Biot-Granier Sensor: A Novel Strategy to Measuring Sap Flow in Trees

Area of Science:

• Plant Physiology
• Environmental Science
• Hydrology

Background:

• Sap flow measurement is crucial for understanding plant water use and ecosystem dynamics.
• Conventional Granier (Gcv) thermal dissipation methods can overestimate sap flow rates.
• Improvements in sensor design and data processing are needed for more accurate plant transpiration estimates.

Purpose of the Study:

• To introduce and characterize the Biot-Granier (Gbt) sap flow measurement methodology.
• To compare the performance of Gbt sensors against conventional Granier (Gcv) sensors and independent measurements.
• To evaluate the effectiveness of the Biot number approach in improving sap flow estimations.

Main Methods:

• Development of modified Granier sensors with improved temperature sensing.
• Implementation of an algorithm incorporating the Biot number approach for absolute temperature measurement.
• Performance evaluation through trials with potted olive trees and vineyard experiments, comparing with gravimetric data, vapor pressure deficit, and eddy covariance.

Main Results:

• Gbt sensors showed better agreement with gravimetric measurements compared to Gcv sensors, with Gbt overestimating by 1.5 times versus Gcv's 4 times.
• The Biot number adjustments in the Gbt method significantly reduced sap flow overestimation.
• Gbt sensors demonstrated higher resolution and sensitivity due to improved temperature sensor positioning.

Conclusions:

• The Biot-Granier (Gbt) methodology offers a significant improvement in sap flow estimation accuracy.
• The Biot number approach effectively corrects overestimations inherent in conventional sap flow techniques.
• Enhanced sensor design and data processing in Gbt contribute to more reliable plant water use assessments.