Sycamore is a deciduous broadleaf tree native to central, eastern and southern Europe. Mature trees can grow up to 35m and live for 400 years. The bark is dark pink-grey and smooth when young, but becomes cracked with age.
Figure 1. Cross-section of a Sycamore tree.
A. Growth rings: marks indicating the yearly growth of the trunk.
There are 3 main things you can tell from growth rings:
1. Age of the tree.
2. Growth of the tree and factors
affecting it e.g. reaction wood, fungal attack, where branches grew (knots),
site conditions.
3. Past weather patterns,
particularly rainfall.
B. Pith: central part of the trunk, that is usually spongy and
soft. This tissue is sometimes referred to as the medulla. The main function of
the pith is to store nutrients and transport them through the stem, branches,
leaves and roots of the tree. New pith growth is usually white or pale in
colour, indicating that the pith of the tree above is very new growth. In older
branches, the pith is often replaced by a woody substance called xylem. In some
instances, the middle of the stem can dry out and disintegrate, resulting in a
hollow trunk.
C. The heartwood and Sapwood: consists of old cells and unlike the younger sapwood, it no longer conducts water. This is the dead part of the tree that nevertheless provides structural strength. Figure 2 displays the cross-section of another tree, where the heartwood is clearly visible. This part of the tree is usually darker, denser, less permeable and more durable than the younger sapwood. All wood begins as sapwood, which is formed just under the bark by the cambium. The cambium produces bark cells on the outside and wood cells on the inside of the tree. In young trees, all of the wood in the stem is sapwood, but as the tree gets older and increases in diameter, the entire trunk is no longer required for conducting sap. In addition to this, the tree requires extra structural support, so the cells nearest the centre of the tree die, and therefore become heartwood. The cross-section displayed in Figure 1 appears to be from a relatively young tree that has not yet formed heartwood. Sycamore trees tend to mainly consist of sapwood which is the living wood in the tree through which the raw sap rises from the roots to the leaves.
Figure 2. Cross-section of a tree with visible heartwood.
D. Outer Bark: protective outside covering of the trunk. The bark protects the underlying layers against physical influences such as temperature, rain, wind, sun, fire or mechanical influences and serves as a defence against pests and infections. Figure 3 shows the outer bark of sycamore tree.
Figure 3. The outer bark of a Sycamore tree.
E. The phloem (bast) is also called the inner bark. It conveys the food-bearing sap developed in the leaves down to the various parts of the tree. The bast tissue of a living tree is moist and in relation to the wood and bark it is often very soft. Having said this, it is also reasonably tough and resilient.
F. The cambium is a thin layer of cells, which produce phloem on one side and xylem (sapwood) on the other. Xylem is made of vessels that are connected end to end for the maximum speed to move water around. They also have a secondary function of support. When someone cuts an old tree down, they reveal a set of rings. Those rings are the remains of old xylem tissue, one ring for every year the tree was alive.
G. Diseases: There are a range of damaging diseases and pests that affect sycamore trees. Some of the most common include Sycamore Anthracnose, powdery mildew and lace bug. Others include root ranks, canker, wood rots and mistletoe.
H. Knots are common blemishes in trees, often causing lumps or holes within the trunk of the tree itself. In most cases knots are caused by the natural growth of the tree, though the specific circumstances under which they form determines how they will appear. Some knots are formed by fungal infections.
References
Dreistadt, S. (2004). Pests of Landscape Trees and Shrubs: An Integrated Pest Management Guide. California. University of California Division of Agriculture and Natural Resources.Rodd, T. & Stackhouse, J. (2008) Trees: A Visual Guide. Weldon Owen Inc.
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