Post-fire redistribution of ¹³⁷Cs and algal communities in contaminated forest soils in Belarus

This study was carried out in the forest area of the Gomel region of Belarus contaminated by ¹³⁷Cs following the Chernobyl accident of 1986. The aim of the study was to explore the effects of different types of wildfires on the biological availability of radionuclides and the distribution of algal communities in fire-affected soils. Soil samples were collected in 2017 and 2018 from sites burnt by surface and crown fires, and from two unburnt reference locations. The soil samples were analyzed for radioactivity, agrochemical characteristics and the abundance of photoautotrophs. The proportions of various ¹³⁷Cs fractions, according to our findings, differ between fire-affected and unburnt forest soils, and also between the different types of wildfire. The forest soil affected by surface fire is characterized by an increased amount of easily exchangeable and mobile fractions. In the forest burnt by the crown fire, where the above ground vegetation was almost completely destroyed, the mobile fractions of ¹³⁷Cs are easily washed out from the topsoil, allowing them to penetrate into deeper soil layers. Soil algae play an important ecological role in sustaining terrestrial ecosystems and are sensitive to various physicochemical properties of soil, such as pH level, nutrient content and moisture. Most of these physicochemical properties are known to stimulate the growth of algal cells, however no evidence has been found in this study regarding the relationship between ¹³⁷Cs activities in soil and the algal species richness.