Definition of sapwood

The term "sapwood" originates from the biological function it serves in trees. Sapwood is the outermost layer of a tree's trunk and branches that transports water and nutrients from the roots to the rest of the tree. This layer is called "sapwood" because it initially contains sap, the watery fluid that circulates through the tree. Initially, the sapwood is living tissue, and as the tree grows, new layers of sapwood are added to the outside. However, over time, the innermost sapwood ages and becomes relatively less active in carrying water and nutrients. This section is called heartwood and is denser and darker than the sapwood, as it no longer contains living cells. The outermost portion of the sapwood closest to the bark is known as the phloem, which also transports sugars and other organic compounds from the leaves to the rest of the tree. Together, the sapwood and phloem make up the tree's blueprint or circulatory system, which is vital for its growth and survival. The study of sapwood and its decomposition by fungi, insects, or other natural processes is known as dendrochronology, which helps in understanding the age and growth history of trees and their response to climate change.