Speaker
Description
Intensive forestry operations can lead to soil compaction, plastic soil disturbances, and rutting, which negatively impact soils, vegetation, and water bodies. Although many studies have explored the main factors influencing soil damage, it remains unclear whether wood extraction methods and driving direction affect the impacts of forest machinery. Specifically, the differences in soil damage between skidding (SKI) and forwarding (FOR) are not well understood, especially regarding the extent of soil compaction beyond wheel ruts and the influence of driving in curves or in straight lines. This study aimed to compare soil bulk density (BD), soil penetration resistance (PR), and rutting when driving in curves and on straight lines, while considering the total area of soil impacted by wheels and load. The same forest machine (a forwarder) was used during both FOR and SKI to keep machine parameters constant; in FOR, the machine transported logs as an ordinary forwarder, while in SKI, long trunks were fixed with chains to simulate a clambunk. Soil compaction was evaluated using BD and PR in the area impacted by wheel ruts, between the ruts, and by the load outside the wheel ruts. Rutting was quantified using drone imagery and Structure-from-Motion photogrammetry (SfM) to create 3D soil surface reconstruction, allowing for measurement of rut depth and soil volume changes.
In general, both BD and PR increased significantly after 20–25 machine passages on this sandy soil. Across treatments, PR increased by 49-120% within ruts and by 24-71% between ruts, indicating lateral propagation of compaction and a widening of the impacted zone beyond the wheel tracks. When comparing driving straight ahead with driving in a curve at the same transported wood volume (20 FOR and 25 SKI passes), PR within ruts was consistently higher in a curve for both extraction methods (FOR: 3.22 to 4.34 MPa; SKI: 2.82 to 3.85 MPa), and PR between ruts showed the same overall pattern (FOR: 2.45 to 3.07 MPa; SKI: 2.64 to 3.23 MPa). Photogrammetry-derived 3D soil reconstruction further showed that the area affected by the wheel ruts increased in curved segments for both FOR and SKI, and that the total area affected was larger in SKI due to the additional disturbance caused by dragged trunks, resulting in a wider footprint when driving in a curve. Rut depth increased significantly with traffic intensity in FOR; in contrast, in SKI, rut depth estimates were affected by rut concealment, thereby reducing measurement reliability. These results show important information on soil impact, useful for the development of a new wood extraction technique. 3D reconstruction measures soil volume changes and rut depths better than manual measurements.
| Keywords | Bulk density; Penetration resistance |
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