The study found a gradually decreasing trend in Congo rainforest greenness, sometimes referred to as "browning," suggesting a slow adjustment to the long-term drying trend. This is in contrast to the more immediate response seen in the Amazon, such as large-scale tree mortality, brought about by more episodic drought events.
The browning of the forest canopy is consistent with observed decreases in the amount of water available to plants, whether that is in the form of rainfall, water stored in the ground, water in near-surface soils, or water within the vegetation.
These changes in available water were detected in part with NASA satellites including the NASA/JAXA Tropical Rainfall Measuring Mission, NASA's Quick Scatterometer (QuikScat), and NASA's Gravity Recovery and Climate Experiment, a joint mission with the German Aerospace Center.
"Combining measurements from different sensors has given us more confidence in the results of the MODIS data and provided us with insights into the environmental and physiological mechanisms of the browning observed by the MODIS data," said co-author Sassan Saatchi of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif.
Climate factors known to affect vegetation growth were also in line with the observed browning. Land surface temperatures, for example, were observed to increase over most of the study area. Decreased cloudiness allowed more solar radiation to reach the plants, which typically promotes photosynthesis, but in this case it likely posed an extra stress on the plants from the resulting depletion of soil moisture.
"Forests of the Congo basin are known to be resilient to moderate climate change because they have been exposed to dry conditions in the past few hundred years," Saa
|Contact: Kathryn Hansen|
NASA/Goddard Space Flight Center