Analysis of water distribution pattern between stem and branch of tree by simultaneous multipoint measurement of diameter changes and computer simulation technique.

人们普遍认为，树木直径的日变化是由树木含水率和树液流量的波动引起的。本研究的目的是通过对树体直径变化的同步多点测量，获取可用于开发全树水分关系模拟程序的信息。这棵树是在法国蒙彼利埃的Restinclieres的农林实验场种植的。在这棵树的最大分枝底部、树冠内侧、树干底部、3个水平树根和1个主干树根上安装了光电树干测量仪。测量时间为2003年7月至8月。在测量前，对核桃树进行了根部开挖程序，证实了该程序对根径变化的影响较小。核桃树的直径变化表现为两种类型：持续加厚生长和包括收缩和膨胀的日直径变化。其中一个水平根增粗最旺盛，其次是枝条。在七个测量部分中，丝锥根的厚度最小。在地上部分和地下部分，直径日波动的幅度都强烈地依赖于大小。树干根部与树冠内侧、两条横根或主根之间存在明显的时滞。然而，主干与枝条之间或一个水平根之间的这种时滞并不明显。这些结果表明，水分在整个树木中的运动是非稳定的。进一步的研究正在进行中，如树木内部结构的解剖调查，树干液流和直径日变化的同步测量，以及直径变化的可持续测量。

It has been widely accepted that daily diameter changes in tree are induced by the fluctuation of water content and sap flow-of tree. The purpose of this research project is to gather information available for the development of simulation program about water relation in a whole tree, by performing simultaneous multipoint measurement of diameter changes in a tree.Diameter changes of stem, branch and root of a Juglans nigra L. x regia L. (age 9 years, height 6 m, diameter at breast height 20 cm) were measured simultaneously. This tree was planted in an agroforestry experimental site at Restinclieres, Montpellier (France). Opto-electronic dendrometers were attached on seven portions of this tree: base of a largest branch, inner-crown, base of trunk, three horizontal roots and one tap root. Measurements were done from July to August 2003. Before the measurement, an excavation procedure of roots had been done, and confirmed that this procedure had less influence for diameter changes of roots.The Juglans tree showed two types of diameter changes: continuous thickening growth and daily diameter changes comprising shrinkage and swelling. One horizontal root thickened most vigorously, followed by branch. Tap root showed least thickening among the seven measuring portions. Amplitude of daily diameter fluctuation was strongly size-dependent both in the upper-and under-ground parts. Remarkable time lag was recognized between trunk base and inner crown, two horizontal roots or tap root. However such time lag was not clear between trunk base and branch or one horizontal root. These results suggest non-steady state of water movement in a whole tree.Further researches are on-going, such as anatomical investigation of internal structure of tree, simultaneous measurement of sap flow and daily diameter changes and sustainable measurement of diameter changes.