Traipsing Through Trees: Educator Resource

Trees are amazing structures that children love, whether they are climbing in them, playing under their shade, or collecting sticks, leaves, flowers and seeds for creative play. Trees are tree-mendous!

What is a Tree?

Trees are perennial plants with a single woody stem that supports branches and grows to at least 5 meters tall when mature. However, this definition is not a scientific one, and there are many exceptions to the rule. There are also many things that look like trees but are not. Some interesting ones include:

bamboo, which has a hollow stem and is a grass
banana trees, which have a ‘trunk’ made of tightly rolled leaf stalks and are a herb
cactus, which are also a herbaceous plant
grass trees (Xanthorrhoea) are neither grass nor trees but a herb with a trunk similar to a banana made from tightly compacted leaves.

There are also some plants that you might think are not trees, but they are, including:

tree ferns
mangroves
yuccas
and palm trees.

Tree Rings

You might know that you can tell a tree’s age by counting the rings in a cross-section of the trunk. When you look at the rings, they will be in pairs of light, wide rings and dark, narrow rings. The light rings are the growing season, and the dark rings are the dormant season. In the northern hemisphere, spring is usually the growing season, with late summer and autumn being when growth slows and the tree goes dormant. In Australia often the light rings are winter and spring when there is plenty of rain and sun, and the dark rings are the hottest part of summer. The pair of these rings together represents one year of growth.

Tree rings can also tell us about changes in the microclimate around the tree. Small tight rings can indicate drought, with wider rings showing good growing weather. You can also see evidence of fires, and damage to the trees, for example by insects or disease.

Benefits of Trees

Trees are key to the survival of life on our planet. Not only do they produce oxygen, but a fully grown tree will absorb around 21 kilograms of carbon dioxide in a year. While they take in nutrients and water from the soil, the absorption of carbon dioxide is where they get most of their ‘building material’ to create the tree's structure. Mature trees capture more carbon than young trees and are significant players in reducing the impacts of climate change.

Mature trees in Australia provide another benefit: tree hollows. Eucalyptus trees, in particular, drop branches as they mature. When the branches get shaded out by new growth and aren’t able to photosynthesise (produce energy), the tree will cut off the water and energy supply to that branch and let it die. Eventually, the branch will fall off, and the place where the branch was will form a scar. Over time, the scar will break down. Animals will dig into the wood, looking for insects to eat. Eventually the scar will form a tree hollow.

A tree needs to be about 100 years old before it can have hollows. These hollows are important nesting sites for birds, bats, and possums. When mature trees need to be cut down for safety, sometimes arborists will do a ‘habitat cut’. This is where the main trunk of the tree is left standing, hollows are left in the trunk, and the top and branches are cut in a way that lets water and insects in to promote the rotting process and create habitat sooner.

It's not ideal to have possums and bats move into your house’s roof. The best way to keep these creatures out is to leave habitat trees standing and provide additional nesting boxes to replace the habitat they have lost.

Traipsing Through Trees: Hollow for a Home

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