The outer surface of a tree is important because the sensitive vascular cambium is situated directly beneath the bark. It is here that new tissue is constantly being produced-wood on the inside and bast fibers and new bark on the outside. This is also where the system of ducts for carrying glucose form the leaves to all other parts of the tree is situated. The young sapwood found immediately below the cambium is also very soft and therefore highly susceptible to attack by a range of enemies.
If the bark itself is injured, trees such as conifers open their resin channels, allowing resin to disinfect and close the wound, thereby acting as a barrier to harmful bacteria. The bark on some trees is so thick and strong that it is even able to protect trees form the extreme heat generated by forest fires.
Bark provides a tree with protection-although is also gives it an individual 'personality'.