Graphic collage of various scenes from the 2003 San Diego Wildfires
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Southern California is characterized by a Mediterranean-type climate, meaning we enjoy a climate typified by cool wet winters and long dry summers. During winter and spring, mild temperatures and precipitation promote abundant vegetation growth. However, during the summer months this abundant vegetation dries out and overtime builds up to create a large amount of dry fuel on the landscape. When these fuels are ignited (either naturally by lightening, or by humans) large expanses of woodland, shrubland and grassland can burn.

As a result, many of San Diego’s habitats are adapted - in one way or another - to living with fire. In general, plants are considered to be fire-adapted if they have traits that allow them to maintain their structure and not be altered by the fire, or that allow them to rapidly regenerate afterwards. Thick bark, for example, allows some trees to resist fire damage. Other traits allow for resilience, or the ability to rapidly recover after being burned. Examples include seeds that germinate only in response to very high temperatures and plants whose underground parts survive and allow for rapid post-fire regeneration by re-sprouting.

It has been a little over a year since the fires of October 2003, and our habitats are already well on the path to recovery. In the first spring after the fires, there was an explosion of wildflowers and other herbs on the burned areas arising from seeds stored in the soil or from underground bulbs. Herbaceous species that were abundant following the October fires include: morning glory, popcorn flower, whispering bells, phacelia, lupine, snapdragon, and mariposa lily.

Each habitat, however, recovers from fire in its’ own way.

 

Beach/Salt Marsh/Lagoon Habitat

San Elijo Lagoon                                    © Bill Wechter

The direct effects of fire on these coastal habitats are negligible, but the indirect effects can be significant. Increased sedimentation due to disturbances in the watershed, such as fire, can result in changes in a lagoon or marsh through closure to ocean tides. Closure of a lagoon or marsh can be detrimental to many resident species, often resulting in their exclusion from the habitat.  However, the fires of 2003 had no direct or significant indirect effects on this habitat.

 

Coastal Sage Scrub Habitat

Photo by Roland Roberge         

         Oak Canyon at Mission Trails Regional Park, two years after the Cedar Fire (April, 2005)          

When a fire burns through coastal sage scrub, the aboveground parts of the majority of the shrubs are consumed. Post-fire recovery occurs through re-sprouting from underground parts (often referred to as root crowns or ligonotubers) and the germination of seeds that are insulated from the fire in the soil or transported into the burn site from unburned areas. The first post-fire season often sees a flush of colorful herbs, some of which are only found following a fire (called fire followers or fire annuals). These species germinate and flower during the first post-fire growing season then the seeds lay dormant in the soil – sometimes for decades – and wait for the next fire.

    

© 2003 Michael Charters   Fire-following annual Phacelia  © 1999 Gerald and Buff Corsi

Many of the same fire annuals found in coastal sage scrub habitats following a burn are also found after fire in chaparral. Vegetation recovery in this habitat to pre-fire conditions typically occurs after approximately five years.  As is the case in all our habitats, there is no single community-wide pattern of recovery representative of all coastal sage scrub communities. Rather, the pattern of recovery varies depending on location, how hot the fire burned, when the last fire occurred, and the season in which it occurred.

Throughout southern California, fires that occur too close together in time (high fire frequency) has contributed to the ‘type-conversion’ of coastal sage scrub to annual grasslands dominated by non-native grasses.  Type-conversion from high frequeny fires also occurs in chaparral habitats. Normally, a fire will occur in coastal sage scrub about every 30 years, but when the interval become every 2-3 years the native shrubs are unable to recover and non-native grasses takeover. Once established, these grasses inhibit the recovery of native species.

 

Photo by Richard Halsey (2004)

Chaparral site located east of the Viejas Casino being type-converted to weedy, non-native

grassland. The far left shows 34 year old chaparral last burned during the 1970 Laguna fire.

The middle/left of the picture shows an area recovering from the Viejas fire of January 3, 2001.

To the right is a portion of the Viejas fire scar reburned in the Cedar fire October, 2003. As you

can see the Cedar fire scar is now filled with non-native grasses. The interval between the

two fires was too short, causing the eliminationof the chaparral shrub community.

                                                                                                       

The coastal sage scrub habitat at Torrey Pines State Reserve is home to one of only two remaining populations of the Torrey pine – the rarest pine species in the country. Torrey pines are fire-intolerant, and mature trees are killed by even low-severity fires. However, cones remain on the fire-killed tree and gradually drop seeds onto the mineral-rich soil following a fire. Cones can remain on a tree and release seeds for up to 15 years. Seedlings grow successfully in the post-fire environment because there is reduced competition from other plants and populations of seed-eating rodents are small.

 

 

Photo by Heather Karnes-Schmalbach                                             © 2000 John Game        

Torrey Pines State Reserve and close-up of Torrey Pine needles and cones.

 

Grassland

Historically, fire was regularly used by Native Americans and early European settlers to convert shrublands into grassland for foraging and grazing purposes. Grasslands are quick to recover following a fire, typically regenerating after the first post-fire year.

 

Photos by Dorothy Leonard

Left: Grassland at Mission Trails Regional Park in December 2003 (2 months after the Cedar Fire).

Right: Same area in April 2004 (almost 6 months following Cedar Fire), showing quick recovery.

2004 - Recovering grassland at the base of Iron Mountain near Poway        Photo by Barbara Barnes

Chaparral

see Fire in Chaparral

 

Chaparral burn-off following Cedar Fire (March, 2004 Cuyamaca Rancho State Park)

 

Photo by Rick Halsey

Chaparral recovery near Green Valley Falls, Rancho Cuyamaca State Park (2004)

 

Oak Woodland

 

Fire is a natural part of California’s oak woodland habitat. Thus, native oak species have evolved mechanisms to survive periodic burning and suffer little long-term damage from the burning of their foliage. Their thick bark offers protection even from high-intensity fires and the trees are able to re- sprout (that is, to grow new stems and leaves) afterwards. Although an oak tree may appear dead (with brown leaves and black bark) following a fire, it may still recover and re-sprout new foliage up to a year after being burned.

Oaks are able to re-sprout from their upper branches and trunk, as well as from their base. If the above ground portion of the tree is completely consumed by a fire most will still re-sprout from the base and, overtime, this results in a mature tree with multiple trunks. How vigorously an oak re-sprouts following a fire depends on the species of oak, its size prior to the fire, and water availability during the recovery phase.

Photo by Barbara Barnes

Coast live oak resprouting from trunk following Cedar fire

(Cuyamaca Rancho State Park, January, 2005)

Photo by Barbara Barnes

Coast live oak resprouting from branches (Cuyamaca Rancho State Park, January, 2005)

Photo by Barbara Barnes

Close-up of recovering Coast live oak (Cuyamaca Rancho State Park, January, 2005)

                        

                       Photo by Barbara Barnes                           

Recovering oaks three year's after Pines Fire (January, 2005 near Ranchita)

 

Riparian (Streamsides)

Fires are rare in riparian habitats. One factor contributing to infrequent fires is the high water content of streamside vegetation, rendering it inflammable under all but the most severe fire weather conditions (e.g. Santa Ana winds). One of the most common streamside trees, Fremont cottonwood, has thin bark and is easily killed by fires. Several other tree species found in this habitat (namely sycamore and willows), however, show some resilience to being burned. Although readily top-killed by fire, these species recover by re-sprouting within a couple of years, but the development of a mature canopy may take a decade or more.

Photo by Heather Karnes-Schmalbach

Sycamore resprouting at Mission Trails Regional Park

following the Cedar Fire (March, 2005)

Streamsides bordered by more fire-prone habitats, such as chaparral or coastal sage scrub, have a greater likelihood of being burned. Fires that occur during the summer when moisture levels are low tend to cause greater tree mortality since less heat energy is required to dry-out plant tissues to the point where they will burn.

When an intense fire does burn through a streamside community, the effects on the stream itself can be significant. The vegetation that borders a stream, or any waterway, serves several important functions: it helps maintain cool water temperatures by providing shade, provides food resources for aquatic wildlife, filters sediment, chemicals and excess nutrients from runoff thereby maintaining water quality, and its roots stabilize banks and prevent erosion. When this vegetation is removed by fire, increases in erosion and water temperatures result in a decrease in water quality and an increase in the likelihood of flooding.

Photo by Dr. Janet Franklin

Severely burned riparian habitat at SDSU's Sky Oaks Field Station after Coyote Fire, 2003

 

Freshwater Marsh/Montane (mountain) Meadows/Vernal Pools

Wetland habitats such as marshes, montane meadows and vernal pools burn relatively infrequently because they are usually wet, and thus may be important in inhibiting the spread of a wildland fire. When these habitats do burn, it is usually during the dry season and the fire spreads from adjacent, more fire-prone vegetation (e.g. coastal sage scrub, chaparral, mixed conifer forest).

Photo by Linnea Spears

Recovering montane meadow in Cuyumaca Rancho State Park after Cedar Fire (June, 2004)

Many marsh and meadow species are able to regenerate through rhizomes (horizontal underground stems that can sprout new stems and roots), allowing them to recover quickly following fires. Studies have also shown that plants and animals found in vernal pools can survive fires that occur during the dry season, when the pool is dried-up and the plant seeds and animal cysts are insulated within the soil. Animal cysts, or ‘resting eggs’, are capable of withstanding both heat and prolonged desiccation and will wait to hatch until water is available.  In a study of the vernal pools found on Naval Air Station Miramar, recovery occurred when the pools filled with water for the first time subsequent to being burned in a wildfire.

Photo by Barbara Barnes 

Recovering meadow on Cuyamaca Peak (West Mesa area) after Cedar Fire (June, 2005)

Mixed Conifer Forest

 

See Fire in Mixed Conifer Forest

            

Photo by Linnea Spears

Conifer burn-off, West Mesa (March, 2004 Cuyamaca Rancho State Park)

Photo by Barbara Barnes 

Panoramic view of burned and surviving conifers, Paso Pacacho area (January, 2005

Cuyamaca Rancho State Park)

Photo by Barbara Barnes 

Blackened Jeffrey pines (January, 2005 Cuyamaca Rancho State Park)

 

Same area in May, 2005 showing  recovering meadow and oaks                                   Photo by Barbara Barnes 

 

Desert

Fire was historically infrequent in most desert shrublands, especially those dominated by creosote bush and saltbush, like those found in the Colorado Desert (Anza Borrego State Park). Estimates of the historical fire regime range from 50 to over 100 years. Thus, little is known about the effects of fire on this habitat. Desert plant communities historically lacked a large grass component, and the native vegetation of these regions did not provide sufficient fuels to carry fire. In addition, the bare spaces between widely dispersed shrubs prevented fires from spreading far beyond points of ignition.

Native perennial shrubs are poorly adapted to fire, as evident in their low rates of recovery. Repeated fires may also be disastrous to some species of cactus, such as barrel cactus whose recovery may take more than 15 years. Frequent fires may gradually reduce succulent populations, although some are able to recover by resprouting. One species in our desert, the California fan palm, benefits from fire through increased fruit production and seedling growth.

 

Photos by Michael Simpson

Left: Resprouting Beavertail cactus nine months after the Coyote Fire (2003) at Sky Oaks Field Station

Right: California Fan Palm, Anza Borrego State Park

With the invasion of species like non-native annual grasses, fuel loads have dramatically increased, the fire cycle has been significantly shortened and fires are more likely to spread. The result has been the conversion of desert scrub landscapes to "weedscapes" dominated by non-native, invasive plants.

The fires of October 2003 had no direct effect on this habitat.

 

Sources:

Brooks, M.L. and D.A. Pyke. 2001. Invasive plants and fire in the deserts of North America. Pages 1-14 in K.E.M. Galley and T.P Wilson (eds.). Proceedings of the Invasive Species Workshop: The Role of Fire in the Control and Spread of Invasive Species. Fire Conference 2000: the First National Congress on Fire Ecology, Prevention, and Management. Miscellaneous Publication No. 11, Tall Timbers Research Station, Tallahassee, FL.

Cox, G. W., & Austin, J. (1990). Impacts of a prescribed burn on vernal pool vegetation at Miramar Naval Air Station, San Diego, California. Bulletin of Southern California Academic Sciences, 89, 67-85.

California coastal sage and chaparral - http://www.worldwildlife.org/wildworld/profiles/terrestrial/na/na1201_full.html (accessed 1/17/2005)

Keeley, J. E., & Keeley, S.C. (1984). Postfire recovery of California coastal sage scrub. American Midland Naturalist, 111, 105-117.

The Living Desert, Plant Fact Sheet - California Fan Palm. http://www.livingdesert.org/plants/california_fan_palm.asp (accessed 4/19/2005)

Lovich J.E. 1999. Human-induced changes in the Mojave and Colorado Desert ecosystems: recovery and restoration potential. In, pp. 529-531, 541-542, M. J. Mac, P. A. Opler, C. E. Puckett Haecker, and P. D. Doran (eds.). Department of the Interior, U.S. Geological Survey, Reston, Virginia. [Book Chapter]

McCreary, D.D. (2004, June). Fire in California’s oak woodlands. Berkeley, CA: University of California Cooperative Extension.

Roberge, R. (2005). Photo of Mission Trails Regional Park. Retrieved April 14, 2005 from Mission Trails Regional Park Online at http://www.mtrp.org/fires.asp

The Nature Conservancy. (2005) Fire management. Retrieved January 17, 2005 from http://tncfire.org/

USDA Forest Service: Fire Effects Information System – http://www.fs.fed.us/database/feis/ (accessed 1/17/2005)

Wells, M. L., Hathaway, S.A., & Simovich, M.A. (1997). Resilience of anostracan cysts to fire. Hydrobiologia, 359, 199-202.

Winter, K. (2004). Expected vegetation recovery of the cedar fire. Forest Biologist, Cleveland National Forest.

World Wildife Fund. (2005). California coastal sage and chaparral. Retrieved January 17, 2005 from worldwildlife.org at http://www.worldwildlife.org/wildworld/profiles/terrestrial/na/na1201_full.html

U.S. Fish & Wildlife Service. (2005). Willow Flycatcher Recovery Plan. Retrieved January 17, 2005 from Arizona Ecological Services Field Office at http://arizonaes.fws.gov/SWWFFINALRecPlan.htm

Photo Credits:

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

Charters, M. (2003). Photo of fire following Phacelia brachyloba. Retrieved April 22, 2005 from from CalPhotos: Plants at http://elib.cs.berkeley.edu/photos/flora/

Corsi, G., & Corsi, B. (1999).Photo of fire following Phacelia brachyloba (California Academy of Sciences). Retrieved April 22, 2005 from from CalPhotos: Plants at http://elib.cs.berkeley.edu/photos/flora/

Franklin, J. (2004). Selected research photograph of Sky Oakes Research Station. Department of Ecology, San Diego State University.

Game, J. (2000). Photo of Torrey pine cone. Retrieved April 22, 2005 from from CalPhotos: Plants at http://elib.cs.berkeley.edu/photos/flora/

Halsey, R.W. (2004). Photograph of Viejas and Green Valley Falls chaparral recovery. Retrieved April 21, 2005 from Sothern California Field Institute at http://www.californiachaparral.com/pages/7/index.htm

Leonard, D. (2004). Photos of Mission Trails Regional Park. Retreived April 16, 2005 from Mission Trails Regional Park Online at http://www.mtrp.org/

Schmalbach, H.K. (2004). Photo of sycamore. Department of Ecology, San Diego State University.

Simpson, M.G. (2005). Photographs of beavertail cactus and fan palms. Retrieved February 23, 2005 from Plants of San Diego County, California, San Diego State University at  http://sci.sdsu.edu/plants/sdpls/indexf/html

Spears, L. (2004). Selected research photographs of Cuyamaca Rancho State Park. Department of Ecology, San Diego State University.

Wechter, B. (2005). Photo of San Elijo Lagoon. Retrieved April 26, 2005 from San Elijo Lagoon Conservancy at http://www.sanelijo.org/index.htm

 

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Copyright 2004 San Diego State University Foundation