Coastal
Sage Scrub
46.45 acres of Coastal Sage Scrub (CSS) occur from east
to west on San Marcos Foothills, but almost exclusively
where slopes exceed 20%. Coastal Sage Scrub lines the margins
of arroyos surrounding the West Mesa; it is nicely developed
along Atascadero Creek, and is not well-represented near
Cieneguitas Creek.
Coastal
Sage Scrub was probably previously present in several areas
that now support grassland. Foothills Needlegrass colonizes
primarily under Coastal Sage Scrub, but it can persist in
the absence of CSS. Thus, areas on San Marcos Foothills
dominated by Foothills Needlegrass suggest the former presence
of Coastal Sage Scrub (Ferren, personal comm.). Throughout
our region Coastal Sage Scrub is considered a habitat at
risk (Davis et al., 1995). But Coastal Sage Scrub on flatlands
is practically non-existent. The combined pressures of cattle
grazing, conversion of land for agriculture, and human development
are the principal agents of its elimination. Small patches
of flatland Coastal Sage Scrub exist at the north end of
No Name Creek where cattle are excluded.
Coastal
Sage Scrub is a broad and generously inclusive habitat incorporating
many different dominance types depending upon soils, slope,
aspect, and hydrology. Dominant species near the West Mesa
include California Sage, Coyote Brush, California Fuchsia,
and Poison Oak. Along Atascadero Creek, dominant species
include Purple Sage, Coyote Brush, Canyon Sunflower, Sawtooth
Goldenbush, Santa Barbara Honeysuckle, and Fuchsia-flowered
Gooseberry. Fire may change the species that dominate Coastal
Sage Scrub.
Many
of the vertebrate species found in Oak Riparian also use
Coastal Sage Scrub. Species that heavily rely on Coastal
Sage Scrub on San Marcos Foothills include California Quail,
Costa’s Hummingbird, Bewick’s Wren, Wrentit, Blue-gray
Gnatcatcher, California Thrasher, California Towhee, Spotted
Towhee, Lazuli Bunting, Rufous-crowned Sparrow, and Western
Fence Lizard. [Policy Rim-4.1]
Wetlands
51.75 acres of Wetlands occur throughout San Marcos Foothills.
Actually, Wetlands are a melting pot of habitat types that
share (either periodically, seasonally, or persistently)
submerged or high soil moisture conditions beyond the duration
of the rainy season. On San Marcos Foothills surface water
occurs as seeps, springs, intermittent and persistent creek
and arroyo bottoms, riparian zones, flows from leaky well-heads,
cattle pond diversions along stream channels, and diversions
from natural springs to leaky cattle troughs. (See Map 5,
Wetlands.) Our inquiries into Wetlands on San Marcos Foothills
are based on data provided by Magney (1998) and augmented
by a series of trips between 1999 and 2001. Neither source
should be viewed as providing definitive data on the existence
of Wetlands; rather they represent in many cases our inferences
based on indicators remaining from wetter periods. Each
wetland mapped is a hypothesis that requires further investigation.
Where
underlying clay layers are close to the surface, it appears
that wetlands are supported. Surface evidence of this is
shown on Wetland Areas Map (Map 5). Wetlands on San Marcos
Foothills provide numerous benefits, including general support
for habitats, support for cattle ranching, minimal water
cleansing and sediment-trapping, groundwater recharge, and
basic support for a wide range of organisms.
