Graphic collage of various scenes from the 2003 San Diego Wildfires
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Chaparral canyon fire near Rancho Peñasquitas (1995)                               Photo by Rick Halsey

Although many chaparral plant species require some fire cue (heat, smoke, or charred wood) for germination, chaparral is not “adapted” to fire per se. Rather, individual species are adapted to particular fire regimes involving season, frequency, intensity, and severity of the burn.  Despite fire based regeneration requirements of some indvidual species, the chaparral community itself is extraordinarily resilient to very long periods without fire. Old-growth chaparral in excess of one hundred years old remains a productive, dynamic ecosystem.  In fact, seeds of many chaparral plants actually require 30 years or more worth of accumulated leaf litter before they will successfully germinate.

 

        Photo May, 2002 by Isabelle Kay

Camp Elliot Chaparral Reserve (near Miramar Marine Airbase)  -- before Cedar fire

Photo November 3, 2003 by Isabelle Kay

Camp Elliot Chaparral Reserve -- after Cedar fire      

Photo November 3, 2003 by Isabelle Kay

Camp Elliot Chaparral Reserve looking NW at Scripps Ranch. Pinapple looking plants are yucca that

survived the fire (90% survival rate) and are now flourishing.                  

In responding to fire, chaparral shrubs and herbaceous perennials can be classified into five different groups, each with its own survival strategy:

Obligate resprouters: Survive fires by resprouting only (toyon and scrub oak).

Toyon resprouting from base                                  Photo by Rick Halsey

Scrub oak resprouting from base                             Photo by Rick Halsey

Obligate seeders: Adult plants die in fire. Seeds require a fire cue to germinate (ceanothus).

Photo by Rick Halsey

Ceanothus seedlings following the Cedar fire

Endemic fire followers: Annuals. Seeds require a fire cue to germinate (whispering bells).

Photo by Rick Halsey

Whispering bells

Facultative seeders: Adult plant resprouts and seed germination is enhanced by some fire cue (chamise).

Mature chamise and seedlings                  Photo by Rick Halsey

Frequent fire followers: Annuals. Seed germination enhanced by some fire cue (snapdragon).

Snapdragon                                                 Photo by Rick Halsey

The search to discover the dynamics of post-fire germination is an amazing story involving both scientific discipline and imagination. The first species to be shown to respond to charred wood was whispering bells in 1977 by D.T. Wicklow. Obligate seeding shrubs, such as the majority of ceanothus and manzanita species, could be considered the true “chaparralians” because their life cycle requires a fire regime specific to the chaparral ecosystem. There are other plants that retain their secrets.  For example, mission manzanita may or may not require some fire cue for germination. The species commonly resprouts, but seedlings of the species appear to be non-existent or extremely rare in both mature chaparral stands and post-fire environments.  Whether something in the environment has changed enough to prevent germination or there are other mechanisms involved we do not know.

Banner Grade chaparral recovery (April, 2005)                                                    Photo by Barbara Barnes

The idea that older chaparral is responsible for causing large fires is related to one of the most repeated misconceptions regarding the system: past fire suppression efforts have allowed an “unnatural” accumulation of brush to develop within the chaparral, leading to huge, catastrophic wildfires. This belief appears to be based on the misapplication of studies relating to dry ponderosa pine forests showing that undergrowth has increased over the past century due to successful fire fighting activities. In the past, surface fires burned through these forests at intervals anywhere between 4 to 36 years, clearing out the understory and creating a more ecologically balanced system.  However, this conclusion has nothing to do with California shrublands.

Detailed analysis of historical fire data has shown that not only have fire suppression activities failed to exclude fire from southern California chaparral as they have in ponderosa pine forests, but the number of fires is actually increasing in step with population growth. Whenever chaparral burns, everything goes, no matter the age. This is characteristic of a crown fire regime as opposed to the surface fire type found in ponderosa forests. A young, 5-year-old stand of chaparral has already produced more than enough material to fuel and carry a wildfire across the landscape during extreme, Santa Ana wind conditions when all catastrophic fires occur. Overall, how old a recovered chaparral stand happens to be has very little to do with its chances of burning. Weather is the primary determinate in both fire size and spread.

Understanding the chaparral’s relationship to fire is important because the system is incredibly sensitive to increased fire frequency. If the public thinks chaparral needs to burn and that older stands are unhealthy, it will lead to land management policies that could threaten the system’s continued existence. If the interval between fires drops below 10 to 15 years, many plant species are eliminated and chaparral is destroyed, typically being replaced by non-native, weedy grassland.

Old-growth chaparral stands represent some of the region’s most valuable natural resources and need to be protected. Although there are still large tracks of chaparral throughout California, the combination of increased fire frequency and development will seriously compromise the ecosystem’s health and integrity over the next century. As California’s population continues to grow, available flatland is quickly diminishing and developers are spying the backcountry for additional building opportunities. Considering development, increased fire frequency and the possibility of continued drought conditions, the future looks extremely difficult for southern California’s remaining stands of native chaparral.

Photo Credits:

Barnes, B. (2005). Assorted photographs from San Diego County, 2005. WhiteSage Cafe@AOL.com

Kay, I. (2002-2003). Photographs of Camp Elliot Chaparral Reserve. Retrieved March  20, 2005 from Daniel Udovic's Photo Gallery of post-fire recovery of an obligate plant-pollinator mutualism at http://yucca.uoregon.edu/wildfires.html

Halsey, R.W. (2005). Photos of Rancho Peñasquitos, toyon, scrub oak, ceanothus, chamise. Retrieved April 24, 2005 from Southern California Chaparral Field Institute at http://www.californiachaparral.com/pages/1/index.htm

Halsey, R.W. (2005). Photos of snapdragon and whispersing bells. In Fire, chaparral, and survival in Southern California. San Diego, CA: Sunbelt Publications.

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Copyright 2004 San Diego State University Foundation