Pictures of changing leaf colors might not tell the whole story, according to a recent scientific study of trees on Martha’s Vineyard.
Scientists from Brown University and the Marine Biological Laboratory in Woods Hole found that pictures of forests do not directly correspond to peak levels of chlorophyll in leaves. A press release said the study had implications for how scientists study trees and climate change.
The work was led by Brown graduate student Xi Yang and is published in the Journal of Geophysical Research: Biogeosciences. The press release said that automated photography has been used in the past as an easy way to do research in forests, and has produced significant findings in recent years. But to test the accuracy of the photographs, scientists placed a camera on a 50-foot tower above the Manuel F. Correllus State Forest, and timed the camera to take photos every hour for five hours a day from April to November 2011. The scientists also took weekly leaf samples from the forest and tested them for chlorophyll, which makes the leaves turn green, and senescence, the process of plant aging that makes the leaves turn red in the fall. The photos showed that the leaves reached peak green color around June 9, but chlorophyll levels peaked 20 days later.
The results were more aligned in the fall. The peak redness captured by cameras matched the peak in red pigment found in the lab.
The press release said the results have implications for studying how trees regulate the amount of carbon dioxide in the atmosphere. When photosynthesis peaks, so does absorption of carbon dioxide. The information about leaf color and photosynthesis can help scientists explore how forests are responding to climate change.