Water-Soluble Components of Organic Matter of Forest Litters in Podzolic Soils of a Chronological Series of Cutting Areas

The composition of water extracts from litter horizons of podzolic soils under a native bilberry–green moss spruce forest (TP-1) and under secondary mixed (birch–spruce) forests of 12 (TP-2) and 43 (TP-3) years in age developing on cutting areas in the middle taiga subzone of the Komi Republic was studied using high-temperature catalytic oxidation (TOC-VCPH analyzer), gas chromatography, and gas chromatography–mass spectrometry. Forest litters from test plots TP-1 and TP-2 were similar in composition and consisted of the needle litter and products of moss destruction. They had close pH values of water extracts and close total nitrogen (Ntot) and water-soluble carbon (Cws) contents. Forest litter on TP-3 consisted of the leaf litter of birch and aspen at different stages of decomposition, which was is reflected in higher contents of total and water-soluble carbon and total nitrogen and a decrease in acidity. The set of identified water-soluble carbon compounds was represented by 25 compounds: 12 carboxylic acids, 9 carbohydrates, and 4 alcohols with the major contribution of carbohydrates (hexoses). In the native spruce forest (TP-1), a tendency for a decrease in the proportion of acids and alcohols and an increase in the proportion of sugars from the upper (O1) to the lower (O3) part of the litter was observed. In forest litters of former cutting areas (TP-2, TP-3), an increase in the proportion of alcohols (especially in the O2 subhorizon) and a decrease in the proportion of sugars were noted.