Evaluation of Thinning Efficiency in Pineries of Dry Forest Sites of the Kazakh Uplands

According to the current Forest Code of the Republic of Kazakhstan, in the forest plantations of specially protected natural areas, the main forestry measures aimed at the conservation and enhancement of the protective functions of forests are intermediate felling, that is, thinning. Pinus sylvestris L. is one of the main forest-forming species in Kazakhstan. Increasing the stability of forest plantations and the possibility of forming recreationally attractive landscapes through thinning is an urgent problem for plantations growing in arid conditions. The research purpose is to analyze the effectiveness of thinning of high intensity in dry pine forests of the Kazakh Uplands for a 70-year period, using dendrochronological methods. It was proved that in dense pine forests growing in dry conditions, there is an increase in radial growth in each subsequent 10-year period after thinning. It was found with statistical certainty that the greatest response to changes caused by thinning of high intensity was observed between 1949 and 1960. Analysis of indexed tree-ring chronologies using regional curves (indexed average tree-ring chronologies of pine) using a cubic spline function revealed differences in pine radial growth indices from the site where thinning of high intensity were carried out and from the control site (time periods: 1947–1955, 1961–1970, 1981–1990, and 1995–2015). The data obtained show a positive effect of thinning of high intensity on the radial growth of trees in the considered pine forests. In dense pine forests of dry growing conditions of the Kazakh Uplands it is recommended to make 1 or 2 cuttings with thinning intensity of 25–35 % at the age of 20–25 and 40–50, respectively, with subsequent increment thinning.