Pothier D, Margolis H A
Département des sciences forestières, Faculté de foresterie et de géomatique, Université Laval, Sainte-Foy, Québec, Canada G1K 7P4.
Tree Physiol. 1990 Dec;6(4):371-80. doi: 10.1093/treephys/6.4.371.
In the autumn of 1987, young balsam fir (Abies balsamea (L.) Mill.) and white birch (Betula papyrifera Marsh.) trees were thinned and their water relations followed during the next two growing seasons. At the beginning of the first summer following treatment, thinned trees of both species had lower osmotic potentials at full saturation (Psi(pi,sat)) and at turgor loss point (Psi(pi,tlp)) compared with controls. At this time, Psi(pi,sat) was linearly related to the percentage of full sunlight reaching the trees. A higher sugar concentration in leaves was an important component of the lower Psi(pi,sat) of thinned trees. For the other two sampling dates during the first growing season after treatment and all three sampling dates during the second growing season after treatment, little osmotic adjustment of the thinned trees relative to the control tress was observed in either species. The absence of osmotic adjustment during the second growing season following thinning suggests that other mechanisms were responsible for the acclimation of the treated trees to the higher atmospheric evaporative demand. Sapwood permeability (k) of white birch was higher than that of balsam fir, but no differences in k or in sapwood area were found between treated and control trees of either species. Predawn water potentials (Psi(pred)) of treated trees were less negative than those of controls.
1987年秋，对年幼的香脂冷杉（Abies balsamea (L.) Mill.）和白桦（Betula papyrifera Marsh.）进行间伐，并在接下来的两个生长季节监测其水分关系。在处理后的第一个夏季开始时，与对照相比，两种间伐树木在完全饱和时（Ψ(π,sat)）和膨压丧失点（Ψ(π,tlp)）的渗透势较低。此时，Ψ(π,sat)与到达树木的全日照百分比呈线性关系。叶片中较高的糖浓度是间伐树木较低Ψ(π,sat)的一个重要组成部分。在处理后的第一个生长季节的其他两个采样日期以及处理后的第二个生长季节的所有三个采样日期，两种间伐树木相对于对照树木几乎没有观察到渗透调节。间伐后第二个生长季节没有渗透调节，这表明其他机制负责处理后的树木适应更高的大气蒸发需求。白桦边材的渗透率（k）高于香脂冷杉，但两种间伐树木与对照树木之间在k或边材面积上均未发现差异。处理后树木的黎明前水势（Ψ(pred)）比对照树木的更不呈负值。
