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The formation of soils on loamy deposits during the primary succession of vegetation after biological reclamation of a technogenically disturbed area (quarry) in the middle taiga subzone of the northeast of European Russia (Komi Republic) is considered. The planting of Picea obovata on the reclaimed area activates the formation of the tree layer and helps to accelerate pedogenetic processes. In drained conditions, by the beginning of the third decade of succession, litter horizons were formed, soil bulk density in the upper mineral horizons decreased, and a tendency towards redistribution and differentiation of the clay fraction and iron and aluminum compounds in the soil profile was noted. The latter may indicate the beginning of eluviation. The heterogeneity of the quarry surface (presence of highs and lows with a height difference of up to 2–6 m) contributes to the redistribution of moisture within the quarry and the appearance of areas with surface waterlogging. Under these conditions, the role of conservation of organic residues (peat formation) is enhanced, and gleyzation processes are activated. With an increase in the degree of surface waterlogging of soils, the soil acidity and the stocks of soil carbon and nitrogen increase, which is typical for an analogous series of background soils. The calculated rate of organic carbon accumulation in the soil layer of 0–20 cm in drained soils of the quarry is about 0.4 t/ha per year. In the waterlogged soils, it increases to 1.0–1.2 t/ha per year. The stocks of organic carbon in the upper 20 cm of the profile of young soils remain two–four times lower in comparison with the background native soils. [ABSTRACT FROM AUTHOR]

The research was conducted in the European northeast of Russia (Komi Republic), in the reclaimed quarries for mining construction sand in the middle taiga subzone, in the course of two decades after the forest reclamation (Pinus sylvestris) had been applied. The specific features of initial pedogenesis on substrates of different textures have been revealed. On sands and sandy loams, the dynamic soil sequence is composed by abralith (the 0-moment) → residual-calcareous humus psammozem (11th yr) → humus-raw-humus residual-calcareous podzolized humus gleyic psammozem (18th yr). On the loamy substrate, the following soil sequence is formed: abralith → humus residual-calcareous pelozem (3rd and 11th yr) → humus-raw-humus residual-calcareous eluviated gleyic pelozem (the 18th year). The formation of litter and humus-accumulative horizons are the leading soil forming processes. Their intensity is determined by the degree of plant community development. By the end of the second decade, the humus-accumulative horizon (0–20 cm thick) of sandy loamy soils accumulates up to 2.7 t/ha of organic carbon. Organic carbon pool in loamy soils reaches 6.3 t/ha. The stocks of soil nitrogen reach 0.1 and 0.4 t/ha, respectively. The rate of organic carbon accumulation in soil reaches 0.16 (sandy-loamy substrates) and 0.37 t/ha per year (loamy substrates). The organic matter of humus-accumulative horizons in the young soils of quarries is characterized by a higher content of water-soluble and labile components of humus and a low degree of condensation of humic acids as compared to the background soils. Initial pedogenesis on quarry substrata is characterized by an increase in the acidity of soil water extracts from pH 8.0 in abralith to pH 6.3–6.7 in the W horizon of the forming soils. The rate of acidification in loamy soils is lower than in sandy and sandy loamy soils. Carbonate leaching is confirmed by the absence of calcite and dolomite in the mineral composition of the upper W horizons of the forming soils, a decrease in the total content of calcium oxide from 4% in abralith to 2–3% in the W soil horizon and in the content of calcium carbonates (3 and <0.5%, respectively). In 18 years, weakly expressed features of eluviation, illuviation, and gleying appeared in the soil profiles. [ABSTRACT FROM AUTHOR]

Abstract: Exchangeable acidity in samples from organic and mineral horizons of taiga and bog soils with strongly acid reaction (pHKCl < 3.3 and ≤ 4.4) was determined by the Sokolov method of potentiometric titration of KCl extract before and after the addition of a sodium fluoride solution. In the same extracts, the contents of Al, Fe, and Mn ions were determined by the atomic emission method. NaF was added in an amount sufficient for binding all metal ions into fluoride complex compounds. It was found that the content of metals determined by atomic emission is lower than that calculated from titration results in 1.5-2 times in organic horizons and by 20-25% in mineral horizons. Even a higher difference between the two methods was observed for exchangeable protons: from the titration data, their content in organic horizons was 10-12% of the content determined as the difference between total exchangeable acidity and total metal ions determined by atomic emission, and 3-15% in mineral horizons. The revealed differences were attributed to the underestimated results of determining exchangeable protons in the presence of NaF, which was confirmed by the potentiometric titration of model solutions of strong and weak acids prepared from a KCl solution. It was found that the addition of NaF during the titration with a strong acid results in reaching the point of equivalence after the addition of a smaller amount of base. Reasons for the shift of the point of equivalence during titration with a strong acid in the presence of NaF require special investigations. It is recommended to estimate the exchangeable acidity of strongly acid soils due to metal ions by atomic emission or other adequate methods. [ABSTRACT FROM AUTHOR]