Abstract
Two methods of removing a hung-up tree manually in early thinnings of Cryptomeria japonica were investigated: pulling down a hung-up tree to the felling direction with a wire rope (method A) and rotating down the trunk with it (method B). The average resistance force acting on the crown of a hung-up tree for method A and method B was 30.0kgf and 14.1kgf, respectively. The resistance force caused by the deflection of branches and the trunk might be larger for method A than for method B. Furthermore the average resistance moment acting on the crown of a hung-up tree was much larger for method A (193.5 kgf・m) than for method B (4.2 kgf・m) because the moment arm from the center of the rotation to the line of action of the resistance force was much longer for method A. In conclusion, it is effective to use a light subsidiary tool such as a long pole with a hook for pulling down a hung-up tree at a higher position or a short lever for rotating down it.
