Rainforest greener during 'dry' season

Although the Amazon Jungle may appear to be perpetually green, a University of Illinois researcher believes there are actually seasonal differences of photosynthesis, with more occurring during the dry season and less during the wet season. Understanding how a rainforest that occupies 2.7 million square miles of South America functions is crucial to the future health of the entire planet.
"With the potential negative effects of climate change, one key question we are trying to answer in the study of tropical ecology is how a tropical forest responds during a long-term drought," says Kaiyu Guan, an environmental scientist at the University of Illinois. "If we don't know their daily performance or their seasonal performance, what confidence can we have to predict the forests' future 20 years, 30 years, or longer?"

Analyzing data from several sources, including individual leaves, camera data from towers above the leaf canopy, and decadal long satellite images, Guan and his colleagues measured the photosynthesis rate over the landscape. Photosynthesis -- the process green plants use to convert energy from the sun that plants use to grow -- from tropical forests, plays a huge role in determining global atmospheric CO2 concentration, which is closely linked the global temperature and rate of climate change.
"Bringing all of the data together, we find that the dry season in the Amazon has increased photosynthesis," says Guan. "There may be less photosynthesis in the wet season because of the cloud cover which limits the amount of light the plants can use."