Plugged into the environment

CHI sensor package diagram

By Kathleen Wong, UC Natural Reserve System

The field sciences are often thought to have remained unchanged since Victorian times. A good pair of binoculars, a water-resistant notebook, and infinite stores of patience have long been considered the stock in trade, right alongside a pith helmet and khaki shorts.

In reality, field researchers are embracing advances in technology right alongside the rest of society. The UC Natural Reserve System’s California Heartbeat Initiative (CHI) is a prime case in point.

The program seeks to revolutionize our ability to measure the water available to California ecosystems. To evaluate how hydrated plants are, scientists have long had to sample the leaves of individual plants both before dawn and in the heat of the day. This makes it hard to measure more than a few plants at a time, much less an entire landscape.

From soil to outer space

CHI is working to automate this entire process using remote sensing. The project is marrying those gold-standard hand measurements to data gathered from climate stations, drone flights, and satellite imagery. In time, scientists should be able to obtain environmental moisture measurements right from their home computers.

Getting to that point, though, requires a whole lot of information about weather and how it affects conditions for plants. CHI has centralized the detection of these conditions into one compact package. Mounted atop a tripod that can flex with the wind, the CHI sensor package bristles with a suite of research grade sensors capable of detecting a wide range of environmental characteristics.

Brimming with sensors

Crowning the tripod is a miniaturized climate station. Able to measure the usual weather characteristics, from humidity to rainfall and temperature to windspeed, it can also measure the availability of light wavelengths capable of powering plants, thanks to a photosynthetically available radiation (PAR) sensor. A radio listens for electrical bursts of a specific frequency to count lightning strikes. And a pair of leaf-shaped sensors hanging off the side measures the degree of wetness nearby leaves are experiencing.

Cables from the tripod power instruments on a nearby tree and beneath the ground. The instrument lashed to the tree is a sap flow meter. It measures how fast fluid is moving from the tree’s roots toward its leaves. Leaves need water to make sugar through photosynthesis, then transpire that water into the atmosphere. The sap flow meter pulses heat into the fluid within a tree’s vessels, and measures how long it takes for the warmed sap to rise to a nearby heat sensor.

From down in the dirt to up in the trees

Beneath the surface, the cables fuel instruments that measure soil moisture at range of different depths. These readings give a sense of how much water is available for plant roots to absorb.

A data logger clipped to a leg of the tripod stores the information gleaned from all of the instruments. Finally, an adjacent transmitter sends the data wirelessly to reserve headquarters. From there, it is uploaded to the internet and available to researchers in real time.

Thanks to the solar panel that powers all of the instruments, the sensor package can be deployed far from any buildings. Able to be deployed in just about any location, it’s the high-tech way NRS field researchers stay plugged into the environment.

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