Zoogenic mechanisms of ecological rehabilitation of urban soils of the park zone of megapolis: Earthworms and Soil Buffer Capacity
Earthworms (Oligochaeta: Lumbricidae) are typical representatives of the funcitional group of ecosystem engineers. They actively participate in formation and stabilization of soil fertility through their effect on its buffer capacity. Buffer capacity defines in many aspects soil potential, supports immobilization and mobilization of certain elements of fertility – first of all mineral elements essential for plants, productive moisture, heat energy of soil, gas composition of soil air. Park soils within megapolises territory are their integral components and this defines conditions of growth and development for green plants. To evaluate the contribution of the earthworms’ coprolites into acidic-base (pH) buffer capacity of two categories of soil within the city – urban soils and urban grounds (urbanozems) of the park zones within the plots planted with Norway maple (Acer platanoides L.) trees on the territory of two parks – “Zeleny gai” and Pisarzhevsky Park (city Dnipro, Ukraine), soil and coprolites samples were collected. Buffer capacity of coprolites and anthropogenically transformed soils (urban soils) was evaluated according to Arrhenius method after “buffer area”. It was established that acid-base buffer capacity of coprolites (earthworms’ excretes), which are new formations of zoogenic origin in soil statistically significantly higher than for initial types soil within city parks. For urban soil with upper humified layer of calcic chernozem within the acidic diapason of external load it was 22.9% higher, which, in average, accordingly was 22.9 and 18.7 convectional units, within alkaline – 18.4% higher and was, accordingly, 24.2 and 20,4 convectional units, in sum (acidic-alkaline) – 20.6% higher and was 47.1 and 39.1 convectional units. For urban ground (urbanozem) with within the acidic diapason of external load it was 44.9% higher and acidic–alkaline buffering capacity, in average, accordingly, was 25.5 and 17.6 convectional units, in sum (acidic-alkaline) – 20.6% higher and was 42.8 and 35.4 convectional units accordingly. Thus, soil saprophagues, such as earthworms, in the conditions of magapolises in the recreation zones within the territories of city parks’ green plantations is one of the natural factors of ecological rehabilitation of urban soils. This, in general, improves ecological state of green plantations on the urban soils within park areas and recreation zone edaphotopes revitalization and support optimization of human living and recreation environment.