Category Archives: nature

Chaparral Freeze

Freeze damaged Laurel Sumac in Malibu Creek State Park.

Updated March 6, 2007

As evidenced by their survival, native plants are generally well adapted to the environment in which they live. Fire, flood, drought, heat or cold, they’ve seen it all – or nearly so.

On January 14, 2007 many new record low temperatures for the date were set in the Southern California area. Several locations in the San Fernando Valley recorded temperatures in the 20’s. Pierce College in Woodland Hills plunged to a record low of 20°F (-6.7°C).

The freezing temperatures resulted in extensive damage to fruit crops, nursery stock, and landscaping. The brown leaves of freeze damaged shrubs, trees and other plants are a common sight in the Los Angeles suburbs.

Since the freeze, I’ve run in several areas of the Santa Monica Mountains, Santa Susana Mountains and Simi Hills, and most native chaparral shrubs appeared to have weathered the cold temperatures well, exhibiting very minor, if any, visible damage. However, there are some exceptions.

One obvious exception is laurel sumac (Malosma laurina). I first noticed instances of laurel sumac with damaged leaves and stems on a run at Sage Ranch on January 24. Initially, I thought the damage might be limited to sprouting laurel sumac in the 2005 Topanga Fire burn area, but on subsequent runs damaged plants were seen in several areas unaffected by the fire, including Topanga and Malibu Creek State Parks. Now that the dead leaves and stems have turned brown, the affected plants stand out in the chaparral, and the extent of the damage is easy to see.

The sensitivity of Laurel Sumac and other chaparral plants to freezing temperatures and drought has been studied extensively by Dr. Stephen Davis of Pepperdine University’s Seaver College Biology Department. This research confirms that the leaves and stems of laurel sumac are not as tolerent of freezing temperatures as some other chaparral shrubs. This reduced tolerance probably affects the distribution of the plant, favoring its growth in warmer coastal locations and inland microclimates.

Dr. Davis reports that, in addition to laurel sumac, other species that have been damaged at the lower, colder distributions in the Santa Monica Mountains include green bark ceanothus (Ceanothus spinosis), big pod ceanothus (Ceanothus megacarpus), sugar bush (Rhus ovata), and some hairy-leaf ceanothus (Ceanothus oliganthus). The lowest temperature recorded at his field sites was 10.4°F (-12°C).

A factor in the damage is that the freeze occurred during a period of relative drought. As of January 14, Downtown Los Angeles (USC) had recorded only 1.31 inches of rain since (but not including) May 22, 2006 – a period of nearly 8 months.

Although some of laurel sumac’s adaptations to fire and drought may adversely affect the resistance of its foliage to freezing temperatures, it is precisely these adaptations that will enable most of the freeze damaged laurel sumacs to resprout and survive.

The photograph of freeze damaged Laurel Sumac was taken on the Backbone, Bulldog & Beyond run.

Shooting Stars

Shooting stars (Dodecatheon clevelandii) at Sage Ranch Park, in the Simi Hills, northwest of Los Angeles.

Shooting stars are among the first wildflowers to bloom following soaking Winter rains. These appear to be Dodecatheon clevelandii ssp. patulum.

The flowers produce a semitransparent, otherworldly seed capsule that traps moisture. This is an adaptation to an environment that may be cool and damp one day, and then hot and dry just a few days later.

From a run at Sage Ranch Park.

A La Nina During an El Nino?

Grass along the margins of the main drag in Upper Las Virgenes Canyon Open Space Preserve,formerly Ahmanson Ranch.

Sporadic rain in the Los Angeles area has finally produced a little green in local open space areas. Here, along the margins of the “main drag” in Upper Las Virgenes Canyon Open Space Preserve (formerly Ahmanson Ranch).

As of today, (preliminary) NWS climate data indicates Downtown Los Angeles (USC) has recorded 1.92 inches of rain since July 1. This is 7.31 inches below normal. Leafing back through weather service data prior to July 1, this is the total rainfall recorded since May 22, 2006 – a period of nearly nine months.

What happened to our El Nino rains? According to NWS scientist Ed Berry, “the global circulation has been generally La-Nina like since about late November.” This is despite an El Nino event that peaked in November or December, and persisted at moderate strength into January. See his blog Atmospheric Insights for the technical details.

A period of unsettled – possibly showery – weather is forecast for the Los Angeles area beginning Sunday evening and continuing pretty much through the week. At the moment* the best chance for measurable rain appears to be on Monday and Thursday. We’ll see!

*Updated Saturday, February 17, at about 11:00 a.m.

Related posts: The Color of Rain, El Nino Drought, Sunset Snow Shower, Rainy Morning on Rocky Peak Road.

Sunset Snow Shower

Low angle rays of the setting sun highlight a snow shower over the Rocky Peak

When I heard the news reports of snow in the Santa Monica Mountains along Kanan-Dume road near Malibu, I hoped to find a little snow or hail up at Sage Ranch Park on my afternoon run.

The isolated snow showers, hail and sleet were produced by convective cells that developed as a result of instability associated with a passing upper level low. Some of these cells also generated some lightning and thunder.

There was no snow on the ground at Sage Ranch, but the low angle rays of the setting sun did highlight a snow shower over the Rocky Peak Park area. In March of last year there was snow at Sage Ranch and Rocky Peak.

Related posts: Chumash Trail Snow, Oat Mountain Snow, San Fernando Valley from Rocky Peak.