By Geoffrey Coffey
Wednesday, May 18,
2005
Water paints the divided contours of the Valley of the Moon
with shifting colors.
Blues and greens of oak and bay forests on
protected north-facing slopes complement the fire and earth tones of chaparral
on the south-facing sides. At the southern end of the basin, riotous riparian
woodlands follow snaking Stuart Creek through a steep canyon to Agua Caliente,
the pepper of volcanic springs beneath the valley floor. Lowland meadows collect
water in seasonal puddles, where vivid wildflowers come and go with the equinox.
On two sides of Highway 12, one such meadow is divided by two
authorities. The southwest side of the field falls within the boundaries of
Sonoma Valley Regional Park, a public 162-acre parcel near Glen Ellen; the
northeast side belongs to the Bouverie Preserve, a 500-acre jewel in the private
necklace of Audubon Canyon Ranch.
A former quarry beside the Bouverie
visitor center (rumored to have supplied the stone for the nearby Jack London
House) is today a vernal pool, a depression of hardpan that fills with water in
winter and goes bone dry in summer. Smaller pools and swales sweep the adjacent
meadow in a network of linked seasonal wetlands -- up to Highway 12, of course
-- then continue as another isolated system on the other side of the road.
Spring sees the transition from flood to drought in these unforgiving flats, a
mere sliver of time in which a succession of highly adapted native plants take
the stage and dance with the reaper for a week or two, then disappear again.
Just now in the quarry, popcorn flower (Plagiobothrys
stipitatus var. micranthus) and wooly marbles (Psilocarphus
brevissimus var. brevissimus) are on the back side
of their annual appearance. Both are called "belly flowers" because
you have to get down on your belly to see them. The
popcorn flower has a thin green stem and tiny white
flowers; the wooly marbles look like felt, a sweep
of low-growing, gray-green shaggy foliage and a post-bloom
seed pod like cotton balls; both species occur in
sweeps at the edges of vernal pools and flats. These
flowers start to fade in May, and next month they
will be gone; but we can hope that insect pollinators
have done their duty, spreading seed that will bring
the flowers back next year.
Last month saw the rise and fall
of the annual Dwarf Downingia or Downingia pusilla, a rare plant in California
(though common in the vernal pools of Chile) that sprouts to a mature height of
1 inch. Fifty of these blossoms could fit on the face of a penny; each resembles
a tiny white five- pointed star, with a three-lobed upper lip touched in gold.
This year's plants have already passed on, but their twisted seeds lie waiting
in the sun-baked earth, patient for the return of the rains.
Before that
it was Blennosperma nanum var. nanum, a small but
showy annual with a bright yellow bloom in March,
mass quantities of which light up the margins of
vernal pools in golden rings. The rays of this micro-sunflower
are thrown back as if in joy, thrusting up the disc
flowers to the light in a gesture of enthusiasm or
Eros. But it, too, has followed the mandate of its
annual lifecycle, and won't be seen again until next
spring. Collectors, take note -- the genus name is
Greek for "slimy seed."
These sequential waves of dominant species
coming and going are parallel to the natural patterns that occur in any
ecosystem -- but here the fast rate of succession makes it more dramatic.
Once upon a time, the native plant communities of
the vernal pools enjoyed a high degree of invulnerability
from competition: No other plants could live under
such extreme conditions, especially in the nutrient-poor
substrate that results from a centuries-long cycle
of rain-fed inundation and sun-driven evaporation.
But the airborne pollution of mankind has leveled
the playing field: Smog settles in microscopic particles
upon the land, altering soil chemistry and fertility.
Studies have revealed that Bay Area smog sends "dry
deposits" of nitrogen molecules into the soil of
adjacent wildlands at the approximate annual rate
of 20 pounds per acre, the equivalent of five large
bags of concentrated industrial lawn fertilizer per
acre per year via the tailpipes of our cars.
Emboldened by all that nutritious nitrogen, weedy European
grasses are storming the vernal swales. Vigorous interlopers like ripgut, wild
oats, Italian rye and other monoculturalists have marched down from the
hillsides, as they have done across the entire state; their taller habit shades
out the low-growing natives and annihilates them. The ratio of exotic to native
in California is now so lopsided, we can never turn back the tide. But we can
manage the invasion. Better yet, we can learn from it.
On the Bouverie
side of the road, ecologist Dan Gluesenkamp keeps
an eye on the meadow. He mows certain patches, pulls
weeds by hand and recently introduced a grazing program.
Just this month, he and "conservation cowboy" Joe
Pozzi, a fourth-generation Sonoma County rancher,
fenced the perimeter and introduced two dozen head
of cattle. These animals prefer to eat the nitrogen-
rich exotic plants rather than the low-nitrogen natives,
and their occasional nibbles on native upland bunchgrasses
mimic the appetites of elk and other now-extirpated
ungulates.
The cows are a boon for the beleaguered native plants. Many open space
managers consider moderate grazing a crucial element of modern grassland
management, and perhaps vernal swales should fall under this rubric as well. In
a few months or so, the cattle will be moved along to avoid overgrazing.
Gluesenkamp is gathering data on the many changes
wrought by the grazing program upon the plants and
animals of the vernal swales. Changing plant composition
will influence the insect and annelid communities,
for example, which could affect the diets of local
birds. These ever-widening spheres of influence are
deep and interconnected beyond measure -- but Gluesenkamp
gives it a try. Using smaller "exclosures" within
the larger enclosure, he charts the rise and fall
of exotic slugs in a system with or without cows.
He also keeps similar exclosures on the margins of
the upland forest to study the effects of the exploding
populations of exotic wild turkeys. Ongoing plant
surveys triage struggling species, monitor ongoing
operations, and assess future management choices,
all based on observable data.
Across the road in Sonoma Valley
Regional Park, by contrast, allocations for resource observation and protection
are currently negligible to nil, and the only fenced enclosure designed for
animals is a 1-acre, off-leash dog park. Unfortunately, the hound playground was
built within the reaches of the vernal swale system, so that canine waste has
now surely added itself to the complex seasonal wetland equation.
But
plans are afoot for the regional park and the Bouverie Preserve to cooperate on
an important new project: the study and protection of rare and endangered
Blennosperma bakeri, which was spotted here in March 2004 growing on the
regional park side of the road. Gluesenkamp hopes for a joint effort with the
park, starting with a foundation of science -- measure the levels of nitrogen
deposition here from Highway 12, count the B. bakeri plants (somewhere between
100 and 100,000), and determine if the population is expanding or shrinking.
This information would influence the direction of a nascent (and, one hopes,
ongoing) management program. A good, easy first step would be simply to mow the
exotic grasses in the swales annually, early in the season -- some would
question why this hasn't already been done. Lack of funding appears to be the
primary obstacle, or perhaps inertia.
There's a fine line between
laissez-faire and neglect, between getting better and getting worse, between
lives that go dormant as reproductive strategy and species that are dead.
Education and public awareness can play an important role in lobbying for
change. We work for the seeds of the future, wherever they may fall.
The column "Locals Only" will no longer appear in this space, but Geoffrey Coffey will
continue to write for the Home & Garden section. Look online for seedlings
at www.geoffreycoffey.com <http://www.geoffreycoffey.com> or
e-mail him at home@sfchronicle.com.
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