Chapter 3 - Natural Resources - Marine Corps Base Camp Pendleton

Integrated Natural Resources Management Plan [March 2012 - Update]
subject to wave action, and deposition and removal of sand and gravel. Foredunes are the
first line of dunes subject to sand deposition, high winds, and salt deposition, but only
rarely subject to wave action or overwash; backdunes may be stable (not subject to
deposition or erosion by the wind) or moving (having sand deposited or removed). Where
cliffs face the ocean, the exposure to high-winds and high salt deposition creates another
distinctive habitat – coastal bluffs.
On Camp Pendleton, the coastal strip is mostly a relatively narrow stretch of sandy beach
lying below a typically steep bluff cut into poorly consolidated sediments of the coastal
mesas.
Foredunes on Camp Pendleton, consisting of shifting-sand substrate, are classified as
southern foredune and are sparsely vegetated with plant cover ranging from 30% to 60%.
On Base, this plant community is dominated primarily by Ambrosia chamissonis (beachbur,
10% to 30% cover) and substantial populations of Abronia maritima (sand verbena),
Carpobrotus chilensis (sea fig, nonnative), Cakile maritima (sea rocket, nonnative), and
Camissonia cheiranthifolia suffruticosa (beach evening primrose) that cumulatively
account for 5% to 15% of groundcover (Biosystems Analysis 1994). This community is
estimated to occupy less than 25 ac on Base.
The regularity and extent of tidal flushing, the magnitude and frequency of freshwater
runoff, sedimentation rates, soil types, salinity, nutrient relations, and human uses all
influence the structure of the coastal wetland systems of the Base’s estuaries and lagoons.
Watershed flows and natural tidal prism are important factors in maintaining the viability
of these wetlands. A strong
correlation exists between the
regularity of tidal flushing and
the diversity and abundance of
the flora and fauna present in
coastal wetland habitats.
Interruption of tidal flow has
dynamic ecological effects and
can greatly influence the
distribution and abundance of
organisms within these coastal
wetlands; openings and closures
of river and creek mouths are
allowed to occur naturally on
Base to maintain a sound
balance of biodiversity within
the ecosystems. Tidal
circulation provides moisture
during periods of low
FIGURE 3-4.
SANTA MARGARITA RIVER ESTUARY
(PHOTO SOURCE: CAMP PENDLETON)
precipitation typical of the southern California summer months. Nutrient concentrations,
salinity, temperature, oxygen, strength of water currents, and light penetration all respond
to the open or closed condition of river and creek mouths, allowing some species to
flourish while others fade. For example, changes in these factors are stressful for many
Chapter 3 – Natural Resources 3-13