Soil physical and hydrological properties following logging and slash burning in the Eucalyptus regnans forest of southeastern Australia

Abstract

Logging causes soil profile disturbance (mixing and/or removal of soil) and compaction. Regeneration slash fire causes burning of surface soils. This may change soil physical and hydrological properties, which may affect site productivity and catchment water quality. This study was undertaken to quantify the effect of logging and slash burning on areal distribution of soil profile disturbance, fire intensity class and physical and hydrological properties of the 0–100 mm surface soil in the Victorian Central Highlands, southeastern Australia. Following clearfelling logging and slash burning, four coupes were surveyed using a systematic grid sampling technique. Each coupe was classified into the following operation categories: snig tracks, log landings and general logging areas. Each coupe was also classified in terms of both level of soil profile disturbance: undisturbed, litter disturbed, topsoil disturbed and subsoil disturbed; and intensity of fire: unburned, low intensity, moderate intensity and high intensity. The soil physical and hydrological properties were measured in two of the four logging coupes. Measurements were made in the snig tracks (primary, secondary and tertiary tracks), log landings and general logging areas. Within the general logging areas, plots were located for two classes of soil profile disturbance: undisturbed and topsoil disturbed. Within each of the two classes of soil profile disturbance measurements were made for three levels of fire intensities: unburned, moderate intensity and high intensity burn.Following logging and slash burning, on average 11% of the coupe area remained undisturbed, 11% litter disturbed, and 78% had mineral soil exposed. The snig tracks, log landings and disturbed general logging area occupied about 19%, 3% and 66% of the coupe area, respectively. On average, 52% of the coupe area remained unburned and 8% was affected by high intensity burn.Soil profile disturbance significantly changed particle size and organic matter distribution, increased bulk density, decreased aeration porosity and saturated hydraulic conductivity in the unburned general logging area. Soil compaction significantly increased bulk density, water-filled porosity (< 30 μm) and availabel water, and decreased aeration porosity and saturated hydraulic conductivity in the primary snig tracks and log landings.The high intensity slash burning significantly reduced clay and organic matter content in the undisturbed soil profile conditions but not for disturbed soil profile conditions. Implications for changes in these soil properties are discussed in terms of eucalypt establishment and growth and soil erosion potential.