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Effects of forest machine operation on black soil that easily becomes muddy


Article title

Influence of mechanized harvesting operation on black forest soil:A case of cut-to-length operation using wheel-type mechines

Author (affiliation)

Hidenori Suzuki (a), Masahiko Nakazawa (a), Tatsuya Sasaki (a), Takumi Uemura (a), Chikashi Yoshida (a), Masaki Jinkawa (a), Kenichiro Toda (b), Shinjiro Oya (b), Tsuyoshi Takano (b), Michiharu Kondo (c)

 (a) Department of Forest Engineering, FFPRI, Tsukuba, Ibaraki, Japan.

 (b) Nagano Prefecture Forest Research Center, Shiojiri, Nagano, Japan.

 (c) Former Nagano Prefecture Forest Research Center, Shiojiri, Nagano, Japan.

Publication Journal

The Japan Forest Engineering Society, 32(3): 123-130, July 2017, DOI: 10.18945/jjfes.32.123( External link )

Content introduction

The cut-to-length (CTL) system*) is an advanced system in which the entire process from cutting logs to transporting them is done. This system improves the productivity as well as the safety of workers. However, driving the machine used in this system through forests is a concern because of negative effects such as compaction of forest soil. Although black soil*) is common throughout Japan, the effects of driving on soil that becomes soft due to muddied soil*) is not fully known.

This study investigated soil compaction when the CTL system was used to cut logs on black soil. The results showed that black soil became harder as it was driven over the first few times but became softer as it was driven over more, resulting in muddied soil. Despite these results, when the soil was examined after two years, it was hard, regardless of the presence or absence of muddied soil, indicating that reduction in hardness due to muddied soil temporarily occurs immediately after driving over the soil. This disproved the previously well-accepted understanding and suggested that soil hardness increases even in black soil when machines stop operating on the soil.

These results indicated that when the CTL system is used to cut logs on black soil, the soil becomes hard after a short period of time, regardless of the presence or absence of muddied soil. In general, the effects of compaction are known to be recovered in approximately 10 years. Therefore, our future task is to clarify long-term changes in the soil and effects on remaining forest trees and young trees that are planted after clear-cutting. Clarifying these will also be meaningful for finding methods suitable for the characteristics of black soil.


*) CTL system: an operation system that uses a harvester to cut standing trees and trim branches to make logs and a forwarder to load and transport the logs.

*) Black soil: black-colored soil that is mainly composed of volcanic ash; has a high moisture content.

*) Muddied soil: softening of soil by repeatedly being stomped on, which often occurs to soils with high moisture content, such as black soil and Kanto loam.


Photo. A wheel (tire)-type harvester used in the CTL system

Photo. A wheel (tire)-type harvester used in the CTL system; it cuts standing trees and trims branches to make logs as it drives through the forest.