Impacts on soils from cable-logging steep slopes in northeastern Tasmania, Australia

Abstract

Cable-logging is a method commonly used to harvest native forests on steep slopes in Tasmania, Australia. A study was carried out to determine impacts on site disturbance and selected soil properties resulting from cable-logging wet eucalypt forest developed on granite substrates in northeastern Tasmania. The results show that both the area and depth of soil surface disturbance are relatively minor, with ca. 11% of the study coupe affected by moderate (litter and part topsoil removed) or severe (subsoil exposed) disturbance. Cable draglines accounted for just over 7% of the soil disturbance (7% moderate and 0.2% severe), whereas tree uprooting associated with the logging accounted for a further 3% moderate disturbance and 1% severe disturbance. Measurements of soil properties in the surface layer (0–10 cm) show that bulk density is ca. 20% higher and organic carbon content (kg/ha) is 15% lower on cable draglines compared to undisturbed sites. However, the dominant type of soil disturbance caused by cable-logging appears to have been displacement of the upper 10 cm of topsoil from the centre to the outside edges of draglines rather than compaction in situ. Comparison of the data with studies of ground-based logging of wet native forests elsewhere in southeastern Australia shows that cable-logging has resulted in significantly less impact on both area of soil disturbed and soil properties. The results are also discussed in relation to relevant sustainability indicators (soil erosion, organic matter and compaction) specified in Criterion 4 of the Montreal Process together with recently proposed threshold values.