Sapwood is the younger, living wood of the tree that grows around the outside of the older, dead center. Sapwood can be distinguished by its lighter color in comparison to the wood that it surrounds, which will become more prominent over time as it is exposed to sunlight. Since it is the living part of the tree where the sap and water flow, sapwood has a high moisture content. This causes the wood to shrink as it dries and makes it more susceptible to decay and fungus.
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