Abstract
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 (Ri) of spruce and fir was measured for three sites per species and one mixed spruce-fir site in Maine and New Hampshire. Spruce with Ri > 250 k.OMEGA. (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 Ri < 100 k.OMEGA. (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.

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