On the Use of Sap Flow Measurements to Assess the Water Requirements of Three Australian Native Tree Species

Xi Sun,Donald Cameron,Gregory Moore,Jie Li

doi:10.3390/agronomy12010052

Abstract

The measurement of sap movement in xylem sapwood tissue using heat pulse velocity sap flow instruments has been commonly used to estimate plant transpiration. In this study, sap flow sensors (SFM1) based on the heat ratio method (HRM) were used to assess the sap flow performance of three different tree species located in the eastern suburbs of Melbourne, Australia over a 12-month period. A soil moisture budget profile featuring potential evapotranspiration and precipitation was developed to indicate soil moisture balance while the soil-plant-atmosphere continuum was examined at the study site using data obtained from different monitoring instruments. The comparison of sap flow volume for the three species clearly showed that the water demand of Corymbia maculata was the highest when compared to Melaleuca styphelioides and Lophostemon confertus and the daily sap flow volume on the north side of the tree on average was 63% greater than that of the south side. By analysing the optimal temperature and vapour pressure deficit (VPD) for transpiration for all sampled trees, it was concluded that the Melaleuca styphelioides could better cope with hotter and drier weather conditions.

Highlights

Plant transpiration, the evaporation of water from leaf mesophyll cells, accounts for80% to 90% of evapotranspiration [1]
Sap flow instruments based on heat ratio method (HRM) were employed to evaluate water use of three tree species located in the eastern suburbs of Melbourne through the monitoring of sap flow over a 12-month period
The monthly sap flow volume comparison for the three species clearly showed that C. maculata outperformed the other two trees in terms of whole-plant water use and transpired substantial amounts of water in the spring months

Summary

Introduction

The evaporation of water from leaf mesophyll cells, accounts for80% to 90% of evapotranspiration [1]. Measurement of xylem sap flow using heat pulse velocity-based sap flow sensors has been widely used to estimate whole-tree transpiration in the field due to the low cost of the equipment, reliability and the low power requirements [2,3,4,5,6,7]. Many studies have monitored sap flow in trees in different locations to assess the spatial variability of sap flow around the stem. Through the study of hydraulic redistribution in a Douglas-fir tree in Brno, Czechia, Nadezhdina et al [9] found that sap flow at the south side of the trunk was twofold lower than that on the north side and concluded the difference was attributed to a lower crown projected area on the south side. Fernández et al [11] found that sap flow in the northern roots of Olea europaea L. was 1.4 times higher than that in southern roots and Juice et al [12]

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