热量法茎流测定技术的发展及应用

The Development and Application of Thermal Methods for Measuring Sap Flow

概括介绍了热量法测试茎流的发展史。用热量示踪茎流的技术始自１９３２年。热波速法（ＨＰＶ）根据沿茎流方向传导的热脉冲，在特定距离的点上随时间波动求得茎流速度。茎流的数量则根据流体的几何特征、茎横断面积与茎流速度推算。热平衡法（ＴＨＢ）８０年代已有研究。该方法以茎流介质内的热扩散理论为基础。实际的茎流量根据被茎流带出的热量推算。采用热量法不会由于自然环境破坏而影响蒸腾过程。ＴＨＢ主要应用于大田及园艺作物的茎流测定。不论是ＨＰＶ还是ＴＨＢ所需的设备都比较复杂。据此。

The historical development of thermal methods and techniques for the measurement of stem sap flow is described briefly in this paper. Thermal technique has been used as a tracer to measure the velocity of sap flow since 1932. In the heat pulse velocities (HPV) method, the timed transport of a temperature pulse over the distance from the source to a given point downstream yields an estimate of the velocity of the sap flow. The quantity of sap flow is calculated from flow geometry, cross sectional area and flow velocity. In another development, stead state thermal heat balance (THB) method was proposed in the 1980’s. The theory of THB is based on the pattern of diffusion within the flow medium. Actual flow is calculated by determining the amount of heat taken away by the flow. Use of this method does not alter any of the environmental or physiological factors affecting the transpiration process. THB was mainly used in field crops or horticulture plants. Both HPV and THB techniques require relatively more complex instumentations, they are only suitable for scientific use in the near future.