Plant Communities of Santa Cruz County
Northern Foredune (21210)
Description
The northern foredune is
dominated by perennial grasses (to 70 cm tall) and low, often succulent,
perennial herbs and sub-shrubs (about 10 cm tall). Coverage varies from
nearly complete to scattered. The species typically are zoned, with Abronia,
Ambrosia, and Cakile usually occurring in the sites most exposed to the
wind, and Calystegia and Camissonia in more sheltered sites. Growth and
flowering are most active in late spring and early summer, but continue
at a reduced rate all year. (Holland 1986)
History
One can only speculate that
these ecosystems are very old and have been in existence in one form or
another, as long as the necessary sand and substrate have been present.
They have probably fluctuated during the various glacial periods.
As glaciers formed they probably gradually expanded downward toward the
sea as sea level fell. Would the flow of sand have been different during
glacial periods? As glaciers melted and sea levels rose, these communities
may have been inundated by the sea and eventually worked their way back
into surrounding plant communities. Sand production was probably greater
during the periods of warming and glacial melt. (FMc 7/94)
Before 1850, dunes were low
and parabolic. With the introduction of European beach grass (Ammophilia
arenaria), the dunes have become more vertical and immobile. European beach
grass was used extensively as a sand stabilizer to prevent the filling
of shallow harbors and burial of coastal roads and railroad tracks by windblown
sand along the San Mateo-San Francisco coastline. Golden Gate Park in San
Francisco was created from sand dunes stabilized by the grass. Very little
of original community in its undisturbed or natural cycles remains if we
include the effects of introduced species. (FMc 7/94)
Distribution
The northern foredune strand
is located in areas of sand accumulation along the coast, including all
locations where active coastal dunes occur and many less extensive areas
as far south as Point Conception. (Holland) Commonly found along the north
coast from Santa Cruz north to San Francisco, local examples are found
at Ano Nuevo and Franklin Point and in the La Selva Beach area from the
Pajaro River North to Seascape. (FMc 7/94)
Site Factors
The foredune plant series
is normally situated on foredunes, as well as on upper beaches. The sites
are similar to Active Coastal Dunes, but with less wind and/or a smaller
supply of sand and/or more available ground water. The relatively favorable
conditions allow the establishment of plants which reduce the amount of
blowing sand and partially stabilize the dunes. Drainage is rapid, but
the deeper zones may be relatively moist. Plants are subject to desiccating,
salt-bearing winds. (Holland 1986)
Successional Stages
A. Non human-cyclic or catastrophic
(fire, floods, landslides, etc.):
Changes in coastal land
forms, and geological movement can increase, or block the movement of sand
along the coast and onto the beaches. The changes at Ano Nuevo, from a
peninsula to an island within the last 100 years or so, are a good example
of this. Changes in stream-flow volume and sediment loads in our coastal
streams and rivers can affect the extent of these communities and cause
successional changes. (FMc 7/94)
B. Human caused (logging,
agriculture, urbanization, grazing, etc.):
Off-road vehicles, commercial
and housing development, livestock grazing, sand mining, road construction,
and effects of introduced species of plants like European beach grass and
sea fig and hottentot fig as ground cover have been the principal cause
of successional change and destruction of this ecosystem. Reclamation and
natural succession are possible in disturbed areas, but it is labor intensive
and expensive. Some revegetation projects are underway by Caltrans around
Pescadero Creek. (FMc 6/94)
Associated Communities
Sometimes it can be overrun
by active dunes, or integrated with active coastal dunes toward the coast
or with coastal scrub inland. It needs sand for rejuvenation. (Holland
1986)
Associated Plants
(Chorizanthe cuspidata cuspidata) San Francisco Bay spineflower
(Chorizanthe robusta robusta) robust spineflower
(Erysimum ammophilum) coast wallflower
(Horkelia marinensis) Point Reyes horkelia
Associated Animals
Plover
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