Plant collage
 
 

Plants At Torrey Pines State Natural Reserve

by William Brothers and Rick Halsey

Vegetation Communities | Coastal Strand | Coastal Sage Scrub
Chaparral
| Torrey Pine Woodland | Salt Marsh

Climatic Conditions

The coastal strip of San Diego has a long growing season resulting from its maritime influences and Mediterranean climate of mild wet winters and warm dry summers. The temperature ranges from a January minimum of 45F to an August maximum of 80F, with a yearly average of 62F. The majority of rainfall comes during the winter and early spring, with a seasonal average of less than ten inches. Blankets of coastal fog also add moisture to this semiarid desert environment via the condensation of water on the plants and soil. Fog also increases the humidity of the air, lowering the plants' evaporation rate, which is especially vital during summer. It is common for fog to persist the entire day along the coast while temperatures inland soar, especially during June and July.
Wild flowers
Photo by Eva Armi

A unique climatic condition in Southern California is caused by the Santa Ana winds. These dry and usually warm winds blow fiercely from the East, especially in autumn. They are quite effective in drying out the vegetation. The winds along with the dry vegetation are responsible for feeding the infamous fires of the chaparral vegetation.

The plant communities discussed below include the coastal strand, coastal sage scrub, chaparral, Torrey pine woodland, and salt marsh. The riparian and freshwater marsh communities are not included, even though they slice through the coastal strip at various locations.

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Vegetation Communities

The vegetation of coastal San Diego is categorized into plant communities. Each community contains specific plants adapted to the physical, chemical, and biological parameters of their microenvironments. Specific parameters include temperature, solar radiation, wind exposure, soil composition, salinity, moisture, and types of interacting organisms present. The boundaries between plant communities are not distinct but overlap into neighboring communities. An example is the intermingling of plants from the coastal sage scrub and chaparral communities.

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Coastal Strand

The sandy beaches and sand dunes of the coastal strand plant community encounter the edge of the sea. This arrangement creates a harsh environment for plant growth and survival because of persistent winds laden with salt and sand. The forever shifting sands with their poor water-holding ability and low fertility also stress plants. The few species adapted to this region are usually prostrate and have creeping stems which can root at their nodes. These features aid in anchoring the plant with its continuous lateral growth into large colonies. Some plant species contain deep tap roots, which serve the dual purpose of anchoring the plant to the soil and in acquiring water.

The presence of pubescent or fuzzy leaves on some species serves as a surface for water condensation, which nourishes the plant and reduces water loss by lowering the effects of evaporation. Water is also stored in the succulent leaves and stems of some plants.

The major species in this plant community are Sand Verbena (Abronia umbellata); Beach Primrose (Camissonia cheiranthifolia); and Sea Rocket (Cakile maritima).

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Coastal Sage Scrub

The coastal strip of San Diego has a long growing season resulting from its maritime influences and Mediterranean climate of mild wet winters and warm dry summers. The temperature ranges from a January minimum of 45 F to an August maximum of 80 F, with a yearly average of 62F. The majority of rainfall comes during the winter and early spring, with a seasonal average of less than ten inches. Blankets of coastal fog also add moisture to this semiarid desert environment via the condensation of water on the plants and soil. Fog also increases the humidity of the air, lowering the plants' evaporation rate, which is especially vital during summer. It is common for fog to persist the entire day along the coast while temperatures inland soar, especially during June and July.
Cactus
Photo by Stephen Bowers
Coastal Prickly Pear ( Opuntia littoralis)

Coastal sage scrub plants are typically low-growing, nonscleraphyllous (soft) shrubs with many brittle branches and are sometimes referred to as soft chaparral. The roots of these plants exploit the upper soil layers for moisture, allowing for rapid growth after winter rainfall. Their growing season is usually longer than that for typical chaparral plants. Some species survive the dry summers and autumns by utilizing water from their succulent vegetation or by dropping their water-demanding leaves. At this time these deciduous plants may appear as dried dead bundles only to spring back to life with green foliage during the rainy season.

The dominant shrubs in this community are: California Sagebrush(Artemisia californica); California Buckwheat (Eriogunum fasciculatum); Black Sage (Salvia melifera); Deerweed (Lotus scoparius); Bush Sunflower (Encelia californica); Lemonadeberry (Rhus integrifolia) which is also a plant of the chaparral; Live Forevers (Dudleya spp.); Coastal Prickly Pear (Opuntia littoralis); and Bladderpod (Isomeris arborea).

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Chaparral

Coastal Chaparral
Photo by Rick Halsey

The chaparral plant community normally inhabits the mesas and mountain slopes of the interior but also intermingles with the coastal sage scrub community along the coast, particularly on mesas and north-facing slopes where moisture is more plentiful. This community is composed of mainly sclerophyllous (meaning “hard-leaved” in Greek) shrubs with distinctive small, thick evergreen leaves which persist on the shrub for several years.

Chaparral sometimes forms an impenetrable thicket of vegetation with a large canopy five to fifteen feet high. This elfin forest lacks herbaceous understudy and is a haven for fauna and adventurous children who love to explore. Chaparral is California’s most extensive and characteristic plant community. 

Chaparral is drought tolerant and has special adaptations to survive wildfires. Some shrubs, such as laurel sumac, live through the hot summer droughts by utilizing extensive root systems for gathering water deep underground. Others, such as California lilac, have shallow roots and smaller leaves with the ability to tolerate extreme water loss. Some chaparral species, like lemonade berry, have a waxy coating on their leaves which reduces water loss through evaporation. The chaparral community has been shaped by recurring wildfires, but is extremely sensitive to when and how frequently fires occur. Richard Halsey, a fire ecologist from the California Chaparral Field Institute, www.californiachaparral.com, says that, “Fire in the chaparral should be viewed as a disruptive force leading to the selection of fire survival strategies. For example, the seeds of many chaparral plant species require heat, smoke, or charred wood to stimulate germination. Does this mean the chaparral “needs” to burn? Not at all. Chaparral remains a vigorous plant community between fire events no matter its age.  Old-growth chaparral (75 years plus) continues to grow and support a dynamic population of animals.  Chaparral plants have evolved fire-related adaptations in order to survive and carry on AFTER a fire, not because they need to burn. If fires come too frequently, less than 20 years apart, the chaparral ecosystem can be converted to a weedy grassland dominated by invasive, non-native species.”

Torrey Pines State Natural Reserve has a very special and rare form of chaparral called maritime chaparral. It is has been shaped by ocean winds and the extra moisture it obtains from coastal fog. As you explore the Reserve, look for rounded hummocks of chamise overlooking the ocean and old, twisted California scrub oaks forming tunnels through which some trails meander.

The major shrubs of the chaparral are chamise (Adenostoma fasciculatum); manzanita (Arctostaphylos spp); Nuttal’s scrub oak (Quercus dumosa); ceanothus (Ceanothus spp); toyon (Heteromeles arbutifolia); and mountain mahogany (Cercocarpus minutifolus). The Nuttal’s scrub oak and warty-stemmed ceanothus (Ceanothus verrucosus) are characteristic of the Torrey Pines’ maritime chaparral plant community.

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Torrey Pine Woodland

Torrey Pines Woodland

Photo by Roger Isaacson

The Torrey pine (Pinus torreyana) is the most restricted and rarest pine in North America. It grows in the Torrey pine woodland or Pacific coniferous forest. This pine is probably the remnant of an ancient coastal forest which has been reduced during the drying period of the last ten thousand years to the sandy soils of the sandstone bluffs and ravines of Torrey Pines State Natural Reserve and Santa Rosa Island. Extensive root systems and blankets of summer fog aid in the tree's survival and propagation. The trees along the bluff are twisted and gnarled into spectacular shapes by the omnipresent winds, while those which are sheltered are more robust and erect.
The vegetation associated with the Torrey pine woodland is a mixture of plants from the coastal sage scrub and chaparral plant communities. Further studies need to be undertaken to examine the woodland microclimate and plants normally absent from the previous two plant communities.

External link to 2010 Tree Census Study

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Salt Marsh

The coastal strip of San Diego has a long growing season resulting from its maritime influences and Mediterranean climate of mild wet winters and warm dry summers. The temperature ranges from a January minimum of 45F to an August maximum of 80F, with a yearly average of 62F. The majority of rainfall comes during the winter and early spring, with a seasonal average of less than ten inches.

Salt Marsh
Photo by Stephen Bowers
Salt Marsh

Blankets of coastal fog also add moisture to this semiarid desert environment via the condensation of water on the plants and soil. Fog also increases the humidity of the air, lowering the plants' evaporation rate, which is especially vital during summer. It is common for fog to persist the entire day along the coast while temperatures inland soar, especially during June and July.

These environmental conditions vary as the marsh transforms into upland plant communities. Thus, a vertical pattern of plant distribution occurs, with different species being abundant in different zones.

The salt marsh is a highly productive ecosystem, making it an extremely important wildlife habitat. It serves as a nursery for fish and shellfish and a feeding and nesting ground for resident and migratory birds.

The common species include Salt Grass (Distichlis spicata); Pacific Pickleweed (Sarcocornia pacifica); Parish's Pickleweed (Anthrocnemum subterminale); Pickleweed (Salicornia depressa); Alkali Heath (Frankenia grandifolia); and various species in the amaranth family.

Updated 05 May 2011

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Aerial photos of Torrey Pines State Beach
 

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