Battle for Sunshine Shapes Forest Structure.

• Position: TROPICS

Despite their diversity, the structure of most tropical rainforests is highly predictable. Scientists have described the various sizes of the trees by a simple mathematical relationship called a power law. In a study using data from a rainforest in Panama, researchers determined that competition for sunlight is the underlying cause of this common structure, which is observed in rainforests around the globe despite differences in plant species and geography.

The finding can be used in climate simulations to predict how rainforests absorb excess carbon dioxide from the atmosphere.

The study was conducted by researchers at Princeton (N.J.) University, the National Institute for Mathematical and Biological Synthesis, the Smithsonian Tropical Research Institute, and collaborating institutions.

The researchers found that the rainforest structure stems from what happens after a tall tree falls and creates a gap in the canopy, which enables sunlight to reach the forest floor and fuel the rapid growth of small trees. Over time, the trees' crowns grow to fill the gap until the point where not all of the trees can fit in the sunlit patch. Some will be left behind in the shade of their competitors.

"This process of moving from fast growth in the sun to slow...