By Lee Anna Sherman
The science of mountain airsheds requires a strong back as well as a sharp mind — especially when you’re lugging a 65-pound golf-cart battery in your pack.
An interdisciplinary team of OSU students spent 10 weeks this summer scaling the steep slopes of H.J. Andrews Experimental Forest to enable researchers to unplug their high-tech gear — the sensors they use to study the ebb and flow of carbon-laden air through old-growth and second-growth landscapes. Their project, funded by the National Science Foundation, represents a new generation of ultra-low-power sensing devices and novel methods of “harvesting” power that save energy and vastly extend the range of existing equipment in mountainous terrain.
The three seniors — Drew Smith, Erin Wyckoff and Brian Wilson — pooled their individual expertise in electrical engineering, soil science and atmospheric science to test and refine a networked wireless system for monitoring what OSU’s Terra magazine calls the “exhaled byproducts of the forest” (see Grasping for Air). Their goal: to make those monster batteries obsolete in the Andrews. Thanks to their efforts, the miles of electric wire that currently snake through the experimental watershed in glistening black tangles will be relegated to the dustbin of technology.
“Wires are hard to work with,” says Adam Kennedy, the forest science faculty research assistant from Kennewick, Washington, who coordinated the team. “They degrade, animals chew through them, we trip over them. Battery-free wireless sensors offer a promising solution to these limitations. This could totally reshape the design of future research sites.”
For their project, the students used equipment ranging from scrounged (10-year-old temperature sensors scavenged from a professor’s storage cabinet) to super-sophisticated (a shiny new $18,000 soil-sampling machine with a robotic arm). Two or three times a week, they would set out from their labs on campus to the damp coolness of Oregon’s western Cascades. Rising into the lush understory of Watershed 1 is a 120-foot tower of steel that captures air quality data every 15 minutes, sending measurements to a nearby computer. An electronic “net” of other sensors throughout the watershed adds data on sap flow, soil moisture, solar radiation, wind speed and air temperature.
The research is novel in rugged terrain like the Andrews. That’s because most ecosystem sensing work has been done on flat ground, where impediments are fewer. But understanding mountain forests — which cover a significant percent of Earth’s surface — is becoming critical to investigations of climate-change dynamics. “I’m looking at how this research fits into the bigger picture of soil CO2 flux and global warming,” says Wyckoff. “At least 60 percent of Earth’s terrestrial carbon is held in the soil. It’s a huge part of the puzzle.”
One typical workday in early August, Smith could be seen tapping away at his laptop as he crouched among ferns at the base of the creek bed, reprogramming a custom-fabricated circuit board — the “hub” of the integrated system. Dwarfed by Douglas fir, lulled by the burble of the crystalline stream, dappled by shadows and filtered sunlight, the electrical engineering major from Bozeman, Montana, pored over some 800 lines of computer code while Wilson and Wyckoff trekked the trails, positioning and repositioning the sensors in search of sweet spots that picked up signals. The crackle and pop of their handheld emergency radios broke the forest’s stillness as they communicated back and forth under the green canopy.
The team moved on. After scaling a nearby slope with the speed and agility of a mountain goat, Wyckoff turned her attention to the Andrews’ prized auto-sampler, a state-of-the-art machine that measures carbon flux in soil. The environmental science major from Gresham, Oregon, programmed the “brains” of the machine to work without wires. Instead of tramping across sensitive undergrowth to download data from probes that record moisture, decomposition, soil chemistry and other data, scientists will be able to tap readings remotely through handheld computers such as a BlackBerry or Palm Pilot.
Wilson’s task was to upgrade the Andrews’ air-sensing system, to gather vertical temperature and pressure profiles continuously and in real time. On a clear blue day, the environmental science major who grew up in Portland pumped helium into a bright orange plastic “blimp” the size of a minivan. With paperclips, he attached 10 sensors at intervals along the rope tethering the big balloon to the forest floor. Eventually, he will replace the rope with a fiber-optic temperature-sensing cable to more accurately measure the cold-air drainage that flows down the watershed each evening after the sun goes down.
Once researchers develop robust sensor networks that operate without wires and batteries, they will see a bump in efficiency, a drop in blisters and sweat and a decline in disturbance to the fragile forest ecosystem. With data more readily accessible, the mysteries of mountain forests will be easier to unravel.
Funding Note: The students’ work was made possible by a National Science Foundation REU (Research Experience for Undergraduates) supplement to an ongoing interdisciplinary project involving the colleges of Forestry, Engineering and Oceanic and Atmospheric Sciences.