Wildfire effects on soil carbon and water repellency under eucalyptus forest in Eastern Australia

Abstract

Soil properties can be considerably modified as a result of wildfire. This study examined the impact of wildfire on total carbon and water repellency at two study sites, namely Cranebrook and Wentworth Falls, located 45 and 75 km west of Sydney, Australia, respectively. Within each study site, we measured soil properties at two depth intervals from five burn severity classes along 15 transects (10 sample points per transect). Samples were taken 6, 12 and 36 months after wildfire. Soil total carbon was measured using LECO combustion analysis and potential soil water repellency was determined using water drop penetration time. Two-way analysis of variance (ANOVA) was used to analyse the results, with burn severity and time as factors. Burn severity had a significant effect on both soil total carbon and water repellency at both study sites, whereas time was only significant for soil carbon at Wentworth Falls. Soil total carbon and water repellency were variable through time due to local environmental variables, such as rainfall and temperature. The relationship between soil total carbon and water repellency was strong for Cranebrook in the surface soil (r = 0.62) and lower in the subsurface soil (r = 0.41), but weaker at Wentworth Falls, with values of r = 0.22 and r = 0.15 in the surface and subsurface soils respectively.