Aftermath of Fires for Mesophytic Forests' Soils in Western Caucasus

Every year, vast areas of forests burn down during fires all over the world. The literature contains contradictory data on the effects of fires on individual components of ecosystems, in particular on soils. This necessitates the study of the aftermath of fires in different climatic and soil conditions. The aim of this work is studying the consequences of a ground fire on the properties of phaeozems of the Khamyshinsky district forestry unit of the Adygea Republic 4 years after the impact. The chemical (CEC, hydrolytic acidity, pH, organic carbon and active carbon content) and biological (activity of catalase, dehydrogenases, invertase, urease, phosphatase) properties of post-pyrogenic soils on one fully and two partially burnt areas have been studied. The ground fire did not cause significant changes in the composition of the forest stand for burnt areas No. 2 (1159 m above sea level) and No. 3 (1359 m above sea level), while the burnt area No. 1 (651 m above sea level) was characterised by completely charred trees, abundant growth of pontic rhododendron, and poorly developed herbaceous vegetation. A 51% decrease in catalase activity compared to the control was found in the three areas. The activity of dehydrogenases and urease in post-pyrogenic soils exceeded the control values by an average of 62%. The activity of invertase and phosphatase varied depending on the study area. In general, there was a tendency toward an increase in the activity of these enzymes. At the same time, a high spatial variation in the activity of soil dehydrogenases and invertase was found for burnt-out area No. 1. There also was an increase in hydrolytic acidity by an average of 43% compared to the control values. The CEC, the content of organic and active carbon differs to a lesser extent from the control values 4 years after the fire. The acidity index (pH) of the area devoid of grassy vegetation reaches 5.8, with control having pH of 4. Notably, higher values of the CEC correspond to higher pH values. Factor analysis showed that changes in the enzymatic activity of post-pyrogenic phaeozem are associated with the peculiarities of the soils' chemical properties. The activity of hydrolases (urease, phosphatase) is closely related to the content of organic carbon, and the activity of other enzymes - to the CEC, hydrolytic acidity and pH. The content of active carbon changes insignificantly and does not affect the enzymatic activity.