Missouri Botanical Garden
Climatron Conservatory

Climatron interior

What is a tropical rainforest?

Many forested areas in the tropics are not rainforests. In fact, tropical rainforests comprise only 40% of the world's tropical forests and only 20% of the world's total forests. Other kinds of forests include tropical dry forests, seasonally dry rainforest, and tropical montane forest. Here are the characteristics of the average tropical rainforest:
  • Lies between the Tropic of Cancer and the Tropic of Capricorn, or 1,400 miles north and south of the Equator.
  • Receives rainfall distributed regularly throughout the year, about 6-33 feet a year.
  • Remains frost free and warm all year long, with temperatures between 70 and 85F with very little daily fluctuation.

The rainforest inside the Climatron imitates these conditions. The building is kept at 64 to 75F by a computerized temperature control system. The average humidity is 85%. Plants are watered by hand daily with purified, tempered water similar to rain water.

Special Rainforest Characteristics

Species diversity - The tropics do not contain the largest plants, or even necessarily the most unusual plants, but they do contain a greater number of different kinds of plants than all the other areas of the world put together! The contrasting figures for tropical animals, especially insects, are even greater. Among this great diversity are plants that have medicinal potential that could benefit many people.

Structure - The tropical rainforest is composed of three layers: the canopy, the understory, and the forest floor. The canopy is formed from the large trees whose crowns form a tight, continuous layer above the ground. The canopy is home to 90% of organisms found in the rainforest! In the wild, most animals spend their entire lives in the canopy, never touching the ground. The understory tends to be dark and relatively open, and contains smaller trees and shrubs. The forest floor receives only what little sunlight escapes through both the canopy and the understory, so not many plants grow here. The ones that do are well adapted to a very low level of light.

Soil - Many tropical rainforest soils are very poor and infertile. Millions of years of weathering have washed most of the nutrients out of the soil. Despite the amount of vegetation in the rainforest, the soil contains less organic matter than that of temperate forests, because the warm humid conditions encourage faster decay and recycling of nutrients back into living forest.

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