Compartmentalization of Discolored Wood in Heartwood of Red Oak

SHIGO, A. L., and W. C. SHORTLE. 1979. Compartmentalization of discolored wood in heartwook of red oak. Phytopathology 69:710-711. Discolored wood associated with holes drilled into heartwood of living indicate that heartwood in red oak is not a dead, nonresponsive tissue; the red oak (Quercus rubra) trees was strongly compartmentalized after 2 yr; classic concept that heartwood-rotting fungi grow unrestricted through discolored wood associated with similar holes in trees that were girdled heartwood is not true. The concept of heartrot must be revised to include immediately after wounding was weakly compartmentalized. The results compartmentalization. The classic concept of heartrot in living trees is that heartrot is a hr at 104 C. Duplicate 0.5-g samples were taken for mineral progressive decay by hymenomycetous fungi that infect fresh analysis. Tissues were wetted and digested by nitric-perchloric acid. wounds (1,2,7) of the dead nonresponsive heartwood in trees. Trees Amounts of potassium, calcium, and magnesium were determined of Acer spp. and Betula spp. have no central core of dead with an atomic absorption spectrophotometer. heartwood. How, then, can they have heartrot? The expanded concept of tree decay is that trees are RESULTS compartmentalized plants that wall off injured and infected wood In nongirdled living trees, the configuration of the drill bit was associated with wounds (compartmentalization) and that many the configuration of the discolored wood as viewed on the microorganisms are involved in the processes (succession) that transverse surface 5 cm above the wounds, regardless of when the result in discolored and decayed wood (3-5). trees were wounded (Fig. 1). The column of discolored wood above This paper further supports the expanded concept of tree decay and below each wound was longest along the heartwood-sapwood by showing that heartwood in red oak (Quercus rubra L.) boundary. The discolored wood associated with the drill-bit compartmentalizes injured and infected tissues. MATERIALS AND METHODS Forty red oaks in a 6-ha forested area at Alfred, ME, were selected for freedom from mechanical wounds or large exposed branch stubs. The trees were about 60 yr old, 15-25 cm in diameter at 1.4 m above ground, and 11.5 m tall. Each tree was wounded twice in 1975. Eight drill-bit wounds, 1.4 cm in diameter and 1.5 cm deep, were made during the first period and eight more during the second period (16 wounds total). Wounding periods were: trees numbered 1-10, January and August; 11-20, March and August; 21-30, March and June; and 31-40, May and June. In the first set of wounds for each tree, two holes were drilled opposite each other on the trunk at approximately 0.5, 1, 1.5, and 2 m above ground. Each of the holes in the second set were drilled at 900 from the first set. Twenty trees, five from each wounding-period group, were girdled with an ax immediately after the first wounding. Ax cuts were made approximately 3 cm into the heartwood completely