Calibration of Thermal Dissipation Probes for Date Palm (Phoenix dactylifera L.)

Fouzia Alla,Hanane M’Hamdi,Mashail N Alzain,Kawtar Jdaini,Omar Noman,Hamza Mechchate,Nurah M Alzamel,Mohammed Aziz Elhoumaizi,Jamal Mimouni

doi:10.3390/horticulturae8020107

Abstract

The quantification of water flow through the stem is vital for date palm (Phoenix dactylifera L.) to promote a good water stress management. The thermal dissipation probe (TDP) method developed by Granier is widely used to evaluate transpiration of forest trees; however, there are contradictory reports regarding its reliability. Considerable errors in estimated sap flux density, which might be due to a lack ofspecies-specific calibrations. The TDP method uses a mathematical model that is based on an empirical equation to estimate sap flux density, which is claimed to be applicable to all tree species, independently of wood structure and anatomy. At the laboratory, we compared the rate of water uptake by cut stems with sap flux estimates derived from the TDP method to assess the validity of the method.Our calibration results were considerably different compared to the Granier’s original equation. Moreover, sap flux density was overestimated by 18.2 ± 0.5% when the original calibration parameters of Granierare employed. However, using new calibration parameters improved the accuracy of sap flow measurements. Our results indicated that it is not appropriate to use a general equation for different species. Therefore, previous estimations of date palm’s water requirement through thermal dissipation probes should be revised.

Highlights

Introduction iationsDate palm (Phoenix dactylifera L.) is the principal horticultural crop in the arid and semi-arid regions [1]
In the opposition to coefficient α of the Granier equation (119 g m−2 s−1 ), the coefficient α obtained from our measurements ranged from 133.7 to 135.2 g m−2 s−1, whereas values obtained for exponent β ranged from 1.517 to 1.677 (Figure 2)
The re-calibration results for different species have yielded an alpha parameter which range from 119 [7] over 58,100 g m−2 s−1 for ring-porous temperate tree species [14].Using α and β parameter values derived from our study, we improved the sap flux density measurements, from those originally developed by Granier [7]

Summary

Introduction

Introduction iationsDate palm (Phoenix dactylifera L.) is the principal horticultural crop in the arid and semi-arid regions [1]. The date palm plays an integral role on economic, ecological and social plans. It is one of the most important commercial crops, and it is the main source of income of oases inhabitants [3]. Despite its environmental and socioeconomic importance, knowledge about the real water requirements of date palms in Morocco remains limited, and the few available studies about palm water management are based mostly on climatic, or soil water data approaches [4]. Sap flow techniques remain the most widely accepted [6]. These techniques include thermal dissipation probes [7,8], heat field deformation [9], heat pulse velocity [10,11], and heat

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