环境温度对活立木横截面电阻值的影响

为研究环境温度对活立木内电阻值的影响,采用树木电阻断层成像仪在不同温度下对落叶松和小叶杨两种活立木进行检测,获取截面二维电阻图像并分析其变化,量化横截面内各点电阻值及其与温度之间的关系。结果表明:①落叶松横截面心材电阻值较低,边材较高。随温度降低,边材红色区域(高电阻区)面积减少,心材蓝色区域(低电阻区)面积增大; 而小叶杨电阻图像呈现完全相反的规律。但随温度降低,两树种整体平均电阻值均增大。②样本立木电阻值与环境温度之间存在极显著的指数函数关系(P<0.01),模型相关系数R≥0.822,小叶杨甚至高于0.926,因此认为模型有很好的拟合优度。 ③在落叶松样本立木中,当温度大于0 ℃时,横截面内沿径向分布的各点电阻值之间变化不明显,最大差值为1 236 Ω(3.0 ℃时); 而温度小于0 ℃时波动很大,最大差值达到3 299 Ω(-5.0 ℃时),曲线存在较为明显的两个波谷和中间一个波峰。④在小叶杨样本立木中,随环境温度降低,横截面内沿径向分布的各点电阻值都呈增大趋势; 从边缘到髓心再到另一侧边缘,沿径向分布的电阻值呈由低向高逐渐增大、到最大值后再逐渐降低的趋势。

Effects of environmental temperature on the electrical resistance on the cross section in standing tree

In order to investigate the effect of environmental temperature on the internal electrical resistance value of standing trees, two standing tree(Larix gmelinii and Populus simonii)specimens were selected and tested using the electrical impedance tomography instrument at different environmental temperatures. Some two-dimensional electrical impedance images of cross section of specimens were then obtained and comparatively analyzed. The electrical resistance value of each point on the cross section was quantitatively examined and the relationship between these values and temperature were discussed. Research results showed that: ① For L. gmelinii, the electrical resistance value of heartwood was lower than that of the sapwood. As temperature decreased, the red area(high resistance region)at sapwood reduced and the blue area(low resistance region)at heartwood increased. For P. simonii, the result was completely opposite. However, the average electrical resistance values for overall cross section increased as temperature decreased. ② There were highly significant exponential regression models between the sample electrical resistance values and temperature(P<0.01)with the correlation coefficients of ≥0.822(L. gmelinii)and ≥0.926(P. simonii). ③ For L. gmelinii, when temperatures were above 0 ℃, the fluctuation of radial resistance value was not obvious, and the maximum difference was 1 236 Ω(at 3.0 ℃). When temperatures were below 0 ℃, it fluctuated greatly, and the maximum difference was 3 299 Ω(-5.0 ℃). There are two troughs and one peak in the middle of the trend line. ④ For P. simonii, the resistance value of each point in the radial direction showed a trend of increase with the decrease of temperature. The resistance value increased initially and then decreased from one edge to the other in the radial direction.