SOIL WATER REPELLENCY IN AUSTROCEDRUS CHILENSIS FORESTS AFFECTED BY FIRES

MORALES, D.V. , L. LA MANNA Y C. M. ROSTAGNO

Puerto Madryn, Chubut

Workshop; 1st South American Symposium on Fire Ecology and Management; 2009

The formation of water repellant soil layers may occur as an effect of fire.  The hydrocarbons from organic matter that are vaporized by the increase in temperature, are re-precipitated generating hydrophobic coatings on mineral particles. This water-repellent coating reduces infiltration, water storage capacity and increases the risk of erosion. This study aims to evaluate the tendency to hydrophobicity in volcanic soils disturbed by recent fires.  Two study sites with A. chilensis forests were selected in Chubut and Río Negro provinces which were affected by fires in February 2008 and January 2009, respectively. In each site, an unburned area and two levels of disturbance by fire were identified. Samples of the mineral soil at two depths (0-2.5cm and 2.5-5cm) were randomly taken and their hydrophobicity was determined. Data showed a high heterogeneity with no significant differences; however some tendencies were found. In the most recent fire the water-repellency tended to be higher in the area most affected by fire, with respect to control soil and also to the less disturbed forest. One year after the fire, the hydrophobicity tended to be greater in the 2.5-5cm samples. The hydrophobicity was high even in unburned control soils. This result could be related to the intrinsic properties of the parent material of soils (i.e., volcanic ash).