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ANNUAL RANGELAND MANAGEMENT
PRINCIPLES AND PRACTICES: THE
CALIFORNIA EXPERIENCE
Melvin R. George
ABSTRACT
1979). Response to nitrogen fertilization is dependable
between 15 and 30 inches of annual rainfall, but economic
feasibility varies with site productivity and ranch forage
alternatives.
Dr. Merton Love joined the College of Agriculture in the
1940's to develop native or exotic perennial grasses for seeding on annual rangelands. Several perennial grasses were
shown to be adapted to California's mediterranean rangelands, but competition from resident annual species limited
the success and dependability of perennial grass seedings.
Dr. Love found greater success when he imported and
tested rose clover (Trifolium hirtum) in the 1940's and 1950's
(Love 1985). Rose clover has been so successful that it has
spread naturally throughout many areas of the northern
Sierra foothills. Annual legume seeding success improved
with the development of Rhizobium inoculation technology
(Holland and others 1969). Seeding of subterranean clover
(Trifolium subterraneum), rose clover, and lana vetch (Vicia
dasyacarpa) continues to be a common practice for improving forage production and quality (Murphy 1973).
Prevailing weather has a greater influence on annual
rangeland forage production than grazing management
and agronomic practices. However, these practices can
be used to manipulate species composition, forage produc·
tivity, and forage quality. Annual rangeland vegetation
dynamics on a site can be described using state and transition models. Transitions between states may be controlled
by natural events or managerial inputs.
RANGE IMPROVEMENT
The development of annual rangeland management principles and practices can be traced back to early integrated
research beginning in the 1930's in the College of Agriculture and at the USDA Forest Service San Joaquin Experimental Range (SJER) in the central Sierra Nevada footbills. Throughout the past 60 years management principles
have emphasized resource values associated with forage
and livestock production. While basic research focused on
ecological and physiological principles of forage production,
applied research focused on managing livestock and manipulating forage production, forage quality, and species
composition.
Menke (1989) described vegetation management activities
used to manipulate forage productivity, forage quality, and
species composition. Prescribed fire has been used alone or
with mechanical and chemical controls to convert woody
plant-dominated communities to open grasslands (Kay and
Leonard 1979; Nichols and others 1984). Seeding of native
or introduced perennial grasses, annual legumes, or both,
was part of the type conversion process from shrubland or
oak woodland to open grassland. Less frequently, fire has
been used to reduce annual grass competition with native
or introduced perennial grasses (Ahmed 1983; Fossom 1990;
Heady 1973; Hervey 1949; Zavon 1982).
Annual rangelands are nitrogen deficient as well as phosphorus or sulfur deficient. Consequently, a great deal ofbasic and applied research has focused on fertilizer responses
(Jones1974) and nutrient cycling (Jones and Woodmansee
GRAZING MANAGEMENT
Year-long or seasonal continuous grazing has been the
traditional practice on annual rangeland. Annual variation
in forage productivity due to prevailing weather usually has
a greater impact on livestock performance than grazing systems. Livestock performance may be reduced or unchanged
by seasonal compared to continuous grazing systems. Moderate grazing that allowed about 80 to 90 pounds of dry matter per animal unit per day from February through July at
SJER produced the optimum combination of animal performance and per-acre productivity (Bentley and Talbot 1951;
Wagnon and others1959).
The need to control intensity of forage utilization on
annual rangelands has resulted in the development of residual dry matter standards and assessment procedures
(Clawson and others 1981). Recommended minimum residual dry matter (RDM) levels depend on average precipitation and slope. Adequate RDM moderates the seed germination and seedling establishment microenvironment.
Too much RDM or a dense mulch results in a thatch that
inhibits early response of new forage growth. Low RDM
tends to maintain forbs such as filaree (Erodium spp.) and
annual legumes. High residue tends to increase the grass
composition (Bartolome and others 1980). Hooper and
Heady (1970) found that high RDM was followed by higher
forage production the following spring.
Paper presented at the Symposium on Ecology, Management, and Restoration oflntermountain Annual Rangelands, Boise, ID, May 18-22, 1992.
Melvin R. George is Cooperative Extension Range and Pasture Specialist, Department of Agronomy and Range Science, University of California,
Davis, CA 95616.
392
'-
DESmED PLANT COMMUNITIES
We have accumulated a great deal of information in the
past 60 years that is useful in managing annual rangelands.
Unfortunately, few natural resource managers working in
annual rangelands are conversant with this knowledge base.
New and recurring resource management objectives including biodiversity, rare and endangered species, and ecological restoration can benefit from this knowledge base developed primarily for livestock and range forage management
purposes.
To more adequately extend this information we propose
to use state and transition models (Westoby and others
1989) to describe desired plant communities (states) and
the natural and managerial events (transitions) required
to reach them. Site protection, biodiversity, habitat, forage, and other resource values will be described for each
plant community.
STATE AND TRANSITION MODEL
While annual grasslands are generally considered to be
stable (Heady 1977), communities are made up of several
transient states that are often described by species dominance. Transition between these states may be triggered
by natural events (weather, fire, etc.) or management
(brush control, seeding, change in stocking rate, etc.), or
combinations of the two. Transitions may occur very
quickly (fire) or over an extended period (biological invasions, climate change) (Svejcar and Brown 1991).
Figure 1 and associated descriptions (next page) describe
a state and transition example for a shallow gravelly loam
site in the Sierra foothills ofYuba County, CA. This approach provides a map for ecosystem management for use
--
~----------~ye
I
Medusahead
dominant
.......
....
-
II
T5
Filaree and/or I~
annual legume ~
dominant
----------~~ T1 ......----...-------' T 2
by land managers and a means for more quantifiably testing hypotheses about ecosystem response to disturbance
and management.
The state and transition model can be applied in the
field and used for planning managerial inputs. The transitions describe managerial actions (inputs) required to
progress from one state to another. Resource value ratings can be assigned to stable states and potential products (outputs) can be projected. Probabilities of natural
phenomena (disturbances) and managerial success can
be assigned to transitions.
For example, if a grassland is in State I (fig. 1) and the
objective was to convert to the grassland in State m, managerial inputs described in Transitions 1 and 2 would be
prescribed. Early rains and favorable growing seasons
would accelerate progress toward State III while drought
and fire would tend to delay progress for 1 to 3 years. Removal of livestock earlier to leave more residual dry matter would facilitate progress from State II to State ill. Application of nitrogen fertilizer may accelerate progress from
State II to State III. At State III, management inputs can
be designed to maintain State III or to set course for a new
objective.
The resource value for cattle grazing would increase
with progress from State I to State III, while State II
would be of greater value for sheep grazing than cattle.
Maintaining adequate cover while increasing forb populations (State II) would enhance upland bird habitat. Increasing cover (State Ill) would reduce habitat value for
ground squirrels (Spermophilus beecheyi). As the grassland progresses from State I to State III, increasing cover
and residual dry matter may improve the grassland's value
as watershed. The landowner's goals, enterprises, and
markets would determine the most advantageous mix of
patch states on the landscape.
Ill
T4
Soft chess I~
ripgut brome
and wild oats ~
T3
dominant
I
~~----~------------------~
v
Ceanothus,
manzanita, and
poison oak
dominant
Purple
needlegrass
dominant
J~
T9
T10
VI
Oak trees,
saplings, and
seedlings with
annuargrass
understory
Figure 1-5tate-and-transltion description for a shallow gravelly loam foothill range site in
Yuba County, CA, with 675-875 mm of annual rainfall.
393
IV
T11
.....
.......
.......
........
T12
VII
Oak trees,saplings
and seedlings with
needlegrass
understory
Catalog of States
State 1-Medusahead (Taeniatherum asperum) forms
nearly pure stands with heavy litter that effectively excludes
most other annual grasses and forbs. High silica content is
believed to slow decomposition, resulting in litter accumulation that effectively suppresses establishment of associated
species. Late maturity allows medusahead to most effectively exploit soils containing clay (Young and Evans 1970).
State ll-Filaree (Erodium cicutarium) dominates the
seedbank and the aboveground standing crop. Medusahead density is substantially reduced. Soft chess brome
(Bromus mollis) is present in the seedbank and standing
crop but in small amounts. Seeded annual legumes may
partially replace filaree.
State W-Wild oats (Avena fatua), ripgut brome (}Jromus
diandrus), and soft chess dominate patches. Filaree and
other species are present in small amounts. Medusahead
is infrequent or not present. Perennial grasses such as purple needlegrass (Stipa pulchra) may be present in small
amounts.
(T. hirtum) may partially replace filaree if medusahead
control is followed by seeding these legumes. Application
of phosphorus or sulfur increases the vigor and productivity
of these annual legumes. Close grazing maintains legumes
by reducing grass shading.
Transition 2--Filaree dominance is reduced as other
species, especially annual grasses, successfully invade and
colonize the patch from adjacent patches. Increased aboveground production and light to moderate herbivory increase
litter during summer and fall resulting in decreased summer soil temperatures and reduced fall filaree germination.
Increased litter also improves grass seedling survival by
reducing desiccation. Regular or above-average rainfall
through the fall and winter increases grass seedling survival. Application of nitrogen fertilizer may accelerate herbage production and litter accumulation if annual rainfall
is between 15 and 30 inches. Shading by annual grasses
reduces annual legumes, especially subterranean clover.
Rose clover remains in the sward due to hardseed in the
seed bank.
Transition 3--Annual plant dominance is seemingly
irreversible. Purple needlegrass recruitment and survival
is suppressed by intense competition with annual species
and season-long herbivory. Germination of purple needlegrass is suppressed by moisture stress and high levels of
litter (Bartolome and Gemmill1981). Reversal may be possible with a high level of managerial control of season and
intensity of grazing and periodic prescribed burning. Fire
reduces litter and annual plant density (Zavon 1982). Heavy
early spring grazing followed by late-summer burning increases the frequency of needlegrass seedling emergence
and survival (Fossom 1990). Adequate rest between grazing periods improves needlegrass vigor.
State IV-Purple needlegrass (Stipa pulchra) dominates
the grassland. While it is the most common native grass
present in today's California annual grassland, it may not
have been the dominant perennial grass in the original
California grassland (Bartolome and Gemmill1981). Nodding needlegrass (S. cernua), blue wildrye (Elymus glaucus), pine bluegrass (Poa scabrella), junegrass (J{oeleria
cristata), or California oatgrass (Danthonia californica)
may have been present in the original grassland.
State V-Wedgeleaf ceanothus (Ceanothus cuneatus),
whiteleaf manzanita (Arctostaphylos viscida), and poisonoak (Rhus diversiloba) dominate the community.
Transition 4-Year-long continuous grazing, drought,
and competition from annual species reduce needlegrass
vigor and survival.
State VI-Blue oak (Quercus douglasii) and interior live
oak (Q. wislizeni) savanna with an annual grass understory
dominated by wild oats, soft chess brome, and ripgut brome.
Transition 5-Filaree increases in response to low litter
levels or early fall rains followed by several weeks without
precipitation. Poor growing season production or heavy
herbivory reduces litter levels. Long periods of inadequate
rainfall within the normal growing season reduce grass as
a component of the herbaceous composition.
State VII-Blue oak and interior live oak savanna with
a perennial grass (purple needlegrass) understory.
Catalog of Transitions
Transition 1-Medusahead seedbank reduced by 50 to
90 percent. This can be effected by several forins of disturbance (Hilken and Miller 1980; Major and others 1960), including herbicide applications, cultivation, late May fire, or
short-duration, high-intensity grazing throughout the growing season for 2 consecutive years. These disturbances reduce litter and open the site for establishment of other species. Filaree will invade from surrounding patches or become
established from residual hardseed. Low levels of litter in
summer and fall lead to filaree dominance within patches.
Litter abundance is primarily a function of the intensity of
herbivory during spring and early summer. Low litter cover
increases soil temperature and seed germination with the
first fall rains (Rice 1989). Timing of fall precipitation can
also influence filaree composition. Early germinating rains
followed by several weeks of drought favor filaree. Filaree
is more tolerant of drought than annual grass and forb competitors because of the ability to rapidly elongate a tap root.
Subterranean (Trifolium subterraneum) and rose clover
Transition 6-Medusahead gradually increases in the
patch. Plants produced from the postfire seedbank produce
seed, increasing medusahead in the seedbank. Medusahead
increases and dominates the patch and gradually invades
adjacent patches if clay content of the soil is adequate.
Transition 7--Summer wildfire or controlled burning
removes shrubs. Grazing and recurring fire maintain
grassland.
Transition ~Protection from grazing and fire facilitates shrub invasion. Shrubs become dominant in 10 to
20 years. Herbaceous understory declines as shrub canopy
increases (Johnson and Fitzhugh 1990).
Transition 9-Drought, wildfire, controlled burning,
or herbicides remove blue and interior live oaks leaving
an open grassland dominated by annual species.
Transition 10-High density of annual plants suppresses
oak seedling emergence and root growth. Competition for
394
soil water with annual species contributes to the increased
rate of blue oak seedling mortality (Gordon and others 1989).
Blue oak savannas are believed to be more xeric today than
during presettlement conditions due to high annual-plant
densities and reduced litter associated with domestic livestock grazing (Welker and Menke 1990).
Transition 11-Same as Transition 3. Like purple
needlegrass, oak recruitment and seedling survival is
suppressed by competition with annual species.
Transition 12-Year-long continuous grazing and
drought reduce needlegrass vigor and survival.
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