Impact of Forest Fires on the Stability and Distribution of Soil Organic Matter Fractions in Agroforestry Systems

Abstract

Forest fires pose a significant threat to soil ecosystems by reducing soil organic matter, which is essential for maintaining soil structure and fertility. While the effects of fire on soil physical properties have been widely studied, the relationships between POM fractions, soil biophysical properties, and vegetation remain poorly understood. This study evaluated POM content under different land-use systems in the UB Forest following fire and examined its relationships with litter production, canopy cover, bulk density, porosity, and soil texture. Three land-use systems were investigated: protected forest (HL0), unburned agroforestry (AF1), and burned agroforestry (AF2), at soil depths of 0–10 cm and 10–30 cm, with four replicates per treatment (24 samples). Data were analysed using ANOVA and correlation-regression analyses. Protected forest had the highest total POM content (5.20 g kg⁻¹), whereas burned agroforestry had the lowest (1.93 g kg⁻¹), with the coarse POM fraction showing the greatest sensitivity to fire. Fire reduced total POM by 35% in the 0–10 cm layer compared with the deeper soil layer. Total POM was positively correlated with canopy cover and porosity but negatively correlated with bulk density, while no significant relationship was found with litter production or soil texture. These findings highlight the importance of maintaining vegetation cover and enhancing soil organic matter for effective post-fire ecosystem restoration.