20 cores in the north-south directions were taken. We measured the width of annual rings by MBS-1 microscope with an accuracy of 0.1 mm.
The average values of the beech radial increment were determined in the groups of trees from 1992 till 2013. We applied climate indices according to the values of the Nyzhni Vorota Weather Station located at the altitude of 500 m a. s. l. at the distance of 4.5 km from the research plots. The correlations between absolute average value and climatic indicators as well as statistical indicators were calculated by means of the B. O. Dospekhov method (Dospekhov 1985).
We calculated multiple correlation coefficients of radial increments of the beech stands and climatic factors during the growing season. The results showed that radial increment has high correlation (R = 0.74) with humidity and a lack of moisture, it has moderate correlation (R = 0.48) with air temperature and moisture, and significant correlation (R = 0.56 and 0.59) with temperature and rainfall, humidity and soil moisture deficit, rainfall and humidity, rainfall and moisture deficit.
We analyzed the influence of climate indices on the radial increment of the middle-aged beech stands in the mountain conditions on the slopes of different exposure. As the result, we came to the conclusion that the range of a tree ring width in the beech stands growing on the northern slopes more tightly correlate with climatic indices than those growing on the southern slopes. We found significant correlations and obtained regression models for the relationship between the beech radial increment and climatic indices complex during the vegetation period (a deficit of moisture, air humidity, average annual temperature and rainfall). Moreover, the research showed that radial increment of the middle-aged beech stands is the most influenced by humidity and air temperature. It also defined the climatic indices values for the observed minimum or maximum radial increment of the beech stands. At the average of many years air temperature of 11–12°C and the moisture deficit of 3–4 MB and precipitation increase up to 800–1100 mm along with air humidity of 76–80 % the value of radial increment of beech is maximum and is in the range of 1.92–2.28 mm.
2 Figs., 3 Tables, 16 Refs.