Unlike people, trees increase in height by growing up from the top of the main stem and the tips of the branches. Annual growth occurs only from these two growing points. Similar to people a tree grows outward and upward from the centre of the stem or body. Both the stem and branches gain length in the branches and height giving the tree a tapered look. The base of the tree is the oldest, has the greatest accumulation of annual diameter growth and is, therefore, the largest part of the tree.
The growth in the diameter of the tree is most rapid early in the growing season, at the beginning of the rainy season. This “earlywood” that is produced at this time consists of large, light-coloured cells. We refer to it as sapwood and are usually softer than the rest of the center part of the tree. The “latewood” cells produced later in the growing season are smaller in size with thicker walls and so they appear darker. Each pairing of light and dark bands compose one ‘annual ring’ which marks another year in the life of the tree. These bands are very visible in softwood trees but very slight in the darker Indigenous trees of Zambia. These growth lines are also called the ‘grain’ of the tree when they are exposed in finished timber.
The tree feeding system of the trees has two systems: the first is called the Phloem and is the vascular tissue or pipes of the tree in charge of transporting and the distribution of the organic nutrients that feed the tree. Once these pipes that make up this feeding system become old they will become part of the outer bark of the tree and is part of the tree’s protective system. The second system is called the Xylem, the same vascular tissues but conveys water and dissolved minerals collected from the roots to the rest of the tree and also provides physical strength to the tree. And when they die they fill with resin and harden to become part of the heartwood of the tree adding permanent strength and reinforcement to the center of the tree. The liquids found in a tree are commonly known as sap and is comprised of organic nutrition, water and minerals.
From the seed, the tree builds itself into a self-sufficient factory. The roots anchor the tree to the earth and absorb water and minerals from the soil around the tree. The leaves manufacture sugar from these raw materials from the air. The most common element is carbon. This is where the term Carbon sequestration comes from as it is the storage of carbon in a tree.
The tree is a marvelous dynamic living system offering so many benefits to people, animals, and not only to the whole natural environment but to our social environment too.
Garry Brooks
World citizen
SUSTAINABLE FUELWOOD IN ZAMBIA 