A silver station wagon loaded with climbing gear, computers, electrical wiring and a few scientists from Harvard University stops near a stand of pine and oak trees in the Harvard Forest, about 70 miles west of campus. Physiological ecologist Andrew Richardson, leader of this expedition, slips from the driver’s seat and grabs gear to ascend a metal tower among the trees. Its peak affords Richardson a clear view of his living laboratory: the forest canopy.
Above the treetops, he checks a cluster of instruments that analyze the lush canopy as a collection of numbers: the amount of carbon being inhaled from the atmosphere, the concentration of water vapor in the air and the precise mix of hues the leaves exhibit.
Different pigments serve different functions: Green chlorophyll, which dominates during the growing season, absorbs light energy for photosynthesis, the conversion of carbon and water to sugar. In the shortening days of autumn, red anthocyanins and yellow carotenoids take over to help protect leaves against light damage.
To document this subtle seasonal color change, a webcam atop the tower snaps high-resolution images of the canopy every 30 minutes from dawn to dusk and uploads them to an online database.
During the past decade, Richardson has spearheaded an effort to install more than 80 such cameras at sites across North America, from the arctic tundra near northern Alaska’s Toolik Lake to the tropical grasslands surrounding Hawaii’s towering Mauna Kea.
This PhenoCam Network amasses thousands of photos per day. Over time, Richardson hopes the resulting trove of color data will help scientists understand — and better predict — how ecosystems like the Harvard Forest respond to changes in the climate.