The article considers the long-term (100 years) dynamics of the forest cover of the southernmost unit of Siberian pine forests on the West Siberian plain. A key feature of forest management is that Siberian pine seeds are a valuable food product and, when cutting forests, this tree species, as a rule, is preserved. The basis of the experimental data was the material of the national forest inventories of 1915, 1974 and 2015 for a total area of 1,420.41 ha. During the period from 1915 to 2015, the forested area changed slightly (96.2 and 94.0%), while the share of Siberian pine stands increased significantly from 48.4 to 58.7%. Grassy Siberian pine forests (32.1%) of optimal age (120–140 years), which are characterised by the best seed productivity and the largest share of Siberian pine in the community (77%), predominate. Basically, human economic activity results in an increase in the area of Siberian pine stands, when deciduous stands with Siberian pine undergrowth are used for fuel and as building material. A decrease in the area of Siberian pine forests occurs mainly under the impact of fires. In the conflagrations of 1915–1920, 7 to 38% of silver birch forests have no Siberian pine undergrowth and are considered long-term secondary communities. In the remaining area, the proportion of Siberian pine undergrowth is 20–30% with a density of 800–1200 seedlings ha−1, which is sufficient for the natural formation of Siberian pine forests.
The paper considers the information and energy assessment of soil fertility. It is shown that soil cultivation is accompanied by an increase in soil humus content, absorption capacity, content of biophilic elements, accumulation of energy in the soil, optimization of information relationships in the soil. Thus, the energy content in poorly and well cultivated sod-podzolic soils was 351.7 and 510.7 million kcal/ha, respectively. When cultivating soils, the content of mobile forms of biophilic elements in them increased, the relationship between soil properties and crop yield became more stable. It is shown that on more cultivated soils it is more profitable to grow crops that are more demanding of fertility, accumulating more energy on these soils than crops that are less demanding of fertility. The change of optimal soil properties for individual crops depending on the level of intensification of production is shown. Keywords: SOIL, FERTILITY, ENERGY STORAGE IN THE SOIL AND IN THE CROP YIELD
In the conducted studies, the influence of salinization on the soil-plant system on the soils of Russia and Vietnam was evaluated. It is shown that the nature and degree of soil salinization vary over time and in space, including on individual elements of meso- and microrelief. For soils, plants and biota, it is advisable to allocate their optima and maximum permissible salinity concentrations. They differ for different soils, for individual plant species and microorganisms. It is shown that optimal and acceptable indicators of soil salinity differ from a combination of parameters of plant life factors and soil functioning: temperature, humidity, combination of soil properties, phases of soil and plant development, etc. It was found that the composition of the soil extract differs significantly from the composition of the soil solution not only in the concentration of salts, but also in their composition, which must be taken into account in the agroecological assessment of salinity. The possibility of increasing the resistance of plants to soil salinization when they are fed with biophilic elements, stimulants, complexons is shown. Keywords: SALINIZATION, PLANTS, MAXIMUM PERMISSIBLE CONCENTRATIONS, OPTIMIZATION
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