雨氷害を受けたカラマツ人工林における林分構造と被害率との関係  [in Japanese] Relationship between Stand Structure and Damage Rate in Japanese Larch Forests Damaged by Glaze  [in Japanese]

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Abstract

森林の雨氷害を軽減する知見を得るため,2004年2月に北海道日高町で発生した雨氷害の調査データを解析したところ,直径階ごとの本数被害率の分布形状は,大きく五つのタイプ((1)中庸木に被害が多い,(2)劣勢木に被害が多い,(3)優勢木に被害が多い,(4)立木のサイズに関係なく被害率の変動が激しい,(5)直径階の大小に関わりなく被害率が一定)に分類された。分布形状に差異がみられるのは,風や着氷量などの気象因子が少なからず影響したためだと推察される。また,密度管理図上で軽害林分と激害林分間の判別分析を行った結果,的中率は75%であった。判別分析で得られた判別式と収量比数0.9線を用いて安全域と危険域の境界線を描き,被害軽減が期待できる範囲を密度管理図上に示した。次に,林分平均樹高との限界形状比の関係をロジスチック式で近似して限界形状比曲線を求めたところ,生育段階で限界形状比は異なることが示された。これらの結果は,森林の雨氷害を軽減するためには,植栽密度に沿った適切な間伐が重要であることを示唆している。

Data on the Japanese larch (<I>Larix kaempferi</I> Carr) forest damaged by glaze in Hidaka Hokkaido in February 2004 was analyzed to work toward developing a system that minimizes glaze damage. The distribution shape of the percentage of damaged trees in each diameter class reflects that the trees can roughly be classified into five types: (1) trees with mean diameter that were more damaged than the rest, (2) trees with smaller diameters that were more damaged than the rest, (3) trees with larger diameters that were more damaged than the rest, (4) trees with variable damage rate regardless of the diameter, and (5) trees with fixed damage rate regardless of the diameter. It was assumed that these differences in the distribution shape were related to meteorological factors such as wind and icing. A linear discriminant analysis of the light and heavy damaged stands through a stand density control diagram showed that the discriminant rate had reached 75%. To identify the region where damage reduction is expected in the stand density control diagram, the borderline between the safe and the unsafe regions was drawn using the linear discriminant function and yield index (<I>Ry</I>=0.9) curve. Moreover, the critical slenderness ratio curve elucidated the relationship between the average tree height and slenderness ratio obtained by logistic approximation, and we found that the critical slenderness ratio changes with every growing stage. These results suggest that thinning in proportion with initial density is important in order to reduce glaze damage in forests.

Journal

  • Journal of the Japanese Forest Society

    Journal of the Japanese Forest Society 89(1), 39-44, 2007-02-01

    Japanese Forestry Society

References:  27

Codes

  • NII Article ID (NAID)
    110006882851
  • NII NACSIS-CAT ID (NCID)
    AA12003078
  • Text Lang
    JPN
  • Article Type
    ART
  • ISSN
    13498509
  • NDL Article ID
    8775112
  • NDL Source Classification
    ZR21(科学技術--農林水産--林産)
  • NDL Call No.
    Z18-340
  • Data Source
    CJP  NDL  NII-ELS  J-STAGE 
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