The Deciduous Forest Biome
The mid-latitude deciduous forest biome is located between the polar regions and the tropics. Because of its location, air masses from both the cold polar region and the warm tropical region contribute to the changes of climate in this biomeMid-latitude deciduous forests have both a warm and a cold season (see climograph). Precipitation ranges from 30 to 60 inches and is evenly distributed throughout the year. Much of the human population lives in this biome. Although evergreens are found in this biome, this biome is characterized by an abundance of deciduous trees."Deciduous" means to fall off, or shed, seasonally. Just as the name implies, these deciduous trees shed their leaves each fall. Lying on the forest floor, the leaves decay. As the leaves decompose, the nutrients contained in the leaves are absorbed by the soil. For this reason, the soils of this biome tend to be very fertile. Because this biome has fertile soil and a long, 5 to 6 month, growing season, many deciduous forests have been converted into agricultural regions.
Animals
Deciduous Forest: AnimalsA wide variety of mammals, birds, insects, and reptiles can be found in a deciduous forest biome. Mammals that are commonly found in a deciduous forest include bears, raccoons, squirrels, skunks, wood mice, and, in the U.S., deer can be found in these forests. While bobcats, mountain lions, timberwolves, and coyotes are natural residents of these forests, they have nearly been eliminated by humans because of their threat to human life. Other animals that were native to this biome, such as elk and bison, have been hunted to near extinction.
Animal Adaptations
Migration and hibernation are two adaptations used by the animals in this biome. While a wide variety of birds migrate, many of the mammals hibernate during the cold winter months when food is in short supply.Another behavioral adaptation some animals have adopted is food storage. The nuts and seeds that are plentiful during the summer are gathered by squirrels, chipmunks, and some jays, and are stored in the hollows of trees for use during the winter months. Cold temperatures help prevent the decomposition of the nuts and seeds
Plants
Trees of this biome include both broadleaf, deciduous trees, such as maple, oak, hickory, and beech, and evergreens, such as hemlock, spruce, and fir. A deciduous forest typically has three to four, and sometimes five, layers of plant growth.Tall deciduous trees make up the top layer of plant growth, and they create a moderately dense forest canopy. Although the canopy is moderately dense, it does allow sunlight to reach the forest floor. This sunlight allows plants in the other layers to grow. The second layer of plant growth includes saplings and species of trees that are naturally shorter in stature. A third layer (or understory) would include shrubs. Forest herbs, such as wildflowers and berries, make up a fourth layer. During the spring, before the deciduous trees leaf out, these herbs bloom and grow quickly in order to take advantage of the sunlight. A fifth layer would include mosses and lichens that grow on tree trunks.
Plant adaptations
In the spring, deciduous trees begin producing thin, broad, light-weight leaves. This type of leaf structure easily captures the sunlight needed for food production (photosynthesis). The broad leaves are great when temperatures are warm and there is plenty of sunlight. However, when temperatures are cold, the broad leaves expose too much surface area to water loss and tissue damage. To help prevent this damage from occurring, deciduous trees make internal and physical adaptations that are triggered by changes in the climate.Cooler temperatures and limited sunlight are two climatic conditions that tell the tree to begin adapting. In the Fall, when these conditions occur, the tree cuts off the supply of water to the leaves and seals off the area between the leaf stem and the tree trunk. With limited sunlight and water, the leaf is unable to continue producing chlorophyll, the "green" stuff in the leaves, and as the chlorophyll decreases the leaves change color. The beautiful display of brilliant red, yellow, and gold leaves, associated with deciduous forests in the fall, is a result of this process. Most deciduous trees shed their leaves, once the leaves are brown and dry.