Effect of soil conditions on the state of tree plantations in the green zone of Astana

Abstract

Creation and maintenance of a green zone around the capital of the Republic of Kazakhstan, Astana, is complicated not only by sharply continental climate, but also by soil salinity. In this regard, plants characterized by resistance to drought, frost and soil salinity are chosen for landscaping of these areas. Avoiding or minimizing the impact of negative consequences of afforestation of saline areas can be achieved by understanding the mechanisms by which forest trees and shrubs are able to survive in such conditions. The purpose of the study was to investigate the salt content in the soil under forest crops in the green zone of the Astana city and their influence on the condition of woody plants. The objects of the study were artificial plantations of the dwarf elm and maple ash planted in 2015. The main research method used was the establishment of sample plots in healthy, weakened and dead plantations. Maple ash was found to be more tolerant to higher salt content in soil than the dwarf elm. It was found that high content of toxic ions and low concentration of cations in the soil are related to the condition of crops, with more toxic type of salinization prevailing in the areas with weakened and dead plantations. According to the research results, it can be seen that the soil of healthy plots is characterized by a higher content of Ca2+, Mg2+ and Na+ cations than the soil of the weakened plantations. HCO3–, Сl– and SO4 2– anions are present in significant amounts in the soil under weakened crops, and the content of НСО3– ions is much higher in the areas with dead trees, which may be one of the reasons for severe soil salinization and vegetation death. It was also determined that sulfate-chloride-hydrocarbonate salinization and magnesium-calcium chemistry with toxicity greater than 0.17 mg-eq НСО3– negatively affected plant health. Sulfate-chloride type of salinization prevails on the healthy plots, in the weakened and dead plantations – the more toxic sulfate-chloride-hydrocarbonate type is found.