Bleby Timothy M, Burgess Stephen S O, Adams Mark A
Ecosystems Research Group, School of Plant Biology, Faculty of Natural and Agricultural Sciences, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.
Funct Plant Biol. 2004 Jul;31(6):645-658. doi: 10.1071/FP04013.
We validated and compared two heat-pulse methods for measuring sap flow in potted Eucalyptus marginata Donn ex. Smith (jarrah) saplings. During daylight hours and under well-watered conditions, rates of sap flow (0.1-0.5 kg h) measured by the established compensation heat-pulse method (CHPM) and the newly developed heat-ratio method (HRM) were similar to rates measured with a weighing lysimeter, and most of the time there was no significant difference (P<0.001) between methods. The HRM accurately described sap flow at night when rates of flow were low (< 0.1 kg h) or near zero, but the CHPM was unable to measure low rates of sap flow due to its inability to distinguish heat-pulse velocities below a threshold velocity of 0.1 kg h (3-4 cm h). The greatest potential for error in the calculation of daily sap flow was associated with the misalignment of temperature sensors, the estimation of sapwood area and the method used to acquire total sap flow from point measurements of sap velocity. A direct comparison of the two heat-pulse methods (applied synchronously) revealed that the HRM had a more convincing mechanism for correcting spacing errors and was more resistant to random fluctuation in measurements than the CHPM. While we view the HRM more favourably than the CHPM in some key areas, both methods are valid and useful, within their constraints, for measuring transpiration in jarrah and other woody species.
我们验证并比较了两种用于测量盆栽边缘桉（Eucalyptus marginata Donn ex. Smith，红柳桉）幼树液流的热脉冲方法。在白天且水分充足的条件下，用既定的补偿热脉冲法（CHPM）和新开发的热比法（HRM）测得的液流速率（0.1 - 0.5千克/小时）与用称重蒸渗仪测得的速率相似，并且在大多数情况下，两种方法之间没有显著差异（P<0.001）。当夜间液流速率较低（<0.1千克/小时）或接近零时，HRM能够准确描述液流情况，但CHPM由于无法区分低于0.1千克/小时（3 - 4厘米/小时）的阈值速度的热脉冲速度，因而无法测量低液流速率。计算每日液流时最大的潜在误差与温度传感器的未对准、边材面积的估计以及从液流速度的点测量获取总液流所使用的方法有关。对两种热脉冲方法（同步应用）的直接比较表明，与CHPM相比，HRM在纠正间距误差方面具有更令人信服的机制，并且对测量中的随机波动更具抵抗力。虽然在某些关键领域我们更看好HRM而非CHPM，但在其各自的限制范围内，这两种方法对于测量红柳桉和其他木本物种的蒸腾作用都是有效的且有用的。
