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Image or reality? Leaf study needs photos and lab analysis

January 27, 2014

Every picture tells a story, but the story digital photos tell about how forests respond to climate change could be incomplete, according to new research. Xi Yang, a graduate student in Geology at Brown and MBL, and other scientists have shown that the peak in forest greenness as captured by digital pictures does not necessarily correspond to direct measures of peak chlorophyll content in leaves, which is an indicator of photosynthesis. The study, which focused on a forest on Martha’s Vineyard, has significant implications for how scientists use digital photos to study forest canopies.

The use of digital photography to study how forests change has increased in recent years. The technology provides an inexpensive way to monitor forest change closely over time, an approach that isn’t labor-intensive. Cameras can be set up, programmed to take pictures at certain intervals, and then left to do their thing for long periods. This type of research has produced significant findings in recent years. Researchers are currently using networks of cameras around the country to monitor the timing of when leaves sprout in the spring and drop in the fall. Both events are expected to be sensitive to climate change.

Using cameras to see when leaves sprout and when they fall off is one thing, but Yang and his colleagues wanted to see how well photos could capture what happens in between. Could cameras be used to tell when leaves reach peak photosynthesis in the summer or when photosynthesis slows in the fall?

The work was led by Yang and is published online in the Journal of Geophysical Research: Biogeosciences.

Read more of Kevin Stacey's article about digital photos to study forest canopies.