Blaze fierce in CA despite resistant vegetation

As fires cloak the San Gabriel Mountains in southern California, workers are attempting to carry out controlled burns along the perimeter of the fire.

Firefighters battle part of the blaze in Glendale, CA. Photo courtesy Gina Ferazzi for the Los Angeles Times.

These burns will reduce the amount of fuel around the current fire so that if the fire reaches this radius, it will have a higher chance of burning itself out.

The concept of controlled burns has been used by forest managers for decades; these burns help to clear understory brush in areas with thick forest cover so that when naturally-occurring fires erupt, they don’t burn as hot and are easier to contain. But fire is in effect bad for global warming: burning fuel releases carbon into the atmosphere, increasing greenhouse gases.

In a study due out in Frontiers in Ecology and the Environment next month, ecologists attempted to figure out the best scenario that reduces forest understory fuel, but releases less carbon to the atmosphere. Matthew Hurteau of Northern Arizona University and his colleague Malcolm North of the US Forest Service modeled eight different combinations of fire and manual understory thinning on carbon release from forests. They found that low-density forest that’s dominated by fire-resistant trees, such as pines, are the best balance of both worlds for reducing fire severity and keeping carbon in the forest. (See this post for more info on thinning techniques.)

But this vegetation type is common in much of the San Gabriels, which are in many places dominated by spaced-out Jeffrey pines. Yet these fires still burn rampantly, in no small part due to the extreme drought and hot weather in southern California. Models can do their best to predict reality, but in this case environmental pressures seem to override the vegetation type in predicting the spread of this fire.  As the authors write in their paper:

Wildfire effects on forest conditions and C emissions will vary across a burn landscape in response to local fuel conditions and the interaction of fire behavior and weather.

Read more about the fires at the LA Times.

Hurteau, M., & North, M. (2008). Fuel treatment effects on tree-based forest carbon storage and emissions under modeled wildfire scenarios Frontiers in Ecology and the Environment DOI: 10.1890/080049