Fire on the Mountain

Crown-sprouting 20130817-FS-UNK-0083 by USDAgov

There are few things that inspire more anxiety than the sight of smoke plumes billowing in the sky. After earthquakes, wildfires are the most destructive natural force in California. Last year alone, over a million acres burned here. The fires in LA destroyed 16,255 structures and killed 30 people. We live in a beautiful place, and sometimes we pay a high price for it.

 

The uncomfortable truth is, we're surrounded by chaparral. And chaparral burns. Native tribes knew this and utilized control burns to keep fire manageable. It is generally believed that fires occur every 65 years in coastal areas, and every 30 to 35 years inland (Barro and Conard 1990). While insurance companies may or may not help the humans, natural communities have evolved specific adaptations to regenerate after a fire.

 

Structures in the trunk base called burls safeguard plants like toyon, manzanita, and chamise. Fire stimulates buds within these protective burls to sprout. Many oaks can sprout from their root crowns, the junction between the root and shoot of the plant. They also have extensive root systems, allowing the plant to survive even after the destruction of everything above soil level.

 

A number of our local species have seeds that can lay dormant for long periods and are stimulated to germinate by the chemicals in smoke. Manzanita and chamise are in this category. The Mariposa lily is an example of a "fire follower". The seeds of fire followers lie dormant until fire removes sun-blocking overbrush and enriches the soil.

 

Another common adaptation is fire-resistant bark and/or leaves. Blue oak has a tough fire-resistant bark, which contributes to its wide dispersal in fire prone areas. Have you ever noticed the thick, juicy leaves on a manzanita? Those leaves are filled with water.

 

You may start to notice a pattern emerge. The species that utilize several different mechanisms to ensure survival dominate our area. Here, Coast Live Oak reigns supreme. It has deep roots, thick bark, the ability to crown-sprout, and high moisture content in the leaves, making it less likely to ignite from an ember.

 

The Chimney Fire and other local fires have provided a snapshot of what happens after a burn. In the first few years, annuals thrive on hillsides cleared of litter and excess canopy. A succession of typical chaparral species follows: chamise, sage, buckwheat, poison oak, and bush sunflower. Ceanothus and manzanita will germinate from fire-scarified seeds. Oaks and toyon will sprout from crowns and burls. Within four to ten years, the burn area will once again be dominated by oak, chamise and ceanothus, until the next fire starts the cycle all over again.