Fire danger not reliant on canopy percentage

As a forester who has spent close to four decades working in the forests of Northern California, writing forest management plans for individuals and fire management plans for communities in Trinity County, and helping to manage the Weaverville Community Forest, I read with interest Tom Partin's (president of the American Forest Resource Council) reason for objecting to the Browns Project, namely that "70 percent retention doesn't do the job for wildfire prevention and forest health." Perhaps a few observations from my experience will shed some light on that statement.

In 1999 I worked for two months on the Megram Fire, which burned more than 140,000 acres in western Trinity and eastern Humboldt counties. That fire burned under a variety of weather, topographic and forest fuel conditions. At one point it advanced almost five miles in one day in front of 40 mph winds. That day it burned over Lone Pine Ridge, in a section where the second growth forest had been thinned to an 80 percent canopy closure. Typically ridges are where we would expect the highest fire severity. But on this day the crown fire that killed all trees below the ridge dropped to the ground when it came to the ridge. It proceeded to burn along the ground through the light surface fuels, most of which had been piled and burned following the thinning. The trees were spared.

Near the top of another ridge, an entirely different result occurred in a clearcut where a few very large old growth trees had been left to provide seed for a new crop. Here the fire killed all the big trees in the unit, despite piling and burning of the slash following logging. The canopy retention was less than the 30 to 40 percent Partin thinks is necessary to prevent a crown fire.

The point is that the effects of wildfire are not always predictable based on canopy closure. What we do know is that most crown fires are dependent on surface fires providing heat to keep the fires moving through the canopy. Under unusual weather conditions crown fires will advance through a forest independently of a surface fire, but that is not true for the majority of crown fires.

The Browns Project is mostly located on gentle slopes and flat ridges, areas least likely to experience hot fires. The trees that will be left following thinning of the smaller trees will be larger trees with more fire resistant bark and live branches from 40-60 feet above the ground. The fuels that could carry fire into the upper canopy, the ladder fuels, will be removed and slash will be chipped, burned, or sold as firewood. By leaving a denser canopy, regrowth of shrubs and trees will be hampered by lower light levels and increased competition for soil moisture. It will be impossible for a crown fire to initiate in the resulting forest. And since the fuels have been or are being treated in the community forest surrounding the Browns Project, it is unlikely that wildfires burning into the project area will be hot enough or with high enough flame lengths to initiate a crown fire.

The Browns Project has multiple benefits for the community of Weaverville and for the forest. The original project was modified by the Forest Service based on input from local professional foresters, environmentalists and community members. It is interesting that the two groups that threatened to appeal it are based in Oregon and Montana. Don't they have something better to do with their time and money in their own neck of the woods?