3. RESULTS
Carbon Erosion Comparing the topo sequences reveals an average carbon content of 1.07% in healthy soils, while the average does not exceed 0.8% in fire-affected soils. The C/N ratio, which is an indicator of soil functionality, plays a crucial role. An elevated C/N ratio (>12) signifies slow organic matter degradation, while a low C/N ratio (<8) indicates excessive soil activity.
The C/N ratio in Galite is generally low in both treated cases (healthy and burnt), primarily due to the rapid decomposition of organic matter, resulting in significant nitrogen production during decomposition (considered as a fertilizing effect).
The low C/N value (3.98) in the burned areas seems plausible. Regarding nitrogen, the situation is more complex. In absolute terms, nitrogen is less abundant on the soil surface after a fire because almost all the nitrogen in the burning fuel is lost through volatilization. However, many studies have shown a significant increase in mineral nitrogen in the soil after fire. Research indicates that a few hours after controlled burning in Aleppo Pine forests, the amount of mineral nitrogen in ammonium form in the top two centimeters of soil is four times higher than before the fire, while nitrate-form mineral nitrogen had decreased. It’s worth noting that the ashes are poor in mineral nitrogen. Christensen (1977) measured that less than 1% of the total nitrogen found in the ashes was in a mineral form, with 99% being in organic form. This immediate production of ammonium nitrogen in the soil does not appear to be related to ash input but is likely due to the heating of the surface soil layers and the hydrolysis of proteins. However, these ashes, which become incorporated into the soil, serve as a potential source of mineralizable nitrogen. The mineral elements contained in the ashes deposited on the soil are vulnerable to losses through erosion (wind or runoff) and leaching into deeper layers beyond the biologically active zones. These losses can vary based on slope, post-fire weather conditions, and soil characteristics. (Table 1)
Table 1: Descriptive Statistics of Natural Sample Topo sequences