欧亚国际

摘要

树苗、草本植物和小尺寸植物部分的汁液流动动力学已成为植物生态生理学研究的热点。目前，这些应用中使用最广泛的sap流量传感器有阀杆热平衡、微型HRM（热比法）和微型HFD（热场变形）传感器。每个传感器都有各自的优缺点，但当除了测量正、负sap流量外，还需要高时间分辨率时，只有mini-HFD能够满足要求，因为原始的热平衡方法无法区分正、负sap流量，而mini-HRM使用热脉冲而不是连续加热，这部分牺牲了其时间分辨率。因此，无创微型HFD有望用于研究树苗的水力再分配研究。然而，当迫使水通过切割的支管来校准mini-HFD时，在较高的负流量下会出现问题。商用HFD中使用的比例对于迷你版来说不是最佳方式。为了解决这一问题，基于微型HFD传感器测量的三个温差，开发了一种新的计算方法。在本文中，miniHFD已针对-20至20 g h-1的流量进行校准，在山毛榉（Fagus sylvatica L.）幼树上将该传感器安装。第一个结果是有前景、是一种更好的计算方法，可用于miniHFD传感器测量sap流量动态。

关键词：生态生理学，微型树液流量传感器，植物水分关系，水力再分配，逆流，双向液流，山毛榉

Analysis of sap flow dynamics in saplings with miniHFD (heat field deformation) sensors

Abstract

Sap flow dynamics of saplings, herbaceous species and plant parts with small dimensions have become an increasing point of interest in plant ecophysiological studies. At present, the most widely used sap flow sensors for these applications are the stem heat balance, the mini-HRM (heat ratio method) and the mini-HFD (heat field deformation). Each sensor has its own advantages and drawbacks, but when a high temporal resolution is needed in addition to measurements of positive and negative sap flow, only the mini-HFD suffices as the original heat balance method cannot distinguish between positive and negative sap flow, while the mini-HRM uses heat pulses rather than continuous heating partly sacrificing its temporal resolution. As such, the non-invasive mini-HFD is promising for studying hydraulic redistribution in saplings. However, when calibrating the mini-HFD by forcing water through cut branches problems arose during higher negative flows. The ratio used in the commercially available HFD was not optimal for the mini version. To resolve this shortcoming a new calculation method has been developed based on three temperature differences measured with the mini-HFD sensor. In this paper, the miniHFD has been calibrated for flow rates ranging from -20 to 20 g h-1, whereby sensors were installed on beech (Fagus sylvatica L.) saplings. First results are promising and indicate a better calculation method for sap flow dynamics measured with the miniHFD sensor. 

Keywords: ecophysiology, miniature sap flow sensor, plant-water relations, hydraulic
redistribution, reverse flow, bidirectional sap flow, beech (Fagus sylvatica L.)