Speaker
Description
Ground-based forest harvesting operations can substantially disturb soil through mechanisms such as compaction and rutting, posing long-term risks to forest productivity and sustainability. In boreal forest systems, soil trafficability maps derived from the depth-to-water (DTW) index are commonly used to identify areas vulnerable to machine-induced soil damage. However, the applicability and reliability of this approach in non-boreal forestry environments have not been sufficiently evaluated. The objective of this study was to assess the performance of the DTW index as a predictor of soil trafficability in plantation forests outside the boreal context
To address this objective, we examined DTW-based soil trafficability maps across three Pinus radiata plantation forests in New Zealand. Skid trails were selected within areas classified as potentially sensitive (DTW ≤ 1 m) and less sensitive (DTW > 1 m). Field measurements included soil moisture content, rut depth, and indicators of soil compaction, specifically bulk density, penetration resistance, and shear resistance. The data were analysed using linear mixed-effects models to account for site-level variability.
The results indicated no significant relationship between the DTW index and soil moisture at the time of sampling. This lack of correlation is likely attributable to temporal differences between harvesting activities and soil measurements, reflecting seasonal variability in soil moisture conditions. Despite this, rutting was consistently more severe in areas with DTW values ≤ 1 m, demonstrating that the DTW index is effective in identifying zones susceptible to surface deformation caused by machine traffic
Overall, the findings indicate that DTW-based trafficability maps are useful for highlighting areas where machine traffic is likely to exacerbate soil disturbance, but they should not be interpreted as defining zones that are entirely resistant or “safe” from impact. While DTW mapping represents a valuable planning tool for reducing logging-related soil damage in New Zealand plantation forests, its predictive capability could be enhanced by incorporating real-time soil moisture information and developing regionally specific flow initiation area (FIA) parameters. Future research should focus on refining DTW-based models to improve their robustness and applicability across a broader range of forest types, climates, and operational conditions.
| Keywords | DTM; DTW-index; Soil, Compaction |
|---|
