Sap-flow measurements have become increasingly important in plant science. Since the early experiments with dyes, many methods have been developed. Most of these are based on the application of heat in the sapwood which is transported by the moving sap. By measuring changes in the temperature field around the heater, sap flow can be derived. Although these methods all have the same basis, their working principles vary widely. A first distinction can be made between those measuring the sap-flow rate (g h^–1) such as the stem heat balance and trunk sector heat balance method and those measuring sap-flux density (cm³ cm^–2 h^–1). Within the latter, the thermal dissipation and heat field deformation methods are based on continuous heating, whereas the compensation heat pulse velocity, Tmax, heat ratio, calibrated average gradient and Sapflow+ methods are based on the application of heat pulses. Each of these methods has its advantages and limitations. Although the sap-flow rate methods have been adequately described in previous reviews, recent developments in sap-flux density methods prompted a synthesis of the existing but scattered literature. This paper reviews sap-flux density methods to enable users to make a well founded choice, whether for practical applications or fundamental research questions, and to encourage further improvement in sap-flux density measurement techniques.

中文翻译：

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勘误表：汁液通量密度的测量方法：工作原理和适用性。

液流测量在植物科学中变得越来越重要。自从使用染料进行早期实验以来，已经开发了许多方法。这些中的大多数是基于边材中的热量的施加，边材是由移动的树汁传输的。通过测量加热器周围温度场的变化，可以得出液流。尽管这些方法都具有相同的基础，但是它们的工作原理差异很大。可以将测量树液流量（gh ^–1）的方法（例如茎热平衡和干部扇形热平衡方法）与测量树汁通量密度（cm ³ cm ^–2 h ^{–1的方法）区分开来。}）。在后者中，散热和热场变形方法基于连续加热，而补偿热脉冲速度，Tmax，热比，校准的平均梯度和Sapflow +方法则基于热脉冲的应用。这些方法中的每一种都有其优点和局限性。尽管在以前的综述中已经充分描述了液流速率方法，但是液流密度方法的最新发展促使人们对现有但分散的文献进行了综合。本文回顾了树汁通量密度方法，使用户能够针对实际应用或基础研究问题做出合理的选择，并鼓励树汁通量密度测量技术的进一步改进。