About Trees
Trees are classified as being at least 15 feet in height when full grown with a developed crown of branches protruding from a single stem that, at the very least, is several inches in diameter. Trees have many different parts, including roots, leaves, flowers, twigs, fruits, bark and buds. There are many families and types of trees. The gymnosperms include the pines and fir trees of the world, while the angiosperms, or true flowering plants, are comprised of such trees as the elm, oaks, maples and birches, among many others.
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Leaves
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The leaves of trees may be either deciduous, meaning they come off the tree each year, or evergreen, staying on year round. Trees are often identified by their leaves, which can be arranged on the branches in different patterns. Alternate leaves are those that appear by themselves at each node on the branch where they can grow. Opposite leaves grow two to a node, one on each side, while whorled leaves grow more than two at a node. Compound leaves are several leaves growing out of one stem. Leaves can vary in shape and size as well.
Bark
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Trees have bark that is composed of layers of dead plant cells on the outside and a substance called phloem on the interior. Phloem has living cells, and it aids in the transport of food throughout the tree. The bark of a tree has many functions. It keeps the tree from losing large amounts of water, protects the tree from insects and disease, and acts as insulation to guard against temperature extremes. The bark of a tree will change in appearance as the tree ages. Many species of tree have very distinctive bark that helps to identify them.
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Function
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The roots of a tree serve to anchor it in the soil and help it to grow straight with stability. They also will absorb nutrients and water from the surrounding soil so that the tree can grow and develop. The seeds of a tree will be produced depending on the species. Flowers that will develop into fruits, seed pods and cones are all forms of reproduction for trees, with the end result being some type of seed. The leaves of a tree will grow on the twigs, which are on the branches. The upper portion of a tree is called the crown and is made up of the branches, twigs and leaves.
Types
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In the United States, some common types of gymnosperms are the pine trees, of which there are 35 different species. Almost 40 spruce species grow in the U.S. with four kinds of hemlock trees, nine forms of fir trees, and two types of redwood trees. Redwoods are among the largest living organisms on the planet, often growing in excess of 250 feet high and having trunks that are 10 feet in diameter. The giant sequoia is also up to 250 feet tall but with a much larger base; some are estimated to be almost 4,000 years old. The angiosperms are divided into two kinds of trees. The monocots include such trees as the palm tree, pineapple and banana and are rarely found in northern climates. The dicots make up the largest number of tree angiosperms in the U.S. Maple, oak, hickory, aspen, beech, birch, walnut, alders, sycamores and ash are all classified as dicots.
Benefits
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Trees have a multitude of benefits for the environment. They regulate air temperature by blocking sunlight and by the evaporation of water through their leaves. They reduce erosion in the ground and block the wind. Trees will absorb noise and are effective as sound barriers. The leaves that fall from trees decompose and provide a wealth of nutrients for the soil. Trees are important parts of the ecosystem for many animals, including insects, birds and many mammals. Trees absorb carbon dioxide from the atmosphere and emit oxygen as well as provide humans with lumber for building and fuel.
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Resources
- Photo Credit www.shannontech.com
