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Cross-section through a yew tree trunk (the light-colored sapwood is clearly differentiated from the dark heartwood)

Sapwood is the young, physiologically active wood below the cambium in the trunk of a tree . Its capillaries conduct water and nutrient salts into the treetop and store sugar and starch in the parenchyma . With increasing age, the sapwood loses its vitality and in some tree species turns into heartwood . This process is called nucleation . Heartwood and sapwood differ in terms of density and strength . That is why sapwood cannot be used in many tree species.

Sapwood trees are trees with no heartwood formation, there are no differences in color or moisture between heartwood and sapwood. These include B. birch , alder and sycamore and norway maple . Your wood has the character of sapwood across the entire cross-section. The wood of these trees tends to form cavities.

In timber construction , sapwood has no natural durability . For wood used outdoors, the sapwood is either removed during processing or its durability is increased by adding chemical wood preservatives . Wooden poles are an example of this area of ​​application .

With oaks and some other tree species, light, concentric zones of seemingly non-core wood appear within the heartwood (moon ring). This feature is often mistakenly referred to as trapped sapwood. However, it is not sapwood, but incorrectly potted wood. The cause is considered to be damage to the parenchyma during the nucleation as a result of severe frosts in combination with severe branch fractures in winter.

The disadvantage of sapwood is the risk of infestation by fungi, which cause blue stain and prefer the sapwood from conifers. However, these mushrooms hardly affect the mechanical properties, only the visual quality.

Hygric properties of sapwood

The water content of freshly felled wood is generally between about 40 and 60 percent. In extreme cases, for example in the sapwood of the fir, it can reach up to 67%. In this case, the wood contains twice as much water as solid components.


Individual evidence

  1. Gerhard Stinglwagner, Ilse Haseder, Reinhold Erlbeck: The cosmos forest and forest lexicon . 4th edition. Franckh-Kosmos, Stuttgart 2009, p. 686. ISBN 3-440-12160-7 .

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