C h a r a c t e r i s t i c s   o f   a   R a i n f o r e s t

Soils of the typical lowland rainforest are often shallow. In much of Amazonia, there’s only a few inches of soil above reddish clay. Many roots stretch out over the surface, rather than burrowing underground. Here many trees use wooden buttresses (like the buttresses which support the giant Gothic cathedrals of Europe), organic flanges which grow out from the base of the tree on all sides to balance it. Some biologists say this shape also allows the tree to gather nutrients from a greater surface area of soil since lots of small rootlets extend down from the bottom of the buttresses.

Stilt roots
In other places, so-called “prop” or “stilt” roots emerge like slanting rods from the main trunk 1 to 2 meters above the ground to help support the trunk. (The LFRF Guide provides a way to explore these engineering feats of Nature in Activity 1.2.) This particular kind of root is often found in flooded or mangrove forests, where it also protects the tree against waves and currents.

Drip tips
Rainforest leaves also have distinctive features. Many have “drip tips”—a pointed shape which helps drain excess water from the leaf and reduces vulnerability to mold and predation. Researchers often speak of how different plants try to prevent ”herbivory”—the eating away of vegetation by insects or other parasites—and minimizing moisture with drip tips is one such strategy. When it fails, leaves become a lacy net of holes and fibers.

Mutualistic relationships
With the constant fight for light and water, nutrients and energy, many rainforest species come to rely on each other, and develop intimate and exclusive relationships. Some plants, for example, provide “ant houses,” home to a particular species of ant whose soldiers defend the leaves against other would-be insect predators. Other plants provide leaves with tiny feeding troughs, pools of sugar-solution, enticing ant patrols with sweet rewards. (You can find more information on these “ant-defended plants” in the LFRF Teacher Resource video which is part of the Multimedia Kit.)

In addition, however, to listing and marveling at such distinctive aspects of rainforests, we should also try to comprehend the myriad relationships and interactions to be found in them. As Alexander von Humboldt wrote, “...more beautiful still than all the wonders individually is the impression conveyed by the whole... in its entirety.”

(For more on rainforest relationships, please explore “ECOsystem” online, and if you’re a teacher or youth leader, consider implementing the Tropical Rainforest Food Web Game [Activity 2.3] which helps bring these intricate interactions to life.)