Influence of Fires on the Enzymatic Activity of Сinnamonic Soils and Burozems in the Western Caucasus

Abstract

The results of studying the effect of fires on biological properties of cinnamonic soils of xerophytic forests (Skeletic Leptic Cambisol) of the Utrish State Nature Reserve, Krasnodar krai (crown fire of 2020), and burozem of mesophytic forests (Haplic Cambisol (Loamic)) of the Khamyshinsk forestry, Republic of Adygea (ground fire of 2018) are presented. Changes in the soil reaction, in the organic carbon content, and in the activity of enzymes: catalase, urease, phosphatase, and invertase involved in the cycle of carbon, phosphorus, and nitrogen have been studied. The reaction of enzymes to pyrogenic effects depends on the enzyme kind and the soil type. The factor analysis was also performed. The activity of catalase and invertase decreases by 47% on average for two soil types in the 0–3-cm-thick layer, while the reaction of phosphatase and urease depends on the soil type. Two years after the fire, the phosphatase activity in the surface layer of post-pyrogenic cinnamonic soils approached the control values; and the urease activity regenerated more slowly as compared to other enzymes. Four years after the fire, the values of urease activity in the 0–3-cm-thick layer of the post-pyrogenic acid burozem, on the contrary, approached the control values. An increase in pH by 30% on average and a decrease in the C_org content by 12% on average were also recorded for both two soil types. The mean activity of all the studied enzymes in the 3–10-cm-thick layer increased in cinnamonic soils and, on the contrary, decreased in acid burozem. The factor analysis showed a relationship between the soil reaction, the organic carbon content, and the activity of enzymes, and the strength and nature of relationships differed depending on the soil type. The results obtained testify to the effect of soil properties on the response of enzymatic activity to the pyrogenic impact.