What a forest’s glow can reveal about the impact of environmental change

“In this photograph, I’m installing a chlorophyll fluorometer into a Scots pine tree (Pinus sylvestris) at a forest station in Hyytiälä, Finland, which is 200 kilometres north of the main campus at the University of Helsinki. I’m 20 metres above the ground, on a scaffold.

The tool records the light emitted by leaves or needles in the far-red part of the spectrum. Almost every chlorophyll-containing organism creates this light. The intensity is very low — only about 1% of absorbed light is emitted as fluorescence – but its variations make the signal informative.

Measuring the wavelength and intensity of this light, and comparing them with changes in carbon dioxide levels and the emissions of some volatile organic compounds from plant leaves, might make it possible to draw a relationship between them. Eventually, fluorescence data obtained remotely, from towers, drones, aircraft or satellites, might lead to a better understanding of how trees and plant ecosystems are responding to a rapidly changing environment.

My colleagues and I have placed fluorometers and automated chambers in this hectare of forest to measure gas exchange. The area is filled with the sound of machinery — the hissing of the pumps that operate the gas-exchange chambers, the humming of small motors and the beeping of detection equipment. These aren’t the sounds of a normal forest, but they are the sounds of our science.

My work is all about zooming in and out to understand plants at different scales, and how they interact with the environment on a local to global scale. Future work might move towards a detailed understanding of a single leaf or chloroplast. In many respects, the complexity inside a leaf is comparable to what we find in a forest ecosystem, but it is much more difficult to measure.”

This interview has been edited for length and clarity.