Red Fir Roulette

November 6, 2004

    When he was the winter caretaker of the Reds Meadow Resort behind and below Mammoth Mountain, Bob Sollima almost got used to the sound of falling fir trees. Almost.
    These weren’t adolescent trees falling around him. These were the dark reddish brown firs, some as tall as 180 feet, that stand sentry over the centuries in the forests of the Sierra Nevada. When they fall, frequently because of invisible “heart rot,” they command attention, to say the least.
    Sometimes these magnificent trees fall in storms, the sound of the crash mingling with the howling wind to create a truly terrifying aural dissonance. An intrepid backcountry skier, Sollima said that sometimes these towering trees would fall for no visible reason. No one can tell which one will be the next to go. Sollima had a name for the phenomenon: Red Fir Roulette.
    Indeed, to the naked eye, according to forester Scott Kusumoto of the Inyo National Forest, it would be hard to tell which red fir trees are likely to come crashing down to the forest floor.
    “Fir trees have a tendency to develop heart rot within the tree,” Kusumoto said.  “The reason for that could be an injury to the bark, which might introduce fungus into the tree, or from another sort of scar.
    “Insects can allow fungus to infiltrate the tree, too. Or birds creating nesting holes also could lead to decay. Older firs definitely seem to develop decay at the base.”
      Brown rot and white rot are the two general types of wood decay caused by fungi, according to Forest Service pathologists J.W. Kimmey and H.H. Bynum, Jr.
Brown rot results from the action of fungi, which destroys the cellulose and leaves a dry, brown, crumbly mass. Wood containing brown rot, even in the earliest stages of decay, so weakens a tree that it will fail quickly.
    White rot is caused by fungi that destroy both lignin and cellulose. These fungi leave a more or less fibrous residue that may be white, tan, or brownish. As the decay progresses, affected wood often is reduced to a wet, pulpy mass. Later this wood may be completely destroyed, leaving a hollow in the tree.
    White rot is responsible for about four-fifths of the decay loss in red fir and white fir. The percentage of trees affected is impressive.   
According to Kimmey and Bynum, heart rots caused by fungi attacking the heartwood of living trees affect about 13 percent of the total fir population in California.In red fir (Abies magnifica),  heart rot affects about 10 percent of the trees, and in white fir (Abies concolor), about 15 percent.
And if that’s not enough to get you looking over your shoulder, Kusumoto added another warning.
“Depending on soil conditions,” said the Inyo’s Kusumoto, “with a big wind, a green tree is just as likely to fall as a dead one.”

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