Effects of heating on some soil physical properties related to its hydrological behaviour in two north-western Spanish soils

Abstract

Two forest soils rich in organic matter but differing in texture (sandy loam and silty loam) were heated under controlled laboratory conditions in order to examine the consequences of the heating effect that accompanies the passage of a fire on the physical properties of soil. Three samples of both soils were heated for 30 min in a muffle furnace at temperatures of 25, 170, 220, 380 and 460°C. At each temperature, the following parameters were determined: dry aggregate size distribution, water aggregate stability, total porosity, pore size distribution, water repellency and hydraulic conductivity. Heating the soils at 170 and 220°C caused no significant changes in aggregate size distribution or total porosity but increased water aggregate stability and the volume of pores 0.2–30 μm. Also, increased water repellency and strongly decreased the hydraulic conductivity. All parameters underwent much more dramatic changes at 380 and 460°C that can be ascribed to the combustion of organic matter. At such temperatures, water repellency was destroyed and the low hydraulic conductivity can be attributed to the aggregate breakdown observed under dry and wet conditions.

Effect of burning temperature on water repellency and aggregate stability in forest soils under laboratory conditions

“…Different responses have been found by various authors. Increasing aggregate stability has been reported by Giovannini et al (1988), Mataix-Solera et al (1996), Díaz-Fierros et al (1987), Guerrero et al (2001), and Arcenegui et al (2008), and decreasing aggregate stability by Sanroque et al (1985) and García-Corona et al (2004). A direct consequence of retarded wetting in water repellent soils is the enhanced structural stability of soil aggregates (Chenu et al, 2000;Mataix-Solera and Doerr, 2004).…”

“…Destruction of organic matter during burning should lead to a decrease in the stability of aggregates, but the effect of wildfires on aggregate stability depends also on other factors such as severity of fire (Úbeda, 1999), soil mineralogy (Giovannini et al, 1988), changes in organic matter content (García-Corona et al, 2004) and enhanced water repellency (Giovannini and Lucchesi, 1983;Mataix-Solera and Doerr, 2004). Different responses have been found by various authors.…”

Can terra rossa become water repellent by burning? A laboratory approach

“…: DeBano and Krammes, 1966;Doerr et al, 2004;García-Corona et al, 2004). However there are a few cases, where no changes in WR after burning have been observed (Giovannini and Lucchesi, 1983;Busse et al, 2005).…”

“…: DeBano and Krammes, 1966;Doerr et al, 2004;García-Corona et al, 2004;Dlapa et al, 2008). In many studies it has been observed that fire induced WR in hydrophilic soil, and either enhanced or reduced the surface WR in an already water repellent soil (e.g.…”

Distinctiveness of wildfire effects on soil erosion in south-east Australian eucalypt forests assessed in a global context

“…They found that when slightly repellent Californian chaparral soil was heated for 5-20 min, repellency remained essentially unaltered at temperatures <175 8C, became enhanced at 175-200 8C and destroyed at 250-300 8C, depending on heating duration. Although the changes reported at lower temperatures are now known to vary, destruction of repellency at 250-400 8C has been firmly established for coniferous and eucalypt forest soils in diverse locations (Savage, 1974;Scholl, 1975;DeBano et al, 1976;Robichaud and Hungerford, 2000;García-Corona et al, 2004), including sandy soil from south-east Australian eucalypt forests , provided sufficient oxygen is available for oxidation of the hydrophobic compounds .…”