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    Home / Science lessons / Learn About Trees & Forests
    • Learn About Trees & Forests

      All About Trees

      There are many kinds of trees in the world. Scientists use a system called classification to organize different types of trees and make them easier to identify and study. Classification breaks different kinds of similar things (such as trees) down into smaller groups so that all the objects in the group have things in common.

      All trees have several parts. The basic parts that all trees have in common are roots, a trunk, branches, and leaves. These are things that make trees trees. This is the first step in classification. It tells you that a tree is a tree and not an animal or a different plant.

      Even though all trees have leaves, there are some major differences in what happens to those leaves. Trees that lose all of their leaves at once during one season (usually Fall) and grow new ones in a later season (usually Spring) are called deciduous trees. In contrast, some trees have leaves all year round. They do lose some of them, but new ones grow back right away. These types of trees are called evergreens.

      Within the groups of deciduous and evergreen trees, there are lots of differences. There are fruit trees and trees that just get flowers, there are trees that don't have any flowers, and there are trees that have pinecones. All of those different trees are classified in different groups. Are you starting to understand how classification is helpful?

      Tree Trunks

      A tree's trunk is very important. It is how nutrients and water get from the tree's roots to its branches and leaves. It also gives the tree support — the trunk holds up the whole tree! So, what makes a tree trunk so special? Let's start from the outside layer.

      You've probably touched many trees and maybe even climbed a few. If so, you know that some trees have smooth bark and some have very rough, chunky pieces of bark. Bark protects the tree from things like very cold or very hot temperatures, insects that try to get inside and eat the tree, and diseases that could harm or kill the tree. 

      Have you ever seen a tree stump leftover from a tree that was cut down, or looked at the end of a log? If you have, you may remember seeing lots and lots of rings or layers inside the trunk. These layers are created by the cambium (a thin layer in between the wood and bark of every tree), where new cells are made. Tree trunks grow a new layer each year, making the tree bigger and stronger.

      The reason you can see the layers inside a tree trunk is because they start out a light color when they begin to grow in the spring, and by summer the outside of the new layer is much darker! Then, the next year, in the spring, a new layer will start that will be a light color again. The wider a ring is, the more the tree grew that year. That usually means that the tree received lots of rain. Narrow rings usually mean that the tree had trouble growing that year, or didn't get as much water or sunlight as it needed. If you want to see a drawing of the different parts of a tree, look here.

      Woods & Forests

      Woods and forests cover nearly one-third of all the land on earth. What's the difference between woods and forests? If you look up in a wood you can see lots of sunlight coming through the branches. A forest has lots of shade because trees grow very close together and it is sometimes hard to see the sun. Woods are usually smaller than forests and contain fewer kinds of plants and animals.

      Forests that have deciduous and evergreen trees are called temperate forests and cover North America as well as parts of Europe and Asia. In colder climates there are forests that only contain evergreen trees, which have short needles and produce cones. These forests spread across Canada and parts of Europe and are called boreal forests or Taiga (say: TIE-gah).

      How does a forest grow? Clumps of trees begin growing naturally and over time spread out, creating a dense forest. Deciduous and evergreen trees spread through seeds that the tree has dropped. Seed pods of different trees look very different. For example, the seeds of a pine tree are all inside of a pine cone. As animals come to live in the wooded habitat, they spread the trees' seeds so that new trees can begin to grow. The animals that live in woods and forests include deer, bears, raccoons, foxes, squirrels, rabbits, and many types of birds. Ants, beetles, and other insects live on the ground of a forest and also in trees.

      Science Words

      Classification- a way to organize things into groups to make them easier to study. Things that are similar are grouped together into one group, such as animals. Then that large group is divided into smaller groups, such as birds and mammals, and so on.

      Deciduous- trees that lose all their leaves at once each year (usually in the fall).

      Evergreen- trees that only lose a few leaves or needles at a time. When they do lose them, new ones grow back right away, so they have leaves all year round.

      For science projects to use with this topic, click here.

      Help kids review the differences between deciduous and evergreen trees with this two-page puzzle worksheet. Younger kids may require some assistance as this requires cutting and pasting.

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