On Topanga Canyon Road in the Santa Monica Mountains, January 9, 2005. After nearly 16 inches of rain, the boulder fell about 30 feet from its original position. AP Photo/Damian Dovarganes.
California State Rock!
Serpentine, a metamorphic rock found in central and northern California, produces soil that is inhospitalable to many plants. What plant community can thrive on it? Chaparral!
Don't Take Schist for Granite!
When exposed to heat and pressure deep underground, the igneous rock granite (top) can be changed (metamorphized)
into schist (bottom).
Geology is one major reasons why species richness in California
is about seven times higher than anywhere in the U.S.
Geology provides a laboratory for diversity!
With its characteristic thin, red bark and urn-shaped flowers, the genus Arctostaphylos is remarkably adaptable. It is a major component of the montane chaparral community, growing in granitic soils above 1400 m with an average annual rainfall over 90 cm, as well as in sandy soils found in the southern maritime chaparral of Del Mar, California, with an average annual rainfall of 33 cm.
The threatened endemic Ione manzanita (Artostaphylos myrtifolia) is mostly restricted to a narrow corridor in Amador County, California, where it grows in acidic soils with high aluminum content (see images below).
Within a 35 km diameter circle, centered near San Luis Obispo on California’s central coast, one can find seven localized endemic species of manzanita (Arctostaphylos obispoensis, A. pilosula, A. luciana, A. rudis, A. pechoensis, A. osoensis, and A. morroensis). Similar to Ione manzanita, these seven species are confined to edaphic “islands,” outcroppings of particular soil types (serpentine, Monterey shale, granitic, and Pleistocene sands) where chaparral is typically found among a landscape of forest, coastal scrub, and grassland. See map.
These islands may have served as genetic reservoirs for the genus, with different species migrating onto and off the soils during the numerous Ice Ages.
Map from Field Guide to Manzanitas by Kauffmann, Parker, Vasey (2015).
The Endemic Manzanitas and Friends
Tom Parker and Mike Vasey, manzanita experts par excellence. More from Dr. Parker and the amazing midnight marauders here.
Del Mar manzanita grows in nutrient poor sandstone soils in San Diego County. It is a federally listed Endangered Species.
A solitary manzanita making a living through a small crack in this huge granite boulder in the Sierra Nevada. Photo: Tom Barr.
Serpentine soil, with toxic levels of nickel, chromium, and cobalt, is a tough one to grow in, but that also provides lots of opportunities for the chaparral to create endemic species. To the left is a yerba santa shrub struggling to thrive on near solid serpentine. In the background, right, are mounds of chamise and manzanita.
Ione manzanita adapts to hostile soils
Growing in oxisol soil rarely found outside of tropical areas, the Endangered Ione manzanita (Arctostaphylos myrtifolia) survives on a geologic island of about 1,000 acres in north central California. Oxisols have high concentrations of iron and aluminum oxides and hydroxides, hence their characteristic reddish - yellowish colors. The Endangered Ione buckwheat (Erigonium apricum) is also restricted to this area.
The tiny leaves of Ione manzanita (Arctostaphylos myrtifolia) and the red nascent Inflorescences (early flower buds) catch the early morning light.
The extremely hard "ironstone" covering of the Ione soil deposit makes it difficult for plants to establish themselves. Here is an Ione manzanita (Arctostaphylos myrtifolia) struggling to gain a foothold.
The strange, sandy terrain of the Ione region. The primary material being mined was lignite (a form of coal) that contained montan wax that was used in making carbon paper, phonograph records, polishes, and a rubber wax used for industrial purposes. Also, silica and quartz sands from the white kaolinite were extracted here.
Pollution from surface mining in the Ione area colors water deposits that have collected in open mining pits a light blue. The white deposit is kaolinite, high in aluminum and silica. In the foreground is whiteleaf manzanita (Arctostaphylos viscida). Arctostaphylos manzanita is nearby on more normal soils mixed with oaks.
Fungal infections are causing havoc for Ione manzanitas. A branch canker caused by a species of Fusicoccum, including F. aesculi, causes some mortality. But it's the root and crown rot caused by Phytophthora cinnamomi that's responsible for destroying entire stands of Ione manzanita, preventing its regrowth in patches of infested soil. Note dying shrubs and bare soil.
A healthy stand of Ione manzanita.
Interesting papers on the impact of soils on chaparral plant communities:
A geographical area where any water spilled will eventually end up in the same place
Everyone resides within a particular watershed, and everything we do affects the watershed we live in. Water sheds can be seen as an organizing principal in maintaining healthy ecosystems and human communities. Find your own watershed and start a movement! Keep our home watershed safe, clean, and ecologically healthy - meaning, protect California's most important watershed cover, the chaparral!
Watersheds of the United States. You can obtain a detailed, high resolution copy of this remarkable map here. Notice the massive watershed of the
Missouri and Mississippi Rivers (pink) in the central part of the United States.
Detail of California's watersheds. Notice the large number of separate watersheds along the coast. This is why there once were so many natural estuaries in California. Only a few remain, many in San Diego County.
An example detail of local watersheds, in this case, coastal San Diego County.