Transient thermal dissipation method for xylem sap flow measurement: implementation with a single probe.
Transient thermal dissipation method for xylem sap flow measurement: implementation with a single probe.
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DOI：
10.1093/treephys/tpr020
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发表时间：
2011-04
期刊：
影响因子：
4
通讯作者：
F. Do;S. I. N. Ayutthaya;A. Rocheteau
中科院分区：
文献类型：
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作者：
F. Do;S. I. N. Ayutthaya;A. Rocheteau
通过使用简单和低成本的木质部液流率测量，可以方便地比较处理、物种和地点之间的树木水分关系。瞬态热耗散（TTD）法是Granier恒热耗散（CTD）法的一种变体。它具有限制热干扰和节约电能的优点。在这里，我们关注的是测试迈向简单和低成本的新一步：TTD方法的适用性与单探头，即没有参考传感器，遵循10分钟加热和10分钟冷却的循环，并使用相同的热指数和多物种校准，之前用双探头评估。首先，在实验室的人造木屑液压柱中，比较了双探针和单探针在0.3到4.0 l dm（⁻²h）的流量密度范围内的反应。其次，我们比较了一棵幼树的昼夜动力学，它的边材参考温度连续5天快速变化，最高可达5°C h⁻¹。在相对稳定的参考温度下，实验室结果表明，在整个液通量密度范围内，单探头产生的温度信号和热指数与双探头相同。在树内，加热探针的冷却温度，线性内插，被证明是参考温度随时间变化的准确指标。从逻辑上讲，当内插冷却温度时，单探头的温度信号和液通量密度估计值与双传感器测量值没有差异。此外，在木屑柱水力实验中，热指数的响应符合多物种校准的变异性。这一结果支持了之前对弥漫性多孔介质TTD方法非物种特异性校准的评估。综上所述，我们的结果表明，TTD方法可以直接应用于单个探针。指出了该方法的局限性和可能的发展方向。这种测量系统可能是目前可用来测量木质部液流的最简单的技术。
Comparisons of tree water relations between treatments, species and sites are facilitated by the use of simple and low-cost measurements of xylem sap flow rates. The transient thermal dissipation (TTD) method is a variant of the constant thermal dissipation (CTD) method of Granier. It has the advantages of limiting thermal interference and of saving electrical energy. Here, our concern was to test a new step towards simplicity and low cost: the applicability of the TTD method with a single probe, i.e., without a reference sensor, following a cycle of 10 min heating and 10 min cooling, and using the same thermal index and multi-species calibration previously assessed with a dual probe. First, the responses of the dual and single probes were compared in an artificial hydraulic column of sawdust in the laboratory over a complete range of flux densities, from 0.3 to 4.0 l dm⁻² h⁻¹. Second, diurnal kinetics were compared in a young tree with rapid changes in the sapwood reference temperature of up to 5 °C h⁻¹ for 5 consecutive days. With a relatively stable reference temperature, laboratory results showed that a single probe yielded the same temperature signal and thermal index as a dual probe for the full range of sap flux densities. Within the tree, the cooled temperature of the heated probe, linearly interpolated, proved to be an accurate indicator of the change in the reference temperature over time. Logically, the temperature signals and estimates of sap flux density with the single probe did not differ from the dual-sensor measurements when the cooled temperature was interpolated. Additionally, the responses of the thermal index, yielded in the hydraulic experiment with the sawdust column, fell within the variability of the multi-species calibration. This result supports the previous assessment of a non-species-specific calibration for the TTD method with diffuse porous media. In conclusion, our results showed that the TTD method can be directly applied with a single probe. Limitations and possible future progress are pointed out. This measurement system is probably the simplest technique currently available to measure xylem sap flow.