Santa Monica Mountains National Recreation Area - Trees

Coastal Sage Scrub

In the Santa Monica Mountains, coastal sage scrub occurs on drier sites and lower elevations than chaparral, especially on coastal south-facing slopes. Coastal sage scrub is also common in inland areas of the Simi Hills within the SMMNRA. P lants, characterized by soft-leaved, grayish green, aromatic shrubs, include purple sage (Salvia leucophylla ), California sagebrush (Artemisia californica ), coast goldenbush (Haplopappus venetus ) and coastal buckwheat (Eriogonum cinereum ) and are usually dotted by larger laurel sumac (Malosma laurina ) or lemonadeberry (Rhus integrifolia ) shrubs. Good examples of coastal sage scrub can be found in the mouth of Zuma Canyon and in coastal Point Mugu State Park.

Chaparral

Chaparral, the dominant vegetation community in the Santa Monica Mountains, is characterized by deep-rooted, drought and fire-adapted evergreen shrubs growing on coarse-textured soils with limited water-holding capacity. The drought-adapted leaves of chaparral plant species are often small, leathery, thick, fuzzy and/or waxy. After fire, chaparral plants may reproduce either by seeds or stump-sprouting, or both, depending on the species. Chaparral often forms a nearly impenetrable vegetative wall of stiff stems and leathery leaves. Underneath the dense shrub cover, the ground is devoid of herbaceous vegetation, except for an occasional clump of foothill needlegrass (Nassella lepida ) or cluster of wildflowers. Chaparral subcommunities are defined by one or more dominant species. Within the mountains, chaparral subcommunities include mixed chaparral, red shank chaparral, ceanothus chaparral and chamise chaparral.

Coast Live Oak Woodland

This community is found on north slopes and in shaded ravines or canyon bottoms and is characterized by coast live oak (Quercus agrifolia ), hollyleaf cherry (Prunus illicifolia ), California bay laurel (Umbellularia californica ), coffeeberry (Rhamnus californica ) and poison oak (Toxicodendron diversilobum ). Groves are formed across valleys and along streams and intermittent watercourses. Live oaks, like their name suggests, are evergreen. Preferring permanent water, the deep tap roots of live oaks can reach to the water table. Well-developed oak woodlands can be found at Trippet Ranch in Topanga State Park and at Rocky Oaks.

Riparian Woodland

Riparian woodland is one of the most endangered plant communities in California. It is estimated that less than 10 percent of the original 200,000 acres of Riparian Communities remain in California (NPS 1982a). Riparian Woodlands occur along canyon and valley bottoms with perennial or intermittent streams in nutrient rich soils, or within the drainage of steep slopes. Four kinds of riparian communities are easily identifiable in the Santa Monica Mountains: walnut riparian woodlands, m ule fat dominated riparian areas, willow riparian areas, and s ycamore riparian woodlands. Dominant species may include arroyo willow (Salix lasiolepsis ), California black walnut (Juglans californica ), Sycamore, Mexican elderberry (Sambucus mexicana ), California bay laurel (Umbellularia californica ) and mule fat (Baccharis salicifolia ). Big Sycamore Canyon in Point Mugu State Park, Malibu Creek, or Medea Creek in Cheeseboro Canyon contain good examples of riparian woodland.

Valley Oak Savanna

Valley oaks (Quercus lobata ) reach the southernmost extension of their range in Malibu Creek State Park. Endemic to California, valley oaks were once widely distributed from the Sacramento and Pit River Canyons, 500 miles south to the Santa Monica Mountains. These trees, which reach truly majestic proportions, originally spread over the native grasslands in the wide valleys of central and coastal California. Valley oaks reach ages of 400-600 years and may have trunks six or seven feet in diameter. They present a graceful appearance on the landscape, widely spaced with branches that may drape to touch the ground. Over the last 150 years though, valley oaks have succumbed to widespread agricultural and residential development, which has focused on their prime habitat;alluvial valleys. Although thousands of acres of valley oak savanna remain, they are vastly changed; much of the grassland understory is comprised mainly of alien European annual grasses that have outcompeted and crowded out the native species over the decades since they were introduced. Aside from valley oaks, characteristic native grasses which dominate valley oak savanna include purple needlegrass (Nassella pulchra ), and alien grasses such as wild oats (Avena fatua ) and ripgut brome (Bromus diandrus ) as well as black mustard ( Brassica nigra ) and intermittent wildflowers, such as Mariposa lilies ( Calachortus catalinaea ) and coast goldfields ( Lasthenia chrysotoma ).