Effect of forest fire on soil microbial biomass and enzymatic activity in oak and pine forests of Uttarakhand Himalaya, India

Abstract

Background: Forest fire incidences in the Himalayan region of Uttarakhand, India are very common in summers. Pine and oak are the principal and dominant species of Himalayan subtropical forest and Himalayan temperate forest, respectively. Forest vegetation influences the physicochemical and biological properties of soil and forest fire in pine and oak forests may have a different effect on the physicochemical and biological properties of soil. Therefore, the present study was carried out to assess the impact of forest fire on soil microbial properties, enzymatic activity, and their relationship with soil physicochemical properties in the advent of forest fire in the pine and oak forests of the Garhwal region of Uttarakhand Himalaya, India. Results: The soil microbial biomass carbon and nitrogen, soil basal respiration, and acid phosphatase activity decreased, whereas dehydrogenase activity increased at burnt sites of both forest types. The overall change in soil microbial biomass carbon was 63 and 40% at the burnt oak forest and burnt pine forest, respectively. Dehydrogenase activity and acid phosphatase activity showed a strong positive correlation with soil organic matter (r = 0.8) and microbial indices, respectively. The ratio of soil microbial biomass carbon/nitrogen was reduced at burnt sites of both forest types. Factor analysis results showed that fire had a significant impact on soil characteristics. The soil basal respiration was linked with macro- and micronutrients at burnt sites, whereas at control sites, it was linked with physicochemical properties of soil along with nutrients. Conclusion: Forest fire had a significant impact on soil properties of both forest types. The impact of forest fire on soil microbial biomass carbon was stronger in the oak forest than in the pine forest. Forest type influenced soil enzymatic activity at burnt sites. The bacterial community was dominated over fungi in burnt sites of both forests. Soil microbial indices can be used as a selective measure to assess the impact of fire. Furthermore, forest type plays an important role in regulating the impact of forest fire on soil properties.