Deciduous Forest INTRODUCTION Temperate deciduous forests are found in middle latitudes with temperate climates. Deciduous means that the trees in this forest change with the seasons. In fall, the leaves change color. In fall and winter the leaves fall off the tree. In spring the leaves grow back. Examples of deciduous trees are maples, oaks, and elms. Courtesy of Wayne Herron and Cindy Brady, U.S. Department of Agriculture Forest Service Fall colors in the Chattahoochee-Oconee National Forests along the Russell-Brasstown National Scenic Byway. Page 1 of 6
ABIOTIC DATA Temperate climates are not considered to have extremes of hot or cold, compared to deserts or polar regions. The average annual temperature in a temperate deciduous forest is 10 C (50 F). Weather changes throughout the year, however winters have short days with little sunlight. Summer days are long and sunny. The temperature in January might drop to 12 C (10F). In summer, it might be as warm as 27 C (81 F). The growing season lasts 140 to 200 days, or 4 to 6 months. Data from Missouri Botanical Garden The annual rainfall in a temperate deciduous forest is 75 to 150 centimeters (30 to 60 inches) a year. Temperate deciduous forests receive more rain annually than any other environment except rain forests. In winter, precipitation may fall as snow. Annual precipitation ranges from 75 to 150 centimeters (30 to 60 inches) a year. BIOTIC DATA Animals and plants in temperate deciduous forests have adaptations to cope with seasonal changes in heat, moisture, and food. Some mammals hibernate. Others grow thick coats of fur to protect them from winter temperatures. Many birds migrate south during winter. The temperate deciduous forest contains a variety of trees and other plants. Deciduous trees dominate the forest, although there may be some coniferous and broad-leaf evergreen trees, too. There are usually three to four species of trees per square kilometer. Species include oak, hickory, beech, hemlock, maple, basswood, cottonwood, elm, and willow. Deciduous trees are also called hardwoods. These trees are usually slow growing and very long lived. They are desirable woods for furniture and woodworking. The forest canopy is moderately dense and allows light to penetrate. This available light results in well-developed and richly diverse vegetation below the treetops. The understory supports a wide variety of shrubs and bushes. Many bloom in early spring before canopy trees have full-grown leaves. Shrubs and bushes are also found in open meadows and at the forest edges. The understory includes rhododendron, azalea, dogwood, berries, and springflowering herbs. Page 2 of 6
A pair of wild turkeys stroll through this deciduous forest. A robin searches among the grass for earthworms and insects. Deciduous trees and plants have special adaptations for survival. During the winter, little water is available and days are short. Photosynthesis stops, leaves fall off, and the tree or plant is relatively dormant. When the days are longer and water becomes available again in the spring, leaves grow back and photosynthesis begins again. When deciduous trees shed their leaves, a layer forms on the forest floor. This thick layer of leaves decays and enriches the soil. The result is a fertile habitat for fungi, bacteria, earthworms, and insects. Small birds, such as thrushes, and mammals, such as mice, eat these organisms. Larger creatures, such as snakes, hawks, coyotes, and mountain lions, prey upon these smaller animals. Temperate deciduous forests provide abundant food for a variety of life-forms. A raccoon is one of the residents of a deciduous forest. Courtesy of the U.S. Fish and Wildlife Service Whitetail deer are one of the most numerous wildlife species in the United States today. They are important prey for cougars, grizzly bears, and wolves. The U.S. Fish and Wildlife Service estimates their population at 15 20 million. Regulated hunting seasons help control whitetail populations. Why Do Leaves Change Color in Fall? One of the most spectacular times in a deciduous forest is fall, when green leaves turn brilliant red, orange, gold, Page 3 of 6
and even purple. During spring and summer, leaves use photosynthesis to manufacture the food necessary for a tree's growth. Photosynthesis takes place in the cells that contain chlorophyll, a pigment. Leaves also contain smaller amounts of red, orange, and yellow pigments, masked much of the year by green chlorophyll. As the days become shorter and nights cooler, photosynthesis stops. The chlorophyll breaks down, revealing other pigments. Other chemical changes can create even more pigments yellow, red, and blue which you see in the red and purple of maples or the bronze or brown of oak and beech. Colors on the same tree can vary from year to year. When fall is dry and cold, colors are brilliant, but a warm and rainy fall is less colorful. Fall colors on a forest road. This northern cardinal adds some welcome color to the winter landscapes of deciduous forests. Fires in a Forest Ecosystem Forest fires can occur from lightning strikes or through human carelessness. Fires are essential to the natural succession of a forest. As a forest matures, a dense canopy formed by older trees blocks sunlight to the forest floor. Leaves, fallen branches, and debris build up. Fires destroy some of the mature trees, but open up areas and let in the sunlight. Grasses, wildflowers, and small trees and shrubs quickly take over and grow in these forest meadows. These areas eventually develop into mature forest. This change to the forest vegetation is called succession. A healthy forest has a mix of mature forest, meadows, and everything in between. Each area provides different habitats for wildlife and assures a rich diversity of organisms. Page 4 of 6
Courtesy of Bureau of Land Management Fires can be started by natural causes such as lightning or by human carelessness. ISSUES The issues that affect deciduous forests are similar to those of other forested areas. Temperate deciduous forests are one of the most altered biomes on Earth. If you compare a map of population density of the world with one showing temperate deciduous forests, you will find that a good portion of the world s population lives in this temperate region. Humans have used trees for firewood, construction, and paper for a long time. When the first European settlers arrived in America in the 1600s, forests stretched from the Atlantic Ocean to the Mississippi River. Deciduous trees dominated most of these forests. Settlers cleared much of this forested land for their homes. The trees were used for building and fuel. The forest soils provided rich farmland. Today large stretches of temperate deciduous forests have reclaimed some of the farmland in the eastern United States. Courtesy of Charles Steinhacker, Environmental Protection Agency Logging trucks check in at the Oxford Paper Mill at Rumford on the Androscoggin River, Maine. An area of forest that has been clear-cut. Trees are cut for firewood, construction material, and paper. They are still cleared for farming and building sites. Forest fires destroy old forest, as well as human structures. Valuable lumber sources can also be destroyed. Even Page 5 of 6
if a natural fire is good for the overall health of the forest, the destruction of resources and wildlife may seem too much waste for many people. Whether or not a forest is allowed to burn ignites controversy on both sides. About 7.9 million hectares (19.5 million acres) of deciduous forest disappear every year. The largest share of moist decidous forest disappears in Latin America and the Caribbean, with 3.2 million hectares (7.9 million acres) lost. Forty percent of the world's dry deciduous forest disappears from Sudan, Paraguay, Brazil, and India. Destruction of large areas of forest creates environmental catastrophes, including alteration of local rainfall patterns, accelerated soil erosion, floods, and habitat loss for millions of species of plants, animals, and insects. Weather and climate also affect the temperate forests. Northern hemisphere temperate deciduous forests lie in the areas that are most affected by severe winter weather. Scientists are looking at information that suggests that Earth is gradually warming. This would affect the habitats of plants and animals. As weather patterns shift, these areas might receive even more precipitation or might receive even more severe weather. A warmer climate might affect the types of plants that grow in the area, and a shift in precipitation patterns might make the area too dry for some tree species. Changing climate is expected to increase both evaporation and precipitation in most areas of the United States. In those areas where evaporation increases more than precipitation, soil will become drier, lake levels will drop, and rivers will carry less water. Lower river flows and lower lake levels would affect navigation, hydroelectric power generation, and water quality, and reduce the supplies of water available for all types of uses. Page 6 of 6