In mid-September, I got tired of the never-ending heat in Tucson, and escaped to the White Mountains in east-central Arizona. I spent a few days camping at lovely Luna Lake, and spent my time poking around in the forest. A huge wildfire had engulfed this place just over a year before. As far as I could see, the forest had burned – 841 square miles in total. But like most wildfire, it was patchy, some places were skipped, some burned lightly, and in some places the trees, shrubs, and ground were torched to blackness. It was fascinating to see the recovery (or not) after one rainy season, a snowy winter, and another rainy season. Most places were carpeted with lush grasses and wildflowers. Some of the aspen stands were resprouting, with baby aspens densely covering the ground a yard deep.
One day I hiked up Escudilla Peak, the 3rd highest mountain in Arizona. I hiked through aspen, aspen, and more aspen. From the lookout at the top of the mountain, I looked out over the most extensive aspen stands I’ve ever seen. Most of the aspen was black. Walking through the dense forests of blackened trees was almost magical. It was very quiet, except for the popping sounds of the aspen bark splitting and falling to the ground. The fluttering of aspen leaves was absent. The occasional bird flitted through but did not stay. But other wildlife sign was abundant: elk came in to forage on fireweed and lick up the ash; black bears left sooty footprints on almost every aspen with bark already peeled (licking sap?). A variety of wildflowers poked up through the ash and charcoal.
The contrast in sound between the dead forest and a living aspen forest not far away was remarkable. To me, it was all the more remarkable for its ephemeralness. The popping of the bark on the dead aspens was a rare sound; only occurring after the trees had been dead for a particular time. This winter’s snows and winds will likely peel the remaining bark off of the trees. Perhaps the sound next year will be the groaning and crashing of falling trees.
The expansiveness of the aspen stands, and their vigorous regrowth following the fire made me ponder the evolution of these high altitude forests. Current federal forest policy is predicated on the idea that reduction of fire due to suppression and grazing during the last 120 years has led to an overgrowth of the forest, which is promoting the major wildfires we’ve seen in the last 10 years or so. But when I look around and see the extensiveness of the aspen, it looks to me like a catastrophic wildfire went through here some 100-150 years ago or more. The aspen stands may have been created (and destroyed and created and destroyed) by catastrophic wildfire as much as by more frequent low-intensity fires. I believe that as long as their has been drought in the southwest, there has been catastrophic wildfire.
A recent article in the New York Times highlights research that comes to a similar conclusion (https://www.nytimes.com/2012/09/18/science/earth/forest-survey-questions-effect-of-prescribed-burns.html?pagewanted=1&_r=1).
The article hints at, but doesn’t elucidate, a simple statistical artifact of using tree ring data to estimate fire frequency. Catastrophic fires that killed trees often burned up the evidence of their passing. Only the trees that survived the low-intensity fires persisted to be sampled, thus creating a biased sample. Dead men tell no tales.
Recording notes: Dead aspen recorded with a Zoom H4n. Recording amplified and subject to high-pass filtering to remove a little wind noise. Live aspen recorded with Zoom H4n and Audio-technica AT2022 with FEL SK3 pre-amp. Recording subject to high-pass filtering to remove a little wind noise.