For the timber exploitation of forest stands, transport machines pass several times along the same track and this operation can cause soil compaction. This paper aimed to evaluate the soil compaction level as related to the number of passes of a forwarder and weight of the timber load. The study was carried out in Santana do Paraíso country, Minas Gerais State, Brazil, in a six year-old eucalypt stand with 3 x 2 m spacing on an caulinitic Oxisol. The trees were felled by a chainsaw and removed from the area by hand. Then plots of 144 m² (four tree interrows 12 m long) were outlined to conduct two trials;. In the first, the number of passes of a forwarder loaded with weights of 11.9 tons and 8 m³ (wood density 480 kg m-3) was tested in the following situations: no passes (wood removed by hand), 4, 8, and 12 passes. In the second trial, forwarder wood loads of 0, 4, 8, and 12 m³ were tested by driving the machine four times along the same track. In each plot, the passes affected four tree interrows. The soil of the area is clayey (510 g kg-1 clay) and the moisture content during the trial was 15.6 and 17.1 dag kg-1, at depths of 0-10 cm and 10-20 cm, respectively. These layers were assessed for soil density and water-stable aggregates. Soil penetration resistance was evaluated up to a depth of 60 cm. Soil surface coverage by the harvest residues was also evaluated. Forwarder traffic increased the soil compaction and penetration resistance and reduced aggregate stability and soil coverage. Even with an empty forwarder, strong disturbances were observed after only four passes.
Soil bulk density; water-stable aggregates; soil penetration resistance; forest harvest
