The effect of the composition of plant residues on soluble organic substances formed in forest litters

This review examines published data on the composition, properties, dynamics and amounts of DOM formed in the litter of forest soils. The amount and properties of DOM depend on the composition of plant residues forming the litter horizon. In most cases, the leaf litter DOM differs from the fall of needles in a high content of nitrogen, polyphenolic compounds, carbohydrates, hydrophobic acids, higher extinction coefficients and a lower C/N ratio. However, DOM properties and quantity are significantly influenced by the genus and species of plants, leaves and needles age, and growing conditions. In situ the stock of forest litter plays an important role, therefore, DOM concentrations in soil solutions of coniferous litter are higher than deciduous ones. With decomposition of organic residues, DOM quantity and variety of water-soluble organic compounds decreases, the proportion of hydrophobic and hydrophilic acids and aliphatic compounds increases. The composition of the soluble transformation products of litter inherits proportions, structural features and resistance to biodegradation of the original components. Forecasting the composition and rate of production of DOM in forest soils requires taking into account the litter character (ratio of different subhorizons), composition and transformation conditions of the plant debris.