Annual precipitation:
15-35 inches
Some of the dominant plants
Valley Oak
(Quercus lobata), Blue
Oak (Quercus douglasii), Coast
Live Oak (Quercus agrifolia), Interior
Live Oak (Quercus wislizenii), and Gray
Pine ( Pinus sabiniana), with companions of manzanita
(Arctostaphylos spp.), Coffeeberry
and Redberry
(Rhamnus spp.), Currant
and Gooseberry (Ribes spp.), and Toyon
or California Holly (Heteromeles arbutifolia). Annual
goldfields (Lasthenia spp.), Poppies
(Eschscholzia spp.), Lupines
(Lupinus spp.) and other forbs glorify the open areas
in spring.
Central Oak Woodland or Foothill Woodland has
many flavors.
We refer to it as Central Oak Woodland instead of the older
name Foothill Woodland because foothill implies that it is only
in the foothills. Nope; this plant community formerly occupied a
number of valleys, but the flat land was easier to clear for
farming, and the trees were easier to harvest. Moreover, the
water table in many areas of the San Joaquin Valley has dropped,
due to overpumping, from standing water (Tulare Lake) in the
early 1800's to 800 feet under the surface presently. Many of the
native trees, notably Valley
Oak (Quercus lobata), require a water source within 70
feet. Central Oak Woodland is sometimes referred to as the Digger
Pine belt. (Some people are offended by the term 'Digger Pine',
most of our customers of indigenous heritage ask for digger
pines, but that's an aside) and we suspect that Digger Pine trees
are missing in many of the areas where they occurred because of
frequent fires and removal by man.
Oak
trees in California usually have two types of root systems, one
deep (for bringing up water) and one shallow (their nutritional
and immune system). Oak trees act as a water lift, pulling water
from deeper soils and sharing with their companion plants.
Associated plants that grow in the deeper soil openings and under
the oak tree canopy have roots in different soil levels than the
oak. A shallow oak root system is directly under the litter layer
(oak leaf mulch layer). This oak leaf mulch layer, or litter
layer, is critical to the health of the oak tree. At the place
where the oak leaves contact the soil, a specific group of
microorganisms prevent the quick breakdown of the leaves, and so
hold that nutrition in so-called storage, and at the same time,
slowly break down some of the leaf material, and so extract
nutrients as needed, and share these with the oak tree. If the
litter layer is replaced by alien plants (alien, annual grasses,
vinca, ivy, thistles, and many others) and their litter (dead
alien plant parts laying on the ground), this oak leaf- bare soil
interface is missing, which is the mini-habitat for the specific
group of microorganisms, and so they die out, and are replaced by
another group of microorganisms that can live in the thick thatch
of alien plants and their litter, and very few oak leaves. Where
do the oak leaves go when the alien plants and their litter
replace the oak leaf litter? We are not sure, but believe that
either they are broken down quickly by the new group of
microorganisms, or removed by small fauna, or removed by some
other means, or maybe the oak tree, reacting to the stress of
losing the litter layer, is not dropping as many leaves onto the
ground but holding them on the tree (The answer to this question
would be a great thesis for some enterprising student). Anyway,
the oak leaf-bare soil interface habitat is gone, and the ability
to acquire food or nutrients, is lost, and the oaks are left with
essentially only their deep root system and will weaken and be
more susceptible to a variety of diseases and decline. For
information on what to do if you inherit a weak and sick oak
surrounded by alien grasses and weeds, see here.
Where the soils are shallow, less than three feet, you'll find
forbs and wildflowers seasonally rotating through this plant
community. These annuals are an integral part of the plant
community, sustaining the oak tree as the oak tree sustains them,
part of the "neighborhood network."
Poison
oak (Toxicodendron diversilobum), Miners
lettuce (Montia perifoliata) , Fair-well-to-spring
(Calrkia unguiculata), Coyote
mint (Monardella villosa), Melic
grass (Melica imperfecta), and Snakeroot
(Sanicula crassicaulis) thrive under a dense stand of
Coast Live Oak
( Quercus agrifolia).
|
Cities and towns that were historically in the Central Oak
Woodland plant community.
 If
your town is between the pink dots, you too are a possible garden
site to create an oak woodland.
Much of this plant community has been completely erased and
replaced with weeds. The trees are gone, their understory plants
and associated plants not even a memory of grandparents. In a
several-thousand-square-mile area, from central Tulare County up
into the Modesto area, there is less than 10% or so of the trees
left, and almost nothing else but weeds.
Planting back a yard, school, acre, roadside or any other
available plot of land with plants from this plant community
within the historic area of the plant community can be quite
rewarding. Small wildlife will find your garden. Hummingbirds,
butterflies and other insects that look like they might be
friendly show up.
In the inland valleys, including the San Joaquin, the Valley
Oak (Quercus lobata) had as its companions, Alkali
Wildrye (Elymus triticoides or Leymus triticoides)
along with Elderberry
(Sambucus mexicana), Coffeeberry
(Rhamnus californica or Rhamnus
tomentella),
some Toyon
(Heteromeles arbutifolia), Honeysuckle
(Lonicera interrupta), and many other species.
 The
picture to the right was taken in the central coast ranges of
California, and is a portion of Central Oak Woodland, with Coast
Live Oak
(Quercus agrifolia) and an understory of Hummingbird Sage
(Salvia spathacea), covering one-half an acre.
On one of the botanical surveys we tripped across a glimpse of
the past in an area of Central Oak Woodland. Most of the Paso
Robles, Shandon, and San Miguel, California, area has been burned
too many times to have much left other than a few trees. The
Central Oak Woodland is far from complete. In one spot, though,
there was an old pocket of plant community that hadn't burned
because of the topography. Big
Berry Manzanita (Arctostaphylos glauca),
Hollyleaf Redberry (Rhamnus ilicifolia), Hollyleaf
Cherry (Prunus ilicifolia), and Toyon
(Heteromeles arbutifolia) were still under the
Blue Oak (Quercus douglasii and Valley
Oak (Quercus loabata). Under the shrubs were Yerba
Buena (Satureja douglasii), Wild
Rose (Rosa californica), Snowberry
(Symphoricarpus albus), Hummingbird
Sage (Salvia spathacea), Maidenhair
Fern (Adiantum jordanii) and many other species! This
patch was a tiny healthy sample of a plant community that used to
exist throughout much of the inner coast ranges and in the lower
elevations of the Sierra Nevada mountains from Keene to maybe,
the foothills above Modesto.
Here's a consequence of grass introduction that I've never
seen in print. Wild Oats were introduced early, either by
landfall of Drake or Cabrillo, or by 'wild' horses from New
Mexico or Mexico. The California Indians living in the interior
commonly burned the leaf litter under oaks to facilitate the
collection and storage of acorns (roasted nuts and no weevils).
These people must have starved when wild oats were introduced.
The first time they burned under an oak with grass present must
have been REAL exciting.
Some
accounts of this plant community by early travelers:
"The country about Visalia, for six or eight miles in
every direction, looks like an old park, because of its
magnificent oaks. These trees, like the oak generally in
California, are low-branched, wide-spreading, gnarled; they are
magnificent in size; many of them must be hundreds of years old;
and they are disposed on the plain in most lovely groups, masses,
and single specimens. You drive for miles among them; and you
meet, very frequently, single trees so large, so stately and
perfect, that a painter of trees would be enchanted with them.
The mistletoe, which is the enemy of the oak in California, does
not seem to trouble these trees about Visalia; I do not remember
seeing any of this parasite, except on some oaks and cotton-woods
near Tulare Lake." Charles Nordhoff, 1873.
"All the road and all these plains are full of very
large, tall oaks having good and large acorns. Likewise there are
many sycamores, and pines bearing good pinenuts with hard shells,
and so leafy that their branches begin near the ground, and,
tapering toward the top, end almost in a conical point. High up
in the sierras are seen large numbers of spruce and other trees.
Along here there are some birds which they call carpenters, which
make round holes in the trunks of the oaks. In each hole they
insert an acorn so neatly that it can be taken out only with
difficulty, and in this way they make their harvest and store,
some of the oaks being all dotted with the acorns in their
trunks." Font 1776 somewhere between Santa Margarita and
Salinas
"We continued to travel all day over a rough and hilly
country, where we occasionally found springs, but rarely grass,
the character of the soil differing but little from what we had
noticed in other parts of the northern portion of Upper
California." James
L. Tyson, M.D 1850
Under
the term oak woodland are three variations that we have observed:
Oak Woodlands, where the oaks and pines were fairly close
together mixed in with tall and short shrubs,and openings of
wildflowers, forbs and few grasses; Oak Savanna, where the trees
were a good distance apart, mostly few to no shrubs, and between
was mostly forbs with little grass. (the woods were thickets in
some places), and Oak Forest where the oaks and pines were
touching and there were several layers of understory, from tall
shrubs to short shrubs to perennial and annual forbs, with a very
small amount of grass.
|
