Fire and rainfall energy effects on soil erosion and runoff generation in semi-arid forested lands

A study on the effects of fire and torrential rainfall on the soil erosion and hydrology of Pinus halepensis L. forest of the semi-arid Central Ebro Valley (NE-Spain) were carried out. A portable sprinkler-based rainfall simulator was used with two levels of rainfall energy (12,6Jm(-2)mm(-1) and 24,7 J m(-2)mm(-1)) and similar intensity (85 +/- 18 mm h(-1)). Rainfall simulations were conduced immediately after artificial burn of litter cover on nine different micro-plots and compared with paired unburned areas (2-soil status x 2 rainfall energies x 9 plots or replicates). In each rainfall simulation, the soil loss, soil infiltration (calculated by Horton model, wetting front, runoff coefficient, and runoff quality (EC and pH) were measured Fire increased significantly the sediment loss: 18.5 times with fine rainfall and 33.6 with coarse rainfall Sediment losses were as solutes dissolved in overland flow, mainly in unburned plots, and as particles in suspension, mainly in burned plots. Fire increased runoff quantity (about 1. 6 times) and decreased quality (by increasing significantly both EC and pH). These results indicate that when litter cover was burned, first rainfalls duplicate runoff and increase 20-30 times soil erosion in relation to unburned plots, especially with high rainfall energy. Soil infiltration decreased significantly in burned plots, with the highest rainfall energy. Because there is a high post-fire degradation risk, a restoration strategy for a short-term response should be designed on steep slopes with erodible soils, especially in and Mediterranean areas where torrential rainfall and wildfire are highly probable and their occurrence will increase with climate change.