Trees for Tennessee Landscapes - Maintaining and Protecting
Bark splitting and sloughing results from a number of environmental factors. Sloughing or peeling of the bark is a normal process, especially in the spring when the tree begins to grow, and is more noticeable in some species than in others. The outer layers of bark are dead tissue and cannot grow, so the outer bark must split in order for the tree to grow in diameter. The inner bark is living, and forms a new protective coat as the outer bark pulls apart. If you look closely at normally furrowed bark, you will not be able to see the wood below. Bark may peel or fall off the tree in sheets (river birch), plates (white oak, sycamore, pine), strips (shagbark hickory, cedar) or blocks (dogwood).
"SP630 Bark Splitting on Trees," The University of Tennessee Agricultural Extension Service, SP630-14M-9/04 R12-4910-045-004-05 05-0065, http://trace.tennessee.edu/utk_agexfores/76