Occurrence of soil erosion after repeated experimental fires in a Mediterranean environment

Abstract

In the Mediterranean area, forest fires have become a first-order environmental problem. Increased fire frequency progressively reduces ecosystem recovery periods. The fire season, usually followed by torrential rains in autumn, intensifies erosion processes and increases desertification risk. In this work, the effect of repeated experimental fires on soil response to water erosion is studied in the Permanent Field Station of La Concordia, Valencia, Spain. In nine 80 m2 plots (20 m long x 4 m wide), all runoff and sediment produced were measured after each rainfall event. In 1995, two fire treatments with the addition of different biomass amounts were applied. Three plots were burned with high fire intensity, three with moderate intensity, and three were unburned to be used as a control. In 2003, the plots with the fire treatments were burned again with low fire intensities. During the eight-year interval between fires, plots remained undisturbed, allowing regeneration of the vegetation–soil system. Results obtained during the first five months after both fire experiments show the high vulnerability of the soil to erosion after a repeated fire. For the burned plots, runoff rates increased three times as much asore than those of 1995, and soil losses increased almost twice. The highest sediment yield (514 g m-2) was measured in 2003, in athe plots of the moderate burned with moderate fire intensity treatment in 1995, which had yielded only 231 g m-2 of sediment during the corresponding period in 1995. Runoff yield from the control plots did not show significant temporal changes, while soil losses decreased from 5 g m-2 in the first post-fire period to 0.7 g m-2 in the second one.