京都大学芦生演習林の天然林における樹木の動態に関する研究 (I) : 試験区設定時の林況

Abstract

天然林の樹木の動態を調べるために京都大学芦生演習林内に試験区を設けた。今回は林分構造と択伐後2年経過した林分の下層木の動態を調べ検討した。択伐前の高木層は, プロット1ではスギ, プロット2はブナによりほとんど占られていた。下層木全体でみると, 択伐前からあった陰樹と伐採後発生した先駆種が多かった。当年生個体で生存数が多かったのは, リョウブ, クロモジ, コミネカエデなど実生により更新する種が多く, 伸長生長は萌芽性の種と種子の大きい種が良かった。1年生以上の個体で枯死率の高かった種は, クマイチゴ, コアジサイなど萌芽性の種で, 個体の地上部は林内では2 - 3年の寿命のようであった。またリョウブなど集中的に種子が落下し発生する種も枯死率が高かった。

The study area investigating for dynamics of trees in a natural forest was set in Kyoto university forest of Ashu. In this paper we discussed with the stand structure and dynamics of lower layer trees over two years after selective cutting. In this stand before selective cutting most of trees in upper layer were dominated by Cryptomeria japonica in plot 1 and by Fagus crenata in plot 2. Many of lower layer trees were occupied by tolerant species and remainders over from selective cutting, and pioneer species germinated after the cutting. Many new trees survived in the autumn were Clethra barvinervis, Lindera unbellata and Acer micranthum, which naturaly regenerated by seeds. High growing species of new trees were those of sprout regeneration type and large seed type. Of more than one growing season trees high mortality species were Rosa crataegifolius and Hydrangea hirta, which were sprout regeneration and aboveground part of the trees had only two or three years life span in a stand. Clethra barvinervis was high mortality as the seeds dispersed under the parent tree in clumped and germinated in patch.