2020 Volume 46 Issue 2 Pages 237-242
To control the Robinia pseudoacacia populations is an important issue in maintaining coastal Pinus thunbergii forests. The authors confirmed the occurrence of numerous root suckers of R. pseudoacacia after thinning works using forestry vehicles. A study was conducted in a coastal P. thunbergii forest with R. pseudoacacia undergrowth to analyze the effect of damaged horizontal roots caused by forestry vehicles on the root sucker emergence of R. pseudoacacia. A crawler type vehicle was turned and run straight in a thinned and non-thinned area of a P. thunbergii forest. After confirming the emergence of root suckers, the horizontal roots were exposed, and the damage of the roots was observed. Visible ruts were formed by the turning of the vehicle, and root suckers occurred in both thinned and non-thinned areas. Few root suckers were formed in the straight running and non-running area. The horizontal roots under the ruts were severed or injured. Root suckers occurred on 17 out of 18 horizontal roots that were cut in the proximal direction. Formation of ruts and the cutting of horizontal roots in the proximal direction are clarified to cause the emergence of root suckers. The control of pine wilt disease is likely to lead to sucker emergence because it involves ground disturbance as well as thinning. In cases of forest works on pine wilt disease, further attention is necessary not to disturb the forest floor for controlling the R. pseudoacacia populations.
