Forest Biomes Chapter 9
9.1 Objectives ~Describe the characteristics of the coniferous forest. ~Explain adaptations that enable organisms to survive in coniferous forests.
9.1 Coniferous Forests Coniferous trees, or conifers are trees that produce seed cones Conifers share an unusual type of leaf called a needle -long, thin leaf covered in a thick, waxy substance Most conifers are also evergreen, meaning they do not lose all their leaves at a given time each year.
9.1 Coniferous Forests The trees often grow in dense stands that prevent sunlight from reaching the forest floor. Some examples of Coniferous trees are pine, hemlock, fir, spruce, and cedar. Because of acidic soil, plants such as ferns, lichens, and sphagnum moss grow on forest floor.
9.1 Coniferous Forests Roles in the ecosystem Snow that falls on the trees acts as an insulating blanket, trapping heat and preventing the ground from freezing solid during the cold winter. This insulation protects the trees roots. Because the Coniferous forests are mainly in the frigid cold, people tend to not inhabit them.
9.1 Coniferous Forests Many animals in the coniferous forest are adapted to the cold and to life in the conifers. Small herbivores such as birds and rodents feed on seeds, and large herbivores such as elk and beavers feed on the plants and bark
9.2 Objectives ~Identify the characteristics of the deciduous forest. ~Describe the organisms that inhabit the deciduous forests.
9.2 Deciduous Forests A deciduous tree is a tree that sheds its leaves during a particular season of the year. Temperatures in deciduous forests vary, from as high as 30 degrees celcius to - 30 degrees celcius. Deciduous forests receive between 50 to 300 cm of precipitation. Deciduous trees are adapted to the highly variable climate of the temperate zone. Growth season for deciduous trees lasts about 6 months.
9.2 Deciduous Forests In Autumn, the shortening daylight and cool temperatures trigger changes in the trees. Trees shed their leaves and become dormant The loss of leaves is an adaptation that enables the trees to conserve water during the cold winter months. The trees grow new leaves come spring time. Maple, oak, birch, beech, ash, and hickory are examples of deciduous trees
9.2 Deciduous Forests Deciduous forests are made up of several different layers, and each layer has its own group of plant species The highest layer of a deciduous forest is called a canopy, which is made up of the upper branches and leaves of tall trees. The next layer under the canopy is the understory, which is made up of trees that are younger and smaller than those of the canopy. Below the understory is the layer of shrubs. The final layer is the mosses, ferns, and other plants that grow on the forest floor.
9.2 Deciduous Forests Because the deciduous forest produces abundant food and has many different habitats, it supports a diverse community of animals and organisms. Fungi and other decomposers, along with insects and invertebrates, are common in the leaf litter and on fallen trees. These organisms are preyed upon by birds, mice, and small mammals.
9.2 Deciduous Forests Herbivorous mammals such as deer are also present. Reptiles and amphibians are common in warmer forests. Predators such as wolves, mountain lions, and foxes fill the higher trophic levels in the ecosystem. Eagles and owls are predatory birds present.
9.2 Deciduous Forests Human activity actively changes the deciduous forest Humans are driven to the deciduous for two things 1. Rich soil 2. The trees themselves This causes communities of forests to come back very slowly if they ever do come back.
9.3 Objectives ~Describe the characteristics of the tropical zone and of the rain forest. ~Illustrate the complexity and the diversity of the rainforest ecosystem.
9.3 Rain Forests The tropical zone is located at the altitudes near the equator Because the tropical zone is near the equator, it receives direct rays from the sun during most of the year. Temperatures stay within 25 degrees celsius all year long. The growing season lasts for 12 months The precipitation of from 100 to 450 cm per year.
9.3 Rain Forests A rain forest is a biome with a dense canopy of evergreen, broadleaf trees supported by at least 200 cm of rain each year. Rain forests contain 70 to 90 percent of all the species on Earth. Rain forests hold 40 percent of Earth s biomass. Thousands of species of cyprus, balsa, teak, mahogany, and other trees grow in this biome. The trees in a rain forest are amazingly diverse. Many trees reach heights of 50 or 60 m, where their leafy tops form a dense canopy. The canopy captures 99 percent of light falling on the floor of the forest.
9.3 Rain Forests The rain forest as an ecosystem contains as many nutrients as, or more than, other biomes. The topsoil is very thin and poor, with 99.9 percent of the available nutrients in the top 5 cm of soil. Rainforest tree trunks widen at the bases. Ridges of wood called buttresses make the trunks seem even wider. The buttresses support the trees, as the trees roots must be shallow to take advantage of the thin topsoil.
9.3 Rain Forests The dead organic matter that enriches the soil in other biomes does not last in the rain forest. Fallen trees and other organic matter are decomposed in days or weeks instead of years. The warm temperatures and constant moisture of the rainforest are ideal conditions for decomposers.
9.3 Rain Forests Most of the activity in the rain forest occurs in the trees. The canopy and other levels of vegetation support countless species. Each species occupies a niche in the trees. The rain forest can be compared to a lake in which different organisms have adapted to the conditions in different water levels.
9.3 Rain Forests Amazing diversity in animals in the rain forest is due to two factors The first factor; Each species of tree or plant provides niches for specialized pollinators and herbivores. High plant diversity leads to high animal diversity The second factor; The wide variety of habitats that exist in the different forest levels. Conditions high in the canopy are different than conditions lower down, and different communities evolve to occupy each habitat.
9.3 Rain Forests Habitats in the rain forest vary from tree to tree and from one part of a tree to another. The result is a complex, three dimensional mosaic of habitats with a tremendous variety of organisms. The food webs that join these organisms are complex, with many species and many connections.
9.3 Rain Forests American biologist E. O. Wilson found 43 species of ants on a single rainforest tree. British ecologist Terry Erwin estimates there may be over 50 million species of insects on Earth, mostly in rain forests. There are millions more species of animals, bacteria, plants, and fungi. Although scientists do not know how many species there are, the more they look, the more they find.
9.3 Rain Forests The destruction of forests as a result of human activity is called deforestation. The force behind the destruction of the rain forests is the human population's need for space and wood. Most of the Earth s rainforests are in developing countries. Rain forest trees are logged for export and burned to make farmland, grazing land, and living space for people.
9.3 Rain Forests When the trees in a rainforest are destroyed, the habitats in the canopy and in lower levels of vegetation are destroyed as well. When these habitats are gone, the animals that have evolved to live in them become extinct.
9.3 Rain Forests If an area of rain forest is burned, it may be able to regenerate after several hundred years if there is more rain forest around it. The diversity in the generated forest will still be low, however, because an ecosystem as complex as a rain forest cannot just reappear. The area that once held a lush forest will only grow weeds. The many organisms that inhabited the forests will be gone forever.