| Abstract |
The growth characteristics of advance reproduction on the forest floor is an important factor in understanding the natural processes of forest regeneration. In this paper, the growth characteristics o...f seedlings and sprouts were analyzed for five deciduous broad-leaved tree species, Changes in growth characteristics induced by sprouting, (which modifies internal factors), are discussed from an ecological view point. The dry matter economy and three aspects of tree architecture, hydraulic, supportive and assimilative efficiencies were examined using several simple indices calculated from tree dimensions and dry matter allocation for seedlings and sprouts of Meliosma myriantha,Magnolia, obovata, Pterocarya, rhoifolia, Styrax japonicus and Styrux Shiraianus. Generally, sprouts increased their proportion of non-photosynthetic organs by sacrificing efficiency in matter economy, In particular, small-leaved or sympodial branching species, S. japonicus, S. Shiraianus and P. rhoifolis, modified their growth characteristics by sprouting from the 'waiting' growth (diameter-preferred growth) type to the 'competing' growth (elongation-preferred growth) type. The latter (competing) was observed in the seedlings of the large-leaved and monopodial branching species, M. myriantha and S. obovata. As a result of this change, small-leaved species and sympodial branching species tended to reduce supportive and assimilative efficiencies through sprouting. These characteristics in sprouts are thought to depend on the role of the original root system of the mother tree.
森林の更新過程を解明する上では，前生樹の生育特性の把握が重要である．本研究では，森林の更新過程に大きく寄与していると考えられる実生椎樹および萌芽椎樹の物質分配特性を比較し，萌芽という現象に伴う内的要因の変化により，個体の生育特性がどのように変化しているかを解析した．エゴノキ，コハクウンボク，アワブキ，ホオノキおよびサワルグミについて，個体の各器官の量的分配とサイズから簡単な指数を用いて，水分通導，支持および同化という樹形の3機能を評価し，樹種毎に実生および萌芽椎樹における樹形の生態的意義の比較を行った．一般に，萌芽では実生と比較して物質経済の有利性を犠牲にしながら非同化器官の比率を増加させる傾向がみられた．特に小型葉で仮軸分枝型の種であるエゴノキおよびコハクウンボクの実生では，大型葉・単軸分枝型の種であるアワブキおよびホオノキに比べて，同化効率と支持効率が高い“待機型（肥大優先型）”の生育特性を持っており，萌芽することによって，大型葉・単軸型の種の樹形でみられた同化・支持効率の低い“競争型（伸長優先型）”へ生育様式を移行させていることが明らかとなった．これらの結果は，萌芽の母樹の既存の根系の働きに支持されているものと考えられた．show more
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