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树液流动密度 (SFD)随边材径向深度的变化对于准确估测流经边材的树液通量是非常重要的 ,后者又制约着HeatPulse的应用精度。但迄今为止 ,只有很少的研究估计了由于SFD随径向的梯度变化而带来的误差 ,SFD沿树干径向分布规律的获得往往依靠对少数几棵树的观测资料。基于在广东雷州半岛对两块 3～ 4年生桉树 (Euca lyptusurophyllaS .T .Blake)人工林 1年的HeatPulse观测 ,探讨了对来自 39株立木大量观测资料的综合处理方法 ,发现这两个样地 (纪家和河头 )的林分中SFD随边材径向深度的变化可以用如下回归方程来描述 :纪家 :y =3.6 6 75x3 - 7.2 95 5x2 +3.6 82 6x +0 .5 6 74 (R2 =0 .9391,n =80 ,P =0 .0 1)河头 :y =5 .0 0 6 2x3 - 9.116 1x2 +4.4 5 4 4x +0 .4 6 34(R2 =0 .80 6 9,n =72 ,P =0 .0 1)式中 :y———某一树液感应器所测得的SFD与不同深度的 4个感应器所测得的SFD的平均值之比 ;x—某一树液感应器在边材中的深度与边材厚度之比。从形成层到心材 ,SFD最初有所增加 ,随后持续减小 ,但由于树木年龄很小 ,最大的SFD只比最小的SFD大 0 .33～ 0 .36倍。
The variation of sap flow density (SFD) with sapwood radial depth is very important for accurately estimating sap flux through sapwood, which in turn limits the application accuracy of HeatPulse. However, to date, only a few studies have estimated the error of the SFD distribution along the radial gradient. The SFD distribution along the tree trunk tends to depend on observations of a few trees. Based on the 1-year observation of HeatPulse on two 3-year-old 4-year-old eucalyptus urophylla (L. Blake) plantations in Leizhou Peninsula of Guangdong Province, the comprehensive treatment of a large number of observations from 39 stands was discussed and found that these two plots (Ji family and river head) in the forest along the radial depth of sapwood with sapwood can be used to describe the following regression equation: Jijian: y = 3.6 6 75x3 - 7.2 95 5x2 +3.6 82 6x +0 .5 6 74 (R2 = 0 .9391, n = 80, P = 0 .0 1) River head: y = 5 .0 0 6 2x3 - 9.116 1x2 +4.4 5 4 4x +0 .4 6 34 (R2 = 0.80 6 9, n = 72, P = 0 .0 1) Where: y --- the ratio of SFD measured by one tree liquid sensor to the average SFD measured by four sensors at different depths; x - the ratio of the depth of a sap inductor in the sapwood to the sapwood thickness. From formation to heartwood, SFD initially increased and then continued to decrease, but due to the small tree age, the maximum SFD was only 0.33-0.36 times greater than the minimum SFD.