It is this enormous flow of water that causes

It is this enormous flow of water that causes a continuous flow of sap from the roots to the topmost twigs. The pith is the central part and around it is the wood. Luckily, birds help to keep caterpillars, borers, beetles and other insects in check. 

When the cambium ring is severed, as by a wire cable, the tree is killed, and since the cambium protects against insects and disease, anything driven into it can wound the tree severely. The stem or trunk of a tree has three parts: the bark, the wood and the pith. In planting or transplanting a tree, and in building on a lot where you wish to preserve the trees, the gardener's chief consideration must be to protect the root structure of the tree. On a summer day, a single birch tree may transpire 700 to 900 gallons of water.

The trunk, limbs, branches and twigs hold the leaves in position to receive the life-giving sunlight and air; they also act as transportation, carrying raw materials between roots and leaves.There are 200,000 known kinds of insects that attack trees, in addition to diseases such as blight, rust and rot, storms and droughts. The materials absorbed by the roots are pulled up by capillary attraction and the osmotic action induced by evaporation of water from the leaves. 

The big roots near the stem anchor the tree to the ground, while the fine root hairs at the ends of the rootlets absorb the water from the soil. Loss of water through the leaves is called transpiration. Outside of man himself, trees have countless enemies. Between custom aluminum die casting engine cover suppliers wood and bark is the cambium, a thin layer that produces new wood and bark