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Ecology and Epidemiology

Electrical Properties and Rate of Decay in Spruce and Fir Wood. Walter C. Shortle, Research plant pathologist, U.S. Department of Agriculture, Forest Service, P.O. Box 640, Durham, NH 03824; Kevin T. Smith, Postdoctoral research fellow, Department of Botany and Plant Pathology, University of New Hampshire, Durham. Phytopathology 77:811-814. Accepted for publication 21 October 1986. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1987. DOI: 10.1094/Phyto-77-811.

Electrical resistance measurements were related to both the occurrence of discolored and decayed wood in red spruce (Picea rubens) and balsam fir (Abies balsamea) sites and the rates of decay in balsam fir in vitro. Internal electrical resistance (R_i) of spruce and fir was measured for three sites per species and one mixed spruce-fir site in Maine and New Hampshire. Spruce with R_i > 250 kΩ (low ionization) had no discolored or decayed wood in stem cross sections at 140 cm above groundline. Within fir sites, as the percentage of trees with R_i < 100 kΩ (high ionization) increased, the mean cross-sectional area of discolored and decayed wood also increased. Electrical properties of aqueous extracts from various types of balsam fir wood were associated with different rates of decay caused by Haematostereum sanguinolentum and other fungi in vitro. Wood located interior to sapwood, nondiscolored, and of relatively low ionization decayed at the slowest rate. Visibly identical wood with relatively high ionization decayed at a faster rate, equal to the rate of decay by H. sanguinolentum of discolored wood. As wood became more altered as a result of the decay process in living trees, rates of decay by tree decay pathogens increased in vitro.