森林立地学会誌 森林立地37(2), 1995, pp, 59〜66
論 文
多雪斜面における積雪動態と樹木の生態的特性
小野寺弘道・田邉裕美・梶本卓也・大丸裕武
奥羽山脈中央部に位置する焼石岳南麓の多雪斜面における積雪動態と樹木の生態的特性との関係について調べた。低木形態をとる落葉広葉樹林の大半は厳冬期季節風に対する風背斜面に分布していた。風背斜面には積雪グライドに起因する雪ジワと雪割れ目が広範囲にわたって分布し，しばしば全層雪崩の痕跡も観察された。林地には積雪挙動による浸食地形がみられた。他方，風衝斜面には中・大径木の根返りに伴って形成されたピットとマウンドが数多く観察され，斜面形は凹凸が連続する階段状であった。風背斜面に優先する樹種は，ヒメヤシャブシ，タニウツギ，ブナなどであり，風衝斜面に優占する樹種は，ブナ，マルバマンサク，ハウチワカエデなどであった。風背斜面の森林は風衝斜面の森林と比較してサイズがきわめて小さく，傾幹幅が異常に大きい葡匐形態をとっていた。傾幹幅には樹種による違いが認められるとともに，優占順位の高い樹種の傾幹幅は風背斜面では大きく，風衝斜面では小さかった。風背斜面においては積雪移動圧に対し，風衝斜面においては積雪沈降圧に対して適応した樹種が個体維持に有利であると考えられた。いずれの斜面にも出現するブナは，積雪移動圧よりもむしろ積雪沈降圧が卓越する積雪環境に適応した，耐雪性の高い樹種であると考えられた。多雪斜面に生育する樹木の個体維持は，風背斜面においては主に萌芽・伏条による更新に，風衝斜面においては主に実生による更新に依存していると考えられた。そのような樹木の生態的な特性は積雪環境の違いを反映し，群落分布に係わる積雪環境要因としては，単に積雪の量だけではなく，積雪の変態過程の違いというような質的要素や，積雪グライド・雪崩などの積雪挙動が重要な役割を果たしていると考えられた。
Hiromichi
ONODERA, Hiromi TANABE, Takuya KAJIMOTO and Hiromu DAIMARU: Snow dynamics and ecological
characteristics of trees on snowy mountain slope: Jpn. J. For. Environment 37,
59-66, 1995
This study discussed the relationship
between snow dynamics and ecological characteristics of trees on the snowy
slope of Mt.Yakeishi, central the Oou mountain range, north east Honsyu, Japan.
Most of dwarf-type formed deciduous broad leaved trees dominated on the lee
ward slope against the winter seasonal wind. The snow folds and snow cracks
caused by glide of snow cover extended over a wide area of the lee ward slope
and also the debris of full-depth snow avalanches were observed at places. And
the scars caused by the snow erosion distributed in the slope. On the other
hand, numbers of pit and mound formations caused by uprooting of middle or
large size stands were observed on the wind ward slope and the longitudinal
shape of the slope showed uneven feature like a staircase. While the dominant
tree species on the lee ward s1ope were Alnus
pendula, Weigela hortensis, Fugus crenata and others, those on the wind
ward slope were Fugus crenata, Hamamelis
japonica var. obutusata, Acer
japonicum and others. The stands on the lee ward slope were extremly small
in the size and showed the groundlinglike form which had extraordinary large
basal bending width in contrast to those on the wind ward slope. The basal
bending width varied with each tree species and that of higher ranking dominant
tree species was larger on the lee ward slope and smaller on the wind ward
slope. It seems advantegeous to the tree species to adapt for the creep and
glide pressure of snow on the lee ward slope and to adapt for the settlement
force of snow on the wind ward slope for the survival of individuals. Fagus crenata dominated on the both
slopes seems to be the species of high snow tolelance capacity adapted to the
snow environment which excelled in the settlement force rather than the creep
and glide pressur of snow cover. The regeneration style of the stand growing on
the snowy slope depend chiefly upon sproutings on the lee ward slope while
seedlings on the wind ward slope. The ecological characteristics of trees above
mentioned are the reflex of the difference of snow environment, and not only
the depth of snow but also the qualitative aspect of snow such as the variety
of metamorphic process and the snow dynamics such as glide and avalanches play
an important role in the snow environmental factor which affect the
distribution of community.