What is the layer between the inner bark and the sapwood called?

The layer between the inner bark and the sapwood is called the cambium. This thin layer of tissue is crucial for the growth of the tree as it produces new cells that will become either phloem (which transports nutrients) or xylem (which carries water and minerals). The cambium is responsible for the tree's growth in width, allowing it to add layers of bark and wood over time. Understanding the role of the cambium is important in forestry and pest management, particularly in termite practices, as it is an area where pests can potentially affect the health of the tree.

In contrast, xylem refers to the woody part of the tree that conducts water and minerals from the roots to the leaves, while heartwood is the older, central wood that is no longer active in water transport and provides structural support. Phloem is the layer responsible for the transport of nutrients created during photosynthesis but is located outside of the cambium.