Biological Sciences, Santa Barbara City College

Biology 100: Concepts of Biology


Adenostoma fasciculatum    Chamise
Chamise, Adenostoma fasciculatum, is an evergreen chaparral shrub in the Rose family (Rosaceae). Chamise brushlands cover about 7,300,000 acres in California. In height, it is between two to twelve feet tall. Leaves are needle-like, about one quarter of an inch long, and clustered on lateral shoots. Chamise is a dicot. It sheds its gray bark in long, thin shreds. Chamise chaparral is one of the hardest plant communities to get through when hiking off-trail.

Stands of pure chamise generally occur on hot, dry, south-facing slopes. (Stands of mixed chaparral are found mainly on north-facing slopes and in ravines). Chamise usually grows in soil that is low in fertility and in areas of rough topography.

When the Chamise is blooming, the slopes of the Santa Barbara frontcountry have a whitish tinge.

 


Four to twelve centimeter clusters of small, white flowers appear from February to July, giving chamise plants a whitish appearance.

 

 

chamise flowers. S Williams photo
The flowers turn rusty brown as they dry up and remain on the plant for most of the summer.

Root systems of chamise are strong and extensive in proportion to its top size, often exceeding 10 feet . There is a tap root, but it is not dominant. The roots do not stop at the topsoil layer, but penetrate into the parent material. Leaf litter is sparse.


Allelopathogens And Herbaceous Growth

Chamise stands generally contain little herbaceous growth, compared to nearby grasslands or woodlands. Normal metabolism results in an accumulation of a water-soluble toxin, or allelopathogen, on the surface of chamise leaves at the top of the plant. Seven to ten years after a fire, allelopathogens created by chamise are dissolved and carried to the soil, where they suppress the growth of other plants. With each rain, new amounts of the toxin are added to the soil. The toxin does not kill directly, but instead suppresses root growth to the point where a slight drought would cause the annual plant to die. The toxin is concentrated in the upper one to three centimeters of soil. Mild heating or exposure to rain and sun can decrease the effectiveness of the toxin. Chamise seeds are inhibited by the toxin, which occurs at its highest levels during the germination period. For this reason, seeds are generally not found in mature chamise stands, but are common after fires.

Other reasons for the lack of herbaceous growth have been suggested. The root biomass is concentrated near the surface, and the roots may prevent herbaceous growth by using the water and nutrients needed by herbs. The density of roots could make chaparral herb growth difficult. Declines in nitrogen and phosphorus in mature chamise stands may also prevent herbaceous growth. Since chaparral soils are porous and shallow, the low water retention capacity could prevent acquisition of nutrients through chaparral herb roots, since nutrient absorption occurs from solution. Herbivory can also limit growth of herbaceous plants.


Chamise And Fire Ecology

Characteristics that make chamise flammable include a high concentration of an oil-like substance and low moisture content during drought. It is this oil-like substance tthat gives chamise its nickname, Greaseweed. Fires occur every 10 to 40 years, and stands over 50 years old are rare.

Fires destroy the stems and foliage above the ground, as well as litter. Large branches are killed, but they remain standing. Increasing fire intensity decreases chamise survival and decreases the number of sprouts on plants that do survive. Plants with fewer resprouts experience an increased mortality rate because the number of sprouts per plant become so small that they can not photosynthesize enough to satisfy the underground respiratory demands. High fire intensity also causes a delay in resprouting. Plants that sprouted out of synchrony with other plants were eaten more often by herbivores.

After a fire, plant growth is slow until the next rainy season. Chamise sprouts from a large basal burl. Crown sprouting is important to the survival of a chamise stand. Only very intense fires destroy the burls.

Heat treatment stimulates germination of seeds of many shrub species, including chamise.Though seed viability is low, shoots grow quickly from a large basal burl. Grasses and fire annuals also begin to grow shortly after fires. Plant species establishment occurs during the first year after a fire, and all species that will be present in the mature community are present at this time. Seedling establishment during the first year does not guarantee survival into the mature stand. Diversity of seedlings is highest during the first and second years after a fire.


Relationships With Animals And Other Plants

Herbivorous insects have little effect on chamise seedlings and small animals cause nearly all damage. Rabbits sometimes graze the resprouting shoots of chamise to less that one centimeter.

Chamise provides cover and food for deer. Deer prefer mixed chaparral, since it provides a wide variety of forage and greater seasonal choice. New shoot growth of Chamise is one of the more palatable plant species for deer. After fires, deer populations increase by a factor of four and jack rabbits by a factor of 5 to 10.

Birds are sparse in pure strands of chamise. Higher species richness and higher bird densities are found in areas with greater complexity of vegetation.


Medicinal Uses of Chamise

Spanish-Mexicans called chamise "Yerba del Pasmo", which means "herb of the spasm". They, and the Native Americans, found it to be a good remedy for colds, convulsions, snake bites, cramps, lockjaw, and inflammations. The foliage, when fried in grease becomes a healing ointment. Native Americans also used infusion of bark and leaves as a cure for syphilis. A scale insect on the plant was used to bind arrows and baskets. (Parsons, 1897)

Abridged from http://www.geocities.com/RainForest/Vines/8620/chamise1.html


Copyright 2010  
Return to previous page
 Go Back  Top