Recovery of Soil Penetration Resistance on Compacted Skid Trails after Forest Thinning in Central Hokkaido.

Abstract

Vehicular traffic on skid trails after forest thinning causes compaction, leading to increased soil penetration resistance. In this study, we investigated the recovery of soil penetration resistance after thinning in a planted Todo fir forest. The soil penetration resistance profile of upper soil (to a depth of 0.6 m) was measured on a skid trail before thinning (2008), immediately after thinning (2008), and 5 and 6 years after thinning (2013 and 2014, respectively). The penetration resistance profile revealed that a hard soil layer formed down to a depth of 0.2 m immediately after thinning; however, soil penetration resistance and the soil compaction index decreased 6 years after thinning. Thus, our results indicate that compaction effects on skid trails disappear 5 or 6 years after the event. A “soil compaction index” (SCI) was created to evaluate the degree of soil compaction. SCI can indicate the degree of soil compaction as one numerical value.