Figure 2. Salt Marsh plants
At first glance, the plant life of the Torrey Pines Lagoon appears to be unexciting. The salt marsh plants are almost all low growing and lacking in brightly colored flowers. These drab looking plants, however, merit far greater attention than they normally receive because they exhibit some beautiful examples of ecological adaptation. Existing midway between the marine environment of seaweeds and the land environment of the upland scrub, the salt marsh plants have evolved the ability to cope with both salt water submergence and long hours of exposure to sun and wind.
The key to the success of salt marsh plants is their ability to thrive in highly saline soil. Unlike their upland ancestors, which cannot survive if the salinity of the soil water rises above 5 %, the salt marsh plants may grow in soil salinities of up to 80%. Some species, such as Salt Grass and Glasswort, can survive even in environments where the soil surface is covered with a crust of salt crystals.
These salt marsh plants have adopted several different devices to enable them to overcome adverse salinity. Many species dilute the salt in their cells by storing large amounts of water; as a consequence, the plants are fleshy and resemble desert succulents rather than plants of an aquatic environment. Other salt marsh species rid themselves of salt by pumping it out through tiny glands that cover their leaves. A few of these plants store salt in their lower leaves, which are subsequently shed.
Figure 3. Pickleweed, a characteristic plant of the lagoon.
Another important adaptation of salt marsh plants is their ability to tolerate the water-logged, clayey marsh soils that are frequently deficient in oxygen. Many of the salt marsh plants store air in large spaces in their roots and underground stems; some appear to have an internal ventilation system through which oxygen travels from the leaves to the smallest rootlets. The spreading underground network of salt marsh plant roots plays an important role in binding the muddy sediments of the marshland, thus preventing rapid erosion. Approximately 30 species of salt marsh plants occur in Los Peñasquitos Lagoon. These species tend to be grouped into contoured zones or belts of vegetation that correspond with average tidal levels in the marsh (Figure 2). At the lowest tidal level in Los Peñasquitos salt marsh (closest to the lagoon channels), an abundance of Pickleweed (Figure 3) and patches of Alkali Heath are found. The Pickleweed (and related Salicornia, Sarcocornia, and Anthrocnemum species) has succulent, jointed stems and tiny leaves that are reduced to membrane fringed triangles clasping the stem nodes. The flowers are minute and remain more or less embedded in the fleshy stems; only the yellow pollen sacs and the delicate white pollen receiving stigmas emerge from the stem, turning the flower bearing shoots into yellow or white fairy dusters in late summer. The Alkali Heath can be recognized by its dark green leaves, the edges of which are download. In late spring and summer, this plant becomes clothed in delicate rose pink flowers which are avidly sought by bees.
At higher elevations in the marsh (that area covered by salt water only during the high spring tides), several other plants appear among the Pickleweed and Alkali Heath. These high marsh plants include Salt Grass, Sea Lavender and California Seablite. The Salt Grass is characterized by slender, sickle shaped leaves that roll tightly inward during dry conditions. The Sea Lavender is most easily recognized in mid-summer when it sends up long shoots bearing filmy sprays of pale violet flowers in the center of a cluster of broad, leathery leaves. These leaves (and those of the Salt Grass and Alkali Heath) are frequently coated with a white film of salt that has been pumped out of the plant by an efficient method of biological desalination. In contrast to the Salt Grass and Sea Lavender, the short, densely packed leaves of the California Seablite are devoid of salt glands but are swollen with water that is used to dilute the internally stored salt. The greenish flowers of the Seablite are small and inconspicuous; however, the leaves of this plant turn orange pink in late summer, forming a feathery splash of soft color.
The uppermost zone of the marsh is wetted only by extreme high spring tides and by storm waves. This zone is generally marked by the presence of Glasswort. This plant is a succulent stemmed shrub, similar in appearance to Pickleweed but brighter green, and with shorter, more slender stem segments. On the southeast side of Los Peñasquitos Lagoon, where the upper lagoon channels give way to broad areas of bare salt pans, the Glasswort is often accompanied by two attractive spring annuals. One of these annuals, the Salt Marsh Daisy, forms conspicuous carpets of golden blossoms in early spring, following a good winter rain. Later in spring, Little Ice plant appears with sprays of tiny white flowers and leaves dotted by crystalline water storing glands; as summer approaches, the flowers disappear but the color of the leaves ripens into an attractive orangeade hue.
On the southwest side of the Torrey Pines marshland, where the fresh water of Los Peñasquitos Creek mingles with the saline lagoon water, the salt marsh vegetation gives way to a group of plants that are adapted to brackish water conditions. Most conspicuous of these plants are Cat-tails, large clumps of Spiny Rush that resemble over-grown porcupines, and low growing mats of Brass Buttons, which, as their name suggests, are dotted with small, golden, dislike flowers during much of the year.
The upland edge of the Torrey pines salt marsh, above the direct influence of tidal water, grades into typical coastal scrub vegetation. In this “transition zone” one will usually encounter familiar shrubs such as Lemonadeberry, Goldenbush, and Deerweed; these plants are also common in the main area of the Reserve.
On the southwestern side of the lagoon, near the highway, the upland border takes the form of an old sand dune that probably formed the inland portion of the Torrey Pines beach prior to the construction of the highway. (Figure 1) This stabilized sand dune area is of interest because it represents a relict of the once extensive system of dunes that formerly lined the Southern California beaches. (Other relicts occur at the mouths of the Tijuana, San Dieguito, and San Marcos rivers and in Camp Pendleton.) At Los Peñasquitos, the most conspicuous among the plants are the sand dune Evening Primrose, the Coastal Cholla, and the Coastal Prickly Pear. These plants also occur on the bluffs in the main Reserve area. Two species of plants grow on the sand dune that cannot be found elsewhere in the Reserve and are also very rare in Southern California: the Beach Lotus, which is a spring annual with a spreading, mat like growth form bearing small 3 to 5 fingered leaves and clusters tiny orange and red pea shaped flowers and the Golden Aster, a low growing perennial, which can be recognized by its silver haired leaves and daisy like, yellow flowers that appear in early fall.
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