Stanislav Vitalievich Chuvanov

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Biological activity of organogenic soil samples under different moisture levelsMoscow University Bulletin. Series 17. Soil science. 2025. Vol. 80. N 2. p.84-95read more272
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The response of biological activity and the content of labile forms of biogenic elements in peats of different genesis to variation in their moisture content was studied under laboratory conditions. Samples of peat soils of the northern and southern taiga (Tyumen and Moscow regions) were used in this work. A series of manipulation experiments were conducted in which the dynamics of such indicators as basal respiration (BR), microbial biomass carbon, labile carbon and nitrogen content were estimated for different peat types at different moisture levels. The effect of the experiment duration and type on the dynamics of peat properties was also assessed. It was found that all the studied peat samples are characterized by a wide range of moisture content, at which the maximum of biological activity is observed. In general, it is in the range from 20–30% to 80–90% of water–holding capacity (WHC). In this range, no significant relationship is observed between moisture content and BR. In most experiments, a reliable decrease in biological activity was observed only in the "extreme" humidity ranges - less than 20% and more than 90% WHC. It is shown that the nature of the response to moistening is individual, determined by the properties of the sample and depends little on the type of sample preparation. In experiments and model calculations, it is proposed to use the obtained sensitivity coefficient to moisture — W20, which is 1.0‒1.2 in the range of 40‒80% WHC for peat samples of different genesis. Long-term variants of incubation experiments showed a more pronounced response to overmoistening and a reliable decrease in biological activity at high humidity values (more than 80% WHC). This may indicate their better applicability for solving problems of modeling the behavior of ecosystems in the event of a change in the hydrological situation.
Keywords: microbial respiration; mineralization rate; water–holding capacity (WHC); peat; carbon dioxide
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Methodological peculiarities of basal respiration measurement of organogenic samples of peat soilsMoscow University Bulletin. Series 17. Soil science. 2025. N 3. p.177-187read more79
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Methodological peculiarities of basal respiration (BR) measurement have been studied on the peat soil samples from two taiga subzones. It is found that the BR values at the initial incubation time (30 minutes) significantly exceed the ‘classical’ variant (24 hours) and gradually decrease with time. It is observed for all types of samples. The dependence of BR on the volume of the gas phase in the system was revealed - the values are higher the larger the volume of the incubation vial and the larger the ratio of the volume of the gas phase: mass (volume) of the sample. Initial values of CO2 concentration do not influence the dynamics of BR, because both at about zero and relatively high (4400 ppm) starting values of CO2 content the results of incubation were similar. It is critical to maintain the same incubation time interval, the same vial and sample volume while assessing the biological activity of soils using the BR method. The standard variant of BR determination during 24-hour incubation showed results that differed minimally depending on vial volumes and is probably preferable in this variant of experiments.Keywords: peat; mineralisation rate; Histosol; soil respiration; biological activity of soils; carbon balance
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