Aftermath of Fires for Mesophytic Forest Soils in the 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 consequences of fires in different climatic and soil conditions. The aim of this work is to study 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, and phosphatase) properties of postpyrogenic soils on one fully and two partially burned areas have been studied. The ground fire did not cause significant changes in the composition of the forest stand for burned areas 2 (1159 m a.s.l.) and 3 (1359 m a.s.l.), while burned area 1 (651 m a.s.l.) was characterized by completely charred trees, abundant growth of pontic rhododendron, and poorly developed herbaceous vegetation. A 51% decrease in catalase activity compared to the control is found in the three areas. The activity of dehydrogenases and urease in postpyrogenic soils exceed the control values by an average of 62%. The activity of invertase and phosphatase varies depending on the study area. In general, there is 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 is found for burned area 1. There was also an increase in hydrolytic acidity by an average of 43% compared to the control values. The CEC and 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 CEC correspond to higher pH values. Factor analysis showed that changes in the enzymatic activity of the postpyrogenic phaeozem are associated with the peculiarities of the chemical properties of the soils. The activity of hydrolases (urease and phosphatase) is closely related to the content of organic carbon, and the activity of other enzymes closely related to the CEC, hydrolytic acidity, and pH. The content of active carbon changes insignificantly and does not affect the enzymatic activity.