Analysis of Changes in Soil Chemical and Biological Characteristics after Fire in Zagros Forests (Case study: Gahvareh, Kermanshah)

Background: Forest fire is very common in all ecosystems of the world that affects both vegetation and soil and is also helpful in maintaining the diversity and stability of ecosystems.The effect of forest fires and prescribed fires on forest soil is very complex.It affects the organic matter, macro and micronutrients, and physical properties of soil, such as texture, color, pH, and bulk density, as well as soil biota.Fire is a natural factor in the forest that temporarily reduces the vegetation on the soil surface.After a fire, the soil can experience long-term, medium-term, and short-term changes, which are different depending on the type of soil characteristics, weather conditions, duration, intensity, and frequency of the fire.The Zagros forest ecosystem is generally in the coppice form, and these forests are not safe from fire, which constantly affects them.Considering that the long-term stability of these forests depends on maintaining the soil quality, it is essential to investigate the effects of fire on soil properties.This study aimed to investigate the effect of fire on Zagros forests in Kermanshah province, Gahvareh city in the Lerini region.Methods: The studied area is a part of Zagros forests in Kermanshah province, Gahvareh city, the Lerini region located at 34 10' 35 E and 46 34' 28 N, with an average height of 1468 m above sea level.In this research, the points were determined by measuring with a meter on transects, and they were sampled regularly in specific time intervals (October, November, February, April, and June).The distance between the samples in each row was 20 m and the distance between the rows was 50 m, and three rows were determined in each of the burnt and control areas.Some soil characteristics, such as pH, electrical conductivity (EC), organic carbon, absorbable phosphorus, soil respiration, microbial biomass carbon, substrate-induced respiration, and metabolic quotient, were measured in soil samples.The effect of the treatments on all measured variables was investigated by the two-way ANOVA.Means were compared by Duncan's Multiple Range Test (DMRT).Data were analyzed using the Windows version of SAS (version 9.4, SAS Institute Inc., Cary, NC).Results: The soil pH decreased with the passage of time and a decrease in air temperature under the crown (unburnt and burned) and outside the unburnt crown.An upward trend in the pH of the soil in these three places occurred after the cold season.The soil pH ranged from 7.31 to 7.66 in all treatments from October to June.The results of the two-way ANOVA showed that the fire and sampling location did not affect the soil EC in different months of sampling.The amount of absorbable phosphorus increased with the occurrence of fire.The highest and lowest amounts of absorbable phosphorus occurred under and outside the burnt and the control crowns, respectively.The range of organic carbon changes indicates that soil organic carbon has increased over time in all treatments.The highest and the lowest increases were observed under the burnt (1.51%) and the control (unburned) crowns, respectively.Examining the changes indicates that the basic soil respiration was high at the beginning of the fire but decreased gradually, and then the initial value also increased in the last months of sampling.In this research, the amount of basic respiration in the soil of burned areas is not higher than that of unburned areas despite the occurrence of fire