Postagrogenic Dynamics of pH, Electrical Conductivity and Redox Potential in Soils of Diverse Texture at the Smolensk Poozerie National Park (Russia)

Postagrogenic soil restoration is typical for many areas of European Russia. Therefore, it is necessary to understand the transformation of chemical properties that affect soil quality. Oxidation-reduction potential (Eh), electrical conductivity (EC), and pH value of humus and mineral horizons were studied in the Smolenskoye Poozerye National Park ('55°32'N. 31°24'E) soils under the vegetation of different stages of postagrogenic succession: agrocenosis, meadow, and forest with diverse age of the tree stand: <30 years, 30-50 years, 50-65 years, and > 66 years old. The variability of the chemical properties of soils under vegetation within one stage of succession was also investigated. According to the tree stand age of forests and field soils descriptions, the stage of postagrogenic succession was determined for 76 soil sampling sites (See Table 1). Within one day after sampling in an aqueous suspension, the pH value was determined using an Expert-pH pH meter (Saint Petersburg, Russia). EC and Eh were measures using a COM80 EC/TDS meter HM DIGITAL (USA, South Korea). Data processing and calculation of descriptive statistics was carried out in the MC Excel (2013) and Statistica 8 programs: Spearman correlation analysis, coefficient of variation, nonparametric Wilcoxon test (See Table 2, Table 3). The pH value of the humus horizon of sandy soils under meadows is higher than that of soils under forests (See Figure 1). In sandy soils, due to lower buffer capacity, pH value changed at a greater depth and changes were more noticeable than in loamy soils. In parent materials, i.e. sands, pH value was restored to the natural level at later stages of succession. The redox potential of organic soil horizons depended on the pH value and vegetation. Eh was lower in meadows than in forest soils. In humus horizons, it changed more contrast in loamy soils than in sandy soils. In mineral horizons of sandy soils, Eh depended on the pH value (see Table 1). The electrical conductivity of post-agrogenic soils of the Smolenskoye Poozerye National Park depended on soil texture. In sandy soils, the application of fertilizers increased EC. Mixing and plowing of loamy soils resulted in decrease of EC. In the studied groups of soils under diverse vegetation, the variability was maximum for EC (the coefficient of variation was 14-136%, see Table 2), which confirmed the dependence of this property not only on vegetation and anthropogenic impact, but also parent materials and topography. The variability of pH and Eh was lower (the coefficient of variation was 1-18% and 1-22%, respectively). For studying temporal variability of soil EC, a larger number of replicates with a comprehensive determination of the physicochemical properties is recommended due to the high spatial variability. The article contains 2 Figures, 4 Tables and 65 References. The Authors declare no conflict of interest.

Keywords

Authors

References