Wordpress Test Post 01
Posted by admin under Category 1, Category 2, Uncategorized on Wednesday Aug 19, 2009
In order to properly prune a tree or to repair damage to the trunk requires a basic understanding of tree structure. A cross section of a tree trunk reveals it is composed of many layers (Figure 1). Each year a tree essentially grows a new “coat of wood” over the older wood. The outside layer of the tree is dead bark which provides protection from the environment. The inner bark layer is composed of live tissue that transports food downward. Between the bark and wood is the cambium layer which is responsible for increases in tree diameter (by creating annual rings) and responds to injury by producing callus tissue. 
The annual rings of wood are composed of large pores that carry water up to the leaves. Each annual ring is essentially a vertical cylinder. The outer 4 to 20 annual rings (referred to as sapwood) are usually alive and light-colored. Wood in the center of a large tree (referred to as heartwood) is composed of dark-colored, dead cells used for storage. Ray cells cut across the annual rings; they distribute food to living cells. 