Post-fire hydrological and erosional responses of a Mediterranean landscpe: Seven years of catchment-scale dynamics

Abstract

We studied medium-term dynamics of fire effects on catchment runoff and sediment yield in a dry-Mediterranean area in Alicante, E Spain. The study area was a mixed forest and agricultural terraced landscape that was affected by a wildfire in August 1998. We measured runoff and sediment yield in two catchments – burned and unburned – during the first seven years after the wildfire. Post-fire vegetation cover dynamics were also monitored. Total runoff and sediment yield in the burned catchment (35 mm and 4563 kg ha − 1 , respectively) were considerably greater than in the unburned catchment (0.03 mm, and 0.12 kg ha − 1 ). Annual runoff and sediment yield increased with time after fire until the third post-fire year, and then decreased progressively. However, even five years after the wildfire, differences in annual runoff and sediment yield between the burned and the unburned catchments were still about two orders of magnitude. Post-fire vegetation cover increased very slowly during the initial post-fire years, and differences between burned and unburned areas persisted six years after the wildfire. Most studies on post-fire hydrology and erosion have identified the first one or two post-fire years as the critical period for high runoff and erosion risk, indicating short-term ecosystem resilience to wildfire. However, we found that wildfire impact on catchment runoff and sediment yield in Mediterranean drylands may be amplified by drought periods that delay plant recovery, and thus wildfire impacts may be still of great importance several years after the fire.