Transformation of Forest Ecosystems in Moscow Megapolis under Recreational Impacts

Аннотация

A comprehensive quantitative assessment of the state of vegetation, soil invertebrate complex, litter horizons, and soddy-podzolic soils (Albic Retisols) in Moscow forest parks (Bitsevskii Forest and Losinyi Ostrov) as dependent on the level of recreational loads is presented. The changes in the main components of forest ecosystems in the forest parks under study have a unidirectional character. At the fifth stage of the recreation-induced degradation, the portion of the trees in good condition decreases by 4–5 times; the canopy density, by 20–30%; and the abundance of undergrowth, by 3–4 times. This leads to an increase in illumination of the surface by more than 30 times. With an increase in recreational loads, the species diversity of herbs in the ground cover initially increases from 9–11 to 23 species owing to the invasion of forest-meadow, meadow, and ruderal plants; then, it decreases. The litter pool becomes lower, and its fractional composition changes: the portion of the active litter fractions decreases by 1.7–2 times, and the portion of mechanically comminuted fractions increases by 3.5–7 times. The density and biomass of mesopedobionts at this stage decreases by 2–2.5 times in the soil and by 4–7 times in the litter. The most pronounced changes in the soil properties take place in the uppermost mineral layer (0–5 cm); in the deeper horizons, they are weaker. According to the results of discriminant analysis, the major contribution to the discrimination of soils at different stages of the recreational degradation is made by the aggregation factor. Individual contributions of changes in other soil properties are small, though their cumulative effect of the discrimination of soils is significant.