Terrestrial Biomes
Tropical Rain Forest Biome
As the name indicates, rain forest biomes receive high levels of precipitation throughout the year. On average, a rain forest receives between 50 and 660 centimeters (approximately 20 to 260 inches) of rainfall annually. There are two types of rain forest areas: tropical rain forest biomes and temperate rain forest biomes. They differ in their locations and average temperatures.
When people think of a rain forest, they usually picture the tropical variety. Located along the equator, tropical rain forests are often associated with the term jungle. They are regions filled with a high diversity of plants and animals. The consistently warm temperatures and high levels of rainfall make tropical rain forests humid and ideal for plant life.
Scientists estimate that more than half of the world’s species live in tropical rain forests. Some of the plant life impacts the lives of other living organisms around the world. For example, during photosynthesis the trees of the rain forests consume large quantities of carbon dioxide. In the same process, they release oxygen, helping to maintain the balance of this gas in the atmosphere. Many organisms in tropical rain forests produce chemicals that have formed the basis of modern medicines. About 25 percent of modern medicines have been derived from rain forest organisms.
There is great biodiversityglossary term (opens in a new window) among the plant species in the tropical rain forest. Four layers exist in the rain forest, each with different conditions that support different organisms. The following table summarizes the four layers of a tropical rain forest.
|
Layer |
Conditions |
Plant Life |
Animal Life |
|
Emergent |
tallest region with lots of sunlight and winds |
tall, wide trees with hardwood and smooth, straight trunks |
eagles, macaws, bats, monkeys, butterflies |
|
Canopy |
forms a roof over the layers below; acts as a UV shield and umbrella to washouts below; abundant food sources |
dense leaves, branches, and vines; leaves shaped like waterspouts |
majority of animal life including toucans, parrots, tree frogs, jaguars, monkeys, sloths, butterflies |
|
Understory |
shady, little air movement, high humidity |
dense growth of vines, broadleaf trees, and shrubs that provide camouflage; trees average four meters in height |
many nocturnal species including tree frogs, bats, owls, and many species of insects like the leaf cutter ants |
|
Forest Floor |
ground layer, very dark, poor soil quality, rapid decomposition by micro-organisms |
few plants; some mosses and ferns |
frogs, lizards, giant snakes, beetles, termites, and many other insect species and micro-organisms |
Although tropical rain forests are productive, they grow on very poor soils. When these forests are cut down, the remaining land is not good for farming. This is because most of the nutrients in this biomeglossary term (opens in a new window) are stored in the plants that grow there, not in the soilglossary term (opens in a new window). Tropical rain forests are being destroyed at an alarming rate—about 80,000 acres each day. As this rain forest is destroyed some of its species may become extinct. Some of these species may have been useful in a variety of ways, such as combating disease.
Temperate Rain Forest Biome
The temperate rain forests are found farther from the equator near coastal areas such as the Pacific Northwest of the United States. Similar to tropical rain forests, temperate rain forests exhibit high levels of precipitation, with more than 300 centimeters, or about 118 inches, falling each year in the Pacific Northwest. However, temperatures of the temperate rain forest are more moderate than those of the tropical rain forest. In fact, the term temperate means “not extreme or excessive.”
The conditions in a temperate rain forest biome are conducive to diverse plant and animal life. Like the tropical rain forest, temperate rain forest can be divided into layers. The canopy is dominated by tall conifers. Some, like the redwoods, can reach 100 meters in height. Other important tree species in the canopy include Sitka spruce, Douglas fir, and red cedar. Where the original forest remains some of these trees are more than 2,000 years old. In the understory below the canopy can be found smaller shade tolerant trees such as dogwood. The ground layer consists of young trees and shade tolerant plants such as various species of ferns and berry-producing shrubs.
Wolves, bears, mountain lions, eagles, owls, rabbits, deer, skunks, rodents, raccoons, moose, hummingbirds, spiders, and many insects all call the temperate rain forest home. These animals have adapted ways to survive the cold winters. Some hibernate or burrow until spring when food is plentiful again. Others migrate to escape the cold and return when temperatures are warm again.
Teacher Note: Connections
In the following item, students identify patterns and variations in the characteristics of the temperate and tropical rain forest biomes. They sort the characteristics to identify which ones describe the tropical rain forest biome, which ones describe the temperate rain forest biome, and which ones describe both biomes.
Deciduous Forest Biome
The temperate deciduous forest biomeglossary term (opens in a new window) is located at the middle latitudes across Earth. This biome experiences a temperate climate with four distinct seasons of the year. Summer weather typically starts with cool mornings that lead to warm days. The winter is cold enough to cause many animal species that live in the deciduous forest to hibernate or migrate. The amount of precipitation among the deciduous biomes averages about 75 to 150 centimeters (30 to 60 inches) each year.
The trees in this type of forest biome are deciduous, meaning that their leaves change color and drop each year when the weather turns cold in the fall. New leaves grow when temperatures rise in the spring. These types of trees tend to have broad leaves and include maples, oaks, hickories, and beeches.
Much like a tropical rain forest, a temperate deciduous forest can be divided into layers based on plant growth. The top layer consists of the tallest trees that form a dense canopy, but still allow sunlight through. The next layer consists of saplings and other short tree species. The third layer from the top is the understory of shrubs and bushes. The fourth layer is where wildflowers, berries, and herbs grow. Finally, the ground layer includes mosses and lichens.
Wide arrays of animals live in the deciduous forest. Many small mammals such as rodents, hares, opossums, skunks, and weasels live here. Predatory animals also live in the biome including bears, foxes, and wild dogs. Many bird species from cardinals to turkeys and especially birds of prey such as hawks and eagles live in the deciduous forest. The bald eagle, a symbol of the United States, calls the deciduous forest home.
