Cross section of the barrel:

  • bark,
  • sapwood,
  • core,
  • core.

Sapwood, core

The wood of the forest species is usually light coloured. In some species the whole mass of wood is painted in one color (alder, birch, hornbeam), while in others the central part is darker (oak, larch, pine).

The dark part of the trunk is called the core, while the light, peripheral part is called sapwood. In some kernelless breeds, the central part of the trunk is darker. In this case, the dark central zone is called the false nucleus.

Annual layers, early and late wood

The cross section shows the concentric layers around the wood. These formations represent the annual growth of wood, i.e. in one growing season. They are called annual layers. In the radial section, the annual layers have the form of longitudinal and straight stripes, while in the tangential section, they have the form of curved, conical lines.

The annual layers increase annually from the center to the periphery and the youngest layer is the outer layer. The age of the tree can be determined by the number of annual layers on the end section on the compole.

The width of the annual layers depends on the breed, growth conditions and position in the trunk. Some species (fast-growing) have broad annual layers (Poplar, willow), others have narrow layers (boxwood, yew).

The narrowest annual layers are located in the lower part of the trunk, and the width of the layers increases upward as the trees grow in thickness and height, which brings the trunk shape closer to the cylinder.

Some species have the irregular shape of the yearlong layers. For example, on the cross section of hornbeam, yew and juniper there is a waviness of annual layers.

Type of annual layers

  • transverse,
  • radial,
  • tangential
  • cuts of wood (pine).

Each annual layer consists of two parts – early and late wood: early wood (inner) facing the core, light and soft; late wood (outer) facing the bark, dark and hard. The difference between early and late wood is clear in conifers and some hardwood species.

Early wood is formed in early summer and is used to draw water up the trunk. It is distinguished by the presence of large, fairly well visible vessels. Late wood is laid off by the end of summer and performs mainly a mechanical function. The amount of late wood depends on its density and mechanical properties.

Core beams

On the cross section of some species are clearly visible to the naked eye light, often glossy, directed from the core to the bark of the line – core rays. Core rays are present in all rocks, but only in a few.

Primary core rays begin at the core itself and secondary rays at different distances from the core. In felled wood, the core rays create a beautiful pattern (radial cut), which is important when choosing wood as a decorative material.

In terms of width, the core rays can be very narrow, difficult to distinguish (maple, elm, elm, linden); wide, clearly visible to the naked eye on the cross section.
Wide rays can be real wide (beech, oak) and falsely wide – bunches of close narrow rays (hornbeam, alder, hazelnut).

On the radial section of the core rays are visible in the form of light shiny strips or ribbons arranged across the fibers. They can be coloured lighter or darker than the surrounding wood.

In the tangential section, they can be seen as dark strokes with pointed ends or as lentil stripes placed along the fibres.

Core Ray Types

  • transverse,
  • tangential,
  • radial cuts of wood.

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