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TWENTY

Grazing Management on California’s Mediterranean Grasslands LYN N H U NTS I N G E R, JAM E S W. BARTO LO M E, AN D CA R LA M. D’ANTO N I O

Grazing management uses ungulates to achieve desired ecological, social, and economic outcomes. It is the least costly and in some ways the most flexible tool for managing vegetation on California grasslands. Grazing can be used to manipulate plant community structure, decrease fuel loads, control invasive weeds, create wildlife habitat, and enhance species diversity (Marty 2005; Pyke and Marty 2005). Grazing is an important natural process in grassland ecosystems (McNaughton et al. 1989; Milchunas and Lauenroth 1993; Perevolotsky and Seligman 1998), and a number of studies have recorded higher biodiversity in grazed compared to ungrazed systems (Noy-Meir et al. 1989; Harrison 1999b; Hayes and Holl 2003a). Like almost any other human-directed or influenced activity in grasslands, grazing can also harm vegetation and wildlife if improperly managed (Painter and Belsky 1993; Fleischner 1994; Freilich et al. 2003). The history of livestock grazing and its impacts in California is controversial and complex (D’Antonio et al., Chapter 6; Jackson and Bartolome, Chapter 17). This chapter concentrates on what is known about goals of contemporary grazing programs and the manipulation of vegetation using domestic livestock.

Understanding the effects of grazing on vegetation in the California grassland is complicated by a large climatic gradient, pronounced interannual variation in weather, strong variation in topography and land-use history, and regional variation in the species pool. At any one site, the impact of grazing arises out of the interaction of land use history, the current and recent grazing management scheme, the abiotic environment, and the species pool in the local plant community (Heady 1984). The influence of the abiotic environment, including soil type, elevation, precipitation, and temperature, is particularly important in the California Mediterranean environment. Because so much of the grassland is composed of annual species, composition, density, and productivity are highly influenced by the annual pattern and amount of rainfall, with production varying by orders of magnitude among

years. California’s heterogenous soils also add to the heterogeneity of the grassland and response to management actions.

For these reasons California grassland scientists have developed methods for managing the grassland that emphasize coping with variation and recognizing the overwhelming role of abiotic factors. Management programs that are based on a conceptual model of long-term, competition-driven vegetation shifts in a relatively consistent environment (e.g., equilibrium-based theory) have limited application in California grasslands, particularly annual-dominated sites.

This chapter first highlights the common grazing management goals of the agencies, private landowners, and conservation organizations that manage most of the California grassland. Next, general principles for developing management practices and plans based on the existing knowledge base for grazing and vegetation in California are presented and discussed. The final section of the chapter reviews the knowledge base for implementing specific practices to achieve some common management goals.

It is widely acknowledged that management varies widely from place to place on California grasslands, potentially providing abundant examples of sustainable and unsustainable management practices on private and public lands. In this chapter we do not attempt a catalog of historic or current practices, an assessment of their detriments and benefits, or a referendum on different kinds of management. Instead, the focus is on the common goals of grazing management in California Mediterranean grasslands, and what we know about the practices that can contribute to achieving these goals.

Landowners, Managers, and Management Goals Most annual grasslands in California are privately owned (Table 20.1). The United States Forest Service, Bureau of Land Management, National Park Service, and Department of Defense also own a small but significant amount of California

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TA B L E 20.1 Examples of California Grassland Ownership in 2002 and Grazing Management Goals

Ownership

Annual grasslands 1,000s of hectares (% of woodlands)

Oak woodlandsa 1,000s of hectares (% of woodlands)

Private

3,806 (88%)

1,733 (82%)

Livestock production based on grassland production, lifestyle benefits, family heritage, working with friends and relatives, making a living (Liffmann et al. 2000; Sulak et al. 2002; Larson et al. 2005).

Speculative

Unknown, included in private

Unknown, included in private

Fire hazard reduction, maintaining land in agriculture for tax purposes.

Land Trust

Unknown, included in private

Unknown, included in private

Invasive species control, maintaining agriculture and facilitating land restoration, fire hazard reduction, biodiversity. Preservation of ranches, rancher stewardship (CRT 2005).

181 (4%)

98 (5%)

The use of BLM rangelands for “grazing is supported by the Federal Land Policy and Management Act of 1976 (FLPMA), the Public Rangelands Improvement Act (PRIA) of 1978, and the Taylor Grazing Act (TGA) of 1934, as amended. The TGA requires the BLM to prevent overgrazing and soil deterioration; to provide for orderly use, improvement, and development; and to stabilize the livestock industry that depends upon the public rangelands” (BLM 2005: 90).

United States Bureau of Land Management (BLM)

Grazing management goal

“To improve the health and productivity of the land to support the BLM multiple use mission and to sustain the health, diversity, and productivity of the public lands” (BLM 2005: 4).

United States Forest Service (USFS)

90 (2%)

126 (6%)

Sustainable use in concert with multiple uses; maintaining and improving rangeland health, restoring rangeland ecosystem functions; managing the vegetation resources across the landscape to serve a multitude of resource needs (USDA-USFS 2005a). “To promote rural economic development and a quality rural environment” (USDA-USFS 2005b). “To manage, maintain, and improve public rangelands to support all rangeland values in accordance with management objectives and the land use planning process. To prevent economic disruption and harm to the livestock industry” (PRIA).

National Park Service (NPS)

15 ( 1%)

17 ( 1%)

“To preserve unimpaired the natural and cultural resources and values of the National Park System for the enjoyment, education, and inspiration of this and future generations” (NPS Organic Act of 1916). Pt. Reyes National Seashore: “To acknowledge the historic, cultural, and ethnic diversity of the area, resources such as the cultural landscapes embodied in the historic ranches, will be preserved” (NPS 2003).

TA B L E 20.1 ( C O N T I N U E D ) Examples of California Grassland Ownership in 2002 and Grazing Management Goals

Ownership State and Other Public Lands

Department of Defense

Total

Annual grasslands 1,000s of hectares (% of woodlands)

Oak woodlandsa 1,000s of hectares (% of woodlands)

241 (6%)

125 (6%)

Fire hazard reduction, management of invasive species and vegetation. Utilizing cattle, sheep, and goats as a vegetation management tool to maintain and improve habitat conditions for resident plants and animals and to prevent wildfires. Ongoing research indicates that moderately grazed areas generally display a greater diversity and density of plant and animal life (EBRPD 2005).

Included in “other public”

Included in “other public”

Fire hazard reduction, restoration of native species, and ecosystem management. Camp Pendleton: “An ecosystem based approach to facilitate maximum support for the military training mission while promoting the sustainability of native species and habitat diversity and compliance with laws and regulations” (USMC 2005). Air Force Instruction 32-7064 (USAF 1997) states, “Agricultural outleasing for cropland and grazing can be used to maintain ecologically sound stewardship of public lands. Outleasing can produce a cash flow to sustain the program, enhance other aspects of the natural resources management program, and reduce the maintenance costs of semi-improved lands. However, all agricultural operations must be compatible with the military mission and long-term ecosystem management goals.”

4,333

2,096

California grasslands are 11% of the state; oak woodlands are 5%.

Grazing management goal

NOTE : CDF-FRAP 2003 p. A-27. Because open oak woodlands often support significant grasslands used primarily for grazing, these are included here.

The available data do not distinguish open oak woodlands known as savannah, from closed canopy woodlands. They are also for total area owned, not grazed acres. aIncludes Blue, Coastal, Foothill, and Valley Oak hardwood types from the California Wildlife Habitat Relationships System as assessed by CDF-FRAP (2003). Montane types are excluded.

grassland habitat. In addition, state, local, and regional agencies and watershed, utility, and recreation districts often manage and own annual grasslands. A growing phenomenon in California is ownership by land trusts: the amount of land conserved by trusts through purchase, transfer, or easement increased by 147% between 1998 and 2003 (LTA 2004), to more than 600,000 hectares (ha). Of this land, 121,000 ha are protected by conservation easements. There are now at least 173 land trusts in California, more than in any other state (LTA 2004). Data on how much of that are grassland is not available.

Although the various ownership groups tend to have different management goals for livestock grazing, maintaining grassland “sustainability” is a common theme. Private landowner goals are usually more influenced by the need to generate income, while agencies and land trusts may be

more focused on goals related to their particular mandates, such as fire hazard reduction, restoration of native species, water quality protection, and protection of endangered species. There is, however, considerable overlap and blending of goals. Agencies and land trusts that use grazing to manage vegetation need to accommodate the goals and needs of those who supply the livestock, just as the livestock provider needs to accommodate the goals of the agency or trust. In the following sections we briefly review goals of different groups.

Private Landowners Livestock producers manage more California grassland than any other kind of owner, and also provide the livestock for

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grazing on millions of hectares of public and private leased land. More than three quarters of grassland parcels larger than 80 hectares are grazed by livestock (Huntsinger et al.

1997, 2007). The low-intensity use typical on many large parcels means that these properties may provide significant wildlife habitat, floristic diversity, watershed, and viewshed.

About 42% of oak woodlands are owned by those who produce livestock for sale, and another 10% of owners produce livestock for their own use only. As estimated from recent surveys, an additional 10% of oak woodland landowners graze stock on their property by leasing out their land to ranchers (Huntsinger et al. 2007). County tax assessor data show that many hectares of California oak woodlands and annual grasslands are owned by corporations and investment groups. A significant portion of these are holding land as an investment, anticipating continued rising land values. Maintaining grazing on these properties reduces fire hazard and qualifies the land for tax benefits based on agricultural use. Homeowners’ associations may also use livestock grazing. At Sea Ranch along the Sonoma county coast, sheep and goats are used to control noxious weeds, reduce the frequency and intensity of wildfires, improve wildlife habitat, and enhance biodiversity within the 4,000-acre residential community (Barry 2005).

The great majority of livestock producers live on their properties and manage the land themselves. Most have owned their land for a long time: 63% of public land ranchers in one survey reported that their families have owned their ranch for more than 100 years (Sulak and Huntsinger 2002). In 2005, only one quarter of oak woodland ranchers in a statewide survey reported that the majority of household income came from ranching, while 10% reported farming as their major source of income. About 22% cited off-ranch wages as their major income source, and another 22% earned most of their income from other forms of “selfemployment,” including investments, pensions, and so forth (Huntsinger et al. 2007). What ranchers say makes ranching worthwhile is experiencing the lifestyle, raising a family on a ranch, working with livestock, and enjoying the natural environment. This is common throughout the west (Bartlett et al. 1989; Gentner and Tanaka 2002; Rowe et al.

2001; Martin and Jeffries 1966; Sulak and Huntsinger 2002; Torell et al. 2005; Smith and Martin 1972). In a three-county California survey more than 90% of ranchers agreed that ranching “makes them feel closer to the earth” and that it is a “good place for family life,” and about a third reported that they belonged to some sort of “environmental organization” (Liffmann et al. 2000). On the other hand, most consider land appreciation an important, long-term financial asset and have planned retirements and estates accordingly. As a result they strongly defend their right to market their land at a good price.

California livestock production is not diverse, with the vast majority of ranchers producing cattle only. In 2004, less than a fifth of oak woodland landowners grazed goats, sheep, or llamas, and most of those also grazed cattle (Huntsinger

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et al. 2007). The majority of ranchers have a herd of cows that produce calves for market each year. After weaning, calves may be retained by the owner if they have adequate feed, or sold to other ranches or feedlots. About 720,000 beef cows grazed California rangelands in 2005, down from a million in 1985, with half a million to a million weaned calves, known as “stockers,” also using rangeland resources, depending on rainfall, markets, and other factors (NASS 2005). Most stockers are produced by ranchers that also have a cow-calf herd, with less than a tenth of oak woodland cattle producers raising only stockers in 2004 (Huntsinger et al. 2007). In 2005 there were 275,000 ewes in California, the mature female sheep of the kind likely to use rangelands, down from 776,000 in 1985 (NASS 2005).

Goats are unreported and uncommon overall. California has significant numbers of dairy cattle, but dairies are rarely grassland-based, except in some northern regions. Young animals may use rangelands.

In a 2000 study comparing northern and central California ranchers in three counties, management goals were similar, although grazing practices varied among areas (Table 20.2; Liffman et al. 2000). Though not a statewide survey, the study allows comparison of ranchers in different parts of the state. The impact of geographical differences is apparent. In Tehama County the summer climate is drier and hotter, and high-elevation mountain ranges are nearby, so moving stock to upland or irrigated pastures during the summer is common, as is using rotational grazing practices that are often prescribed by the land management agencies that manage higher-elevation grazing lands. In coastal Alameda and Contra Costa counties, livestock can be maintained on grassland year-round, but, as a result, more ranchers manipulate water sources for the benefit of their stock so that water is available on low-elevation rangeland in the summer (Table 20.2). Putting in a trough can be simply to water livestock, or it can be to divert livestock from natural watering holes to reduce impacts to these areas. Throughout the state, there are divergences in practices that reflect particular geographic and economic conditions, but nonetheless the commonalities, particularly in the most important goals, stand out.

Ranchers overall rely on sustainable, productive rangelands, and the goals of respondents reflect this need, as they emphasize protecting soils and increasing forage. The most ubiquitous management goals for the surveyed ranchers are to maintain and increase forage and livestock productivity (Table 20.2). However, improving wildlife habitat, protecting scenic values, and reducing the need for herbicides and pesticides are also important goals. A significant proportion use prescribed burning, herbicides, and other methods to clear brush, control invasive species, and make other vegetation changes (Table 20.2). Most respondents reported that they use some form of controlled grazing to manage their lands and leave forage behind after grazing to protect soils from erosion and to create conditions favorable to the germination of valued species (Table 20.2). Many use seeding and fertilizers

TA B L E 20.2 California Ranchers: Goals and Practices in Three California Counties

% Tehama county ranchers (n 132)a

% Alameda & Contra Costa county ranchers (n 113)

P .1 (X2)

78 95 94 89 78 41 79 99

69 97 90 91 67 37 68 98

nsb ns ns ns .05 ns .05 ns

34 35 32 18 65 53 12 40 23 65

25 36 28 18 73 37 40 43 15 57

ns ns ns ns ns .02 .00 ns .06 ns

44 39 38 24 70 46 40 87 85

24 26 39 64 90 71 30 86 87

.01 .09 ns .00 .00 .00 ns ns ns

The following are important goals for my ranch:

Improving wildlife habitat Increasing forage Improving soil stability Increasing livestock production Protect scenic values Diversify operation Reduce need for pesticides and herbicides Improve livestock quality Have carried out the following practices in last 5 years:

Prescribed or controlled burn Herbicides Chaining or thinning Browsing by goats or others Controlled grazing Deferred or rest rotation Continuous year-round grazing Seeding rangeland Fencing riparian areas Leaving behind ungrazed forage for soil and seedbank benefits Commercial fertilizers Manure application Electric fencing Developed springs Put in water tanks or troughs Laid water pipe Stabilized streambanks Overall satisfied with range condition Used volunteer labor by neighbors NOTE:

Liffmann et al. 2000. varies slightly by question. bnon-significant (ns). an

to enhance productivity, and grazing systems such as rotational systems (Table 20.2), where cattle are moved from one pasture to another on a regular basis.

Public acquisition is one way to protect grasslands from development, but it is costly and controversial (Merenlender et al. 2004). Instead, in recent years efforts have been made by the conservation community to offer incentives to private landowners for maintaining the natural characteristics of

their land as a way to conserve open space and wildlife habitat (Barry and Huntsinger 2002; Huntsinger and Hopkinson 1996). The rancher provides on-site management for these “working landscapes,� and the land remains productive agricultural land. The majority of ranchers voluntarily participate in one land conservation incentive program through the California Land Conservation Act (CLCA) of 1965 (also known as the Williamson Act), which allows them

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to pay property taxes at a rate based on the land’s agricultural value as long as they agree to keep their land in agriculture for ten years into the future (for further discussion of such conservation practices, see Chapter 17).

In exchange for much needed cash or tax relief, a small but growing number of ranchers have placed conservation easements on their properties. There are many different kinds of conservation easements, but in general they indicate that the part of the title that allows development of the land has been sold or donated to a land trust by the owner (Sulak et al. 2004; Merenlender et al. 2004). This restriction stays with the land even if ownership eventually changes. Selling an easement can provide capital to the rancher for improvements to the operation, paying taxes, or meeting other personal needs.

Because ranches often contain valuable natural resources, they are also subject to natural resources regulation. The majority of ranchers in the three-county survey believed that overregulation is a problem for them, and despite the widespread interest of ranchers in maintaining and improving wildlife habitat, more than 80% of them reported that they felt the Endangered Species Act was a threat to ranching (Liffmann et al. 2000). Most also felt that “society” is at least somewhat hostile to ranching (Liffmann et al. 2000) and that the state does not do a very good job of consulting with those affected by regulations and other policy. Overcoming these perceptions is one barrier to more collaborative management between public entities, conservation groups, and private landowners. There is some public funding available to help ranchers meet some regulatory requirements for wildlife, water quality, and other resource benefits, and in some areas county agencies have helped farmers and ranchers access these funds as part of an overall county planning effort for land conservation (EDF 2007). This helps to build trust and partnerships (Hart 1991). In general, private landowners prefer voluntary and incentive-based programs that rely on the high value ranchers themselves place on the natural amenities of their property. The full cost and effectiveness of voluntary, incentive-based programs, as opposed to regulatory efforts, varies with the situation, but impacts on the attitudes and perceptions that underlie both short- and longterm landowner decision making must be considered when regulatory versus incentive-based options are debated.

In short, the most widespread goals for the landowners who own most California grasslands are sustainable grassland and livestock production, economic viability, and benefiting individually or as a family from the ranching lifestyle. Few manage for any of these goals exclusively. All goals should be considered when making policy and management decisions.

Public Lands Twelve percent of annual grasslands are in public ownership (CDF-FRAP 2003). A diverse array of public agencies lease public grassland for grazing, including the Bureau of Land

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Management (BLM), Department of Defense (DoD), U.S. Forest Service (USFS), water districts, and local and regional parks. Many California ranchers use some public lands for part of the year, including local as well as federal lands.

About 35% of ranchers in Alameda and Contra Costa Counties used public land in 2000, most of it under local and regional jurisdictions, while about 30% of ranchers in northern California’s Tehama County also used public land, most of it federal (Liffmann et al. 2000). Studies have consistently found strong competition for the available private grassland, with ranchers in the Sierra Nevada foothills stating that competition was intense (Sulak and Huntsinger 2007).

In the San Francisco Bay area region, ranchers are active seekers and users of the available public and private leases (Sulak and Huntsinger 2007). Competition for grazing leases has been augmented by the administrative withdrawal of millions of acres of federal lands from grazing, and the continued decline in grazing permit issuance (CDF-FRAP 2003).

Declining public forage supply stresses the industry and potentially contributes to grazing pressure on private lands (Sulak and Huntsinger, 2002).

On the west side of the Sierra Nevada, montane forage on USFS and private forest land complements the winter forage produced by California annual grasslands. The USFS had 466 grazing leases in California in 2005 (USDA-USFS 2006). Some of these, however, are connected to eastern-Sierran vegetation types rather than Mediterranean grasslands. In a survey of livestock producers using USFS land in the Sierra Nevada, rotational grazing practices were the norm. Interviews with ranchers in the Sierra foothills found them to be active in developing water sources and controlling brush and invasive species in the annual grasslands of their home ranches. On the adjacent USFS lands, activities tended to center on fencing livestock out of riparian zones and wetlands (Sulak and Huntsinger 2002).

BLM leases approximately 162,000 hectares of grasslands in the San Joaquin Valley and adjacent interior Coast Range valleys for grazing. There were 340 permits for cattle and 40 for sheep in 2005 on BLM lands in California (BLM 2006).

Much BLM land is in the southern deserts, however, making it difficult to estimate what proportion of permits are connected to or on Mediterranean grasslands.

Less than 1% of California grasslands are managed by the National Park System (CDF-FRAP 2003). Pt. Reyes National Seashore is one of the rare NPS parks where land is leased for grazing. Grazing, especially now-rare grass-based dairy production, is considered part of the history of the area, as well as a key to preserving agriculture in the surrounding areas.

The private ranches using the “pastoral zone” of the park help support the regional infrastructure that supports beef and dairy production, processing, and marketing in the area (Hart 1991).

The DoD and local and regional agencies administer about 5% of California grasslands (CDF-FRAP 2003) (Table 20.1).

Grassland sites of the DoD include Fort Hunter Liggett (Monterey County, 160,000 acres grassland habitat), Camp

Pendleton (San Diego County, 186,471 acres with 28,000 acres grazed), Vandenberg Air Force Base (Santa Barbara County, 98,400 acres, 23,500 grazed), Beale Air Force Base (Yuba County, 23,000 acres), Fallbrook Naval Weapons Station (San Diego County, 8,850 acres), Concord Naval Weapons Station (Contra Costa County, 12,800 acres, 5,170 acres grassland), Lemoore Naval Air Station (Kings County, 39,173 acres), and a number of other bases and installations. Grazing for endangered species is included among DoD goals; for example, at Fallbrook Naval Weapons Station and Camp Pendleton, the endangered Stephens kangaroo rat does better in grazed habitats (Kelt et al. 2005; USFWS 1997).

Other agencies managing grazing include state, regional, and local parks and water and utility districts. Management objectives vary among these many agencies, together managing about 5% of the grasslands. Some use grazing for fuel reduction or to manage annual grasses for habitat improvement for both native plants and animals. For example, the U.S. Fish and Wildlife Service recently reintroduced cattle grazing to the Warm-Springs Seasonal Wetland Unit in Alameda County to enhance habitat for California tiger salamanders, vernal pool tadpole shrimp, Contra Costa goldfields, and western burrowing owl. The agency found that after 10 years without grazing, habitat for these species had become degraded. The Contra Costa Water District, as another example, uses cattle grazing in the Los Vaqueros Watershed to improve habitat for protected and candidate species such as the red-legged frog, tiger salamander, California kit fox, western burrowing owl, and western pond turtle (CCWD 2005).

One problem faced by most public agencies is that livestock grazing on public lands is controversial. Complaints about manure, damaged trails, possible harm to plants and wildlife, and even threatening cows are common, particularly in areas used for recreation. On the other hand, homeowners with properties adjacent to parks can be adamant in their support of grazing for fire hazard reduction (Huntsinger et al. 1995). Water quality issues are also controversial, with concerns about pathogens and sedimentation (Derlet and Carlson 2006). Studies suggest that buffer strips can help mitigate these concerns in grassland systems (Tate et al. 2004, 2006).

Land Trusts The two biggest land trusts in California are The Nature Conservancy (TNC) and The California Rangeland Trust. The Nature Conservancy has goals for grazing including vernal pool and native grass restoration, maintaining good relations with rural communities, and an overall interest in conserving biodiversity. Conservation easements are often held on ranching properties, where the landowner relies on income from livestock production. Management goals are a blend of TNC goals and rancher goals. Grazing also takes place on some TNC-acquired properties. Researchers for TNC have found significant benefits to vernal pool plant and animal species

from grazing (Marty 2005; Pyke and Marty 2005). Also in the Ramona Grasslands of southern California, TNC uses grazing to control invasive species and thatch buildup and to improve habitat for the Stephens kangaroo rat (Eastman 2005).

The California Rangeland Trust’s mission is to conserve the open space, natural habitat, and stewardship provided by California’s ranches, using conservation easements. There are also many smaller land trusts with varying objectives and resources for management and monitoring of their easements. The Muir Heritage Trust in Contra Costa County, for example, reintroduced cattle grazing to manage a Contra Costa goldfield population when they saw a significant decline in plant numbers following the removal of cattle grazing. At the Bouverie Preserve, part of Audubon Canyon Ranch in Sonoma County, biologists use grazing to maintain diversity and promote native wildflowers (Barry 2005). Again, however, the controversies common to livestock grazing mean that trusts and those who manage conservation properties are faced with the task of convincing donors and the public that grazing programs contribute to their management goals.

Grazing Management Principles To decide what practices to implement, the manager needs reasonable certainty about the outcome of a management action relative to goals. This means knowing as much as possible about how patterns of grazing will affect grassland composition, structure, and function. The more information available about grazing outcomes under various conditions, the more likely it is that management actions using grazing will achieve desired goals. However, uncertainty and risk are ever-present in California’s unpredictable weather.

Grazing management relies on information from ecosystem sciences as well as traditional knowledge and personal experience. Monitoring after actions are implemented increases the information available for making further decisions, especially if similar “control” or untreated areas are established for comparison. Clearly defined management practices, along with monitoring of outcomes and the specific conditions under which particular outcomes were achieved, contribute to the reliability of future predictions of management effects. Controlled experimentation is one of the best ways to improve the information available for management decision making. The resources necessary for establishing large-scale grazing experiments are, however, frequently outside of the purview of managers, and as a result few controlled grazing studies exist from which to quantitatively evaluate management scenarios.

By default, on ranch properties today management is largely based on traditional knowledge and experience, including knowledge of the grazing history of the area and the results of past management efforts. Such knowledge has the advantage of being site specific, based on long-term observation, and time-tested. However, observations vary by the perspective of the individual observer, and what looks

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like “good conditions” to one person may look degraded to another. In addition, ecosystems are changing, so what worked in the past may not work in the present or future.

Further, laws and regulations for grasslands have changed.

Hence, ranchers and managers may have to incorporate new and diverse forms of knowledge into their management.

Scientific knowledge attempts to get beyond individual perspectives using quantitative analyses. It allows testing the use of various practices in a way that reduces the chance that results stem from a random effect rather than being actually due to the implementation of a practice or treatment. Drawbacks are that there is seldom the completeness of information desirable for any given site. A risk is also that scientific results, like traditional knowledge, may be overgeneralized by managers who think that results from one site apply more broadly. Experimentation must always be done within clearly specified site conditions.

Adaptive management is an approach to management that acknowledges uncertainty and the need to learn about the resource to be managed (Walters 1986, 1993; Walters and Holling 1990). The term adaptive refers to managers learning about systems as they attempt to manage them. This learning is accomplished ideally by structuring management activities as experiments to test hypotheses of system functioning.

However, more realistically, it means monitoring the outcomes of management with some “controls,” or unmanaged areas, for comparison, so that the results of management can be distinguished from the results of weather and other forces outside of management control. The results of monitoring are then used to adjust management practices and, as necessary, goals. Eventually, this enables better predictions of management outcomes and increases the likelihood of meeting management targets.

Another benefit of adaptive management is that any form of knowledge can be incorporated. The knowledge a rancher or manager has gained over time through experience and observation can be used to establish management practices at the outset. With controls and monitoring, this knowledge can be refined and improved. Adaptive management offers a structured way to evaluate traditional knowledge and its applicability to current goals.

Much ecological information that contributes to developing management practices and scenarios is presented in Chapter 17. The highly variable precipitation, soils, temperatures, topography, species pools, and land use histories across California mean that the outcome of management practices will be variable over both space and time. The applicability of scientific studies conducted at just one or two sites to diverse sites is often not well known.

Grazing Prescriptions Livestock can be placed on particular rangelands at particular times in specified numbers for a specified period. Though constrained by what available graziers can provide or accommodate, the manager may also have the opportunity to select

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animals of a particular species or breed, experience, and specific age class and physiological state: all these choices affect the ultimate impact of the animals on grasslands and natural resources. Prescriptions are put together using what is known about the ecosystem to be grazed and the animal that is doing the grazing.

In theory, because plant species differ in phenology (e.g., early- versus late-season annuals or annuals vs. perennials), the timing of grazing could differentially suppress or promote species by mitigating competitive interactions or reducing fecundity of grazed species (Augustine and McNaughton 1998). The frequency and intensity of grazing also influences the rate of live biomass accumulation, affecting the development of plant crowding that might suppress some plants (McNaughton 1968; Noy-Meir et al. 1989). The proportion of plant biomass removed increases with the density of livestock and the number of times plants are grazed.

The proportion of biomass removed affects the amount of plant litter at the soil surface, in turn influencing patterns of germination and seedling establishment (Heady 1956; Facelli and Pickett 1991a), a particularly important consideration in annual grasslands, where the grassland renews every year from seed. Grazing livestock also modify physical and chemical properties of soils, with important implications for nutrient cycling, hydrology, and plant composition (Weaver and Rowland 1952; Hobbs 1996; Jones 2000).

Grazing can influence species composition directly through herbivore selectivity (i.e., the plants chosen for consumption) and indirectly through the variation among species in tolerance to being grazed (Belsky 1986; Augustine and McNaughton 1998; Kimball and Schiffman 2003). Selectivity is most strongly expressed when forage within the available space is abundant relative to the number of livestock. As forage supplies become more limited, animals consume a broader variety of species. Plant selection, as well as where animals concentrate their activity, is also strongly affected by animal characteristics such as species, breed, and phenological state and by other causes such as topography and water supplies.

Using fencing, herding, and domestic livestock, then, the following four grazing factors are widely considered to be important in determining grazing patterns, and can be manipulated by the manager (adapted from Heitschmidt and Stuth 1991): 1. The kinds and classes of animals: Are they young, old, pregnant; what species or breed?

2. The spatial distribution of the grazing animals: Are they fenced and crowded in a small pasture or herd, or will they distribute themselves easily over a large pasture or site?

3. The temporal distribution of grazing: When and how long?

4. The density of animals: How many grazing animals per unit area?

These factors, moderated by the environmental characteristics of a site, determine the intensity, timing, and frequency of the grazing of plants in a grazing area. Specific examples of their application to common management goals, including enhancing native species and managing invasives, are found later in this chapter.

For annual grasslands, when managing for resource sustainability, a key management approach is to use these four factors to influence the following year’s germination. By managing grazing to leave particular amounts and patterns of ungrazed plant matter behind at the conclusion of an annual grazing cycle, the manager has the best opportunity, within the confines of weather conditions and other abiotic factors, to influence the next year’s germination and to protect the soil. This is because of the major environmental characteristics that largely control forage productivity and species composition in California annual grasslands, including rainfall, temperature, soil characteristics, and the amount of plant residue that remains ungrazed; ungrazed plant residue is most within the control of the grazing manager.

Research has shown that this residue, or residual dry matter (RDM), can protect the soil from erosive forces (Bartolome et al. 2002; Tate et al. 2006) and create seed bank conditions that, depending on the depth and characteristics of the RDM layer, influence the likelihood of germination of different grassland species (Heady 1956; Bartolome 1979). It can also influence soil characteristics by returning organic matter to the soil, and can be an indicator of impacts to soil bulk density (Tate et al. 2004). Residual dry matter also has the advantage of being easy to measure. It can be monitored at specific spots to evaluate levels of use and to decide when livestock should be moved, and it can be mapped to allow for landscape-scale evaluation of animal grazing patterns. Mapping makes it clear where fencing, herding, or distribution of feed and salt should be used to influence grazing patterns.

Though of course not accepted by everyone, using RDM for monitoring has become the most widely recommended approach to California annual grassland grazing management. The amount of RDM recommended for protecting soils and forage quality varies with rainfall, slope, soil characteristics, and other factors (Bartolome et al. 1980).

Prescriptions are unique to the ecosystem and the goals of the manager. A grazing prescription for California annual grasslands should specify each grazing factor for a particular setting, and in most cases should specify an acceptable range of RDM at the end of grazing. For example, “on this site of 300 acres, 25 mature female cattle will be grazed for three months from January to March, leaving 700 –1,500 lbs per acre of RDM.” The prescription should also include what will be monitored to determine whether the grazing is meeting management goals. In this example, that might be measuring or mapping RDM each year. If there are other goals for the prescription, such as enhancing the proportion of a particular species or reducing an undesirable species, monitoring should be established that will allow the manager to determine whether or not results are being achieved.

For example, in grasslands where a goal might be grazing to increase grassland structural diversity, continuous, yearlong grazing may be appropriate. In another situation, rotational grazing or high-intensity grazing may be used to achieve goals that can include certain levels of RDM, specific timing for grazing, or reduction of targeted undesirable species. Vegetation characteristics themselves influence the potential of a site for grazing use. Some plant species are toxic to some or all herbivores. Some are more nutritious or attractive to grazers at particular times of the year. Others have spines, thick wood, or other features that make them inedible or less preferred during all of part of their life stages. The tendency of a plant to be consumed will also vary by what else grows in its locality: Once the most preferred species are consumed, grazing animals, wild or domestic, will select the next most preferred species. This selectivity must be considered by the manager in predicting grazing outcomes.

In the past, grazing prescriptions often had the goal of creating an even utilization of species. Recently, as grazing has begun to be used to mimic “natural disturbance” or to increase species diversity (Noy-Meir et al. 1989; Collins et al. 1998; Perevolotsky and Seligman 1998; Harrison 1999b; Maestas et al. 2003; Marty 2005) and the limited role of competitive interactions in disequilibrium systems such as the California annual grasslands is more understood, using prescriptions that lead to uneven or patchy use, reflected in an uneven distribution of RDM, may be considered useful for various goals (Fuhlendorf and Engle 2001). In addition, in some cases grazing may be used to suppress undesirable vegetation, and the manager may want to achieve different patterns and intensities of grazing than would be typical for the goal of sustainable livestock production alone (Huntsinger 1996).

Grazing Animals Cattle, sheep, goats, and horses have different diet preferences and grazing behavior patterns, and these also vary by breed and even by individual. There is also evidence that experience and “learning” from parents and the herd can influence animal forage choice (Provenza and Balph 1988).

Although most livestock have considerable dietary flexibility, depending on the goals of the manager, some animals are more likely to meet particular needs than others. Diet preferences of herbivores represent the priorities of the animal in selecting plants to eat (Table 20.3). So goats, known as the archetypical brush eaters, will consume grass effectively if there is no edible brush available, for dietary variety, or if experience and training have caused them to favor grass.

Within the broad generalities of species, various breeds of cattle, sheep, and goats may exhibit differences in behavior and forage preference. Cattle of Asian origin, such as Brahma or zebu cattle, are considered to be more likely to cover greater distances, use less water, and make better use of hilly, hot country than cattle of more common English breeds,

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TA B L E 20.3 Dietary Preferences and Grazing Patterns of Common Domestic Herbivores

Dietary preferences

Grazing patterns

Notes

Beef cattle-brood herd

Grass, forbs

Like lowlands, water

Suitable for open range, develop regular patterns at the landscape scale that is part of herd memory

Beef or dairy cattle, young animals

Grass, forbs

Like lowlands, water

Need to be fenced in, more sensitive to dogs and predators than brood herd

Dairy cattle-mature Grass, forbs (rare on rangelands)

Like lowlands, water; must stay near milking facilities

Not able to spread out or wander as widely as beef cattle; returning to the barn twice a day for milking means that trails can be an erosion concern

Sheep

Forbs, grass (less fiber than goats) Will repeatedly use same bed-grounds, which can lead to overuse of some spots if they are not moved

Can be herded for tighter control; vulnerable to predators and dogs

Goats

Brush, forbs, grass

Like uplands, avoid water

Have extra large liver that allows them to cope with toxic plants; vulnerable to predators and dogs

Horses

Grass, forbs (high-fiber)

Like uplands

Nonruminants, upper teeth allow them to consume very fibrous forage in large amounts

such as the almost ubiquitous Hereford and Angus, which are likely to congregate near water.

Though relatively rare in California, grazing two or more species together can result in more complete utilization of diverse vegetation. For example, grazing cattle and goats together will result in both grasses and shrubs being grazed.

Because their species of concentration are different, in some vegetation types — for example, in mixed shrub and grass areas—goats can be added to a range grazed by cattle with no need to reduce the number of cattle. In California there are now numerous companies offering “prescribed grazing” to landowners for the purpose of controlling invasive plants, reducing fire hazard, and creating a more aesthetic environment. Often these firms use goats, because their propensity to eat brush aids in fire control and complements the foraging of cattle.

Exclusion Livestock can be excluded from landscape features, from pastures, and from grazing particular plants or small areas through fencing. Likewise, parks and reserves may completely exclude livestock for several years because of public pressure. A common management practice of federal agencies is to fence streams to exclude livestock. This may result in increased vegetation cover, and the development of trees and shrubs, within the protected area. Similar results were obtained by fencing streams in northern California to exclude deer (Opperman and Merenlender 2000).

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When an area is fenced to preclude grazing in an otherwise grazed area, it is called a “livestock exclosure.” Interpretations of grazing effects from enclosures can be difficult (McCreary 2001). In California annual grasslands, year-round exclusion has been shown to reduce diversity of herbaceous native and exotic plant species, in some cases to the detriment of threatened species that depend on nongrass species (Weiss 1999; Hayes and Holl 2003a; Kelt et al. 2005; Marty 2005; Pyke and Marty 2005).

Virtually all of the California grassland has been grazed by livestock at some point; hence there is no “pristine” grassland to serve as a baseline for comparison with grazed sites (Fleischner 1994). Exclosure studies compare the community composition of actively grazed plots to that of plots that had been previously grazed but subsequently protected from livestock for varying numbers of years. In California, many shortcomings limit generalization from existing exclosure studies. First, most studies are unreplicated or do not have appropriate controls. Second, studies measure grazing intensity in inconsistent ways (or not at all), precluding standardization across studies. Third, knowledge of the land use history is imperative to the interpretation of results of exclosure studies, yet it is often not reported. Additional considerations include small spatial scales (Bartolome 1989), temporal issues (initial responses of species to protection from grazing may not represent the long-term response), and issues related to propagule availability for colonization of the protected area. Despite their shortcomings, exclosure studies are one of the few practical

approaches to evaluating long-term grazing impacts or the outcome of releasing sites from grazing (Bock et al. 1993; Fleischner 1994).

A common conclusion of exclosure studies is that native plants do not typically become dominant after protection from livestock grazing. One hypothesis to account for this finding is that livestock grazing explains less of the variation in plant distribution than site-specific factors such as land use history, climate, and soils. Stromberg and Griffin (1996) note that many native grassland plants were absent from previously cultivated sites, independent of livestock grazing, and that land cultivation, elevation, soil texture, and aspect all explained patterns of community composition more effectively than grazing (Stromberg and Griffin 1996). Similarly, Harrison (1999b) found that soil type and aspect better accounted for patterns in plant species richness than did grazing. This does not mean that grazing has no impact (see Harrison and Viers, Chapter 12; Jackson and Bartolome Chapter 17), but rather that site-specific factors are extremely important in controlling species composition. The importance of site-specific factors is consistent with the variation in the response of native plants to protection from grazing. This variability underscores the need for studies that employ sufficient replication to permit rigorous analysis and occur over a spatial scale that encompasses environmental gradients.

Grazing Systems Grazing systems are a set of specifications for grazing based on the grazing prescription factors listed in the preceding section. Common systems include “rotational systems” that move grazing animals from one area to another over the year. Some systems also involve “rest,” in which an area is not grazed every year but “rested” one year out of every few. The idea is that plants will have a chance to recover from grazing impacts during the rest period. “Deferment” means that an area is grazed later in the season, after the grasses have set seed, with the idea that this will cause less stress to particular plants. For managing annual grasses as a grazing resource, in terms of their physiology, there is little utility in rest, rotation, or deferment because grasses sprout from the soil in response to rain and the cycle begins anew each year.

Research-based evidence has not shown a consistent response to rotational grazing in annual grasslands and is not sufficient to broadly recommend this practice (Bartolome et al.

2002). However, it remains a tool available if rotational patterns of grazing are known to be more beneficial for a particular species or setting. Having more than one pasture also allows animals to be herded in ways that may cause them to consume plants they would not ordinarily consume, to avoid grazing some plants at certain times of year, to keep from overusing an attractive area, to control weeds, or to benefit native perennials.

“Holistic Resource Management” is a management system for livestock producers that emphasizes goal setting and mimicking “natural” grazing systems by manipulating herd

grazing patterns, typically using a rotation-based system.

Scientific evidence of the benefits of many of the grazing practices typically espoused by this system is lacking for California grasslands, but many ranchers and managers find the goal setting exercises helpful.

Because today the major forage species on California’s Mediterranean grasslands are annual, this grassland has been relatively easy to manage solely for livestock production for a long time, although the recent spread of certain undesirable species challenges that management. Also, interest in using grazing for native species restoration and other goals has made it worthwhile to delve into more complex management practices.

Grazing Plans A grazing plan may include grazing prescriptions, specified grazing systems, and a year-round plan for the livestock herd or, from the agency perspective, for the grazing area.

It should describe the facilities available, the productive capacity of the land, sources of water, minimizing conflict with other uses, and so forth. It may also describe how management could respond to the many vagaries of grazing California grasslands, including unpredictable drought, fire, noxious weed invasion, and so forth. In the grasslands, plan flexibility needs to somehow accommodate annual variations in weather that can cause magnitudes of difference in forage production.

Grazier Constraints and Needs The needs and constraints of livestock producers influence what kinds of prescriptions, systems, and plans can be implemented on a given site, whether on public or private land.

These factors also influence the availability and flexibility of contract grazing. In general, the producer wants security and predictability, e the manager needs to meet specified targets and to be able to adapt quickly to changes in rainfall and other factors. As one management document for a water district states, “the livestock owner/operator must be flexible enough to increase or decrease his herd to meet land management objectives within a very short window of opportunity following notification by the agency” (Nuzum 2005).

Livestock producers, for their part, need to maintain their herd year-round or for a certain number of months somehow, and to protect their income they need to be able to control the costs of forage sources. When their animals are taken off grassland, they must resort to feeding with expensive stored forages such as hay or agricultural by products unless irrigated croplands are available.

Most livestock producers in California are cow-calf producers, and must maintain a herd of brood cows through the year. They cannot easily alter the numbers of animals in their herds. It is difficult for them to cope with lots of variation in forage availability and unexpected events: to have a successful grazing program, it is useful to have alternatives available

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243

in case there is an unexpected need to reduce or remove livestock from an area for a period of time. Grass banks are one way to provide some insulation for the unexpected (NGN 2005). Grass banks are rangeland areas that are set aside to provide forage during drought or when improvements or rest is desirable in their usual grazing areas. For example, southern Arizona’s “MalpaiBorderlands Group” provides access to grass on other ranches for local ranchers who agree to place a conservation easement preventing subdivision on their own land. Ranchers use the grass bank during drought or when prescribed burning is being carried out. This is considered a way to protect the traditional ranching community of the area (MBG 2006). The impacts of sporadic grazing on a grass bank flora would need to be assessed for California sites.

Producers need grazing areas with certain characteristics during breeding, calving, kidding, or lambing periods and may not be able to match this with lessee needs. Markets, fuel costs, family needs and goals, and a host of other factors may also affect what a livestock producer is able to do in a given year. Producers must also be concerned with the safety of their animals and possible conflicts with other users, transportation costs, water supplies, fences, and work that they may need to put into improvements and maintenance. An increasingly common problem for public agencies is providing and maintaining the fences, troughs, and other infrastructure that livestock producers need, especially when funds are available for acquisition but not for maintenance.

Producers often make the improvements in exchange for rent reductions.

In general, cow-calf and lamb producers have the greatest need for stability, and have the least flexibility in their operations. Yet their stability also means that they are likely to form a long-term connection with the leaser and land.

Contract goat grazers face the continuous challenge of finding projects that fill out their year-round needs, and they must transport animals from site to site. Mobile contract goat grazers also usually need herders on site to protect the goats from dogs and predators and keep them confined; goats are notoriously difficult to fence securely, though technological advances in electric fencing have improved the situation and played a large role in enabling the entire nascent industry.

Example Management Approaches Grazing prescriptions become part of a grazing plan that includes needs for facilities such as fencing and water, potential conflicts with wildlife and recreation and how to cope with them, economic considerations, and so on, depending on whether the area to be grazed is public or private, part of a livestock enterprise, or being leased for grazing. Grazing for modification of vegetation is usually most effective when done as part of an integrated management program that considers use of prescribed fire, chemical, mechanical, and hand treatments as options or components of a management plan.

An integrated management plan that follows an adaptive

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management framework, even if truly experimental treatments are not feasible, is one approach to managing grazing.

Here we review what is known about the outcome of grazing practices, including grazing to control yellow starthistle (Centaurea solstitialis, hereafter YST), to reduce brush and control fire hazard, to manage vernal pools, and to restore native grasses.

Grazing Management to Control YST and Noxious Weeds1 Grazing can be used to manage noxious weeds in many rangeland settings (DiTomaso 2000, 2006). Intensive grazing will counteract inherent dietary preferences of livestock, resulting in more equal impacts on all forage species, including weeds, but it can potentially cause damage to native species and soils. Moderate grazing intensity can minimize the impact on native plants and soil disturbance.

Multispecies grazing distributes the impact more uniformly among desirable and undesirable plant species; whether or not this is desired should be decided in advance by the manager (Olson 1999; Walker 1994). In the case of YST, a widespread noxious weed in California, grazing alone will not provide long-term eradication, but it can be a valuable tool in an integrated management program (see DiTomaso et al., Chapter 22).

The ideal time to graze for noxious species control is when individuals of the target plant are most susceptible to defoliation, or when the impact on the desirable vegetation is minimal. Improperly timed grazing can benefit the wrong species. For example, livestock grazing in late winter or early spring will primarily feed on young grasses with an erect growth form, causing little damage to seedling YST rosettes. This increases the amount of light reaching the rosettes and stimulates their growth. By contrast, intensive grazing in late May and June, when starthistle plants are bolting, can reduce YST growth, height, survivability, canopy size, and seed production (Thomsen et al. 1989, 1990). During this stage, YST can provide palatable, high-protein forage, which can be particularly useful when other annual species have senesced. The plant’s crude protein concentration ranges from 28% at the rosette stage down to 11% at the bud stage and should be sufficient to meet the general maintenance requirements for most grazers. When it is abundant, YST appears to have the ability to sustain animals several weeks beyond annual grass “dry-down.” But in the mid to late summer months, livestock will selectively avoid the now spiny mature plants, allowing ample seed production. If it is not grazed in the bolting stage prior to spine production, YST will not be successfully controlled by livestock grazing.

In contrast to cattle and sheep, goats continue to browse YST plants even in the flowering stage (Thomsen et al. 1993).

For this reason, goats have become a popular method for

1. Much of this discussion is developed from the Web site “Yellow Starthistle Information” maintained at the University of California (DiTomaso 2006).

controlling small infestations. Goats preferentially consume seeding stems, reducing the spread and perpetuation of weeds by seed. Even though mature seeds sometimes survive passage through the digestive tract, goats usually consume the seeds in an immature stage, so they would not be expected to survive. Allan and Holst (1996) observed that goats reduced the seed bank of thistles.

Residual dry matter, or thatch, may influence starthistle success, as shading has been shown to reduce YST seedling survival rates (Roché et al. 1994; Gerlach and Rice 2003). In a report by Weber (1985), it was noted that when Roché delayed spring grazing of wheatgrass, starthistle was controlled because ungrazed, taller wheatgrass plants blocked sunlight from the rosettes of starthistle. Since most defoliated YST plants will recover from one-time grazing, it is necessary to bring the animals back up to four times at about two-week intervals under rotational grazing. Alternately, grazers can be left on site for two to three months under a continuous grazing regimen (Thomsen et al. 1993). But adequate residual dry matter should be left to shade YST seedlings in the following year (DiTomaso et al. 2004). Also, excessive trampling by livestock has also been shown to increase the density of YST (Miller et al. 1998), so using grazing to control YST must be done with caution.

Short periods of intensive grazing can result in more uniform and complete utilization of a pasture, including weeds, and minimize the animal’s ability to avoid less palatable species. In such a system pastures are intensively grazed from 3 to 5 days, often with the use of electric fencing. After animals are moved, the grazed area is allowed to recover for at least a month before grazing is repeated. This may or may not be desirable, depending on the ecology of the particular weed. When grazing animals refuse to consume a weed, that behavior can encourage the weed’s growth by eliminating the competition, leading to more rapid infestation. On the other hand, grazing may endanger sensitive nontarget species if they are strongly preferred. Goats are typically browsers and can effectively control certain noxious species. However, when confined they will eat both desirable and undesirable species and may even strip the bark off trees. Livestock can also trample desirable, sensitive species and can spread noxious weeds over a wide range when seeds become attached to hair (DiTomaso 1997).

Grazing for Restoration of Native Grasses and Forbs Despite the position of some environmentalists that livestock grazing is incompatible with native biodiversity preservation, managed grazing practices have been endorsed as a tool for promoting biodiversity in native grassland remnants and for restoration projects in California (e.g., Menke 1982; Edwards 1995, 1996; Reeves and Morris 2001; Hayes and Holl 2003a; Stromberg et al., Chapter 21). This has generated some controversy. Reconciling these views in the context of the California grassland is complicated by the difficulty of separating site, weather, and historic effects from grazing impacts.

Across sites, the interaction between climate and grazing in relation to native plants is likely important but has not been rigorously examined (but see Dyer et al. 1996; Langstroth 1991; Jackson and Bartolome 2002). Also, although studies of grazing in California grassland have gone on for some time (see Table 20.4 for a review), most studies suffer from design flaws, so results cannot always be unambiguously assigned to grazing treatments or cannot be generalized across sites.

Systematic investigations of native plant palatability and species responses to grazing have not been carried out since the early studies of Gordon and Sampson (1939), but scattered anecdotal and experimental evidence is available suggesting variability in tolerance to grazing within and among species. For example, based on observations of moist coastal grassland at Sea Ranch (Sonoma County), Elymus glaucus and Calamagrostis nutkaensis (reed grass) are thought to be unpalatable to livestock, resulting in their persistence on some grazed sites (Dwire 1984). A somewhat better studied species is Danthonia californica, which has been observed to be both palatable and tolerant of moderate levels of grazing in central and northern coastal California (Cooper 1960; Hatch et al. 1999; Hayes and Holl 2003a). Several species of native forbs (e.g., Iris spp., Orthocarpus spp., Ranunculus californica, Limnanthes spp., Orcuttia spp., Limnanthes floccosa) may increase under light to moderate levels of grazing (Edwards 1995; Barry 1998; Hayes and Holl 2003a), possibly as a result of the suppression of co-occurring exotic annual grasses. A study of valley grassland species that employed clipping of plants in the greenhouse and the field found that native and alien species had contrasting responses to biomass removal (Kimball and Schiffman 2003). After clipping, density of European grasses was unaffected, and the alien forb Erodium cicutarium increased, whereas native grasses such as Poa secunda decreased in density and growth, presumably because of being intolerant of biomass losses.

It has been suggested that some grazing regimes may enhance native biodiversity more than others (WallisDeVries et al. 1998). Many manipulations of grazing intensity have been performed in exotic annual grassland sites that had only negligible native plant cover (e.g., Pitt and Heady 1979; Rosiere 1987; Jackson and Bartolome 2002). In these settings species composition appears to be largely unaffected by livestock grazing (Heady 1977; Jackson and Bartolome 2002). In grasslands composed of mixed exotic annual and native annual species such as those that often occur on serpentine soils (see Chapter 12), or in vernal pool grasslands in the Central Valley, grazing is being used as a tool to promote native annual wildflowers (Weiss 1999; Weiss, personal communication; Marty 2005). In the case of serpentine grasslands, wet-season grazing is the preferred management method for reducing the annual grasses that are increasing in response to anthropogenic N deposition (Weiss 1999).

Where grazing is not feasible, mowing is being successfully used (Weiss, personal communication).

In mixed annual and perennial grasslands, the outcome of grazing is more variable. Bartolome et al. (1980) examined

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245

Observational/ release

Grazing manipulation/ release

Grazing manipulation/ release

Harrison 1999b

Hatch et al. 1999

Hatch et al. 1991

Yuba?

San Mateo

Napa and Lake

Sonoma

Observational/ release

Foin and Hektner 1986

Humboldt

Marin

Observational

Cooper 1960

Contra Costa

Observational/ release

Grazing manipulation/ release

Bartolome et al. 2004

Mendocino

Elliott and Wehausen 1974

Observational/ release

Bartolome and Gemmill 1981

Several

Solano

Mulch manipulation

Bartolome et al. 1980

County

Dyer et al. 1996d Grazing manipulation

Study type

Citation

Paddock

Paddock

Pasture

Pasture

Pasture

Paddock

Pasture

Paddock

Pasture

Plot

Scale of treatment applicationa

Stocking rate

Stocking rate

Presence/ absence

Stocking rate (qualitative)

Stocking rate

RDM/stocking rate

Stocking rate?

RDM

Qualitative

RDM

Measure of grazing intensity b

Cattle (nd)

Cattle (15) and sheep (200)

Cattle (nd)

Sheep (nd)

Cattle (1.16–2.63 ha per cow)

Sheep (15)

Cattle (ca. 1,000?)

Cattle

Sheep (high)

Simulated

Grazing agent (density)

Continuous

Continuous

nd

Continuous

nd

Spring/wet vs. summer/dry (2–3)

Winter, summer, or spring and fall (nd)

Spring vs. summer vs. continuous vs. release

nd

Late summer/early fall

Season (duration in days)

1–2

1–2

1–2

1, 3, 5

6 after release

1–4

1

1–6

2, 3, and 23

5

Sample yearsc

TA B L E 20.4 Summary of Studies of the Effects of Livestock Grazing on Native California Grassland Plants

All sites historically grazed

Observations 7 to 13 yr after release from grazing

Ungrazed 6 yr release from grazing

Grazed until 400–500 kg/ha

Crossed with burning after 3 yr of grazing treatments, grazing treatments ceased after 3–4 yr

Comments

Observational/ release, clipping and mulch manipulation

Grazing manipulation

Grazing manipulation

Grazing manipulation

Kimball and Schiffman 2003

Langstroth 1991

Love 1944

Marty 2005

Mendocino

Merenlender et al. 2001

Observational/ release

Yuba

Marty et al. 2005 Grazing manipulation

Sacramento

Sacramento

Solano

San Luis Obispo

San Mateo

Several

Grazing manipulation

Mulch manipulation

Jackson and Bartolome 2002

Contra Costa

Kephart 2001

Grazing manipulation

Jackson, unpublished

Mendocino

Tulare

Biomass/mulch manipulation

Heady 1956

Several (Mendocino south to San Luis Obispo)

Keeley et al. 2003 Observational/ release

Observational/ fenceline

Hayes and Holl 2003a

Pasture

Paddock

Vernal pools

Pasture

Paddock

Pasture and plots

Paddock

Pasture

Plot

Paddock

Plot

Pasture and plot

Goats (500)-yr 1; sheep (40) and goats (7)-yr 2

Cattle and horses

Simulated

Cattle, light to moderate

Simulated

Qualitative

RDM and stocking rate

1 AU/2.4 ha

Stocking rate

RDM/stocking rate

Sheep

Cattle

Cattle

Sheep (264–275 early; 83 late)

Sheep (15)

Presence/absence Cattle and Clipping intensity simulated RDM removal

Stocking rate

Presence/ absence

RDM

RDM

RDM

Presence/absence Cattle

nd

Light vs, heavy winter/spring, vs. continuous vs. release

Dry vs. wet vs continuous vs. release

Spring and summer or fall (20–30)

Spring/wet vs. summer/dry (2–3)

Winter/spring

May (12)

Winter-summer

Late summer/ early fall

Spring (7), summer (7), continuous

Fall

nd

43 years

3

3–4

Same

1–4

2, 3

1–2

1

6

1–3

1–2

(Continued)

Followed permanent plots over 43 years after removal

Treatments crossed with burning

Sampled zones from upland to pool bottoms

Grasses seeded into disked pasture

Grazed until 400–500 kg/ha

Grazing release site unreplicated 11 yr since grazing.

Grazed to bare mineral soil

Long-term grazing

Clipped to fixed height and varying percentages returned

Compared 17–25 grazed/ungrazed pairs in coastal prairie

Observational/ release

Grazing manipulation (no control)

Observational

Observational/ release

Observational/ release

Grazing manipulation

Grazing manipulation

Observational/ release

Micallef 1998

Reeves and Morris 2000

Saenz and Sawyer 1986

Safford and Harrison 2001

Stromberg and Griffin 1996

Thomsen et al. 1993

TNC 2000

White 1967

Monterey

Tehama

Colusa/Yolo

Monterey

Napa and Lake

Humboldt

San Benito

Contra Costa

County

Pasture

Paddock and pasture

Paddock

Pasture

Pasture

Pasture

Pasture

Pasture

Presence/ absence

RDM

RDM

RDM (qualitative)

Presence/ absence

Qualitative

Stocking rate

RDM/stocking rate

Measure of grazing intensityb

Cattle, horses

Cattle

Cattle (18 cow-calf pairs); sheep then goats (20–40)

Cattle (nd)

Cattle

Cattle (nd)

Cattle (nd)

Cattle (nd)

Grazing agent (density)

aplot

NOTE:

1–2

1, 20, 24

Sample yearsc

nd

Rotated November–April

May and 2–3 follow up later in the season ( 3 days)

Seasonal vs. continuous (nd)

nd

27

3

3

23

1–2

Early–late (8 mo) 1 vs. late (4 mo)

nd

nd

Season (duration in days)

nd data not available; experimental unit gen 10 sq. meters; paddock experimental unit gen 0.5 acres; pasture existing unit, generally 0.5 acres; bRDM residual dry matter at end of treatment application, grazed or clipped until a given RDM is achieved cYear data collected after initiation of treatment (or release from grazing) dIncludes Fossum (1991) data and is same experiment as Langstroth (1991).

Study type

Citation

Scale of treatment applicationa

TA B L E 20.4 ( C O N T I N U E D ) Summary of Studies of the Effects of Livestock Grazing on Native California Grassland Plants

Ungrazed for 27 years prior to study except horse pasture

Cattle reintroduced after 11 years of release from grazing

Ungrazed for 51 years prior to study except horse pasture

No ungrazed control

Monitored increased stocking rate

Comments

the response of native perennial grasses to various levels of RDM manipulation in three Humboldt County coastal sites.

Native grass growth was most enhanced by the highest level of RDM employed (1,120 kg/ha), suggesting that a low grazing intensity may be most appropriate for increasing cover of native bunchgrasses. By contrast, Savelle (1977) found that removing mulch from Nassella pulchra tussocks increased seed production, and other experiments suggest that mulch can inhibit N. pulchra seedling establishment (Dyer et al.

1996; Reynolds et al. 2001). In a three-year study testing burning and four different grazing intensities including rotational and continuous grazing, Marty et al. (2005) found no difference due to grazing treatment in N. pulchra mortality, seedling density, or culm production. In general, grazing reduced the height and reproduction of the bunchgrasses, but this did not affect subsequent seedling density, which was driven by weather. Across all plots, including controls, there was a fivefold decrease in bunchgrass density, probably due to declines in rainfall over the study period.

The seasonality of grazing has been hypothesized to be a critical determinant of native grass enhancement. “Properly timed” application of livestock grazing theoretically enhances the establishment and growth of native grasses by suppressing competitive annual grasses. Experimental support for this hypothesis has been mixed. In one study, early spring grazing suppressed the faster-germinating exotic annual grasses, thereby reducing the competitive suppression of perennial bunchgrasses or native forbs, whose seeds germinated later than the grasses (Love 1944; Langstroth 1991; Dyer et al.

1996). Seemingly small differences in timing can have big effects. For example, an early study (Love 1944) in valley grassland in Sacramento County compared the establishment of N. pulchra and N. cernua in plots that were grazed by sheep in early April versus late April. Love (1944) suggested that the greater success of the native grasses in the earlygrazed field was due to the removal of the taller annual grasses, resulting in the release of native perennials from competitive suppression. The late April grazing treatment occurred when the wet season ended and the perennial grasses had not developed sufficient root biomass to survive the dry conditions that followed, and they were more likely to be grazed because the annuals were senescent (Love 1944).

More recently, a series of related experiments on N. pulchra distribution compared the effects of grazing in the wet and dry seasons at the Jepson Prairie Preserve (Solano County; Fossum 1990; Langstroth 1991; Dyer et al. 1996). Seedling emergence and survival were higher in the wet-season grazing treatment (especially in combination with burning) compared to the dry-season grazing treatment and an ungrazed control (Fossum 1990; Dyer et al. 1996). The putative mechanism behind this result was that litter and annual grass removal increased light levels at the soil surface and enhanced Nassella seedling survival (Langstroth 1991; Dyer et al. 1996). However, neither grazing nor burning had a significant effect on survival when the experimental treatments were repeated a year later during a very dry year,

suggesting that the long-term effects of the treatments was ameliorated by climatic conditions (Dyer et al. 1996).

Furthermore, only a tiny fraction of the seedlings that emerged survived after four growing seasons (99.9% mortality), possibly as a result of below-average rainfall (Dyer et al. 1996). For established plants, wet-season grazing decreased the basal diameter of individuals but enhanced reproduction via plant fragmentation, leading to an increased density of N. pulchra plants relative to ungrazed plots. Though wet-season grazing improved the establishment and vegetative reproduction of N. pulchra, plant microsite (i.e., on top of or between mima mounds) exerted stronger effects on plant responses than the grazing treatments (Dyer et al. 1996; Langstroth 1991).

Bartolome et al. (2004) found an increase in N. pulchra with spring (wet-season) grazing compared to summer and continuous grazing over several years, but in their study N. pulchra also responded positively to complete release from grazing.

Other studies have employed specialized grazing regimes with the goal of increasing the native, perennial component in annual-dominated grasslands, although most studies suffer from a lack of control plots (Table 20.4). For example, Reeves and Morris (2000) found that applying a grazing regime based on holistic management principles — basically a short-duration, high-intensity rotational grazing system (Savory and Butterfield 1999)—to grassland in San Benito County resulted in increased abundance of native perennial bunchgrasses over three years, but their study design is unclear and lacks control plots. Observations from coastal grassland in Humboldt County indicate that a change from a continuous, high-intensity cattle-grazing regime to an intermittent, moderate-intensity grazing rotation corresponded with a 10% increase in Danthonia californica abundance and a 35% decrease in the abundance of the invasive exotic grass Taeniatherum caput-medusae over 3 years (Cooper 1960), but, again, no appropriate controls were available. In another setting without control plots, Kephart (2001) used sheep and goat grazing to reduce the dominance of aggressive annual weeds such as Centaurea solstitialis in mixed grassland in San Mateo County. After two years of short-duration, intensive grazing, native species richness increased and native cover increased slightly. Exotic species richness was unchanged, but cover of exotics also increased substantially.

Fenceline and road verge studies have recently been used to infer the impacts of livestock grazing on native species richness in California grasslands. Their usefulness in advising management needs further study. In one study across a wide range of coastal grassland sites, the native perennial grass Danthonia californica appeared to benefit from grazing (mostly continuous grazing), as it was more abundant on the grazed compared to the ungrazed sides of fences (Hayes and Holl 2003a). This is consistent with an experimental study in which it decreased in frequency and cover within grazing exclosures (relative to grazed plots) in a coastal grassland site in San Mateo County (Hatch et al. 1999). In the fenceline study, cover of native annual forbs also appeared to benefit from grazing, but so did the cover and richness of

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exotic annual and perennial forbs. This positive response of exotic forbs to grazing was also seen in a comparison of ungrazed road verges with nearby grazed sites on nonserpentine soils: Safford and Harrison (2001) found that grazed sites had higher exotic species richness than their ungrazed counterparts. In their study, native species were unaffected by grazing.

The results of livestock grazing studies suggest that sitespecific factors (e.g., species pool, land use history, soils) and climate exert an influence on the response of native plant species to manipulations of grazing regime. Indeed, a recent extensive survey of grazed and ungrazed sites in northern California suggested a strong role for slope/aspect and soil type in influencing the outcome of grazing (Gelbard and Harrison 2003), with colder slopes showing different responses than warmer slopes and soil type interacting with these slope/aspect factors. In a broad survey of grassland sites in Monterey County, the consistent lack of recovery of native grasses in sites that had been excluded from grazing for decades but that had been tilled for agriculture, suggests the critical importance of land-use history (Stromberg and Griffin 1996). In these cases, no amount of grazing or specialized grazing regime will enhance native perennial grasses if they have been completely eliminated from the site and no nearby seed sources are available.

If livestock grazing management and the restoration of native grassland diversity are to be compatible goals, sources of variation in the relationship between grazing regime and native plant abundance need to be better understood to provide site-specific guidelines for the development of grazing prescriptions. More information is needed on the response of entire assemblages, particularly native forbs, to grazing treatments (including cessation). Also, the presence of an oak canopy can greatly affect grassland composition and structure (Callaway et al. 1991; and see Tyler et al., Chapter 14), yet we know very little about the interaction of livestock grazing with the presence or absence of oak canopies (Chapter 17).

Because of the variation in response to grazing that is found in the native grassland flora, it is reasonable to assume that no single grazing regime or the complete cessation of grazing will be optimal for all native species. A management plan that varies the timing and intensity of grazing on a landscape scale may better enhance native plant diversity than the uniform application or the uniform elimination of grazing. Properly designed experiments are needed that explicitly examine the response of native species to wellquantified grazing regimes, replicated across a range of sites where site conditions and history are quantified. In many sites, the lack of a seed source for native species will limit responses to grazing, and seeding will need to be combined with grazing to enhance native biodiversity.

Grazing to Control Brush and Fire Hazard Many chaparral species are highly palatable to goats, and these animals have long been used to maintain firebreaks in

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California or to reduce brush in areas that have been converted from shrubland to grassland. In California grasslands, Himalyan blackberry (Rhubus discolor), poison oak (Toxicodendron diversilobum), coyote brush (Baccharis pilularis), and broom species (Cytisus scoparius and Genista monspessulana) are all commonly invasive in coastal and coast range grasslands and can be managed using grazing. In many areas the use of angora and Spanish goats shows promise in controlling Himalayan blackberry (Daar 1983). Crouchley (1980) mentions that blackberry is readily eaten by goats throughout the year, even when there is an abundant supply of other plants. Sheep, cattle, and horses can also be effective in reducing the spread of Himalayan blackberry (Amor 1974), especially when plants are small. Blackberry was reduced by 73.5%, and more than half of the cover of toyon (Heteromeles arbutifolia), coyote brush, honeysuckle (Lonicera hispidula), herbaceous species, and madrone (Arbutus menziesii) was removed by goats on a fuel break in a study in coastal foothills, breaking the sequence of live fuels horizontally up to 1.5 meters, and reducing the amount of one- and ten-hour dead fuels by 33.2% and 58.3% respectively (Tsiouvaras et al.

1989). Regrowth has also been controlled by grazing sheep and goats in areas where mature plants have been removed.

Grazing of poison oak by sheep and goats can be effective for its control. Deer or horses will also graze poison oak when the foliage is young, before the plant flowers (DiTomaso et al.

2001b). Grazing of cattle can prevent the encroachment of poison oak and coyote brush into grasslands in the eastern San Francisco Bay area (Russell and McBride 2003; EBRPD 2005). In this area, goat utilization of poison-oak was 67% in a fuelbreak under controlled grazing, somewhat lower than utilization of toyon, California blackberry, and coyotebrush.

Grazing must be maintained over the long term to control shrubs, since in this rainfall region grasslands tend to convert to shrubland without fire or grazing.

Brooms such as Scotch broom (Cytissus scoparius) appear to be more resistant to grazing, even by goats. In one study goats had a major impact when broom density was low (4% ground cover) but no impact when broom density was at 10% ground cover. Goats stripped bark from broom stems during winter, reducing broom vigor in pastures. Both sheep and goats removed stem and flowering parts, preventing seed production within browse reach and removing new broom shoots over summer. When broom seeds were fed to goats, 8% of the seeds remained viable following ingestion (Holst et al. 2004), so at least some viable seeds could be transported among sites by goats.

The dry grasses left on annual rangelands in summer and fall are fine fuels that promote rapid fire spread. Cattle, sheep, goats, and horses can all be used to reduce fine-fuel loads. The effectiveness of grazing on fire behavior has not at this point been quantified but is inferred from the removal and alteration of fuels. Grazing is an alternative to prescribed fire for fire hazard reduction at urban-wildland interfaces and in other situations where risks of fire escape cannot be tolerated. Goat herders usually charge to graze for vegetation management,

while cattle grazers typically pay for grazing leases. Management is straightforward, emphasizing control of shrub encroachment while protecting other resources.

Grazing Management for Vernal Pool and Small-wetland Biodiversity Although grazing in riparian areas is generally outside the scope of this chapter, vernal pools, small grassland wetlands, and small ephemeral streams are characteristic of and integrate with Mediterranean grasslands in California. Many of these habitats are considered important for native flora and fauna, including threatened species such as the red-legged frog and tiger salamander. Livestock influence vegetation, soils, and water quality in these small wetlands, but the ultimate impacts on species of concern are not well studied in most of these habitats. An adaptive management approach, with careful monitoring of management effects, is recommended. The assumption has often been that livestock grazing, as an “unnatural� influence, is harmful (Barry 1998; Griggs 2000).

However, some recent evidence suggests that grazing can be a tool for improving or maintaining biodiversity in annual grassland vernal pools and other grassland aquatic environments.

One study argues that grazing could mediate the effects of global climate change in vernal pools by reducing cover of exotic annuals that benefit from warmer temperatures (Pyke and Marty 2005). In an extensive study of grazing impacts on vernal pools in the Central Valley, Marty (2005) found that without any livestock grazing, exotic annual grasses dominated pool edges and reduced the duration of pool inundation because of their rapid use of water. By reducing litter buildup and cover of exotic annual grasses, cattle were effective in increasing the diversity of forbs and other species.

Three years of study of numerous pools showed that ungrazed pools had 88% higher cover of annual grasses and 47% lower relative cover of native species than pools grazed for most or all of the year. Without grazing, species richness of native plants declined by 25%. Many of the native vernal pool plants (e.g., Lasthenia spp., Downingia spp., Veronica spp.) are small and require an open environment to successfully germinate and reproduce (Linhart 1988). Cattle grazing may be particularly effective at reducing exotic grass cover, because cattle selectively forage on grasses (Kie and Boroski 1996; Knapp et al. 1999). Removal of sheep grazing has also been reported to result in degradation of vernal pool habitats (Reiner 2001).

In addition to affecting vernal pool plant composition, grazing enhanced invertebrate diversity in vernal pools by 28% (Marty 2005). In ungrazed pools, exotic annual grasses evapotranspired large amounts of water, reducing pool inundation period by 50–80% and making it difficult for some vernal pool endemic animal species to complete their life cycle (King et al. 1996; Marty 2005). Thus, Marty (2005) suggested that grazing prescriptions to protect and promote native species diversity should be based on the practices utilized when pools were identified as having species of conservation concern. There was a low-intensity, October to

June grazing regime, and release from this regime via total exclosure reduced the species of special concern (Marty 2005).

Under an adaptive management scenario, grazing might be adjusted over time to see whether further understanding of the interaction of grazing practices and weather patterns could be gained by establishing and monitoring plots where modifications could be tested.

Small spring-fed wetlands, or seeps, are found in many annual grassland areas. A ten-year study of different levels of grazing in such wetlands showed that plant diversity was not affected by grazing regime in and around the springs, but diversity increased under moderate levels of grazing along the small creeks flowing from the springs. Details of grazing in these springs are discussed in Chapter 17.

Grassland soils act as natural nitrogen sources to springs.

Removal of livestock grazing from small wetlands resulted in a reduced capacity for the system to take up nitrogen, and hence increased nitrates were found in the springs (Jackson et al. 2006b). Indeed, Jackson et al. (2006b) determined with a paired-plot grazing removal experiment that nitrate concentrations in surface waters where grazing was removed for only 2 years were as much as five times greater than in grazed counterparts, far exceeding U.S. Environmental Protection Agency (EPA) standards for surface waters. The authors of this study hypothesized that the buildup of litter in the absence of grazing reduced herbaceous production, and therefore N sequestration, by the vegetation (Typha, rushes, sedges) in and immediately around these springs. On the other hand, direct inputs of animal excrement into ponds and wetlands have been found to increase levels of ammonia and nitrite in small ponds in intensively grazed areas (Clausnitzer and Huddleston 2002; Knutson et al. 2004).

There is widespread concern about the impacts of grazing on riparian areas in the western United States (Belsky 1999), and it has been a difficult topic to study for logistical and experimental reasons. Two studies of grazing around small grassland streams in California grasslands showed little to no impact of a light to moderate grazing regime on channel morphology (Allen-Diaz et al. 1998; George et al. 2002). However, it has been observed that heavy grazing can reduce vegetation cover and decrease the slope of streambanks, resulting in bank erosion and degraded aquatic habitat (Larsen et al. 1998).

Finally, stockponds constructed by ranchers are recognized to provide refugia for aquatic species such as red-legged frog and tiger salamander, especially as vernal pools are lost to urbanization and vineyard production (EPA 2003, 2005).

Their quality as habitat depends on the inundation period, timing of livestock use, and whether predators such as bullfrogs or introduced fish are present. Allowing or creating a dry period can control many such introduced species.

Manager Information Needs Interviews with 35 grassland managers and scientists across the state reveal three major areas of concern (Chadden et al.

2004). First, grassland managers want more information to

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help them set goals and evaluate progress. For those with restoration goals, finding out all they can about the past distribution and composition of grasslands and grassland species is a common enterprise. Restoring past conditions, including native species communities, is one common goal, though complete restoration to past conditions has never been achieved and is widely accepted as impossible. A countervailing narrative by some managers is that ongoing changes to species and communities are irrevocable. Instead of trying to restore past conditions, they define a goal that is reasonable and desirable for each particular situation. This could be maintaining or enhancing native species diversity, improving conditions for broad-leaved plants needed for a threatened butterfly (Weiss 1999), or increasing forage production for livestock. Another approach is to manage for diversity of species composition and structure in general, with the assumption that this will provide habitat for the most diverse array of plant and animal species. In all cases, management flexibility and monitoring are needed to cope with constant change. Commitment to a long-term analysis is essential. Response to management tends to be slow and often difficult to detect because of radical weather-driven changes in the habitat each year.

A second major area of concern of land managers clusters around habitat fragmentation. Increasingly, managers find themselves faced with disconnected pieces of land, subject to urban stresses and the effects of roads and trails. Such effects include incursion by weeds along roadsides and fuelbreaks (Gelbard and Harrison 2003; Merriam et al. 2006).

Goats are increasingly used as vegetation management tools in these settings because they appear to be more acceptable to adjacent homeowners and recreationists than other livestock (R. Budzinski, personal communication), but they are an expensive tool. Fragmentation also destroys metapopulations of various wildlife species and increases predation by dogs and feral cats.

Finally, managers realize that they need more information that is directly applicable to the sites and species that they need to manage. They know that they are unlikely to have an amount of knowledge that they consider “adequate” any time in the near future. Instead, adaptive management, which makes management itself into an experimental process, is seen as desirable. Unfortunately, the resources to design and carry out the sound experiments called for in an “adaptive management” scenario seem to be only rarely available. Monitoring with some controls is usually a more feasible goal.

Recent interviews with ranchers about rangeland conditions and management (Ford and Huntsinger 2006 interview notes) revealed that a major concern is that they are often held accountable for factors outside of their control. General misunderstandings about the California grasslands often result in attempts to use grazing management to influence vegetation characteristics that are controlled by weather and environmental conditions and little influenced by grazing.

Interviewed ranchers shared manager concerns about invasive plants, and they support efforts to improve wildlife

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habitat when such efforts are not highly detrimental or costly to the livestock operation or when the ranchers are compensated for extra conservation measures. In many cases the ranchers believe that in the course of their management they take good care of the land and wildlife already, and protect resource productivity. On public lands, they believe that short and uncertain leases reduce ranchers’ investment in the land and that, without long-term commitments from both lessor and lessee, management is often less than optimal.

Ranchers also argue that while each ranch is unique in environmental and human terms, regulations can be too broad.

Finally, ranchers are concerned about bureaucratic complications that prevent the implementation of projects that have been worked out face to face by ranchers, wildlife biologists, and conservationists. Sometimes such projects are delayed so long that desired habitat quality is lost through a lack of grazing over time or through the infilling of ponds that need maintenance. Such problems take the enjoyment out of ranching, and make ranchers feel that they are “doing something wrong” by ranching. A growing concern in the ranching community is that with current high land prices and the difficulties and costs of navigating a complex regulatory environment, families are leaving ranching and traditions are being lost. The skyrocketing value of land prohibits newcomers from joining the ranching community.

Conclusions California’s grasslands are managed for diverse goals by public and private landowners. There is great variation in the quality of management and in the resources available for management. However, most managers are interested in maintaining the environmental values of the resource, though opinions about what that means and how to get there vary. Basic principles of livestock grazing management can be used to develop prescriptions for accomplishing manager objectives, but grazing impacts occur within the huge annual variation caused by weather patterns and across a heterogenous landscape of varied soils, topography, and land use history. Most quantitative information shows that California grasslands respond quickly to weather (Reever Morghan et al., Chapter 7; Harpole et al., Chapter 10; Dukes and Shaw, Chapter 19) and relatively slowly to management.

Research into the goals and capacities of various kinds of grassland managers is needed to develop programs and practices that fit with their objectives and that will motivate improved management. Demographically, land ownership in the grasslands is changing, with new kinds of owners, more real estate speculators, and more land trusts owning large properties. Yet little is known about the implications of these changes for grassland sustainability and opportunities to enhance values derived from rangelands. Research geared to producing information useful in reducing land fragmentation and habitat loss is needed, as is finding ways to stimulate increased “boundary-crossing” management and protection of habitat.

The interconnections between private and public lands via

grazing leases and public manager/stakeholder cooperation toward attainment of mutual goals have not been well assessed.

As more and more land is converted to urban and suburban development, the environmental services produced by private rangelands increase in value. Yet methods to value these services have been little researched or applied in California.

The most common grazing management approach is to use RDM or “mulch� monitoring as a way of protecting future productivity in annual grasslands (Bartolome et al.

2002). Carefully timed grazing can be used to control invasive species such as yellow starthistle and medusahead. Livestock grazing can also be used to promote native species, including rare ones, in vernal pool settings (Marty 2005).

Nonetheless, a clear relationship between livestock grazing and California’s native grassland plants is difficult to establish. Although an extensive literature documents the impact of grazing in annual grasslands dominated by introduced species (e.g., Heady 1956, 1958; Pitt and Heady 1979; Rosiere 1987; Bartolome and McClaran 1992), relatively few studies have quantified the impact of grazing on a range of native plants, either annual or perennial. The existing data show

that the interactions among livestock, exotic plants, and native plants are variable across regions and years. Grazing can benefit some native plant populations, but a positive response is not universal even across locales for any one species, as demonstrated by the variable response of Nassella pulchra to grazing. Grazing can negatively impact some native plant species, but responses, again, are not universal across species or sites. More experimental research is needed to understand the contingencies that regulate species responses to grazing prescriptions.

Tests of the effects of specialized grazing systems on range production and vegetation composition on different ecological sites would also improve grassland management. With growing emphasis on management for biodiversity, interactions between livestock and wildlife or livestock and threatened and endangered species need more research. As wildfire becomes more costly and suburban development patterns put more residential areas at risk, considerable public investment in reducing fire hazard is contemplated by public agencies. As a relatively low-cost tool, the effectiveness of grazing management for grassland fuel modification needs further study.

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