TreeKiT

A battery-powered dendrometer node that measures the change in a tree's stem diameter, together with air temperature and humidity, and reports wirelessly.

How it works

TreeKiT displacement sensor on its bracket, with the logger box beside it, strapped to a tree trunk

The TreeKiT clamps around the trunk and follows the stem's diameter with a linear position sensor. The tree's daily cycle of shrinking and recovering moves the sensor by micrometres, the sort of precision the TreeKit is designed to capture.

Readings are sent to a gateway on site over LoRaWAN, a long-range, low-power radio link, and from there to the dashboard. A node runs for months on a single charge.

Measure

Stem diameter, air temperature and humidity, every 15 minutes.

Transmit

Each reading is sent over LoRaWAN to a gateway on site.

Read

Readings are shown per tree, per block and per irrigation pivot, and can be downloaded as CSV.

On the tree

TreeKiT logger box with antenna and sensor cable strapped to a tree trunk — Logger box, antenna and sensor cable

TreeKiT sensor on a small bracket, with the logger box behind it — Small bracket

Side view of the TreeKiT bracket, straps and logger box on a tree trunk — Side view of the bracket and straps

Specifications

Displacement sensor

Type	Linear position sensor, resistive output, self-returning rod
Measurement range	30,000 µm (30 mm)
Resolution	~0.23 µm over the full scale
Linearity	±0.05% of full scale
Housing	Anodised aluminium
Shaft	Stainless steel
Protection	IP65 (sensor)

Node

Measures	Stem diameter change, air temperature, relative humidity, battery voltage
Reporting interval	Depending on the application and battery life requirements
Connectivity	LoRaWAN
Power	2650 mAh Li-Po battery, supplemented by a solar panel
Battery life	Up to 12 months, depending on transmission frequency

What the dashboard shows

For every tree, the dashboard works out the following from the raw stem readings.

Tree status

A plain summary: well hydrated, mild stress or drought stress. It compares the current deficit with that tree's own largest deficit over the last 30 days.

Tree water deficit

How far the stem sits below its largest recorded size. A deficit that keeps growing over several days means the tree is not recovering overnight.

Maximum daily shrinkage

The gap between the day's largest and smallest stem size. Larger shrinkage usually means more demand on the tree's stored water.

Daily net growth

The change in the daily peak from one day to the next, which separates lasting growth from the daily swelling and shrinking.

Vapour pressure deficit

How strongly the air is pulling water from the canopy, calculated from temperature and humidity.

Device status

Battery level, radio signal quality and time since the last reading for every node, so a sensor that needs attention is easy to spot.

Dashboard for one TreeKiT showing tree status, daily net growth, maximum daily shrinkage, stem radius, tree water deficit, vapour pressure deficit, and temperature and humidity — The dashboard for one TreeKiT, showing about four weeks of data.