When pruning is complete, the existing living crown should be at least two-thirds of the total tree height. Example: a 36 foot tree should have living branches on at least the upper 24 feet.
On young trees, "temporary" branches may be retained along the stem to encourage trunk taper and to protect trees from vandalism and sun scald. Less vigorous shoots should be selected as temporary branches and should be about 4 to 6 inches apart along the stem. They should be pruned annually to slow their growth and should be removed eventually.
In forest timber management and to develop a higher value tree, you remove limbs from below for clear wood. Removing limbs increases wood quality which increases timber production values. Removing lower limbs can also be of significant health value to certain tree species. Pruning lower branches on white pines can help prevent white pine blister rust.