Effect of Smoke Caused by Fires on the Enzymatic Activity of Forest Soils in the North Caucasus (Russian Federation)

Forest fires can have a significant impact on soils, resulting in changes in biological indicators. Due to fire, high temperatures, and intensive generation of smoke from burning materials of different origin, the activity of soil enzymes is decreased. In this study are presented the results of modelling experiments on the impact of smoke on forest soils (Cambisols according to the World Reference Base for Soil Resources rating) of the Republic of Adygea, Nickel settlement (Russia). The findings demonstrated significant smoke exposure on the enzymatic activity of this type of soil. A decrease in the activity of such enzymes as catalase, peroxidase, polyphenol oxidase, and invertase within 60 min after soil treatment with smoke from burning materials of plant origin (pine sawdust) was established. A significant decrease in the activity of catalase relative to the control by 36%, phenoloxidases by 54–58%, and invertase from the hydrolase class by 31% was found. The integral index of soil enzymatic activity (IIEA) of the studied soils was also calculated. In addition, one of the informative diagnostic indicators is the pH of the soil suspension. The pH value for fumigated water was also determined to identify differences with the suspension. A reduction in the pH towards acidification was observed. The obtained findings may be used in a comprehensive assessment of pyrogenic effects on forest soils. Moreover, indicators are sensitive to this effect, which was confirmed by the results of the present research.