Permalink :  http://hdl.handle.net/2115/58297

KEYWORDS : カラマツ; 長伐期施業; 風倒抵抗性; 樹冠長率; 形状比; Larix kaempferi; long rotation management; resistance to windthrow; crown length/tree height ratio; slenderness ratio

We investigated stand conditions and tree shape factors affecting the resistance to windthrow in 54-80 year-old Larix kaempferi plantations in Tokachi region to examine a management guideline for long rotation management. We estimated the mean slenderness ratio (H/D ratio) and mean crown length/tree height ratio (CL ratio) from tree inventories of the L. kaempferi plantations. Many stands showed low densities, small stand volumes and small yield indices, and it was concluded that most plantations were in the sparse management. Mean H/D and CL ratios were 68-90 and 0.42-0.62, respectively. Mean CL ratios of the investigated plantations were consistent with the value of L. kaempferi plantations resistant to windthrow, however, mean H/D ratios weren't. Consequently, mean CL ratio was more general as an index of resistance to windthrow than mean H/D ratio. We assumed that mean CL ratio ≥ 0.45 was necessary for long rotation management of L. kaempferi plantations and examined a management guideline to keep the mean CL ratio ≥ 0.45. In plantations of site index Ⅰ, the yield index must be less than 0.8 when 25 years old, and be less than 0.6 when older than 30 years old. It was concluded that L. kaempferi plantations must be kept sparse gradually with stand growth for the long rotation management.

FULL TEXT :  PDF