Fitbits for Trees. Say What?

You might look at a tree swaying in the wind and see botanical tranquility—a hypnotic back and forth of life interacting with air. Scientists appreciate that too, but they also see something else: data in motion. It turns out that the way a tree moves says a lot about its biology, the local hydrology, and the landscape at large. And the best way to measure a tree’s swaying is to strap a fitness tracker to its trunk with waterproof duct tape. 

Using off-the-shelf accelerometers, researchers have been quantifying how trees sway differently over time: when they’re warmer or colder, hydrated or dehydrated, weighed down by snow or unburdened. It is like a Fitbit for trees. It’s high-resolution monitoring of tree activity, just like we have high-resolution monitoring of our activity as a human being that tells us metrics on how much energy are we burning? How much sleep did we get?

One of the things researchers really want to monitor is how much water trees are capturing. Measuring precipitation, it turns out, isn’t as simple as tracking how much water falls out of the sky and soaks into the ground as liquid or becomes part of the snowpack.

Trees actually “intercept” much of it, gathering rain and snow in their canopies. In fact, depending on the kind of forest, up to half of the snowfall gets stuck in the canopy. That means it sits there, baking in the sun and evaporating much of that water away—robbing the underlying environment of moisture. The snow that makes it to the forest floor, on the other hand, will be shaded, which slows its melting. 

Forest hydrological models struggle with these intricacies. But with accelerometers, scientists have a new way of measuring how much rain or snow a particular tree in a forest ends up intercepting. Devices like these will be a huge help in understanding forests in the future.