环境温度对活立木内部含水率变化的影响

【目的】分析活立木内部含水率变化的影响因素,研究含水率在不同环境温度下的变化规律。【方法】在室外不同温度(-26"10℃)下采用时域反射计(time domain reflectometer,TDR)对落叶松和小叶杨两种活立木进行检测,获取树内温度和电磁波传播时间的连续变化值,据此推导出不同温度下活立木的含水率。在此基础上,分析了活立木内部电磁波传播时间和含水率的昼夜变化,以及较长时间周期内随温度变化的规律,确定了环境温度与含水率的定量关系,建立了两者之间的关系模型。【结果】在1个昼夜时间周期内,含水率和树内温度变化趋势基本一致,含水率变化略滞后一些,随昼夜平均温度的下降,含水率变化范围收窄;在较长时间周期内,随日均树内温度的降低,活立木样本平均电磁波传播时间和含水率均呈下降趋势,落叶松电磁波传播时间变化曲线没有明显拐点,含水率变化曲线在-6.3℃之前变化率较大(14.75%/℃),之后趋于平稳(0.94%/℃),小叶杨与之变化相似;树内温度和环境温度具有显著线性正相关性,二者线性模型拟合优度较高(R~2=0.91),可以用环境温度预测树内温度;树内温度与活立木含水率的关系分3个变化阶段,均呈线性关系,决定系数R~2均高于0.71。【结论】低温环境下,以环境温度为研究点探究活立木内部电磁波传播时间和含水率变化是可行的,通过相关公式可以推导出活立木内部含水率。

Effects of environmental temperatures on internal moisture content of standing trees

Objective]The influential factors of standing trees internal moisture content variety were investigated. The variety law of moisture content ( MC) in different environmental temperature was studied.Method]In different outdoor temperatures ( between-26~10 ℃) , time domain reflectometer ( TDR) instrument was employed to test Larix gmelinii and Populus simonii tree specimens. The continuous change of temperature and electromagnetic wave propagation time in the tree were then obtained, which were used to deduce the MC of standing trees under different temperature. Based on these, the diurnal variation of propagation time and MC of standing trees were analyzed, and then their variety law in a long time period was further discussed. Finally the quantitative relationship between environmental temperature and MC was determined. Result]In one night and day period, the changing trend of MC were basically the same with the inter?nal temperature of tree. With the decline of the daily average tree temperature, the variation range of MC decreased. The average propagation time and MC of the sample trees decreased with the decline of daily average tree temperature. There was no obvious inflection point in the propagation time curve of Larix gmelinii, and the change rate of MC curve was large before -63℃ (1475%/℃) then tended to be stable(0.94%/℃).The change of Populus simonii was similar to it. There was a significant linear positive correlation between tree temperature and environmental temperature. The fitting goodness of their linear model was higher ( R2=0.91) . Thus its feasible to evaluate tree temperature using environmental temperature. The relationship between tree temperature and MC could be divided into three stages. Their relationship at each stage was described as linear models, their coefficient of determination of R2 were higher than 071. Conclusion]Low temperature environment, at environmental temperature as the research point the stocking internal electromagnetic wave propagation time and moisture content change is possible, through the related formula could be deduced the standing trees internal MC.