IEEE Spectrum - North American - March 2015 - 59

tHe internet oF treeS

Microbes, ants, and oaks: With continuing investigations
starting to come together, Ellison refers to an "ecosystem of
experiments" at the Harvard Forest, whose interconnections
each tree with three sap-flux sensors, each consisting of two mirror those of the forest itself. For example, he has also samneedles, one of which is heated. The temperature difference pled ants from an experiment originally designed to study
between the needles reflects how well water is flowing up the the effects of warming on plants, while other researchers are
trunk, a measure of the tree's overall health. As the seasons making use of an experiment that is manipulating the canopy
progressed, the sap of the red maples slowed down, while (ostensibly to track the decline of hemlock trees) to see how
that of the red oaks did not. Templer believes that the red climatic changes might affect plants and animals beneath.
oaks were less affected by freezing soil because their roots "We do these parallel experiments all the time," he says.
"We would love to have a crystal ball that says, 'In 100 years
generally run deeper into the earth.
The most ambitious simulation, however, involves some of the temperatures are going to increase by x and the forest is
the forest's shortest-lived residents: ants. These insects cre- going to respond with y,' " says Templer. Accurate forecastate an inch of topsoil in North America every two centuries, ing could allow governments to plant appropriately adapted
replenishing soil lost to farming. To observe how warming species, manage development, reduce the spread of invasive
might affect their behavior, ecologist Aaron Ellison set up species, and ultimately make climate change less disastrous
dozens of chambers on the forest floor and heated them to for all of us.
Accelerating data collection is one of the most important
successively higher temperatures, ranging from 0.5 °C to
5.5 °C above those of the ambient air. (The heating bill for techniques that researchers are using to get to that goal. Take
his hot air blowers alone is $50,000 a year.) The ants are "water budgets"-the balance of precipitation, runoff from
free to come and go from the chambers, and their numbers streams, and evapotranspiration, the water returned directly
are sampled each month. Most of the ants at the Harvard to the atmosphere through evaporation and the respiration
Forest adapted to the higher temperatures, continuing to of plants. Many ecologists have been tracking it at various
generate topsoil as before. However, some species at an sites for decades. But this monitoring is typically conducted
identical setup in subtropical North Carolina either left the on an annual timetable. Now, the Harvard Forest can provide
accurate numbers on a daily or even hourly basis.
chambers or perished.

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