From an article I found:
So you don’t want to wait ten to fifteen years for your pears to bloom and bear fruit?
TRY BARK INVERSION
At the Arnold Arboretum one spring many years ago, Dr. Karl Sax gave a successful demon-stration of a procedure he called “Bark Inversion.” He cut a three-inch-high band below the first branches around the entire trunk of an apple tree that was three years old. Then he cut a vertical slit in the band and deftly peeled the band of bark from the wood, along with as much of the cambium as possible, completely girdling the tree. Next, he scraped any remaining cambium from the exposed wood. Then he “grafted” the band back on, but UPSIDE DOWN (hence the name, “bark inversion”). This prevents the sap from descending normally to the roots. As a consequence,the roots don’t get enough nourishment, and the tree’s growth is slowed. Much of the sap accumulates in the top of the tree. This accumulation causes earlier bearing and larger fruits. The tree, which would normally start producing fruit in its eighth year, started producing in its fourth.
A second consequence of bark inversion is a dwarfing effect, since it causes the tree to grow more slowly. If permanent dwarfing is desired, the bark inversion treatment must be repeated several times in succeeding years.