外国産マツ類の育成に関する研究 (III) : テーダマツ幼齢期における根系切断の影響

Abstract

本実験はテーダマツの幼苗の根系を切断すると, その後の苗木の生長や根系の発達にたいしてどのような影響があらわれるかを明らかにするためにおこなつた｡ 当年生テーダマツの無床替苗を, 第1図に示す方法により無切断区, 1/2切断区, 1/3切断区の3種に分け, 第2図のとおり植栽した｡ 試験地の土壤は第2表, 土壤断面は第3図に示した｡ 植栽は1959年1月10日で, 第1年目の調査は1試験区3本, 第2年目の調査は1試験区9本についておこなつた｡ その結果の概要を示せばおよそ次のとおりである｡ 1) 垂直方向にむかつて発達する根の数および総長は無切断区 ‹ 1/2切断区 ‹ 2/3切断区の順に次第に増加する傾向がみとめられた｡ 2) 水平方向にむかつて発達する根の数および総長は, 切断区に比し無切断区のほうが多少多いように思われた｡ 水平方向に伸びた根の樹幹からの距離別の本数割合は, 各試験区のあいだにほとんど差がみとめられなかつた｡ また, 各試験区とも樹幹基部を中心にした半径10cmの範囲に水平方向に伸びた根の本数の最大分布層があり, 中心をはなれるにしたがつて次第にすくなくなる傾向があつた｡ 3) 根の重量は, 切断区が無切断区よりもいくぶんおおきく, 根の発達がややよい傾向がみとめられた｡ またT-R率は切断区のほうが無切断区よりも多少小さい傾向があつた｡ 4) 切断区は無切断区に比し直根型が多少すくなく, 直根の発達のわるい扁平根型が多くなる傾向がみとめられた｡ したがつて強度の根系切断は, 表層に根を多く分布せしめ, 浅根となることがみとめられた｡ 5) 地上部の生長に及ぼす根系切断の影響は, 植栽後2年間ではほとんどみとめられなかつた｡

This experiment was carried out to clarify how root-pruning influences the growth and development of root system of Loblolly Pine (= Pinus Taeda Liun.), and used samples were yearlingseedlings for non transplanting. The experimental treatment was classified as follows: 1): Non root-pruning 2): 1/2 roto-pruning, 3): 2/3 root-pruning. These seedlings were transplanted after root-pruning. The soil properties of experimental place were shown in Table 2 and Fig. 3. The date of planting was January 10, 1659, and investigation was carried out in the 1st year and 2 nd year after planting. The results were summarized as follows: 1. The number and total length of vertically growing roots were in the following order. Non root-pruning < 1/2 root-pruning < 2/3 root-pruning 2. The number and total length of horizontally growing roots in non root-pruning plot were a little more than those in the 1/2 and 2/3 root-pruning plot. In the number of horizontal roots in each distance grade from the stem, little difference was recognized among the three treatment plots. Maximum distribution of root was at 0-10cm away from the center of stem, and the greater the distance from the stem is the less the number of roots. 3. The weight of roots in root-pruning plots was a little more than that in non root-pruning plot. The pruning of roots gave a good effect to the development of roots. The T-R ratio in root-pruning plot was a little less than that in the non root-pruning plot. 4. Seedlings of the tap root type in the non root-pruning plot were little more than those in the root-pruning plot. And it was recognized that the number of seedlings of flat root type increased in the root-pruning plot. Accordingly, strong root-pruning makes distribution of roots greater in the surface layer, and was recognized to produce shallow roots. 5. Influence of root-pruning on the growth of the part above the ground was not remarkable in the two years after planting.