Ultrasonic Acoustical Emissions from Sapwood of Eastern White Pine, Northern Red Oak, Red Maple, and Paper Birch: Implications for Bark- and Wood-Feeding Insects

Abstract

Ultrasonic acoustical emissions (AEs) were recorded from trunk samples of eastern white pine, Pinus strobus L., northern red oak, Quercus rubra L., paper birch, Betula papyrifera Marsh., and red maple, Acer rubrum L., that were cut in winter (February) and allowed to dry indoors. Emission rates were determined for waxed and unwaxed samples at weekly intervals throughout the drying period. Waveform parameters determined for each AE were duration, counts (oscillations above threshold), rise time, amplitude, energy, and average frequency (counts/duration). For all tree species, AE rates from unwaxed samples first increased and then decreased during drying, and they were several times greater than rates for waxed samples. For white pine, mean duration, counts, rise time, amplitude, and energy decreased over time while average frequency increased. Such patterns were often lacking among the three hardwood species. Average waveform parameters differed among species; AEs from white pine were strongest while those from red oak were weakest. Implications for bark- and wood-boring insects are discussed.