lumped into six major habitat types or plant
associations, described below. These associations are
grouped based on a complex network of interactions
between geology, topography, precipitation, climate,
and land use (past and present). Recognizing and
understanding the vegetation communities is
important for the management of the lands, as well
as the conservation and preservation of the land, and
the wildlife and humans that use it.
Background
Soils
Projects
These two plant communities are the most dominant
communities around Lake Berryessa. Oak woodlands
and savannahs are most commonly found on dry,
sunny, rocky hillslopes with soils that range from
coarse to fine, and often times have a higher clay
content. They are characterized by a mix of oaks in
the overstory (in the woodlands: Oak cover is >10%;
in the savannahs: Oak cover is <10%) and annual
grasses in the understory (Californa Oak Foundation
2005). Historically, the understory would have been
dominated by native, perennial grasses, but changes
in land use, namely the introduction of agriculture and
livestock, have helped cause a shift in the plant
species composition, favoring the more opportunistic,
shallow-rooted annual grass species. The oak
woodlands and savannahs are plant communities in
danger of disappearing, due primarily to the loss of
habitat to urban development, and the gradual, but
continuous decline in natural oak regeneration. Oak
woodlands and savannahs also offer important habitat
to many various wildlife species.
The oaks that dominate these plant communities on
much of the land surrounding the lake, consist
primarily of Blue oak (Quercus douglasii), California
Black oak (Quercus keloggii), Interior live oak (Quercus
wislizeni), and Scrub oak (Quercus berberidifolia). The
understory is primarily non-native, annual grass species
that include, Oats (Avena spp.), Bromes (Bromus
spp.), Annual fescues (Vulpia spp.), and Ryegrasses
(Lolium spp).
Quality Projects
Concerns
Opportunities
Chaparral is the second most dominant
plant community around Lake Berryessa.
It is dominated by woody shrubs, many
of which are evergreen with leathery
leaves, and are highly drought-tolerant.
Chaparral is a fire-dependent community,
found on dry, well-drained soils, with
coarse to loamy textures. Plant
dominance in chaparral is primarily
dependent on fire history and aspect,
creating a varying range of shrub
species. Chamise (Adenostoma
fasciculatum) dominates the most
droughty, excessively drained soils, which
are commonly found on the more south-
facing slopes. However, it can be
species. The north-facing slopes, as well as some of
the sites that have not burned for many years, will
shift from a chamise-dominated community to a
community dominated by several different species,
including Manzanita (Arctostaphylos spp.), Ceanothus
(Ceanothus spp.), Mountain-mahogany (Cercocarpus
spp.), Toyon (Heteromeles arbutifolia), and Sumac
(Rhus spp.). Other species that can be found locally
also include: Hollyleaf cherry (Prunus ilicifolia),
Snowberry (Symphoricarpos spp., and Elderberry
(Sambucus spp.).
Chaparral is also an important plant community for
many species of wildlife, namely birds and rodents.
Although riparian areas are a minor component on most landscapes, they are the most biologically
diverse communities and offer important habitat for wildlife. There are several streams, permanent
and intermittent, that feed into Lake Berryessa and offer habitat for many different plant species.
The riparian zone along a stream is defined as the area or zone that creates an interface between
land and water, and the adjacent land if frequently inundated with water. They are the areas
adjacent to water courses that are prone to flooding (Wikipedia 2005). Riparian plant communities
are a complex structure of trees, shrubs, grasses, forbs, grass-likes (sedges and rushes), and ferns
that play an integral role in stabilizing the streambanks; helping to reduce sedimentation and bank
failure; maintaining the proper stream water quality, function, and condition; shading the stream to
lower water temperatures; acting as pollutant filters for land runoff; and providing a source of litter
and snags for many types of wildlife (http://www.ozestuaries.org/indicators/DEF_riparian_vegetation.html).
found in the riparian zones
around Lake Berryessa
include: Valley or California
white oak (Quercus lobata)
seen on the top right,
Fremont’s cottonwood
(Populus fremonttii), California
sycamore (Platanus
racemosa), Poison oak
(Toxicodendron diversilobum),
White Alder (Alnus
rhombifolia), Dogwoods
(Cornus spp.), California
hazelnut (Coryla cornuta var.
californica), Sedges (Carex spp.
), Bulrush (Scirpus spp.), and
Spikerush (Eleocharis spp.).
during the last 200 years, exotic annual grasses were introduced and outcompeted the native
perennials, and now only 2 percent of the state's grasslands are vegetated by native perennial grasses
(ARS 2005).
offering forage, habitat, and cover to many various species of wildlife,
as well as preventing soil erosion with much more substantial rooting
systems than annual grasses. Important native grass species found
around Lake Berryessa include: Purple needlegrass (Nasella pulchra),
California brome (Bromus carinatus), Pine bluegrass (Poa secunda),
Blue wildrye (Elymus glaucus), several other needlegrasses, and many
annual and perennial forbs including, Wild onions (Allium spp.),
Brodeias (Brodeia spp.), Lupines (Lupinus spp.), Blue dicks
(Dichelostemma spp.), California poppy (Eschscholzia californica), and
Wild hyacinths (Triteleia spp.).
grasslands cover a significant portion of
the Central Valley of California.
significantly shorter amount of time
to germinate and establish and also
don't require special soil conditions,
thus tying up necessary resources
for the perennial species to
germinate, and often times require
certain amounts of water and days
at a specific temperature before
they can germinate.
they have shallow rooting systems that offer minimal soil stability, contain
very little nutritional value as forage for livestock or wildlife, and create
higher levels of fine fuels for fires. Common annual grassland species
include: Oats (Avena spp.), Bromes (Bromus spp.), Annual fescues (Vulpia
spp.), and Ryegrasses (Lolium spp).
grasslands in California
http://www.cnga.org/index.php - California Native Grass Society
http://www.puc.edu/Faculty/Gilbert_Muth/napa.htm - Napa County Flora
