WILDFIRE IMPACTS ON SOIL-EROSION AND HYDROLOGY IN WET MEDITERRANEAN FOREST, PORTUGAL

The Agueda Basin, north-central Portugal is comparatively wet (rainfal l, 1600-1800 mm/yr) with frequent, relatively large storms in autumn a nd winter yet the summer drought is sufficiently long and consistent f or frequent forest wildfires. This paper discusses wildfire impacts in such a wet Mediterranean environment on soil hydrophobicity, infiltra tion capacity, overland flow coefficients, soil loss, rainsplash detac hment and small-scale ground level changes for Eucalyptus globulus and Pinus pinaster forest: (1) 0-2 years after fire ('new' burn); (2) 3-4 years after fire ('old' burn); and (3) 'mature' (or long unburnt) sit es. For 'new' burn sites, rainsplash detachment rates are an order of magnitude and soil losses two orders of magnitude higher than for 'old ' burn sites and both are two orders of magnitude higher than for 'mat ure' sites. Soils are hydrophobic in all three categories of sites, bu t infiltration capacities are lower at 'new' burn and 'old' burn than at 'mature' sites. Overland flow coefficients on long unburnt sites we re low while on burnt sites they were high and tended to be higher for summer and autumn than for winter and spring, implying enhanced hydro phobicity under summer drought conditions, causing decreased infiltrat ion capacity and increased overland flow. The distinctiveness of fire effects on soil erosion and hydrology in this wet Mediterranean enviro nment and implications for post-fire management are discussed.