Recovery оf Soil Macrofauna and Litter Properties in Post-Agrogenic Soils of Spruce Forests of the Smolensk Lakeland National Park

The recovery of large soil invertebrates (macrofauna) associated with changes in the properties of the litter during natural spruce reforestation on post-agrogenic weakly acid sandy/silty loam soils in the Smolensk Lakeland National Park (western part of Russia) is studied. This work is based on the data of the study of the chronosequence including the following stages: E0, young fallows and agrocenosis; E1, perennial meadows; E2, young birch forests of 10–30 years of age; E3, middle-aged birch forests (36–64 years old) with spruce dominance in the lower woody layer; E4, forests with birch dominance (70–80 years old) and spruce emergence in the upper woody layer; E5, spruce–birch forests (80–100 years old) with the formation of window mosaics due to birch loss; E6, conditionally indigenous spruce forests 90–100 years old with pronounced window mosaics and windfall–soil complexes. It is shown that the litter stocks and the thickness, the carbon content in it increase during reforestation. In agrocenoses and young fallows, the organogenic horizon is fragmentary and is represented by the fall of current years. Litter consisting of material in an intermediate state of decomposition (Oe horizon) appears in young birch forests. Organic material in an advanced state of decomposition (Oa horizon) is characteristic of the middle and late stages of spruce reforestation. The diversity of invertebrates inhabiting the litter also increases naturally. The diversity of the epigeic macrofauna increases: earthworms appear and the number and biomass of other saprophages (bipedal millipedes, molluscs) and predators (spiders, beetles, labiopods) increase. A positive correlation between the thickness of the Oa horizon and the biomass of epi-endogeic earthworms was found.