My colleagues and I recently installed a large network of tree sap sensors, point dendrometers, and meteorlogical station to study the Lycorma delicatula (Spotted Lanternfly) threat to timber species. An automated system conisting of 16 sap flux sensors and 32 point dendrometers were installed on eight Black Walnut trees. A meteorlogy station including an anemometer, precipitation bucket, radiation sensor, soil moisture sensor, air temperature and relative humidity were installed.
- 165 Watt 12V Mono solar panel
- Victron Smart MPPT Solar Charge Controller
- Deep Cycle Lead Acid Battery (3)
The CR1000X datalogger is the base unit for this system. Two multiplexers are used to allow all the sensors to be wired to just one datalogger. The sensors consist of SDI-12, analog, diferrential, and single-ended measurement protocols. The meteorlogical datasets are being measured every minute and an average for a 15-minute period is recored in the data table with an exceptiono of relative humidity which is only sampled at the 15-minute mark. Sap flux sensors are averaged over a hour and recorded in its table. Sap flux sensors are oriented on the north and side of the trees. Point dendrometers sensors are also averaged over a hour and recorded in its own data table. The dendrometers are oriented east and west on the same trees as the sap flux sensors.
The entire system is powered through a single 165 watt solar panel setup. The panel charges three batteries wired in parellel through a regulator. The load (datalogger) is wired from from the regulator through a 7.5 amp fused connection. The panel is mounted on a post oriented to the south-southeast.
Dynamax Thermal Dissipation Sensors (Sap Flux)
These sensors are relatively simply to install into the trees. Care must be given though to not break or damage the probes as they are very thing and brittle. To install simply drill a 30mm deep hole with a #53 drill bit. A slightly larger bit may be required on some tree types. The bit should be thoroughly cleaned with clorox before drilling. Rinse the holes out with a syringe filled with hydrogen peroxide. A lithium grease can also be applied to help prevent the tree from growing around the probes and make better connection between the probe and woody material. Ensure the heated probe is placed into the top hole. Once probes are inserted a thermal and precipation barrier should be wrapped around the tree covering the sensor. A strap should be placed around the tree and cinched tight at the top of the barrier to hold it up and to help prevent precipation hitting the sensor.
Point Dendrometer Sensors (Sap Flux)
Point dendrometers can be finicky to install depending on the tree. In our case, we had to use a chisel to scrape off the dead portion of the bark that was about one to two inches thick. Caution is needed to ensure live bark portions are not penetrated during this process. Once a relatively flat surface is obtained to mount the platform chisel out a 1.5 x 1.5 cm square down to the xylem. Apply a lithium grease to the exposed are to help slow the growth down allowing the sensor to in place longer. Hold the mount and sensors into position and mark the mounting holes, drill the holes and pound in the mounting bolts. Push the mounting bracket and sensors onto the bolts until you get volt meters readings between the bark and xylem sensor that are within >0.2kOhm and < 1.5kOhm. One other important aspect is to ensure the program on a CR1000X datalogger is using the high resolution in the data table (IEEE4 data type).
Solar Panel Setup