The dissertation presents the results of a study on ecological and micromorphological properties of edaphotopes in the southern variant of ravine forests within south-eastern Ukraine on the example of the «Viyskove» ravine in comparison with the corresponding properties of the northern variant of ravine forests on the example of the «Kapitanovsky» ravine.
Soil micromorphology studies in the «Kapitanovsky» ravine found that the thickest layer of loose, aggregated micro-texture was observed in soils on the middle third of north-facing slope, in thalweg, and on the lower thirds of both exposures, which were characterized by fresh and moist forest-growing conditions. The studies have revealed significant aggregation of the upper horizons in soil profiles, almost complete absence of non-aggregated material. The nature of structure formation is primarily of zoogenic origin. Aggregates, mainly caused by earthworm dejection, contain well-digested plant residues; active humification processes were observed. The average width of elongated interaggregate pores was 0.4–0.6 mm. Interaggregate pores are channel-like, branched, and form a common void network. The visible pore area was 35–45%. Small invertebrate casts occurred in interaggregate pores.
The highest coefficient of soil structure in the «Kapitanovsky» ravine (12.74 and 9.45) was typical for the middle and lower third of north-facing slope, respectively. The lowest values (K) were characteristic of the upper third of south-facing slope. The maximum water resistance index of structural aggregates (V) was also found in fresh lime-ash oakery with Stellaria (95.07 %), and it was very high (93.27 %, 92.03 %) in the lower thirds of the north-and south-facing slopes, respectively. The lowest value of the V indicator (83.43%) was typical for the upper third of south-facing slope, the dryish ash-maple oakery.
Humus horizon thickness in soils of the «Kapitanovsky» ravine was highest in the thalweg, sampling sites in the middle and lower thirds of north-facing slope (90 cm and 87 cm). Slightly lower thickness of the humus horizon was in the middle and lower third of the south-facing slope (85 cm and 82 cm). In the upper horizon of soil profile in a fresh lime-ash oakery, the total humus content was high: 8.83%. Humus reserves were also high: 165.0 t/ha. The profile distribution of humus was gradually decreases. The degree of humification varied from high to very high (34.0–61.0 %). The humus type was humate.
Micromorphological structure of the soils studied in «Viyskove» ravine indicates that the upper humus horizons have a very good structure and humification. The color of micro-slides was dark brown, almost black, due to humus-clay plasma. The products of humification and mineralization give the soil mass a brown tincture and, thus, characterize the decomposition process intensity. Some microstructure heterogeneity is due to the presence of a large number of plant residues. Different humification degrees, the presence of fully mineralized residues, and mainly mull humus type indicate a high rate and activity of decomposition processes of plant residues. The visible surface area is 30–40%.
The highest coefficient of soil structure in «Viyskove» ravine (8.87 and 8.25) was typical for the middle and lower third of the north-facing slope, respectively. The lowest K values (3.79) were typical for the upper third of south-facing slope. The maximum water resistance indexes of structural aggregates V (88.01% and 87.93 %) were also typical for fresh oakery with field maple with Aegopodium podagraria in the lower thirds of the north- and south-facing slopes, respectively.
The humus horizon thickness was highest in thalweg of «Viyskove» ravine on warp soils, sampling sites of the middle and lower thirds of north-facing slope (79 cm and 76 cm). In the upper horizon of the soil profile in a fresh oakery with field maple with Aegopodium podagraria, the total humus content was high (9.3 %). Humus reserves in the 0–20 cm horizon was also high (180 t/ha). The profile distribution of humus was gradually decreases. Humus type was varied from humate to fulvate-humate; humification degree with the depth of the soil profile was varied from high to medium (36.7–29.1).
The scientific researches of complex properties of edaphotopes have shown that in the forest types of the northern ravine variant, compared with the types of the southern ravine variant, soil aggregation was higher, water resistance of structural aggregates was higher, and the thickness of humus horizons in soil profiles on similar slope parts was higher. Topsoil humus content does not have a significant difference. That is, the structural and humus state is better in the soils of the northern variant, which is due to the peculiarities of climatic conditions and, as a result, more favorable floral composition and structure of the soil invertebrate complex.
