CONCLUSIONS
(1) Approximately 50 years after forest planting on the mountainous meadow soils of the Ai-Petri Plateau, the content of aggregates >10 mm in the upper 10-cm-thick layer under the pine, larch, and birch plantations increased by 3.6, 1.8, and 1.6 times in comparison with that in the adjacent meadow soils.
(2) Pre-planting soil tillage and the change in the composition of vegetation during the creation of forest plantations led to a decrease in the Corg content under all tree species. Somewhat higher values of the extinction coefficient (Ecmg/mL) of humic acids in comparison with those in the meadow soil were found under the larch plantation. The Cha/Cfa values were higher under the larch and pine, which could be due to a more intense accumulation of “young” humic substances with low Cha/Cfa values under meadow vegetation and retardation of this process under the forest plantations.
(3) Replacement of meadow vegetation by forest vegetation favored an increase in the soil acidity under all forest species. The sharpest decrease in pH and an increase in the total acidity, the content of exchangeable Al, and its portion among exchangeable bases took place under the larch plantation.
(4) An increase in the soil acidity under the forest species led to an intensive accumulation of Fealk, its maximum amount was also observed under the larch plantation.
(5) An increase in the exchangeable Al and Fealk contents under the larch did not correspond to the regularities of changes in these parameters in relation to the increase in the soil acidification under other tree species and under meadow communities. This may attest to a specific nature of the interaction between larch plantations and soils and should be further studied in order to identify the reasons for this phenomenon.
