Soil responses to fire in Mediterranean forest landscapes in relation to the previous stage of land abandonment

Abstract

The current paper presents a study on the interaction between land abandonment and soil responses to fire in old agricultural terraced landscapes. The study area, located near the Guadalest reservoir (E Spain), was partially affected by a forest fire in August 1998. We monitored burned and unburned areas as well as two pre-fire stand ages since agricultural abandonment: 8–15 years (dry grassland with young Pinus halepensis) and >35 years (mature pine forest). We analysed soil surface structure, water repellency and infiltrability, and we monitored plant response, runoff and sediment production for a period of 7 years after the fire. Aggregate stability increased with both time-since-abandonment and fire. Water repellency increased with land abandonment but was not affected by fire. Unburned erosion plots produced almost no runoff, even during heavy rainstorms. Fire scarcely modified runoff and erosion rates in recently abandoned terraces. A dry period following fire restricted plant recovery in burned pine forest. Burned forest plots registered runoff and sediment yields one to four orders of magnitude higher than unburned forest plots. In burned pine forest, the maximum sediment production was registered 3 years after the fire, when rainstorms took place and plant cover was still low. Old agricultural terraces colonised by pines were found to be both vulnerable to degradation as a consequence of fire and highly dependent on post-fire rain for their recovery.