Changes in the amino acid composition of humic substances of podzolic soils during forest regeneration after harvest cutting
N.N. Bondarenko, Е.М. Lapteva
We studied how cuttings affects the amino acid composition of humic and fulvic acids isolated from the upper horizons of podzolic texture-differentiated soils. Amino acid fragments of the hydrolyzable part of humic acid macromolecules were identified and quantified in soils of spruce bilberry forest and different aged deciduous forests, forming during the post-cutting succession in the middle taiga subzone. We found that mass fraction of amino acids in the humic acids isolated from podzolic horizons of cutting places was higher than that in the intact bilberry spruce forest. In fulvic acids, an increase of the proportion of amino acids was found in the organogenic horizons only at the initial stages of reforestation. The regularities of changes in the amino acid composition of humic substances in the relative molar fractions of identified amino acid groups (acidic, basic, neutral polar and nonpolar) were revealed at different stages of the reforestation after cuttings of blueberry spruce forests. Initial stages of forest regeneration are characterized by a decrease in the ratio of hydroxyamino acids to heterocyclic acids, which indicates a depressed state of the zoomicrobial complex as a result of contemporary waterlogging of podzolic soils. Fulvic acids react most sensitively to changes in the synthesis and destruction of soil organic matter under forest regeneration through a change of species, which is characterized by the largest shifts in the ratio of the molar fractions of both individual amino acids and amino acid groups in the composition of their hydrolysates as a whole.
Keywords: cuttings, different aged deciduous forests, podzolic soils, humic and fulvic acids, amino acid composition.