Plant Communities of Santa Cruz County
Coastal Terrace Prairie (41100)
INTRODUCTION
Much of
our area's coastal prairie has been destroyed due to agriculture and development,
The remaining areas have been invaded by exotic weeds such as annual fescues
(Vulpia bromoides), bromes (esp. Bromus diandrus), velvet grass (Holcus
lanatus), and thistles (esp. Carduus pycnocephalus). The remaining,
in tact areas of coastal prairie are recognized by the patchy presence
of California oatgrass (Danthonia californica) and/or wildflowers such
as native bulbs (Brodiaea and Triteleia species), lupines (Lupinus nanus),
self-heal (Prunellus vulgaris), and many others. The best areas to
view coastal prairie are at UCSC's upper campus (Marshall Meadows), State
Parks' Gray Whale Ranch, and just north of Aqo Nuevo along the coast south
of Franklin Point.
PRAIRIE
SIGNIFICANCE AND RECOGNITION
Somehow,
despite the recent listing of California native grasslands as the eighth
rarest ecosystem in the United States, the rarity of the prairie ecosystem
has not been recognized and thereby continues to be lost through development
or neglected by land managers . One of the difficulties facing the recognition
of the rarity of grasslands is the definition of true "coastal prairie."
Many land managers have recently gained a recognition of native grasses
and assume that a coastal prairie consists of a few species of perennial
bunchgrasses and little else. However, most natural "grassland" historically
consisted of many annual and perennial forb species ("wildflowers") growing
in association with relatively few native grass species. In some areas
of the County, prairie habitats support as many as 250 species of native
wildflowers. For Santa Cruz County, the CNPS lists 13 species of concern
in their Inventory of Rare and Endangered Plants of California (1995) (see
appendix A). The diversity of these prairie wildflower species, in turn,
supports an even greater diversity of insect species, many of which are
severely reduced in numbers (e.g., Schinia sp.- a genus of colorful diurnal
noctuid moths; and solitary bees such as in the families Andrenidae and
Anthophoridae) and some of which teeter on the verge of extinction (e.g.,
Cicindela Ohlone, Ohlone Tiger Beetle and Adela oplerella, Opler's long
horned moth). Some known species have already been lost (e.g., Lytta molesta,
molestan blister beetle) and, undoubtedly, others have disappeared before
even being described. The reduction in numbers of plant species and numbers
of populations of insects leads to a collapse in the prey base for many
other species- birds, shrews, and bats, for instance.
Many
people contend that meadows are artifacts of human intervention (i.e.,
"clearings"). This may be true of some grasslands; however, it is certainly
not true of all meadows in Santa Cruz County which contain an abundance
of meadow dependent species (see appendix B). It can be taken as axiomatic
that a high diversity of meadow dependent species in a given meadow presupposes
the meadow's long history as a stable community. It is theorized that Santa
Cruz's coastal terrace prairie is the oldest, most stable ecosystem of
the temperate world, dating back 600,000 years (Dr. Robert Curry, pers.
comm., 1993). On the other hand, areas with few or no meadow dependent
species may have been recently converted from forest or scrub.
The
current technique for determining meadow diversity (i.e., seasonal botanical
surveys) fails to detect species existing in the soil as seeds awaiting
an improved management regime. For instance, the grassland of the City
of Santa Cruz's Arana Gulch Greenbelt Land could thus have been surveyed
and considered non-native and the assumption would have been made that
this meadow was a human artifact. Yet, a year later, after mechanical removal
of weeds, Holocarpha macradenia (Santa Cruz Tarplant, an endangered species
of prairie dependent wildflower) appeared en masse along with new populations
of native grass (Danthonia californica) and wildflowers (Lupinus bicolor,
small-flowered lupine, Castilleja densiflora, purple owls clover) which
had not been documented in recent surveys. The appearance of Plagiobothrys
chorisianus (artist's popcorn flower, a CNPS list 4 plant) was a great
surprise as it had not been documented on the site despite 12 years of
botanical surveys.
The
significance of meadowland diversity needs to be recognized by both land
managers and the general public who must provide them political support
for land management decisions. More people need to understand the level
of crisis the prairie ecosystem faces. In the meantime, the conclusion
must be that all extant coastal prairie areas should be managed to reduce
weeds and thatch for as many years as it takes to allow the seedbank to
express itself. In the future, standards should be developed for gathering
field samples of soil and nursery growing and identifying the seedlings
therein.. Only after carefully documenting the native flora should decisions
be made as to the fate of the meadowland in question.
DEVELOPMENT
The legacy
of development's impacts on the local prairie ecosystem is extensive. Nearly
the entire first coastal terrace was probably prairie of around 100,000
years of age. Very few areas of this terrace remain with in tact native
prairie (e.g., Franklin Point, San Mateo County; Arana Gulch, City of Santa
Cruz). Much of the Pajaro valley and Watsonville and up the entire north
coast of Santa Cruz has been developed in agriculture and housing. The
second terrace in the City of Santa Cruz has been developed with the exception
of areas of Pogonip and De Laveaga Park. Further North, large areas have
been lost to row crop agriculture. The third and fourth terraces have prairie
in tact in many places on the north coast. Much of the City of Scotts Valley
once was prairie and has been degraded by development.
Prairie
is currently protected by the County of Santa Cruz and the Coastal Commission
which recognize the rarity of the habitat. However, when projects are proposed
that impact prairie, destruction of the habitat is allowed through on or
off site mitigation measures usually including habitat restoration. However,
currently there are no proven methods of restoring prairie habitat and
all such projects fall woefully short of accomplishing their goals.
It
is important to note that areas of prairie habitat persist on private land
zoned for agriculture. Fortunately, these areas have been used for grazing
animals, not for row crops though the latter could be permitted without
environmental review, a fatal flaw in the current zoning laws.
Considerations
before aproving further development which destroys our remaining prairie
areas are: the assessment of the acreage remaining of the community and
the demonstrable efficacy of restoration practices which permit that= destruction.
WEEDS
The degradation
of California's grasslands by the invasion of weedy exotics plants has
long been recognized. A division of these weeds into three groups- perennial
grasses, annual forbs and grasses, and perennial flowering plants- provides
for management prioritization and strategies that help to combat their
impacts.
In
some native prairies the greatest threat is from perennial, introduced
grasses of which five species stand out in particular: Holcus lanatus (velvet
grass), Phalaris aquatica (Harding grass), Festuca arundinacea (tall fescue),
Cynodon dactylon (Bermuda grass), and Pennisetum clandestinum (Kikuyu grass).
These grasses, once established, can only be removed by intensive mechanical
or herbicide treatment which will gravely affect native species as well.
Neither grazing nor fire will eradicate these perennial species, although
both methods can help in slowing their spread. On the other hand, without
either management practice, these species will establish and destroy meadows.
Holcus lanatus (velvet grass) has established in diverse wet meadows and
mima mound prairie in the upper campus at UCSC, endangering Cicindela Ohlone
(Ohlone tiger beetle) and Plagiobothrys diffusus (San Francisco popcornflower)
along with many other rare or uncommon meadow species. Phalaris aquatica
(Harding grass) has invaded the moist swales in the prairie at A=F1o Nuevo
State Park at Franklin Point, creating large monocultural stands. I include
articles on Festuca arundinacea as the threat from this weed is little
understood in California but well documented elsewhere. This grass has
become established on the borders of Gray Whale Ranch and throughout meadows
of the UCSC campus. Cynodon dactylon (Bermuda grass) and Pennisetum clandestinum
(Kikuyu grass) are invading meadows at UCSC and are present in the grasslands
of Big Sur and around Elkhorn Slough. Research into the effects and invasiveness
of Holcus lanatus is currently lacking and information on its effects is
anecdotal.
The
second largest threat to grasslands is from perennial dicots. Of these,
Genista monspessulana (french broom) is the most formidable in Santa Cruz
County. Broom is a major invader of grassland habitats and is well recognized
by land managers as a threat to ecosystem health. At this time, through
the efforts of The Wildland Restoration Team and California Department
of Parks and Recreation, broom is being effectively controlled on state
park land. And, luckily, Gray Whale Ranch has very little broom in its
prairies at this point (Ken Moore, pers. comm., 1997). Other significant
weedy dicots that are slow to spread but are now appearing in grasslands
are: Foeniculum vulgare (fennel), Eucalyptus globulus (blue gum), and Acacia
dealbata (green wattle). Fennel has invaded grassland and shrub areas of
Santa Cruz Island to the exclusion of nearly every other species. It is
now reproducing exponentially at UCSC, Pogonip, and Wilder Ranch in prairie
areas. Eucalyptus has taken over many plant communities including grassland
surrounding Elkhorn slough and throughout coastal Santa Cruz County. Acacia
is currently invading areas of native prairie at Pogonip Open Space, one
of the Greenbelt areas of the City of Santa Cruz.
Annual
species of grasses and flowering plants are threats to grasslands that
are, to some extent, more controllable through low cost management methods.
The original invaders of native prairies, annual grasses are well known
to out compete native grasses and forbs. Of equal importance is their tendency
to produce large amounts of above-ground biomass that forms a thick thatch
inhibiting growth and germination of native species (Menke). The worst
of these species in Santa Cruz County are: Briza maxima (Rattlesnake grass),
Bromus diandrus (ripgut brome), B. hordeaceus (soft chess), Avena barbata
(slender oat), Hordeum murinum (foxtail), Brachypodium distachyon, and
Vulpia myuros (rattail fescue). These species are ubiquitous in meadow
areas of Santa Cruz County. It is important to realize that there are many
species of weedy annual grasses and that the real impact is cumulative.
Annual
forbs are another competitive force against native species. The most dangerous
of these for our area at this time are: Carduus pycnocephalus.(Italian
thistle), Hirschfeldia incana (summer mustard), Raphanus sativa (radish),
and Conium maculatum (poison hemlock). Each of these species is spreading
into grassland areas where management is by benign neglect. Radish, mustard,
and poison hemlock produce chemicals that are strongly inhibit the growth
of other species and are quickly monopolizing large areas with unknown
consequences to the soil seed bank.
All
of these annual species are very controllable through the use of well timed,
carefully managed grazing. Grazing animals reduce non-native seed production
and thatch while creating the kind of disturbance with which the prairie
has evolved (see following section on disturbance). In all the cases where
there is a healthy, diverse prairie remaining in Santa Cruz County, there
are grazing animals. Without the use of grazing and fire, the control of
all weeds becomes impossible on the scale that it is needed.
THE IMPORTANCE
OF FIRE
When timed
correctly (Howe, 1994), prescribed fire can be used to mimic the historical
role of fire while increasing meadow diversity through weed control and
reduction of thatch. The role of fire in prairie ecosystems has been well
documented as maintaining diversity and structure of the community. The
suppression of fire directly threatens grassland communities by allowing
invasion of these areas by shrubs and trees.
Although
fire may not have been a common occurrence prior to the human occupation
of the last approximately 10,000 years, it previously occurred in infrequent
but catastrophic episodes. These fires, along with herds of large herbivores
that became extinct in the late Pleistocene could have been a key factor
in maintaining and perhaps extending areas of meadow coverage . To allow
live oak woodland to invade meadowlands (as is currently the policy at
Wilder Ranch) is to allow the replacement of a rare habitat by a more locally
common one and, thereby, the loss of structural, functional, and species
level biodiversity.
The
use of prescribed fire has been shown to be effective in maintaining grassland
health. Well timed fire reduces thatch , while reducing the seed output
of non-native species. Research at the Jepson Prairie Preserve (near Davis,
California) has shown increases in native species abundance with a corollary
reduction in weedy , non-native species after fire. Locally, prescribed
burning by the California Department of Parks and Recreation at Franklin
Point and by the California Department of Forestry at UCSC has apparently
slowed the invasion of velvet grass and many other weedy species. An accidental
fire at Arana Gulch Greenbelt above the Santa Cruz Yacht Harbor has contributed
to the recovery of an important population of Holocarpha macradenia (Santa
Cruz Tarplant) and other prairie plants.
That
there is a conflict between oak preservation and grassland preservation
is evident and predictable. Trees are often the beneficiaries of plant
conservation efforts in similar ways to lions getting attention while rare
snail darters and flower-loving flies get scorn and ridicule. Public agencies
and CNPS should work together in the future to educate the public about
the importance of prairie habitat and its management requirements.
The
two aspects of prescribed fire that have failed are: 1) an inability to
reverse the invasion of trees and shrubs into the edges of meadows, as
burning along ecotones is prohibited in the interest of safety, and 2)
the extent of fires is often small because of limited resources, leaving
large areas neglected.
LACK OF
DISTURBANCE
As previously
discussed, the majority of prairie plant diversity rests in the annual
wildflowers. All of these species are, to some extent, disturbance dependent.
That is, without soil disturbance and, especially, thatch removal they
fail to germinate. Examples of listed species that occur in Santa Cruz
County meadows include: Trifolium buckwestiorum (Santa Cruz Clover), T.
grayi (Gray's Clover), Plagiobothrys chorisianus (Artist's popcornflower),
Plagiobothrys diffusus (San Francisco Popcornflower), and Holocarpha macradenia
(Santa Cruz Tarplant). Historically, soil disturbance and thatch removal
occurred in conjunction with large herbivores which became extinct in the
late Pleistocene.
Locally,
these species owe their existence to grazing, trail side soil disturbance,
and other human induced disturbances. Without such disturbance, the native
annuals retreat to tiny refugia of very shallow soil too poor and dry to
support weeds. In Santa Cruz County, areas where there are remaining populations
of diverse wildflowers are as follows (with disturbance type in parentheses):
Bombay Corporation Lands, Westside Santa Cruz (grazing), Younger Ranch
and lower UCSC, Westside Santa Cruz (grazing, roads, trails), Marshall
Meadows, upper UCSC campus (trails, fire), Watsonville Airport (light tractor
discing, mowing), Glenwood Grasslands, Scotts Valley (grazing, trails),
and Swanton Road Grasslands (grazing). Areas where many wildflower species
(including rare species) have disappeared after the cessation of grazing
are: Pogonip Greenbelt Area, City of Santa Cruz; areas at UCSC campus;
areas of Glenwood Grasslands- west of Glenwood Drive, near Scotts Valley;
and Arana Gulch Greenbelt Land, City of Santa Cruz.
HABITAT
FRAGMENTATION
The sciences
of island biogeography and conservation biology have enlightened us to
some of the effects of habitat fragmentation including the increased possibility
of local, regional, and global extinctions and the increased susceptibility
of areas to weed invasion.
Smaller,
more fragmented habitats make species more susceptible to extinctions as
each individual area of habitat loses species due to catastrophic disturbance.
A lack of adequate corridors then decreases the chances of recolonization
by the locally extinct organisms from adjacent habitat, and slowly species
lose the overall regional and global numbers they need to survive.
With
local prairie habitat fragmentation, the long term preservation of sensitive,
meadow dependent plant species becomes problematic. Climate fluctuations
require plants to be able to shift the placement of their populations to
areas of varying moisture or sun exposure. For their long term survival,
species need to be able to maintain large enough populations to have a
broad genetic base with which to adapt to changing situations. Habitat
areas need to be close enough together for seeds to be spread by the many
seed dispersal agents: ants, birds, wind, and mammals. The dispersal of
these seeds allows for recolonization of species into unoccupied habitat
and for the transfer of genetic information important to their adaptation
to changing conditions. Restoration science may never progress to a point
where managers can restore even a single species of plant into the wild
for the long term, making it imperative that plant species be given every
opportunity to disperse and multiply on their own.
Another
impact of the fragmentation of prairie habitat is the loss of insect diversity.
Fragmented, small meadows may not contain enough individuals of various
plant species to support pollinators. Therefore, in a deadly circle, both
plant and insect species spiral towards extinction without the space and
population numbers to support healthy populations. For other insects, larval
host plants may not be in enough abundance to support large, healthy populations.
While we flirt with the precipitous decline of thirteen plant species in
the prairies of Santa Cruz County, we must realize that the decline of
these species may cause the extinction of 130 species of insects. The viablility
of these insects' populations may already be more endangered than the plants
themselves due to a large part to the widely spaced, fragmented nature
of the plant populations.
Fragmented
prairie habitat is also more vulnerable to weed invasion. Small meadows
have more edge exposed to roadways, trails, and other sources of weed introduction.
Weeds can then invade to occupy a large proportion of fragmented meadows
in a relatively short period of time. These areas are also harder to manage
with fire or grazing to reduce weed pressure.
With
the north coast of Santa Cruz County and its contiguous prairie habitat,
there is a golden opportunity to plan for the long term survival of meadow
dependent species through the preservation and management of contiguous
and expansive existing prairies.
EROSION
Erosion
also affects most ecosystems in our area. Gully erosion is a common phenomenon
on the deep, high shrink-swell soils of the marine terraces. Currently,
large gullies are consuming areas of grassland and coastal scrub in and
around Wilder Ranch. The cause of these gullies is generally accepted as
being accelerated runoff due to soil compaction and development. Some gullies
may have begun during the widespread disturbance of forest clear cutting
and road building during the limestone quarrying era of the nineteenth
and early twentieth century. Current technology to stop gully expansion
includes large, deeply seated check dams used in conjunction with swales
to channel runoff into adjoining sub watersheds. This is a very expensive
and potentially ineffective treatment. A serious look by qualified soil
scientists and erosion control experts at erosion potential due to long
term, human impacts related to increased trail use through our fragile
prairies is in order. Because of the importance of foot trails to the Ohlone
Tiger Beetle and annual wildflower species, the establishment of more diffused
trail systems should be stressed rather than concentration of traffic on
single trails.
Prairie
Dependent Species
CalPhotoshas
pictures of many of these species; copy scientific names from this list
to the CalPhotos form to retrieve them.
scientific name
|
common name
|
| Amsinkia
lunaris |
| Anagallis
minima |
| Brodiaea
terrestris |
| Brodiaea
elegans |
elegant
Brodiae |
| Calandrinia
ciliata |
redmaids |
| Calochortus
luteus |
yellow
mariposa lily |
| Calochortus
uniflorus |
| Camissonia
ovata |
suncups |
| Carex
brevicaulis |
| Castilleja
densiflora |
purple
owl's clover |
| Cicendia
quadrangularis |
| Cirsium
quercetorum |
brownie
thistle |
| Clarkia
daveyi |
| Clarkia
purpurea purpurea |
four
spot |
| Corizanthe
robusta |
| hartwegiana |
Scotts
Valley Spineflower |
| Danthonia
californica |
California
oatgrass |
| Deschampsia
caespitosa |
tufted
hairgrass |
| Deschampsia
danthonioides |
| Dichondra
donnelliana |
| Dodocatheon
clevelandii |
Cleveland's
shooting star |
| Hemizonia
corymbosa |
| Holocarpha
macradenia |
Santa
Cruz Tarplant |
| Horkelia
marinensis |
Pt.
Reyes Horkelia |
| Isoetes
spp. |
Quillworts |
| Juncus
bufonius |
Toadrush |
| Juncus
occidentalis |
Western
rush |
| Lasthenia
californica |
goldfields |
| Linanthus
parviflorus |
| Lotus
formosissimus |
coast
trefoil |
| Lupinus
nanus |
sky
lupine |
| Microseris
biglovii |
Bigelow's
microseris |
| Microseris
paludosa |
| Panicum
pacificum |
pacific
panicgrass |
| Perideridia
gairderi |
Gairdner's
yampah |
| Perideridia
kelloggi |
Kellogg's
yampah |
| Plagiobothrys
chorisianus |
artist's
popcornflower |
| Plagiobothrys
diffusus |
San
Francisco popcornflower |
| Sanicula
arctopoides |
footsteps
of spring |
| Scirpus
koilepis |
| Sidalcea
malvaeflora |
checkerbloom |
| Spiranthes
romanzoffianum |
western
ladies tresses |
| Trifolium
buckwestiorum |
Santa
Cruz clover |
| T.
variegatum, T. barbigerum, T. microdon, T. depaupertum, T.appendiculatum |
many
other clovers |
| Triphyseria
eriantha |
| Triphyseria
faucibarbata |
| Triphyseria
pusilla |
| Triteleia
hycinthina |
Hyacinth
flowered Brodiae |
| Zygadenus
fontanus |
| Zygadenus
fremontii minor |
Dwarf
starlily |
Non-native
Plants
scientific name
|
common name
|
| Avena
barbata |
slender
oats |
| Avena
fatua |
wild
oats |
| Bellardia
trixago |
| Brachypodium
distachyon |
| Bromus
hordeaceus |
soft
chess |
| Erodium
botrys |
storksbill |
| Erodium
cicutarium |
red
stemmed filaree |
| Festuca
arundincea |
tall
fescue |
| Holcus
lanatus |
velvetgrass |
| Hordeum
murinum |
foxtail |
| Leontodon
nudicale |
hawkbit |
| Lolium
multiflorum |
italian
rye grass |
| Phalaris
arundinacea |
Harding
grass |
| Plantago
lanceolata |
English
plantain |
| Romulea
spp. |
| T.
angustifolium |
| T.
dubium |
| Trifolium
subterraneum |
Native
Animals
(common names)
American
kestrel
western
meadowlark
badger
western
racer
Buckeye
butterfly
white-tailed
kite
burrowing
owl
horned
lark
California
ground squirrel
lark
sparrow
California
ringlet
meadow
vole
ferruginous
hawk
Ohlone
tiger beetle
golden
eagle
oxeye
satyr butterfly
gopher
snake
savannah
sparrow
grasshopper
sparrow
western
bluebird
|
