Effect of surface roughness on runoff and erosion in a mediterranean ecosystem: the role of fire

Mechanisms at the micro (patch) scale influencing runoff and erosion processes following a forest fire were investigated. The study was conducted in a Mediterranean mountainous region with a mean annual rainfall of 690 mm, Terra Rossa soil, and vegetation composed of a dense shrubland of Pinus halepensis and Quercus calliprinos. Simulated rainfall experiments were carried out on plots representing different intervals of time elapsed since a fire; i.e., immediately after fire, two weeks after fire, one year after fire. Unburned plots were also used for comparison. At a local scale, great variability was found whereby some patches produced high runoff and sediment yields following fire, while others did not. The conclusion is that the main effect of fires of low to moderate intensity is to produce a mosaic-like surface containing both rough patches in which there is almost no chance for runoff generation, and relatively smooth patches in which fire can subsequently lead to higher runoff and erosion rates.