AGE DEPENDENCE OF SPIRAL GRAIN IN WHITE OAKS (QUERCUS ALBA) IN SOUTHCENTRAL ILLINOIS

Abstract

Spiral grain, the alignment of wood fibers (trachejds) to the longitudinal axis of h·ees, is thought to be an indicator of old age and is a phenomenon that has been only stndied with destrnctive sampling methods (cutting down trees). In this study, the usefulness of non-fatal sampling methods and existing methods to quantify spiral grain patterns in Jiving and dead deciduous trees are examined, particularly in white oaks (Qi1ercus alba). 111e overall goal is to detem1ine if spiral grain growth is a reasonable indicator of h·ee age. Methods that were tested included the use of a 12 mm increment borer (non-fatal sampling method) and Brazier's method ( 1965) of analyzing grain angles along just one diagonal to get a representative grain angle for the whole circumference at a certain height on a tree. The 12 mm increment borer did not produce consistent results in this study; therefore, . destructive sampling is necessary to study spiral grain in white oaks. Brazier's method (1965) should not be used in white oaks and should not be applied universally to all tree species. Samples from living and dead trees vary in severity and direction of spiral grain. The climatic factors that are roost limiting to tree growth do not influence spiral grain growth in white oaks in this stand. Severe spiral grain does in general seem to be an indicator of age in white oaks, although most trees have severe left spiral grain and not right spiral grain. However, a tree without severe spiral grain is not necessarily young. To judge the severity of spiral grain, grain angles have to be examined in the outermost layer of the wood and not in the bark.