LOOKING AT BARK

The skin that covers a tree – the bark – keeps the tree from drying out and helps to protect it against attack by animals and fungi. Bark may be thin and smooth, or thick and knobbly, depending on the type of tree and its age. Young trees usually have smooth bark on their trunks and brunches. Old bark stretches and cracks or peels, as the trunk grows wider year by year. Just underneath the bark is a delicate layer of tissue called a phloem. It carries nutrients from the leaves to all parts of the tree. If a bark is damaged all around the tree trunk, the flow of food stops and the tree dies.

The appearance of the bark can help you decide what species (type) a tree is. Different trees have different kinds of bark. A mature tree beech tree has smooth, thin bark that is about ½in deep. A redwood tree of the same size has hairy, fibrous bark that is up to 6in thick. Many conifers, such as pines and spruces, have bark that flakes off. Follow the first two projects and become a bark detective, by studying the bark up close and making a collection of your own bark rubbing. The third project will help you estimate the size of a tree.

BECOME A BARK DETECTIVE

Magnifying glass, field guide, notebook, pencil.

STEP 1
Bark does not stretch, but cracks and peels as a tree grows. Use a magnifying glass to search in the cracks during the spring and summer for tiny insects and other creatures.

STEP 2
The bark has fallen away from this dead tree, revealing the holes chewed by beetle grubs underneath. Some grubs live under the bark for several years.

STEP 3
Where the bark is damp, you will often find powdery green patches. These are millions of microscopic plants called algae, which live side by side on the bark’s surface.

BARK RUBBING BOOK

Paper, wax crayons, pencil, colored card, bradawl or hole puncher, ribbon, adhesive.

STEP 1
Ask a friend to hold a sheet of paper steady against the bark. Rub the side of a crayon over the paper with long, even strokes. Write the name of the tree beside each rubbing.

STEP 2
Punch holes into pieces of colored card and bind them together with ribbon. Stick your rubbings on to each page. You could include a silhouette of each tree, too

MEASURING THE CROWN

Compass, marker, yardstick, graph paper, ruler, colored pencils.

STEP 1
Using the compass, walk away from the tree toward north. Ask a friend to call out when you reach the edge of the area covered by the leaves. Place a marker at this point.

STEP 2
Repeat for the other seven main compass directions. Measure the distances back to the trunk with a yardstick and note them down.

STEP 3
Plot your results on a piece of graph paper. Measure ½in on the paper for each yard on the ground. Draw lines from the center of the paper, for each compass direction.

What you have 3 sketched and colored in shows the shape of the area covered by trees leaves and branches (the crown). Count the squares and half squares to find the size of the area of the crown. Do not count part-squares if they are less than a half. Each ½in square represents 1 yard. Compare with other trees in the area. Generally, the older the tree, the more likely it will have a large crown.