Dead Bark
Dead bark or outer bark is a layer of dead tissue which is a proctection for the trunk and branches. It also helps to reduce water loss from the living cells of the tree. Some trees shed thed their dead bark each year while on others dead bark is reduced only by the weathering processes.
Live Bark
Live bark is a layer of living tissue under the dead bark. Food materials produced by the leaves are conducted through the live bark to the branches, trunk and roots of the tree.
Cambium Layer
The Cambium layer is the layer of thin cells, invisible to the naked eye positioned inside the live bark. This layer of cells facilitates all growth in the thickness of the tree trunk. The Cambium grows wood cells on the inside and live barks cells on the outside.
Sapwood
Sapwood is the new wood under the Cambium layer. It is often lighter in colour than true wood or heart wood and it conducts water and mineral salts from the root system of the tree to the leaves.
Heartwood
Heart wood or truewood is made up of cells which are actually dead. It provides the strength necessary to support the tree. Heartwood is formed by the blockage of the channels which conduct food materials. Blockage occurs as stored food materials are converted into tannis, resins and other related substances. Heartwood is much more durable than sapwood.
The Pith
The pith is at the centre of the tree and is a soft, pulpy zone which is usually about one centimetre in diameter. The Pith is sometimes called the medulla, giving its name medullary rays.
The Medullary rays are groups of wood cells radiating from the pith through the truewood and sapwood zones of the tree. Food materials are conducted horizontally in the trunk of the tree via the medullary rays which also act as food storage areas.
The Medullary rays are groups of wood cells radiating from the pith through the truewood and sapwood zones of the tree. Food materials are conducted horizontally in the trunk of the tree via the medullary rays which also act as food storage areas.
Growth Rings
As trees age, they grow in height and width. You can tell the age of a tree by counting these rings.
The annual rings of a tree are made each year when a new layer of wood is added to the trunk and branches of the tree. New wood grows from the cambium layer between the old wood and the bark.
The annual growth of a tree can be measured by the distance between the growth rings shown in the illustration below. As the growth rate slows down in the winter months, the new layers of wood cells (late wood) are smaller and packed more closely together forming a ring which is darker in colour then the wood grain at a faster rate ealier in the growing season (early wood).
The annual rings of a tree are made each year when a new layer of wood is added to the trunk and branches of the tree. New wood grows from the cambium layer between the old wood and the bark.
The annual growth of a tree can be measured by the distance between the growth rings shown in the illustration below. As the growth rate slows down in the winter months, the new layers of wood cells (late wood) are smaller and packed more closely together forming a ring which is darker in colour then the wood grain at a faster rate ealier in the growing season (early wood).