Estimation of wheel ruts and soil compaction with different methods applied in a comparison between skidding and forwarding.

The soil damage extent and severity, caused by wood extraction, are related with soil condition, harvesting system and machine characteristics. Contrasting results have been published about soil damages caused by skidding and forwarding, thus highlighting the needs of further investigations on this topic. In order to analyses the spatial distribution of soil disturbance more accurately, new methods based on the 3D soil reconstruction have been developed. The overall objective of this study was to investigate new methods (portable laser scanner and close-range photogrammetry) and traditional methods (cone penetrometer, manual rut depth measurements, soil bulk density and porosity) for evaluating rutting and soil compaction caused by a loaded forwarder and skidder. Our findings mainly show a relationship between soil compaction (i.e. cone penetration resistance) and rutting (i.e. total reduction of soil volume) in low moisture soil condition. The shortest data acquisition was observed during the portable laser scanning, while in accuracy rutting estimation was higher in close-range photogrammetry. The comparison of photogrammetric and manually-measured profiles confirmed that Structure For Motion photogrammetry can be an accurate instrument for Digital Evolution Model and for morphology description of forest soil disturbance after forest logging. Furthermore, the results showed the effect of harvesting systems and terrain conditions on soil disturbance. In conclusion, soil disturbances were higher for skidder than for forwarder considering the same wood volume extracted.