Report on an experiment of dye injection into xylem sap of a Quercus serrata tree in University Forest in Aichi.

環孔材をもつ広葉樹であるコナラにおける樹液の上昇速度の辺材深さ方向の分布様式を調べるために，愛知演習林赤津研究林内に生育するコナラの樹冠木１個体を対象に樹液の染色実験を実施した。夏の午前中105分間の染色液の上昇高さと辺材深さとの関係を調べた結果，以下のことが確認された。１）年輪幅数ミリ以下の樹皮側１年輪目（当年輪）における染色液の上昇速度は610 cm 105 min－1であり，当年輪以外の辺材における上昇速度（高々80 cm 105 min－1）と比較すると顕著に速い。２）全ての辺材（地際高さ80 cmにおいて深さ38 mm）で染色液が上昇していた。３）おおむね，辺材深さが深くなるほど染色液の上昇が鈍くなる。このような辺材部における染色液の上昇速度の不均一な分布は，コナラの樹液の上昇流速が辺材深さによって大きく変化することを示唆する。本実験の結果を，環孔材をもつ広葉樹を対象にして樹液の上昇速度の辺材深さ方向の分布を調べた既往報告の結果と比較し考察を加えた。A dye injection experiment in a canopy tree of Quercus serrata, which grew within Akazu Research Forest of University Forest in Aichi, was conducted with the purpose of investigating the radial variation of sap fl ow velocity of a ring-porous tree. The relationship between dye ascent height during 105-min of a summer morning and sapwood depth was examined. The result shows that 1) the maximum dye ascent height of 610 cm was found in the latest annual ring, the depth of which was less than several millimeters. On the other hand, in older annual rings, the dye ascent height was 80 cm at the highest. 2) The dye ascent was observed throughout the sapwood, and 3), in general, the ascent height decreased with increasing sapwood depth. The illustrated dye ascent variability within the sapwood suggests a pronounced radial variation in sap flow velocity in Q. serrata tree. The results of this experiment were discussed with previous studies that examined radial variation of sap fl ow in ring-porous species