IMPACT OF EARTHWORMS OF DIFFERENT MORPHO-ECOLOGICAL GROUPS ON CARBON ACCUMULATION IN FOREST SOILS

Abstract

To date, forest ecology has not made any clear conclusions regarding the impact of large saprophagous invertebrates such as earthworms on soil carbon dynamics. Some authors claim that earthworm activities result in decreased carbon accumulation. Other studies show that earthworms contribute to soil carbon accumulation. At the same time, many studies do not take into account the differences between trophic and digging activity of different morpho-ecological groups of earthworms in different soil horizons. The objective of this study was to carry out differentiated assessment of the impact of different morpho-ecological groups of earthworms on carbon accumulation and correspondent soil parameters (nitrogen content and С/N ratio) throughout the change in forest succession status. Field operations were performed in the spring and summer of 2016 and 2018 in three regions: Bryansk Oblast (Bryansk Forest reserve), Moscow Oblast (Moskva–Oka plain, Valuyevsky urban forest) and Northwest Caucasus (Krasnodar Krai, Apsheron forestry; Republic of Adygeya, Caucasian Biosphere Reserve). Three main stages of coniferous-broadleaf forest restoration after clear cuttings were identified in each region. Three test plots 50х50 m were allocated for each stage; geobotanical and soil descriptions as well as earthworm registration were carried out on each plot. It was found out that during the change in forest succession status the species composition and the set of morpho-ecological groups of earthworms became more complicated, but there was no successive replacement of any groups with others. Ambiguous effects of different morpho-ecological groups of earthworms on carbon accumulation in forest soils were revealed. Negative correlation was found between the total biomass of earthworms feeding on the soil surface (epigeic, epi-endogeic and anecic species) and litter store. In the humus horizon, the biomass of epi-endogeic species was positively correlated with the content of carbon. C/N ratio and nitrogen content are unidirectionally correlated with the biomass of earthworms in the horizons of their activity: with an increase in the biomass of earthworms of different morpho-ecological groups, the C/N ratio decreases, and the nitrogen content increases.