テーダマツの造林学的研究 : 第1報 ササ地内の生長におよぼす地拵の影響

Abstract

1) 本研究はテーダマツ (Pinus taeda Linn.) の生長を造林学的に追求する目的で, 1961年3月, 京大上賀茂試験地のネザサ (Pleioblastus yoshidake Nakai) の自生地に全刈 ･ 筋刈および坪刈の各地拵区を設けて1年生テーダマツを植栽し, その後3年間の生長を生理 ･ 生態的に調査研究した｡ 2) 1961年3月の地拵と同年7月の2回の下刈によって, ネザサの高さは試験前に比べて全刈区で1/6, 筋刈および坪刈区で1/4に低下した (Fig. 2)｡ 3) 全刈区では刈払いによるネザサの減少にともない, 新しくススキ (Miscanthus sinensis Anderss) が侵入し (Fig. 4), さらに既存の広葉樹は刈払いによってきわめて矮性になった｡ しかし, 筋刈 ･ 坪刈両区では, ネザサの生育低下が小さく, しかも広葉樹の萠芽がはげしかった｡ 4) 全刈区の光量に比べて筋刈 ･ 坪刈両区の光量は約半量であった (Fig. 5)｡ 5) 植栽木の生存率は各区とも96%以上であった｡ しかし台風による被害は, 刈払い面積の小さい地拵ほど大きくなる傾向がみられた｡ 6) 3年後のテーダマツは, 全刈区で樹高1.8m, 根元直径3.7cm, 樹冠直径1mに生長したが, 筋刈と坪刈区では全刈区に比し樹高で30%, 根元直径で50%の生長低下を示した (Fig. 6)｡ 7) 各区の生長量のちがいは, 主として受光量の多少によって生ずるものと思われる｡

The study was carried out to follow up an inquiry upon the silvicaltural characteristics of loblolly pine (Pinus taeda Linn.). In march 24, 1961, the pine seedlings were planted at the clrar, stripe and spot weeding plots in sasa (Pleioblastus yoshidake Nakai) vegetation stand at the Kyoto University Forest, and they were investigated on their growth during three years after the plantation. The results are as follows: 1) Height growth of surviving sasa was decreased, by two times weedings, to one-six in the clear weeding plot and a quarter in the stripe and the spot weeding plots compared with the height before the experiment (Fig. 2). 2) With decreasing of surviving sasa by the clear weeding practice, pampas grass (Miscanthus sinensis Anderss.) made an inroad gradually (Fig. 4). But the growing reduction of sasa in the stripe and the spot weeding plots was comparatively wanting. 3) Light intensity of the stripe and the spot weeding plots was about one half comapred with that of the clear weeding (Fig. 5). 4) Loblolly pine seedlings in each plot survived 96% over in two growing seasons after the plantation. 5) Seedling in the clear weeding plot at third year grew up to the height 1.8m, the base diameter 3.7 cm and crown diameter 1.0 m. Because they were reduced to 30% in the height and 50% in the diameter growth (Table 2, Fig. 6). 6) It seems that the such growth difference of planted seedlings in each plot mostly ensued from the light intensity.