TREES

By Moira Whitehouse PhD

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Trees can be grouped as:

conifers deciduous or

First, we will consider:

conifers deciduous

Deciduous trees have broadleaves. Broad leaves have large surfaces so they can gather a lot of sunlight.

However, a tree with flat, wide leaves also loses a lot of water through transpiration where water evaporates from the surface of the leaf.

Picture of a deciduous forest in summer.

Deciduous tree leaves often turn bright colors in the fall.

And most drop their leaves in winter or during long periods without rain.

A tree drops its leaves when it is cold or dry in order to save energy. It takes a lot of energy for a tree to keep wide broad green and healthy.

Deciduous forest during winter

Deciduous trees have flowers and reproduce from seeds.

A few have brightly colored flowers in the spring but most do not.

Most have male and female flowers that are dull and green, the same color as the tree so we do not even notice them.

These male flowers from a red oak are long, skinny and green. They hang downward from new branches in spring producing pollen.

Female flowers form later than male flowers and are not visible to the naked eye.

When they fall off, the male flowers sometime look like big green worms on the ground.

When pollen from the male flower fertilizes the female flower, seeds develop. The seeds on a deciduous tree usually grow inside its fruit or in a hard shell for protection like these acorns on a red oak tree.

The seeds are often dispersed when the fruits or nuts are eaten by animals. Since the seeds inside the fruit or shell are not digestible, the animal eventually passes them through its droppings often away from the parent tree. This increases the chance for a seedling to grow in an area that is not shadowed by its parent.

Lastly we will consider the:

conifers deciduous

Trees that grow cones are called conifers.

Coniferous trees grow up instead of out like a deciduous tree and are shaped like a triangle. The leaves are usually long, pointy needles.

Spruce Fir Pine

The cones of the conifers are very important to the coniferous tree because it is there that the tree makes and shelters its seeds.Cones are made up of many scales that serve to protect the seeds.

Most coniferous trees have both male and female cones. Female cones contain eggs. Male cones are small and soft. They produce (make) pollen. Once the pollen is released, male cones shrivel and die.

Female cone

Male cone

When the egg is pollinated a seed develops

Pine cone with seeds. When it's time, the scales of the cone open and the seeds fall to the ground.

Coniferous trees with their long needle like leaves thrive where summers are short and cool and winters long and harsh, with heavy snowfall that can last as long as 6 months.

These needles are pretty amazing adaptations. It is their long thin shape and wax covering that slows down evaporation so the tree doesn't lose much water. It is this adaptation that allows trees with needles to grow in areas where it is cold most of the year and where there is little precipitation.

Conifer trees do lose their leaves but only a few at a time and these are quickly replaced. Since they generally live in colder areas of the world, they always have some leaves so as soon as it warms up and the sun shines, they can make food.

Coniferous trees are triangular shaped and the branches are soft and flexible. As a result snow slides off the tree without breaking its limbs.

This presentation may help you understand why forests of deciduous and conifer trees are found in particular regions where the climate suits their leaves (or vice versa).