Svetlana A. Tishchenko

Sub-Mediterranean ecosystems along the northeastern Black Sea coast remain insufficiently studied despite their importance for the regional carbon cycle and their sensitivity to human disturbance. This study presents an exploratory case study of aboveground biomass carbon stocks in two contrasting plant communities at the carbon-monitoring supersite of the Southern Branch of the Shirshov Institute of Oceanology RAS in Gelendzhik, Russia. The aboveground observations were interpreted together with soil carbon stocks and greenhouse gas fluxes previously reported for the same permanent plots. The investigated communities comprised a terraced pine–oak plantation (SP1) and a natural pubescent-oak shiblyak (SP2). Vegetation was surveyed using the Braun-Blanquet approach. Tree biomass was estimated using the generalized allometric equation of Chave et al., while aboveground biomass was converted to carbon using carbon concentrations determined by elemental analysis of sampled plant tissues. Herbaceous vegetation and forest-floor material were quantified by elemental analysis. Within-plot spatial heterogeneity was visualized using Python-based radial-basis-function (RBF) interpolation for exploratory mapping of local carbon distribution. Because each vegetation type was represented by a single 400 m² plot, all comparisons are site-specific and exploratory and should not be extrapolated beyond the investigated communities. The aboveground carbon density was 64.1 t C ha⁻¹ in the terraced pine–oak stand and 16.1 t C ha⁻¹ in the natural shiblyak. Woody biomass dominated the plantation, whereas litter and herbaceous vegetation contributed proportionally more to the carbon pool in the shiblyak. Previously published soil organic carbon stocks at the terraced site exceeded the measured aboveground carbon pool, whereas the natural rendzinas were characterized by substantial carbonate-associated inorganic carbon stocks. C/N ratios of organic substrates ranged from 11 to 100, indicating a pronounced variation in substrate quality: higher C/N values in woody and coniferous fractions were consistent with slower decomposition, whereas lower C/N values in herbaceous material were consistent with faster mineralization. Exploratory spatial mapping revealed within-plot variation in aboveground carbon of up to two orders of magnitude. Together, these site-specific observations provide the first integrated description of aboveground biomass carbon together with previously reported soil carbon pools for contrasting sub-Mediterranean vegetation on the northeastern Black Sea coast. Despite its exploratory nature, this study establishes a baseline for future replicated, spatially explicit investigations of ecosystem carbon dynamics in sub-Mediterranean ecosystems along the northeastern Black Sea coast.

This study is one of the first comprehensive assessments of soil carbon dynamics on the Black Sea coast of Russia, focusing on the role of soils in the terrestrial carbon cycle and the greenhouse gas balance of sub-Mediterranean ecosystems. Our integrated approach combined soil classification with the analysis of the distribution of organic and inorganic carbon, as well as the measurement of microbial biomass and respiration. Soil respiration components, including substrate-induced respiration (SIR) and basal respiration (BR), as well as greenhouse gas (carbon dioxide (CO₂) and methane (CH₄)) dynamics, were evaluated using a combination of laboratory and field measurements. Our results revealed significant differences between natural Rendzic Leptosols and terraced Skeletic Rendzic Leptosols (Technic and Transportic types). The latter contained higher organic carbon stocks (up to 25 kg m⁻²) associated with buried humus horizons, whereas the former were dominated by inorganic carbon accumulation. Microbial biomass carbon (MBC) ranged from 113 to 1119 µg C g⁻¹ of soil and decreased with depth. Basal respiration averaged 0.39 ± 0.30 µg C–CO₂ g⁻¹ h⁻¹. CO₂ emissions were strongly correlated with soil temperature (r = 0.65, p < 0.05) and negatively correlated with soil moisture, reflecting the predominant influence of abiotic factors. Seasonal chamber observations confirmed that these soils consistently function as CH₄ sinks, with negative CH₄ fluxes recorded across all seasons. Thus, Rendzic Leptosols on the Black Sea coast serve as significant CO₂ sources and stable CH₄ sinks simultaneously, and anthropogenic terracing enhances their potential for organic carbon sequestration. These findings refine our understanding of the carbon balance in sub-Mediterranean forest soils and highlight their dual role in greenhouse gas dynamics under changing climate conditions.

журнал Живые и биокосные системы Применение активности дегидрогеназ в диагностике здоровья почв Юга России в условиях антропогенного воздействия

We studied the physical properties of chernozems subjected to local waterlogging because of different reasons. The secondary soil hydromorphism resulted in insignificant changes in the soil’s texture related to some redistribution of the elementary soil particles by the particle-size fractions. The physical clay content somewhat increased in the lower part of the soil profiles (in the B2 and BC horizons) at the expense of the clay particles. The bulk density of the waterlogged soils somewhat increased, particularly in the B2 horizon. The regular soil waterlogging worsened the soil’s structural status with a decrease in the content of the silt-size aggregates and an increase in the content of the coarse blocky aggregates. The changes in the soil’s structure can be considered a diagnostic feature of the locally waterlogged chernozems. The water stability of the aggregates increased due to the higher contents of the major cementing agents, including the soil humus and carbonates.

The humus state of rainfed chernozems affected by local waterlogging was studied. The total humus content in the hydromorphic chernozems increases, as well as the content of fulvic acids, whereas the content of nonhydrolyzable residue (humin) decreases. A significant increase in the portions of the third fractions of humic and fulvic acids is observed. The role of the fine silt and clay fractions in the binding of humic substances increases in the lower horizons of locally hydromorphic soils. The increase in the content of fulvic acids (fulvatization) is mainly due to their predominance in the clay fraction. The latter is specified by the significant narrowing of the C_ha-to-C_fa ratio, the lower content of the nonhydrolyzable residue, and the increased content of the clay-bound (3rd fraction) fulvic and humic acids. The composition of the humus in the fine silt fraction of the studied soils is characterized by an increased amount of humic acids of the second fraction with a decrease in the relative content of fulvic acids.