Short-term effects of prescribed fires with different severity on rainsplash erosion and physico-chemical properties of surface soil in Mediterranean forests

Prescribed burning may induce erosion and change many physico-chemical properties of forest soils and these may vary with different burn severity conditions. Few studies have compared the effects of prescribed fires on rainsplash erosion and soil properties. Therefore, there is the need to better understand the variability of forest soils burned by prescribed fires with low and high severity under natural conditions. Rainsplash erosion, soil surface covers and physico-chemical properties of surface soil have been evaluated in the short term (15 months) in micro-plots of a burned pine forest of Central-Eastern Spain and compared to unburned areas. The results of the investigation have shown that high-severity fires gave higher rainsplash erosion compared to the unburned plots and areas affected by prescribed fires with low severity by 160% and 95%, respectively. The high-severity prescribed fires changed some soil properties (pH, electrical conductivity, total nitrogen and phosphorus), while no significant changes were observed in others (organic carbon and cations). Low-severity prescribed fires produced a significant disturbance on some soil properties (e.g., electrical conductivity, organic carbon, and total nitrogen), but not others (e.g., pH and cations) in comparison to unburned soils. The multivariate analysis using the Principal Component Analysis coupled to Analytical Hierarchical Cluster Analysis was able to discriminate unburned and burned soils, especially concerning organic carbon and nitrogen dynamics. However, this discrimination was not always sharp when compared to the unburned sites. This smooth difference was mainly due to the limited soil changes after fire, despite the very high differences in soil temperatures during burning. Overall, this study supports a better understanding of hydrological processes and changes in soil chemistry due to fire with different classes of burn severity, towards a more effective planning of pre- and post-fire management in fire-affected areas.