What is a Tree Ring?
Trees are organisms in the plant kingdom that appear to be so simple to us but are very complex in their habitat. The tree trunk is the biggest stem and the trunk possesses many branches which again have stems on them. Leaves are found on almost all the branches and stems of trees. Leaves are present on the top of the tree while the roots found at the bottom take the nutrients from the ground. All plants including the trees have a central medullary region or Pith region made up of parenchyma cells. Leaves are the sites for preparation of food necessary for the tree to survive. Hence it is essential for the tree to supply the water and nutrients to the leaves from the ground through the stem. A tree ring is simply a layer of wood produced during one tree’s growing season. A cross section of a tree often shows a distinct pattern of concentric tree rings. Each tree ring marks a line between the dark late wood that grew at the end of the previous year and the relatively pale early wood that grew at the start of this year. One annual ring is composed of a ring of early wood and a ring of late wood. The growth occurs in the cambium (the thin, continuous sheath of cells between bark and wood). In spring, the cambium begins dividing. This creates new tissue and increases the diameter of the tree at two places: 1. Outside the cambium. The outer cells become part of the phloem. The phloem carries food produced in the leaves to the branches, trunk, and roots. Some of the phloem dies each year and becomes part of the outer bark. 2. Inside the cambium. The inner cells become part of the xylem. These cells contribute most of a tree's growth in diameter. The xylem carries water and nutrients from the roots to the leaves. These cells show the most annual variation: * When a tree grows quickly, the xylem cells are large with thin walls. This early wood or springwood is the lighter-colored part of a tree ring. * In late summer, growth slows;...
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