Architectonics of the root system of Pinus Sylvestris L. in artifical forests at solonetzes in Trans-Ural forest-steppe
The Trans-Ural forest-steppe is characterized by a complex soil cover, which is determined by the large variegation of the parent underlying rocks, often saturated with readily soluble salts. The second type of soils is represented by various solonetzes. Artificial forest plantations aged 8 to 27 years of the Trans-Ural forest-steppe are investigated. The objects of the study are confined to saline soils that differ in the composition of salts, the degree of salinity, the upper boundary of salinity, and the thickness of the supra-solonetz horizon. To assess the possibility of adapting woody plants to saline soils, they attracted such parameters as the ash residue of the needles and its composition. The idea of salt tolerance of plants can be compiled on the basis of studying the architectonics of the root system and the content of toxic salts in its zone of distribution. On the sample plots, a study was made of the root systems of pine trees. The investigation of the pine root system was aimed at identifying pine salt tolerance limits for the region of the Trans-Ural forest-steppe and the influence of the mechanical barrier of the columnar illuvial horizon of solonetz soil, the hardness of which is 17-30 kg/cm<sup>2</sup>. It is established that in pine forests in plantations on solonets of the Trans-Ural forest-steppe there are no adaptive reactions to the specific conditions of the latter, which is expressed in the lower ash content of the needles and a higher content of sesquioxides in comparison with the saline (solonchak) forms of pine. The root system of the pine, penetrating into the soil, passes through a dense and firm solonets horizon and branches into it. The boundary of root propagation deep into the soil is formed by soil layers containing toxic amounts of readily soluble salts. Pine quite satisfactorily grows on meadow-steppe solonetzes with toxic content of HCO<sub>3</sub> -0.065%, Cl - 0.02%, SO<sub>4</sub> - 0.181% (in the presence of gypsum 0.885%) in the soil root zone. In meadow solonetzes, the pine tolerates the content of Cl ions to 0.03%, CO<sub>3</sub> to 0.005%.