The roles of texture and structure in the water retention capacity of burnt Mediterranean soils with varying rainfall

Abstract

Differences in soil texture, structure and water retention capacity between burnt and unburnt soils were studied in an area affected periodically by forest fires in SE Spain. The burnt and unburnt soils were sampled at altitudes ranging from 100 to 1000 m a.s.l., with slight differences in climate between the sampling sites. Comparisons were made at three levels: all-sites, between-sites and within-site. Between all the burnt and unburnt soils only two significant differences were found: greater aggregate stability and smaller clay content in burnt soils. Slight differences in climate between the locations hide other effects of fire on these already degraded soils. However, at some sites, where the burning was thought to have been more intense, the water retention capacity was greater for unburnt than for burnt soils. Multiple regression equations for certain aggregate sizes (mainly 1 – 0.105 mm), textural classes (mainly coarse silt) and organic matter content predict quite well the soil moisture content of burnt soils at different suction pressures.