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

树木直径的日变化是由水分和液流的波动引起的，这一观点已被广泛接受。本研究的目的是通过对一棵树的直径变化进行多点同步测量，收集可用于开发全树水分关系模拟程序的信息。黄花菜(age 9岁，身高6 m，胸径20 cm）。这棵树种植在法国蒙彼利埃的Restinclieres的农林试验场。光电测树仪分别安装在该树最大分支基部、内冠、树干基部、3条水平根和1条主根7个部位。2003年7月至8月进行了测量。在测定之前，先进行了根系挖根处理，确认挖根处理对根系直径变化影响较小，核桃树的直径变化表现为两种类型：连续增厚生长和由收缩和膨胀组成的日直径变化。一个水平根加厚最有力，其次是分支。主根在七个测量部分中表现出最少的增厚。日直径波动幅度在地上部和地下部都具有很强的大小依赖性。树干基部与内冠、两条水平根或主根之间存在明显的时间滞后。但树干基部与分支或一个水平根之间的时滞不明显。进一步的研究工作正在进行中，如树木内部结构的解剖学研究、树干液流和直径日变化的同步测量以及直径变化的持续测量等。

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.