The Earth's vast tropical rainforests sit along the hot, humid regions of the equator. The immense Amazon Basin of South America, the Congo in central Africa and various Southeast Asian areas are the largest. Between 100 and 750 tree species have been noted in single hectares (2 ½ acres), according to Theresa Greenaway in her book "Eyewitness Jungle." Tropical rainforests produce vast amounts of oxygen for the planet, provide habitat for millions of species of plants, animals and insects and hold critical known and unknown value for mankind.
There are no distinct seasons in these lowland jungles. Trees that live with the 12-hours-a-day sunlight and warm rainfall of 80 inches (2 meters) or much more a year grow continuously, with random flowering/fruiting times and no widespread leaf drops. The typical leaf is waxy and wide, with a thin drip-tip that helps shed the rain. Some trees grow large individual leaves; others combine leaves in fanlike spreads. To gain support in the shallow, wet soil some tall trees grow large, curving buttress roots that form a wider base.
Layers of Vegetation
The topmost trees are called "emergents." They reach 200 feet or more, with crowns that may spread over an acre. One Malaysian tualang tree reached a record at 285 feet (87 meters). Another emergent species, the kapok tree, originated in South America and now populates other tropical rainforest areas also.
When an old emergent falls or one is toppled by a hurricane wind or landslide, an opening is created for sunlight to reach the forest floor. Saplings that have been patiently waiting in the gloom with ferns and other lowlight plants then leap into aggressive growth. Their trunks will grow straight through the comparatively open layer called the "understory" and branch out to join the "canopy" layer. Below the tallest trees, the canopy is the heart and soul of the rainforest and provides a home to the teeming variety of plants, animals and insects that live their lives in this dense roof of the rainforest.
Rainforest trees provide wood; fruit, nuts, spices and other foods; medicines, oils, resins and poisons. They also serve as supportive homes for other valuable and beautiful plants, such as orchids and vines.
The kapok tree provides lightweight wood, is known for its long seed pod (up to 7 inches/18cm) filled with fluffy waterproof fibre that gives it the common name of "silk cotton tree" and produces seeds that yield oil. Mahogany, teak, red lauan and balsam are other multi-use woods. Some trees, including the Brazil nut tree and the para rubber tree, are tapped for latex, or natural rubber. The Brazil nut tree is extremely long-lived and gives indigenous people a sustainable and lucrative crop. The tree will only produce nuts in the wild. The cinchona tree's bark is the only source for natural quinine, the malaria drug, which also has been used for many other maladies. Considered divinely given, the cacoa tree was first cultivated by the Aztecs. The tree that brings us chocolate sprouts its small white and pink flowers right from the trunk. They develop into large pods containing the seeds or beans that become cocoa.
Conservation efforts allied with research will continue to foster the discovery of a profusion of beneficial rainforest products from broadleaved evergreen trees and the diverse life forms they support.