Том 74, № 3 (2019)

The mineralization of organic substances in soil solutions extracted from horizons of a podzolic soil using tension lysimeters was studied. The stability of dissolved organic matter (DOM) varies depending on the horizon. The maximum content of DOM resistant to biodegradation (mineralization degree <50%) was registered in upper organic horizons, and it decreases down the soil profile. The share of mineralized carbon is inversely proportional to the relative content of hydrophobic and phenolic fractions in the DOM. Organic matter extracted from horizon ELhi features the lowest share of mineralizable carbon (23%) amid the highest hydrophobic fraction content (44%). In the course of the oxidative transformation, the DOM aromaticity degree goes up: the extinction coefficient (SUVA280) increases by 2–12 times and the share of phenolic compounds by 2–10 times, while molecular mass decreases down to 5–5.5 kDa. These changes are manifested more intensely in solutions extracted from lower horizons. Therefore, the nondecomposable DOM residue consists of substances most resistant to decomposition.

One of the most relevant tasks of modern agriculture is developing and implementing fundamentally new, available, environmentally safe “nature-like” technologies, providing a “sink” of carbon or a significant reduction in greenhouse gas emissions in all the agricultural landscapes, including those engaged in rice cultivation. In field trials conducted in Hunan province (China), the influence of silicon fertilizers on CO₂ sequestration by rice plant roots was estimated. Its value depends on the content of available silicon in agrochemicals, on frequency and duration of their use, and on soil texture. The data obtained indicate the important role of silicon fertilizers in the processes of carbon sequestration and reduction of greenhouse gas emissions in rice cultivation. Their application results in increased crop yields by 12.1–71.2% and increased CO₂ sequestration by plant roots by 0.95–14.9 t ha^–1 in one season. Soil carbon recovery and soil fertility reproduction can be ensured by intensive development of the plant root system and by an increase in root residues’ mass after harvest. Agrochemicals containing silicon available for plants should be included in the 4R-strategy for mineral nutrition of agricultural crops.

An approach is proposed for assessing ecosystem services of landscape’s various components in urban forest parks. The methodology takes into account the environmental and recreational functions of the territory and is based on the interconnection of ecosystem services, ecological functions, and the properties of individual components of the landscape. The assessment is carried out in a differentiated way making provision for the decrease in the quality of the services provided in conditions of significant anthropogenic load. It is shown that the greatest contribution to the cost of services is made by the soil.

The ²²⁶Ra, ²³²Th, and ⁴⁰K vertical profiles were studied in relation to the following soil properties: pH_H2O, the sum of exchangeable Ca²⁺ and Mg²⁺, the saturation with bases, and the content of humus and mobile forms of phosphorus and potassium. An increase in the specific activity of ²²⁶Ra, ²³²Th, and ⁴⁰K as a result of humus accumulation and the biogenic accumulation of mobile forms of potassium and phosphorus was detected in the 0- to 10-cm layer of the A horizon in the soil under an oak forest. The removal of ²²⁶Ra from the middle part of the profile of dark gray forest deep-carbonate soil was recorded. A positive correlation between the specific activity of ²²⁶Ra and the total exchangeable bases of Ca²⁺ and Mg²⁺ in the A, A(AE), AB, and deeper (B1, B2, and B3) horizons was revealed. This indicates the interrelated behavior of these elements-analogues. The removal of ²³²Th from the A(AE) horizon and its accumulation in the AB horizon under conditions of local podzolization of dark gray forest soil in a birch forest was observed.