Bookmark and Share

One barometer of the weather is a plant’s seasonal cycles, such as the date when its leaves sprout in spring or drop off in fall. What these cyclic events, called plant phenology, might reveal about climate change is the focus of a long-term Brown-MBL study in a Martha’s Vineyard, Mass., forest.

An automated camera on a tower can record seasonal changes in overall leaf color, but photos might not always correspond to seasonal biochemical changes within leaves themselves. Credit: Marc Mayes/Brown University

An automated camera on a tower records seasonal changes in leaf color in a Martha’s Vineyard forest. Credit: Marc Mayes/Brown University

“Our overall goal is to understand the phenology of trees in a temperate, deciduous forest, and how it responds to climate change,” says MBL Ecosystems Center scientist Jianwu (Jim) Tang.

Tang and his collaborators have placed digital cameras on meteorological towers in the Vineyard’s Manuel F. Correllus State Forest, at the Nature Conservancy Hoft Farm Preserve, and in a private forest, and have been continuously capturing images of the trees and leaves since 2000.

They discovered recently that forest “greenness,” as captured by the digital images, does not necessarily correspond to direct measures of peak chlorophyll content in the leaves, which is an indicator of photosynthesis. (Photosynthesis levels, in turn, indicate rates of carbon absorption by the leaves, which is important information for modeling the impacts of climate change.) Their results are published online in the Journal of Geophysical Research: Biogeosciences.

“While color of leaves is important information, we found it is not sufficient to derive the real phenology change,” says Tang. They needed to supplement the imaging data by collecting leaves on a weekly basis and measuring chlorophyll levels in the lab. “This is a warning for future study,” says Xi Yang, a graduate student in the Brown-MBL Partnership and Graduate Program and lead author on the new paper. Yi’s advisors are Tang and John F. Mustard, professor of geological sciences at Brown University.

For more information, please see this press release issued by Brown University.

Citation:

Yang X, Tang J, Mustard J (2014) Beyond leaf color: comparing camera-based phenological metrics with leaf biochemical, biophysical and spectral properties throughout the growing season of a temperate deciduous forest. J. Geophys. Res. DOI: 10.1002/2013JG002460