Growth Increment Area Increase
The secondary growth of trees produces unique mechanical and biological solutions to life. From shoot tip to root tip, a new growth increment is deposited on the outside of the last growth increment. This livingsheath of tissue generated (facilitated) by the last growth increment, minimizes transport resistances and pathway defense, as well as spreading out bending, twisting and gravitational loads. As new growth increments generate, some of the most interior increments are internally shed and closed-down. The geometric result is a nearly round in cross-section, longitudinally tapered, nested set of conical shaped growth increment layers.
The link address is: http://warnell.forestry.uga.edu/service/library/index.php3?docID=416&docHistory%5B%5D=2&docHistory%5B%5D=413