Changes in Enzyme Activity in Postpyrogenic Soils (Physical Model Experiment)

Data on changes in the enzymatic activity of soils under pyrogenic impact in model experiments simulating natural fires are given. A series of experiments performed under laboratory and natural conditions were aimed at studying pyrogenic inhibition of the activity and dynamics of recovery of enzymes in postpyrogenic soils. The objects of the study were represented by gray-humus sandy soil (Arenosol) and chernozem with migrational and segregational forms of secondary carbonates (Haplic Chernozem (Loamic, Pachic) of Rostov oblast. Model experiments included soil treatment with gas burner flame (heat amount 87–435 × 103 J) and wood fuel combustion (10–279 × 106 J). The exposure duration was from 1 to 5 min in the first case and from 1 to 120 min in the second case. The revealed response of enzymes (catalase, invertase, urease, peroxidase, and phosphatase) to low-temperature plasma impact (1–120 min) depended on the enzyme group and exposure rate. It was found that the penetration depth of thermal effect of simulated fires was limited by the top soil layer (0–10 cm), and the radius of spread from the combustion source did not exceed 20 cm. The temperature varied according to the exposure period, source of heat, and fuel amount (400–600°C). Sandy soils and chernozem got heated and cooled at different rates. The activities of catalase, invertase, and urease were inversely related to the intensity of pyrogenic impact. The dynamics of restoration of the enzyme activity in postpyrogenic soils was analyzed. The invertase activity recovered faster than the catalase and urease activity, but it the recovery was still in complete in a year after fire. The results obtained testify to a significantly prolonged inhibition of enzymatic activity as a result of simulated natural fires.