Granier Sap Flow Sensors : SF-G / SF-L | Ecomatik

Sap flow sensors are used to continuously measure water uptake in woody plants. The SF-G model corresponds to the classic, two-needle model developed in 1985 by André Granier.

Our four-needle SF-L sensor is an updated Granier sensor. The patented improvements correct the naturally occurring and time-varying vertical temperature gradients in the sapwood. Without correction (i.e. the original Granier sensor, SF-G) and despite isolation, these natural temperature gradients can lead to a temporary over- or underestimation of the measured sap flow values of up to 50% in extreme cases (cf. Do, F., & Rocheteau, A., 2002). Additional temperature measurements with the SF-L sensor enable a correction of the measured sap flow values, which prevents errors caused by the natural vertical stem temperature gradients. This results in a significantly higher accuracy and a stabler zero-point (ΔTmax) of the xylem (sap) flow.

A very helpful option to exactly determine this zero-point would be to use a dendrometer in order to continuously measure the water saturation level of the tree body. This additional measurement allows for a precise determination of zero sap flow conditions: sap flow = 0 if the relative humidity in the crown at 100% and the tree body is 100% saturated with water (no change in diameter according to the dendrometer data). The improved SF-L sensor combined with dendrometer-aided precise determination of zero flow conditions, makes a running nocturnal zeroing of the sap flow (according to Granier) unnecessary. This process enables the recording of a nocturnal xylem flow.

Advantages

Specific to the SF-G model

• Suitable for tree diameters > 1 cm

Specific to the SF-L model

• Greater measurement accuracy
• Correct determination of the xylem flow zero point when supplemented with dendrometer measurements
• Allows measurement of nocturnal xylem flow
• Additional information about tree growth provided by installing supplementary dendrometers

What should you check before choosing this product?

Match the dendrometer geometry to the plant part and expected size changes. Check mounting clearance, measuring range and data logger compatibility before specifying the installation.