Medium and long-term investigation on soil degradation after wood extraction operations: comparing skidding and forwarding

Forest harvesting operations may have a significant impact on soil. The soil disturbance extent and severity are mostly related to soil condition and to the harvesting system. Impacts mainly consists on soil compaction, displacement, and rut formation. Several papers investigated soil damage caused by logging operations on the short-term, but information on the effects of logging on the medium and long-term are still missing. This contribution deals with the effects of wood skidding and forwarding on soil degradation on three sites located in Central Italy. The presented results are related to the medium- as well as the longterm impacts, considering three different periods after forest operations of six months, 1 year and 3 years, respectively. Changes in porosity, bulk density, shear and penetration resistances were investigated on two plots for each wood extraction system adopted, evaluating soil damage. The impact on forest regeneration was also investigated. We found that the restoring time of extraction tracks after logging operations is related to the previous soil compaction level. Skidder did not negatively affect natural regeneration as much as forwarder machine did, while the impact of this latter was lower on sandy soils. In conclusion, the effects on soil of forest machines are still apparent after a long period following forest operations, thus suggesting that the use of previous tracks must be encouraged to avoid the extension of soil disturbance.