Growth of Quercus Acutissima and Q. Serata Seedlings in the Red Pine Forest Floor Under Different Thinning Intensity

27 Mar Growth of Quercus Acutissima and Q. Serata Seedlings in the Red Pine Forest Floor Under Different Thinning Intensity

View Original

Abstract

アカマツ林が主要な植生として分布する公園林において, その一部を季節感や種の多様性の点で優れた落葉広葉樹林, ないしはアカマツー落葉広葉樹混交林に林相転換することを目的に, 間伐強度の異なる3区と全天区の計4区で実験区を用意し, 密生する下層植生を刈り取った後, クヌギ, コナラの2年生ポット苗を植栽した。その後の成長経過を追跡調査した結果, 半日陰条件の強度間伐区の成績が最も優れ, 根元幹直径, 樹高, 枝張りともに良好な成長を示した。立ち木のない全天区は直射日光に阻害されて, 強度間伐区の半分以下の成績にとどまり, 一方, 弱度間伐区や無間伐区は陽光不足のために, 良好な成長の期待できないことが明らかとなった。

English Abstract

Although Red-pine forest composes a typical and popular Japanese forest landscape, it widely spreads as a result of over coppicing in suburban areas especially in the Kansai region, in Japan. Then it is effective to convert a part of Red-pine forest to a deciduous oak forest or the mixture forest from the viewpoint of enhancing the bio-diversityand creating the amenity landscape every seasons. This study aims to ascertain the optimum light condition for growth of deciduous oak seedlings planted in the Red-pine forest floor. In 1993, within the Nishigohri park forest of Osaka Prefecture, the experimental plots of 4 different light condition were prepared with tree thinning and scrub removing, and Quercus acutissima and Q. serrata seedlings were planted. The results are as follows:
The heavy thinned stand of half-shaded condition showed the best growth among the 4 stands, whereas in the open stand, the seedlings were stunted by direct sunshine, and showed half-growth in height and diameter compared with the half-shade stand. On the other hand, it become apparent that the growth was seriously damaged in the light-thinned stand and the none-thinned stand caused by light shortage. According to the results, it is considered that forest clearance should be avoided, and heavy thinning would be recommended for considerable growth of the planted seedlings in the Red-pine forest floor.