Agriculture Reference
In-Depth Information
Other California Vegetation Types
Crown fire chaparral shrublands and surface fire conifer forests provide a useful
contrast illustrating the range of fire regimes present in the California MTC
region. These two ecosystems dominate the bulk of the landscape, yet there is a
rich diversity of other vegetation types, each with its own unique fire regime
characteristics. Some of that variation is reflected in these examples.
Grasslands
Most grasslands in California are disturbed communities that lack much struc-
tural diversity and are dominated by non-native annual grasses and forbs
(Huenneke & Mooney
1989
; Hamilton
1997
). These annual grasslands appear to
be derived from several different origins. In the central coast ranges and southern
California extensive burning of native shrublands by Native Americans replaced
these perennial systems with annual herbs that were susceptible to alien invasion
upon European colonization (Keeley
1990a
). Cooper (
1922
) cited remnant stands
of
Adenostoma fasciculatum
in the northern part of the Great Central Valley
as evidence of a former wider distribution across the valley that had been devas-
tated by Native American burning and this is affirmed by more recent research
(Bloom & Watson
2006
).
Others have long contended that throughout the Central Valley annual grass-
lands have replaced perennial grasslands due to intensive livestock grazing and
extreme droughts during the nineteenth century (Heady
1977
). In the southern
part of the Central Valley and foothills of the Sierra Nevada there is evidence that
extensive “grasslands” were originally dominated by native annual forbs, and
these communities have been heavily invaded by non-native annual grasses
(Hoover
1936
; Hamilton
1997
). Native forbs in genera such as
Amsinckia
,
Cryp-
tantha
,
Lupinus
,
Madia
and
Plagiobothrys
still persist in these annual grasslands
(Keeley
1990a
; Schiffman
2007
; Minnich
2008
)
.
Native grasslands today are limited to widely disjunct and isolated fragments.
Structurally they are more interesting than annual grasslands with diverse growth
forms dominated by bunchgrasses, geophytes, rhizomatous perennials and annual
forbs (Corbin
et al.
2007
). The most widespread native bunchgrass,
Nassella
pulchra
, is endemic to the California MTC region, as are many of the geophytes
such as species of
Bloomeria
,
Brodiaea
,
Calochortus
,
Fritillaria
and
Triteleia.
His-
torically it is believed that native grasslands dominated large portions of the
northern Central Valley (Bartolome
et al.
2007
). Farther south, and throughout
the central and southern coastal ranges, native grasslands are thought to have
been distributed in small patches determined by soil and drainage characteristics
(Huenneke
1989
; Keeley
1993a
).
All grasslands are relatively resilient to frequent surface fires (Reiner
2007
).
Although most annual species have transient seedbanks, the annual seed rain
