Changes induced by forest fires in the aggregate stability andwater repellency of soils in NW Spain

摘要

In this work, the immediate effects of several summer forest fires that occurred in Galicia (NW Spain) in 1999 and 2000 on the aggregate stability and soil water repellency were studied. Changes in such properties were monitored in various soils over a two-year period following the fires. Differences in intensity and duration among the studied fires resulted in differences in aggregate stability and water repellency among the soils. Both parameters exhibited short-term post-fire increases in most soils; however, they decreased or changed very little in others. These different responses may be related to the observed changes in organic carbon contents in the soils. Aggregate stability changed very rapidly over the two-year period studied, so much so that no appreciable differences from unburnt soils were observed 3-6 months after the fires. Post-fire water repellency changes were found to be related to variations in soil moisture content, which exhibited two different temporal trends. In those cases where the fire increased water repellency, this reached levels similar to those in unburnt soils after one year. On the other hand, when water repellency was by the fire, it remained lower than in unburnt soils throughout the studied period.