THE ROLES OF TEXTURE AND STRUCTURE IN THE WATER-RETENTION CAPACITY OFBURNT MEDITERRANEAN SOILS WITH VARYING RAINFALL

Differences in soil texture, structure and water retention capacity be tween burnt and unburnt soils were studied in an area affected periodi cally by forest fires in SE Spain. The burnt and unburnt soils were sa mpled at altitudes ranging from 100 to 1000 m a.s.l., with slight diff erences in climate between the sampling sites. Comparisons were made a t three levels: all-sites, between-sites and within-site. Between all the burnt and unburnt soils only two significant differences were foun d: greater aggregate stability and smaller clay content in burnt soils . Slight differences in climate between the locations hide other effec ts of fire on these already degraded soils. However, at some sites, wh ere the burning was thought to have been more intense, the water reten tion capacity was greater for unburnt than for burnt soils. Multiple r egression equations for certain aggregate sizes (mainly 1 - 0.105 mm), textural classes (mainly coarse silt) and organic matter content pred ict quite well the soil moisture content of burnt soils at different s uction pressures. (C) 1997 Elsevier Science B.V.