Enzyme activity in urban soil structures in the steppe zone

Assessment of the 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, loess-like loam, and high-moor peat. These substrates are traditionally used for landscaping and urban greening purposes in steppe zones. The Haplic Chernozem, located on a watershed plot in the vicinity of the Experimental Station, was studied as a background area. The activities of dehydrogenase, phosphatase, catalase, β-glucosidase, and the intensity of fluorescein diacetate (FDA) hydrolysis were analyzed for the soil constructions and the reference soil. The most informative characteristics of the constructozems were activity of β-glucosidase, catalase, phosphatase, and FDA hydrolysis intensity. Enzymatic activity allows an assessment of the stability of the constructed soils, as well as intensity and direction of biochemical processes occurring in the constructozems. Enzyme activity depends on the substrates used during construction, their combinations, thickness, and the horizon sequence. Some variants of constructozems demonstrate levels of enzymatic activity close to the natural zonal soil (background), indicating functional stability and their ability to perform ecological functions under the climatic conditions of the Rostov Region.