Example of a conifer:
Example of a hardwood:
What are the two major types of trees?
There are hardwoods and conifers. Hardwoods grow broad leaves while conifers have narrower needles instead. Also, most hardwoods are deciduous which means they lose all of their leaves in the autumn and must grow back a whole new set in the spring. Most conifers are evergreen, meaning that as their needles die, new ones take their places right away. Because of that, even during the winter they are green.
What does a tree need to live?
All trees need at least four things to live: sunlight, water, soil and air. The tree leaves have a special chemical called chlorophyll that can turn the sunlight into a type of energy that the tree can use to turn air and water into useable food. Air enters the tree through tiny openings on the underside of the leaf, while water and minerals in the soil get sucked in by the tree’s roots, which may be several feet underground and quite far from the tree’s trunk. Roots are very important because they soak in water and nutrients that the tree needs, and the weight of the soil above the roots also helps keep the tree from tipping over.
The visible parts of a tree are the trunk, the branches, the leaves and the flowers and fruit. In the soil are hundreds of roots. The trunk delivers the nutrients from the roots to all of the other parts of the tree. All of the branches act as mini trunks and continue bringing the nutrients directly to the leaves. The leaves “breathe” in the air in little holes on their undersides and change sunlight into energy. The flowers and fruit may just seem like decorations or delicious food, but they are very important. They create seeds in order to continue the existence of their species. (Different kinds of trees have different ways of making the seeds travel.)
In the autumn, most hardwoods and some conifers stop creating food. The chlorophyll (which is green) disappears and the leaves turn yellow, red, orange or brown. Slowly the leaves lose their moisture and fall from the tree.
First of all, without trees and other plants, humans (and animals) could not live. This is because humans breathe in oxygen and breathe carbon dioxide out. Trees do the opposite. If we didn’t have plants to change carbon dioxide back to oxygen, we would run out of good air very quickly and die. It is also true, though, that without animals, all plants would run out of breathable air and die. So plants and animals do make a very good partnership. Often we use trees for their wood in the trunks and bigger branches. Wood is very important in building things as well as being a good fuel for fires. Also very important is paper, which is made from trees. The paper companies used to cut down a large amount of trees, though, just to make it, before the public noticed and started to lessen the amount of paper they used. Now many people use a lot more recycled paper in packaging, newspapers and such.
Each different type of tree has a different way of creating seeds so that they have a bigger chance of surviving to maturity. The major ways of transportation are water, air or animals. Some seeds traveling by air remain flying for hours (cottonwood trees) while others have only ten seconds to land in the perfect spot to grow (maple trees). A seed can rely on an animal in many different ways. The tree could produce delicious fruit so that a mouse or other animal would eat it and release the seeds in its droppings (apple trees).
This site was developed in June 2002 by
Alexandra Harrington Hoeft,
a student volunteer