Wildfire burned soil organic horizon contribution to runoff and infiltration in a Pinus pinaster forest soil

Abstract

ABSTRACTThe immediate effects of a low soil burn severity wildfire on hydrological parameters and soil erosion were evaluated in a Pinus pinaster Ait. stand by means of rainfall simulations (140 mm h−1). The unburned forest soil was repellent at the mineral surface (100%) at the same degree as the burned ones. The diameter of soil aggregates and the particle size distribution did not differ between burned and unburned soils. The mean storage capacity of the unburned soil organic layer was 0.94–4.85 mm m−2 from the litter to the duff layers. The corresponding values for the capillary capacity were from 7.11 mm to 6.72 mm. In the burned plots, these figures were 1.42 mm m−2 for the mean storage capacity and 5.9 mm for the capillary capacity. The burned plots recorded significantly lower infiltration rates (29 mm h−1) and higher runoff (111 mm) and sediment yields (20.8 g m− 2) compared to the unburned controls. The characteristics of the soil organic layer significantly affected the infiltration rate and runoff volume. In a subsequent experiment, the remaining organic layer was completely removed and a new rainfall simulation was carried out. In unburned soils decreases in the infiltration rate and increases in the runoff volume were recorded with no significant changes in the sediment yields. In the burned plots, removal of the duff layer only led to a significant increase in soil erosion (20.8–51.4 g m−2). The above information could be used to help plan post-fire stabilization actions.