Effects of fire smoke on soil microorganisms: results of a modelling experiment

Wildfires are widespread and have major effects on ecosystems. The sensitivity of soil microorganisms to smoke was studied in experimental conditions using smoke generated from burning pine sawdust. High concentrations of toxicants such as NO (40 mg/m3), NO2 (60 mg/m3), CO (3570 mg/m3), C2H4O (241 mg/m3), CH2O (9.5 mg/m3), C6H6O (4.4 mg/m3), and C6H14 (238 mg/m3) were measured in the smoke. Reduced abundance of Azotobacter chroococcum by 9–62% and of microscopic fungi by 25–57% was found when the soil was treated with smoke for 30–120 min. The abundance of soil microorganisms after exposure to smoke depended on time. Several species of soil fungi (Fusarium oxysporum, Venturia inaequalis, Fusarium moniliforme, Fusarium graminearum, Cladosporium cucumerinum, Penicillium chrysogenum, Rhodotorula rubra, Lipomyces starkeyi), and bacteria (Acinetobacter calcoaceticus, Streptomyces violaceus, Kocuria rosea) were studied. The lowest smoke exposure time at which growth inhibition was registered was 1–5 min. The effect of smoke on the enzymatic activity of Haplic Chernozem soils was also evaluated. Catalase activity was found to decrease by 25%, and peroxidase and polyphenol oxidase by 15% and 33%, respectively. High smoke toxicity contributed to changes in microbial abundance and enzymatic activity.