Zoogeneous trends of soil buffer capacity as a constituent of environmental rehabilitation of urban soil within megapolis park zone

Abstract

Ecoservice role of soil saprophagues, in particular trophometabolic function ofearthworms (Lumbricidae), in formation of urban soils buffer capacity and as markers of soil fertility elements potential within recreation park “Zeleny gai” (city Dnipro, Ukraine)was evaluated. Earthworms can be considered as geochemically active functional group: theyparticipate in physical and biochemical transformation of dead plant material, paddling of it withsoil, interfere physical, chemical and biological soil properties, which are limiting productivityand soil fertility and also define further character of biological elements (and energy) turnover inthe system “soil-plant”. It was demonstrated that in above-ground ecosystems earthworms notonly contributing into biogenic migration processes, redistributing carbon, nitrogen and otherbiogenic elements between phytocenosis and soil, they participating actively in the mechanism ofstabilization and soil fertility formation by improving its buffer capacity. Buffer capacity definesthat share of soil potential, which supports immobilization (deponation) and mobilization (releaseor loss) of certain elements of fertility – first of all mineral elements essential for plants, productivemoisture, heat energy of soil, gas composition of soil air.Urbanization is one of the main character feature of the modern human civilization.In conditions of steadily increasing cities’ population and its densification artificial greenterritories able to compensate gaps in plant cover of urban lands are in great demand. Parkis a specific type of urban space, which has important recreation function, at the same time,parks as big vegetation massives play important microclimatic and sanitary – hygienicrole, improving the quality and comfort of the environment for citizens who are distantfor the nature in their everyday life. They enrich personal and individual aspect of livingenvironment for modern citizen, increase level of culture, leisure time quality, estheticallyoriented harmonized space contributes into upbringing of personal perception, making itmore subtle and this ultimately reflects on the lifestyle of the modern citizen.Park soils within megapolises territory are their integral components and this definesconditions of growth and development for green plants. Such processes as soil profile disturbance,overdensification of root-inhabitant layer, limitation of volume available for the plants’ rootsystem development, loss of nutrients, humus, microelements and fertility, contaminationwith heavy metals and other toxicants, changing in soil acidity and alkalinity, decrease in soilmicroflora and fauna diversity, accumulation of the litter on the surface can be listed amongother ecologically negative consequences for soils in the conditions of urban environment. Thus,optimization of the ecological properties of green plantations’ and parks’ soils in megapolisenvironment, as part of general aim of effective urban management is an actual problem.Results obtained during the present study disclose one of the aspects of environmental creation(pertinent) role of soil saprophages in the revitalization of edaphotopes of the park zones inmegapolises. Positive pertinent role of saprophages in the formation of buffer properties ofurbansoils within recreation zones on the example of city park soil is identified.To evaluate the contribution of the products of tropho-metabolic activity ofsaprophagous (coprolites) on the example of earthworms into acidic-base (pH) buffer capacityof urbansoils of the park zone within the plot planted with Norway maple (Acer platanoidesL.) trees, soil and coprolites samples were collected. Soil was sampled in 0–10 cm depth,fresh coprolites – from the soil surface. Buffer acid-base capacity of coprolites and urbansoils was determined according to Arrhenius method, which is based on pH measurementsof soil solutions after addition of weak acidic and basic solutions. Acid-base buffer capacityof studied soils and new soil formations (coprolites) was evaluated according to “buffer area”within acidic and base intervals of the chemical load. Numerical integration method was usedto calculate the area, employing Simpson formula. Actual soil solutions acidity measurements(pH), substrate without buffer and studied samples were performed in three repeats.Is was established that acid-base buffer capacity of new soil formations of zoogenic origin(earthworms coprolites) statistically significantly higher than for initial soil (urbansoil,upper humified layer of Calcic Chernozem) within the acidic diapason on 22,9 %, in sumacidic-base relation – on 20,6 %. This promotes ecological state of green plantations on theurban soils within park areas and recreation zone edaphotopes revitalization. Thus soilsaprophagues, such as earthworms, in the conditions of magapolises in the recreation zoneswithin the territories of city parks’ green plantations is a major factor of pertinention andone of the natural factors of ecological rehabilitation of urban soils and actively realizesuch ecosystem services as fertility improvement, contribution into nutrients turnover,erosion protection and support optimization of human living and recreation environment.Keywords: pertinent function of saprophagous, urbansoil, buffer capacity of soil, acid-basebuffering, fertile elements potential, city park, megapolis.