Geotechnical Properties of Burned Soils: A Case Study of a Pine-Forest Fire in Southwestern Türkiye

The geotechnical properties of soils such as consistency limits and shear strength are closely related to the erodibility. It is well known that erosion risk is promoted after forest fires. However, the changes in the geotechnical properties of topsoil after forest fires have not been extensively studied in the literature. In addition, the existing studies show contradictory results. Since forest fires exert randomly distributed burning temperatures depending on the slope, aspect, vegetation type, and height, different burn severity degrees can be observed in one fire perimeter. This results in variations in soil parameters due to the fire. In this study, the effect of a pine forest fire on the geotechnical properties of sandy soils was addressed. A total of 69 unburned and burned soil samples were collected from different depths of the soil profile. It was found that the samples taken below 4 cm depth have not shown statistically significant differences due to burning. However, the samples collected from the top organic layer (0–4 cm) showed signs of disaggregation and accordingly, consistency limits increased while shear strength decreased. These results contributed to the existing knowledge that cohesionless shallow soils, typically regosols, respond to natural burning distinctly.