Enzyme Activity in Urban Soil Constructions in the Steppe Zone

Assessment of enzymatic activity of constructed soils (constructozems) was performed during the second year of their functioning at the Experimental Station for Study of Soil Constructs in the Botanical Garden of the Southern Federal University (Rostov-on-Don, Russia). The station consists of 15 autonomous plots representing five different variants of soil constructions created using sand, humus-accumulative horizons of chernozem, loesslike loam, and highmoor (oligotrophic) peat. These substrates are traditionally used for landscaping and urban greening purposes in the steppe zone. Haplic Chernozem on a watershed plot in the vicinity of the Experimental Station located on a plateau area 600 m from the 23rd station was studied as the background reference soil. The activities of dehydrogenase, phosphatase, catalase, beta-glucosidase, and the intensity of fluorescein diacetate (FDA) hydrolysis were analyzed in the soil constructions and the reference soil. The activities of beta-glucosidase, catalase, phosphatase, and FDA hydrolysis intensity were the most informative characteristics of the constructozems. Enzymatic activity allowed an assessment of the stability of the constructed soils, as well as intensity and direction of biochemical processes occurring in the constructozems. It depended on the substrates used during construction, their combinations, thickness, and the horizon sequence. Some variants of constructozems demonstrated levels of enzymatic activity close to those in the natural zonal soil (background) thus indicating functional stability of constructozems and their ability to perform ecological functions under the climatic conditions of the Rostov region.