Effect of fire disturbance factors on the physicochemical properties of forest soil

Fire disturbance is one of the most dynamic factors in forest ecosystem, which changed soil physicochemical properties via ash and heat, influencing the stability of forest ecosystem. However, the relative contribution of ash and heat to the changes of soil physicochemical properties was not clear. In order to investigate the specific mechanism by which ash and temperature modify soil physicochemical properties after forest fires, one control check group and four treatment groups (ash group, charcoal group, flame group, and burning group) was set up by factorial decomposition method. 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. The results showed that: (1) Compared with the control group, pH and total phosphorus content in the ash group increased significantly (P＜0.05), while the water content, pH, and organic matter content in the charcoal group decreased significantly (P＜0.05), the water content, pH, and total nitrogen (TN) in the flame group decreased significantly (P＜0.05), while the water content in the burning group decreased significantly (P＜0.05). (2) Rainfall could obviously changed soil physicochemical properties in each treatment group. Both ash and heat could affect the physicochemical properties of forest soil after fire. Heat could cause soil nutrient loss in a short period, and ash could compensate for this loss and contribute to the recovery of soil physicochemical properties. Ash is an important component of soil recovery after fire.