What part of a tree trunk is considered to be a living part?

The living part of a tree trunk is primarily the cambium layer, which is a thin layer of actively dividing cells located just beneath the bark. This layer is responsible for the production of new phloem (which transports nutrients) and xylem (which transports water). While the outer bark protects the tree and the inner wood (xylem) is mostly dead tissue, the cambium plays a crucial role in the tree's growth and overall health.