Effect of Fire Disturbance Factors on the Physicochemical Properties of Forest Soil

Fire disturbance is one of the most dynamic factors influencing forest ecosystems, affecting them by altering soil physicochemical properties via ash and heat. However, the proportional contributions of ash and heat to changes in soil physicochemical properties following fire events remain poorly understood. This study aims to investigate the specific mechanisms by which ash and temperature modify soil physicochemical properties after forest fires. The study used the factorial decomposition method to establish one control check group and four treatment groups (ash group, charcoal group, flame group, and fire group). Soil samples from 0~10 cm depth were collected to analyze physicochemical properties, including moisture content, pH, organic matter, total nitrogen, and total phosphorus. Additionally, temperature data during the treatment period and meteorological data during the monitoring period were collected at the sampling sites. It turns that: (1) Compared with the control check, the ash group exhibited significantly elevated pH and total phosphorus content (P＜0.05), while the charcoal group showed significant reductions in moisture content, pH, and organic matter content (P＜0.05). The flame group displayed significant decreases in moisture content, pH, and total nitrogen (TN) (P＜0.05), whereas the fire group experienced significant moisture content reduction (P＜0.05) alongside significant increases in pH, organic matter, and total nitrogen (P＜0.05). (2) Pronounced fluctuations in soil physicochemical properties occurred during rainfall on the 20th day post-fire. Both ash and heat affect the physicochemical properties of post-fire forest soils. Heat causes soil nutrient loss in a short period, and ash compensates for this loss and contributes to the recovery of soil physicochemical properties. Ash is an important component of post-fire soil recovery.