Chaparral

Chaparral ecosystems with different names occur in the Mediterranean, South Africa, Chile, Australia, and Mexico. The word “chaparral" is a colloquial adaptation of the original Spanish word, chaparro, meaning "scrub oak" or "dense, low shrub thicket." While the chaparral communities in other parts of the world have the same basic characteristics and very similar adaptations, this article will focus on the chaparral of California and the American Southwest.

Chaparral is an interesting and unique ecosystem. It is an elfin (stunted) forest dependent on fire ecology, and its adaptations to a harsh and variable climate are remarkable. The chaparral’s geology, latitude, altitude, and climate are all related and have played a role in its formation.

In California, the chaparral is located mainly along the central and southern coastal areas, primarily between elevations of 500 and 2,500 feet. It is also found in some areas of the Sierra Nevada foothills, one hundred miles or more inland, and in the lower elevations of some other interior mountains. The geology of most of the areas where this ecosystem occurs is believed to have started with massive upheavals from half a million to ten thousand years ago. The most common substrate was granite. Relentless disintegration resulted in rocky and sandy debris, which would allow increasing amounts of plant life to grow. As the organic matter became more abundant, its debris (leaves, twigs, and decaying dead plants) became more and more mixed into the materials of the granite decomposition. This resulted in a rich, sandy loam.

Chaparral Flora

Because of the cool, moist winters and dry, hot summers, plants evolved to survive these marked changes. In most of the chaparral, there are quite extreme diurnal temperature changes, with fluctuations of fifty to sixty degrees or more. Compounding these harsh conditions are frequent strong, dry winds, often reaching forty miles per hour.

The plants that have become the residents of the chaparral are mainly shrubby, small-leaved evergreens with leathery, thick stems. Shrubs predominate, but there are also small trees, and wildflowers are abundant in many areas. All plants are adapted to conserve water. There is little humus in the soil, which is relatively nutrient-poor. The sandy nature of the soil and the variable periods of dry and sudden rain can cause a quick run-off.

The predominant plants are between three and nine feet tall, with some trees being taller. They hug close to the ground to provide shade. The ratio of the surface area of the leaves and stems to their body mass is reduced, and they tend to have thick, heat-resistant surfaces. Some of the plants are capable of turning their leaves so the edges face the sun, which cuts down the warming effect on their surfaces. All these mechanisms greatly reduce evaporative water loss. Most of the bushes and trees also have unusually long tap roots. A three-foot plant might have a tap root that goes ten or more feet below the surface, enabling it to get more water and nutrients.

The most common plant in the chaparral is the greasewood or chamise bush (Adenostoma fasciculatum). Others that predominate are the Christmas berry toyon (Heteromeles arbutifolia), the coastal sage scrub oak (Quercus dumosa), the Chaparral Yucca (Hesperoyucca whipplei), and the hoary manzanita (Arctostaphylos canescens). The chamise is characterized by numerous small, club-shaped leaves with a waxy substance that protects them from drying. When there is a fire, the chamise burns with intense heat and creates a black smoke (hence the name “greasewood”).

The Role of Fire

The role of fire in the maintenance and regeneration of the chaparral is of paramount importance. The hot, dry summer weather, often fanned by winds, makes the chaparral very prone to fires. Because of the high fuel content in the dense plants, with their waxy and oily components, these fires are very intense and can spread rapidly. Fire is necessary to clear excess growth and allow new seeds to germinate. Indeed, several of the key species need fire to release their seeds, or they will not germinate. The amount and distribution of the canopy fuel can have a marked effect on regrowth and even spatial variation. Naturally recurring fires are usually good for germination. Unusually intense fires, often from years of fire suppression, may do harm by damaging the plants severely.

In much of the chaparral, human interference has allowed the fires to become more damaging when they occur. This creates a difficult paradox since many people now reside in the chaparral, and chaparral fires can spread very rapidly, especially with strong winds. Conversely, in some areas where fire has been controlled, the chaparral has been retreating. A good example of this is on the southern slopes of Mount Tamalpais, a mountain just north of San Francisco.

Fires are important for chaparral plants, but if they occur in intervals shorter than thirty years, the permanent loss of biodiversity becomes more likely. After a fire, the chaparral takes around ten years to regain its healthy state. As climate change causes prolonged droughts, record-high temperatures, and inconsistent precipitation, fires become more frequent, disturbing the ecosystem in potentially irreversible ways. Shrubs, trees, and other plants lose their ability to recover from trauma like drought and fire, and non-native weeds replace the vegetation, which does not support the region's wildlife. Flora and fauna of the chaparral have adapted to survive months of arid, hot weather and relatively slight changes in annual precipitation, but human-caused climate change is threatening species diversity.

Chaparral Fauna

Various reptiles, birds, and mammals make the chaparral their home. They have developed adaptations to survive and thrive in this harsh environment. Several species of skinks, lizards, and a variety of snakes, including gopher snakes, the California king snake, and both the red diamond and western rattlesnakes, are residents. There are dozens of birds, from several species of hummingbirds to the large birds: the turkey vulture, barn owl, roadrunner, and golden eagle. There are many species of rodents, including kangaroo rats, chipmunks, and gophers. The variety of medium to large mammals of common interest is impressive and includes the coyote, gray fox, badger, lynx, bobcat, mountain lion, and mule deer.

Principal Terms

Elfin Forest: a stunted forest growing at high elevations in warm, moist climates

Fire Ecology: an ecosystem that depends on periodic fires to clear underbrush; the seeds of many plants in such an ecosystem require fire in order to germinate

Bibliography

Brown, O. E., and R. A. Minnich. “Fire and Changes in the Creosote Bush Scrub of the Western Sonoran Desert, California.” American Midland Naturalist, vol. 116, no. 2, 1986, pp. 411-22.

“California Chaparral Biome.” California Chaparral Institute, www.californiachaparral.org/chaparral. Accessed 2 July 2023.

Collis, P. H., editor. Dictionary of Ecology and the Environment. 3rd ed., Fitzroy Dearborn, 1998.

Head, W. S. The California Chaparral: An Elfin Forest. 1972. Reprint. Happy Camp, Calif.: Naturegraph, 1998.

Jasson-Holt, Sophie. Unfold the Chaparral. San Francisco State U Chapbook, 1996.

Odion, Dennis C., and Frank W. Davis. “Fire, Soil Heating, and the Formation of Vegetation Patterns in Chaparral.” Ecological Monographs, vol. 70, no. 1, 2000, pp. 149-69.

"Too Many Fires, No Chaparral." California Chaparral Institute, californiachaparral.org/‗‗static/284ae7535b2390a0ff12c7568e29443a/too‗many‗fires‗type‗conversion.pdf. Accessed 20 Sept. 2024.

Underwood, Emma C., et al. "Global Change and the Vulnerability of Chaparral Ecosystems." Bulletin of the Ecological Society of America, 29 Aug. 2024, www.frames.gov/catalog/61103. Accessed 20 Sept. 2024.