The California Native Plant Society (CNPS) is an organization of amateurs and professionals united by an interest in the plants of California. Its chief aims are to preserve the native flora and to add to our knowledge of it. Its members participate in monitoring rare and endangered plants, fostering public education, supporting legislation that protects native plants, and providing expert testimony to government bodies. In 1974 CNPS published Inventory of Rare and Endangered Vascular Plants of California, the first of five successive editions, which have documented the occurrences of rare species. In 1985 CNPS entered into a formal partnership with the California Department of Fish and Game to continue a process of rare plant monitoring. Over time, more information became available about habitats and plant communities with rare species.
In 1990, CNPS decided that the Society's activities in the protection of rare species could be enhanced by a complementary focus on the protection of rare plant communities. The Board of Directors, responding to a suggestion from a small ad hoc subcommittee of the Rare Plant Program, proposed a parallel program to develop comparable information about California's plant communities.
Michael Barbour was invited to chair the committee, and he established a committee of approximately 25 individuals from academia, conservation organizations, environmental consulting companies, and state and federal agencies. The group met for the first time on February 9, 1991.
An early objective of the Committee was to foster adoption of a uniform vegetation classification among private, state, and federal resource agencies with jurisdiction over land management. At that time, several conflicting systems were being used, making it difficult for biologists to communicate. The adoption of a common classification allows conventions, descriptions, and names to be consistent. A uniform vocabulary permits a longer-term objective to be met, the legislative recognition and protection of rare, threatened, or endangered plant communities across administrative boundaries.
By developing quantitative, defensible definitions of rare and threatened communities, we can invoke the California Environmental Quality Act (CEQA) to help conserve them. CEQA specifically calls for the preservation of examples of plant and animal communities within the state. Before working with rare and threatened communities, we need to create a systematic classification of all communities, including the common and extensive, as well as the rare ones.
By providing a common language and clear definitions, the Committee hoped also to facilitate a number of processes linked with the assessment of development projects that must be reviewed under CEQA. These processes include the identification and ranking of plant communities by conservation priority within a project's boundaries. It is anticipated that conservation efforts can now be more accurately addressed through planning documents via CEQA, the National Environmental Policy Act (NEPA), and other laws, regulations, and policies.
The Committee, now numbering 32 members and renamed the Vegetation Committee , celebrates the start of its fourth year of existence with the publication of this book, A Manual of California Vegetation.
The classification schemes adopted in the Manual, the kind of information included, text format, and the review process was collectively agreed upon by committee members. John Sawyer served initially as editor, but it becomes evident that a more efficient approach was for one person to write community descriptions. Todd Keeler-Wolf became increasingly immersed in the project at all levels.
The Start of an Interactive Relationship among Users and Future Editions
This edition is the culmination of a tremendous amount of conservation insight, work, and commitment. The Board of CNPS decided early on that to make a meaningful contribution toward the conservation and appropriate uses of California vegetation, this manual must be based on the best scientific information available.
The Manual also serves as a foundation to shift conservation emphasis from a single species approach to a landscape approach that encompasses groups of species, plant communities, and ecosystems while continuing to incorporate the need for rare and endangered species conservation and management. Viewing and describing landscapes within the framework of a unified vegetational classification provides the common language necessary for managers to make informed decisions. It is hoped that the Manual will be widely used by landuse planners at the county, state, and federal government levels, environmental consultants, conservationists, and natural resource specialists, including botanists, ecologists, foresters, range managers, and wildlife biologists.
California is a wonderfully diverse state. Its flora has been studied for over 100 years and yet new species, even genera, are still being described. It should not surprise anyone who has worked with vegetation in this state that the need to provide a framework and systematic approach to describe and quantify California vegetation is long overdue.
CNPS realizes that many conceivable vegetation series, our formal name of a plant community, are not included in this first edition, because we lack documentation to effectively describe them. Similarly, the distribution of many series throughout the state is inadequately understood. We rely on the cumulative knowledge and submission of new data sets by the users to prepare future editions. As this manual goes to press a computerized database version is being developed that will facilitate easy updating and customized usage of information.
If you have data, literature, or proposed types or vegetation information that could assist the CNPS Vegetation Committee in describing and validating a new series, or add relevant information to existing series and/or their distribution, send the information directly to: CNPS
1722 J Street, Suite 17
Sacramento, CA 95814
attn: Plant Communities Database.
Call: (916) 447-2677
A copy of the CNPS Vegetation committee’s field data form and instructions for using the CNPS sampling protocol is included in the Appendix. This form can be photocopied or additional forms may be requested from CNPS. If you have reconnaissance information on any of the rare vegetation types described in this manual please use the NDDB California Natural Community Survey Form included in the Appendix. For more forms contact:
Natural Diversity Data Base
California Department of Fish and Game
1416 Ninth Street
Sacramento, CA 95814
Call: (916) 324-6857
The Vegetation Communities Committee requests comments from the users on ways to improve the utility of this classification. Hearing from users is the best interactive way to improve future editions. In addition, the Vegetation Committee is seeking quality photographs of series, stands, habitats, and vernal pools for future editions of the Manual and for CD-ROM applications.
What is Vegetation?
Vegetation, is a large part of our state's unique signature. The dark, fog-shrouded cathedrals of its coastal redwood forests, the sunny open foothill woodlands of blue oak, and the low gray-green aromatic sage scrubs of the central and southern coasts are each as representative of California as its scenic coastline, Mediterranean climate, and Yosemite Valley.
Vegetation all the plant species in a region and the way they are arranged is a part of the natural world that humans learn to recognize at an early age. It is our nature to differentiate among a grassland and a shrubland or a meadow and an adjacent forest. The differences among types of vegetation we see initially are strengthened by their diverse resource values that we exploit. We are all vegetation classifiers to some degree.
Unlike an artist's contrasting brush strokes, differences among vegetation types are not defined strongly. Although we can agree that a dense lodgepole pine forest is qualitatively different from an adjacent wet mountain meadow, the closer we look, the harder it is to discern where a meadow begins and a forest ends. We see individual sedges, asters, and buttercups trailing off in decreasing density into the forest as it closes overhead, and young pines and scattered mature trees stationed well out into the meadow. The problem of fuzzy boundaries is characteristic of vegetation science.
Also, unlike the permanence of a master's brush stroke, vegetation patterns change. Because plants are alive, they create a transitory scene. At any location trees, shrubs, and herbs form a unique pattern that shifts subtly from season to season and year to year through the growth, death, and reproduction of individual plants. Patterns can also change profoundly over time following disturbance. However, there is a tendency for a given landscape to have a limited set of vegetation types. Vegetation following fire, seasonal or periodic drought, avalanche, or diseases often approach conditions similar to those before the disturbance.
Some changes, however, are not within the adaptive repertoire of the plants, forcing permanent shifts in the scene. New vegetation types may arise within a geologic blink of an eye. For example, a wet meadow may change to a dry grassland after a single flood. Rapid downcutting of a stream can drop the water table below the reach of the roots of meadow plants.
The pattern in vegetation can be thought of as being driven by environmental variation. Differences in such important environmental factors as moisture, soil chemistry, temperature, and time since disturbance exert powerful influences. For example, the moisture content of the soil ranging from a streamside terrace to adjacent upland slopes has a direct influence on the types of vegetation occupying these areas. These environmental variables may be viewed as gradients, and vegetation changes subtly along these gradients. Conversely, vegetation may change dramatically where there is a "break" in gradients such as between a chemically harsh serpentine soil and a more benign, sandstone soil. The study of how this environmental variation influences vegetation is an important part of vegetation science.
Community-unit Versus Continuum View of Vegetation
Early in this century the lines became drawn in an ideological debate over the fundamental way vegetation is interpreted. Frederick Clements (1916, 1920) metaphorically equated units of vegetation with organisms. He saw that clusters of species repeatedly associated together. He believed that at least some of these species had obligatory relationships with the community much like that of organs within the living creature. In Clements' vision of vegetation, its units had little overlap as many species were confined to a single type of vegetation. The boundaries among adjacent clusters of plants were narrow, with very little overlap of species ranges, except for a few widespread plants.
Henry Gleason (1926, 1939) published his ideas on the continuum view of vegetation soon after those of Clements. His contention was that vegetation was the result of two major factors: the fluctuating arrival and departure of plants, and the equally fluctuating environment. In contrast to Clements' view of plant associations as discrete and interdependent combinations of species, Gleason viewed species ordered along environmental gradients in ways prescribed by the individual requirements of species. Overlap in species distribution was considered largely coincidental and independent. Gleason regarded the clusters of species predicted by the discrete community view of Clements and his followers as merely artifacts of the investigator's perception or of sampling and analysis methodologies.
Recent studies have continued to support the Gleason's individualistic view of vegetation. For example, even understory species in several forest types have been shown to be influenced not so much by the species of trees that shade them in the canopy, but by the presence of shade itself (McCormick & Platt 1980, Parker & Leopold 1983, Rodgers 1980, 1981). Smith & Huston (1989) suggest that the vast majority of spatial and temporal structure in vegetation can be attributed to competition among species for light and water as plants grow larger.
As a direct result of these investigations and theories, vegetation ecologists today are cautious about acknowledging the existence of plant communities. Wilson (1991) suggests that there is very little evidence to support their existence. Others (Dale 1994, Keddy 1993, Palmer & White 1994) suggest that definitions of ecological communities need to be changed before their existence can be refuted or substantiated. Keddy (1993) points out that there are a number of things we define as existing that are difficult to prove empirically (e.g., electrons, individual human beings, individual species). Yet these terms are useful. Palmer & White (1994) suggest that community ecologists should define "community" operationally and thus remove themselves from the ontological dilemma of whether or not communities exist.
Sophisticated techniques have been devised to define associations among plant species and their environmental correlates (Bonham 1989, Gauch 1982, Kent & Coker 1992, Jongman et al. 1987, Mueller-Dombois & Ellenberg 1974). Although these techniques distinguish groupings of plants following quantitative field sampling and analysis, we recognize that plant communities erected using these techniques are arbitrarily drawn. Community boundaries depend on the investigator, the sampling and analysis methods as well as the sharpness of the environmental gradients in the landscape. For this reason, we use the word vegetation type, not plant communities, when referring to plant assemblages.
Clements (1916) popularized the idea that a community grew, matured, died, and reproduced itself though a progression of serial stages, each depending on the previous one. This concept of succession, like his community theory, has been challenged. Egler (1954), McCormick (1968), and others conducted studies in the eastern United States that suggested that succession depends on initial floristic composition, not serial stages. Progression from dominance by shortlived plants to one of longer-lived plants has elements of chance that can create several possible avenues as plants grow and mature. Clements' predictable model of succession to a single persistent state is not realistic.
Recent ideas applied to non-forested environments (e.g., Westoby et al. 1989, Huntsinger & Bartolome 1992) suggest that for major kinds of vegetation, for example, grassland or oak woodland, there is a catalog of possible states and transitions among them. The states represent visually distinct vegetation types, grassland, grassland with shrub seedlings, and dense cover of shrubs with little grass, all in the same area. The transitions represent change from one state to another brought about by changes in environmental conditions, disturbance events, or by the inevitable growth of new species overtopping previously taller plants.
Forest ecologists (e.g., Oliver & Larsen 1990) go as far as to replace the term succession with a new one, stand dynamics, when talking about the way forests change with age. Their domain of interest is not the plant community, but a stand of plants that have the same history. Stands of seedlings become established after a disturbance. As the seedlings grow to be trees, the stand goes through structurally, and possibly floristically, distinct stages. A landscape is seen as a matrix of a few to many stands with different histories and ages.
As the need for conservation and management of vegetation continues, so does the practical need to understand how vegetation develops and how it is defined. Operational views of change and of vegetation classes are destined to replace the metaphorical concepts that initially described them. However, the accuracy of science will never be a substitute for our aesthetic appreciation of the beauty of vegetation patterns across the landscape. It behooves us to pause and reflect.
A classification is a language created to bring order out of apparent chaos. Because it is a language, the basic goal of a classification is to solve a communication problem. A vegetation classification is, therefore, a language developed to meet the need for a single commonly accepted terminology to discuss various kinds of vegetation.
Classifications cannot be all things for all people. The numerous vegetation systems that have been developed reflect a variety of descriptive scales, philosophies, and purposes. We recognize that all classifications are artificial in that the units are subjectively defined and described to meet particular needs.
Reasons for developing a vegetation classification are varied and can include assisting in resource inventory, land use planning, conservation, illustration of ecological relationships, or building a framework for understanding vegetation dynamics. Likewise, the vegetation units created vary and can include: functional resource management criteria, such as timber or range types; descriptions of vegetation associated with landscape units, ecological units, or animal habitats; emphasis on vegetation structure; emphasis on floristic assemblages; or emphasis on units recognizable with aerial photographs.
Scale and Hierarchy in Classifications
Any vegetation classification recognizes a particular level of detail. For example, land use cover classifications and accompanying maps published by the U.S. Department of Agriculture or various California county governments list general units, "grassland, conifer forest, scrub, or marsh". These same classifications may put more emphasis on distinguishing among types of agricultural crops than among natural vegetation units. Wall maps of the vegetation of California, (Küchler 1977, Parker & Matayas 1979, Wieslander & Jensen 1946), show gross patterns of vegetation, but are not accurate at a fine, local scale. In contrast, a vegetation classification and map produced for a small nature preserve or a state park exhibits detail at very fine scale.
The concept of hierarchy has proved valuable in the theoretical organization of vegetation throughout the world, in much the same way that it has been used to express relationships among plant or animal taxa. Several well-defined vegetation classification hierarchies exist. For example, the UNESCO classification (Muller-Dombois & Ellenberg 1974) or the classification developed by Barry (1989) for the California State Park System incorporate many levels of scale, from the individual plant to the biosphere.
In many North America approaches to vegetation classification, the broadest units are defined by vegetational differences correlated with basic environmental differences (e.g., aquatic and terrestrial). Lower levels are arranged around physiognomic features of plants including height and dominant life form (e.g., tree, shrub, herb), canopy cover (open to closed) and its foliage characteristics (e.g., evergreen, deciduous, broadleaf, needleleaf). It is not until the classifier moves well down in the hierarchy that classes are defined by dominant species: for example, the formation-type level in Barry's (1989) scheme, and the series level in Daubenmire's (1939) classification. Beneath that dominant species level is another level, the association, that is defined by secondary species.
Another approach, originated inEurope (Braun Blanquet, 1932) emphasizes floristics throughout its hierarchy with the finest association level being built upon to form alliances, then orders, and classes above that.
Hierarchical approaches to classification of natural environments exist that do not emphasize vegetation. One of the most widely used of these is the wetland and deep water habitat classification of Cowardin et al. (1979). In the Cowardin approach, physical features of the environment are arranged hierarchically. These upper levels relate solely to physical characteristics, such as substrate type, water chemistry, and water regime. Only the lowest level, the dominance-type, is biologically defined. In the case of wetlands, biological dominance may be either botanical or zoological, mussel beds in the marine intertidal zone for case. Ferren et al. (1994) in a recent classification of central and southern California wetlands use a modified version of the Cowardin system to describe hundreds of dominance types, many of which are analogous to the series, alliances, or associations of traditional vegetation systems.
Hierarchical arrangements of ecosystems, for example, the USDA Forest Service ECOMAP project (ECOMAP 1993), utilize synthetic ecological units derived from abiotic (primarily soils, climatic zones, and landforms) and biotic classifications (primarily vegetation) at regional, subregional, landscape, and land-unit levels. The basic landscape and land-unit levels of the ECOMAP project are called "landtypes".
The CNPS Approach to Classification
Our Focus is on Floristics and Rarity
Floristic components of a classification are those that refer to the plant taxa making up the vegetation of a given area. We believe that the most important units of conservation in any hierarchy are the floristically-based lower units of the series or association. Broad physiognomic units are largely synthetic, including units without common species. For example, open stands of singleleaf pinyon pine or Engelmann oak are both described as woodlands, yet they share few if any plant taxa. Recognizing both units as woodlands does not express the level of biological diversity that we are interested in classifying.
Although we recognize the value of higher levels of vegetation, they are not treated in this manual. The current hierarchies developed by UNESCO (Muller-Dombois and Ellenberg 1974), USDA Forest Service (ECOMAP 1993), The Nature Conservancy (1994), and others can be easily blended with this system. A national vegetation classification (http://biology.usgs.gov/npsveg/classification/appendix.html) has recently gained acceptancy by the Federal Geographic Data Standards Committee. It has arisen from the Nature Conservancy's classification and has a mixed floristic and physiognomic hierarchy. In keeping with our recognition of the value for standardization, we have included a table that relates our vegetation series to the upper physiognomic levels of the national vegetation
Some examples of rare California series are:
|Alkali sacaton series||Ashy ryegrass series|
|California oatgrass series||California walnut series|
|Darlingtonia series||Engelmann oak series|
|Giant sequoia series||Grand fir series|
|Idaho fescue series||Ione manzanita series|
|McNab cypress series||Native dunegrass series|
|Parry pinyon series||Santa Lucia fir series|
|Sargent cypress series||Sitka spruce series|
|Teddy-bear cholla series||Valley oak series|
|Washoe pine series||Water birch series|
Some of these rare series are representative of extensive series that occur beyond California's borders, while others are endemic. Some were once extensive, now reduced to a small part of their original range; others were never extensive. Some are diverse and include several associations, while others may be represented by a single association.
The process of quantitative vegetation classification is often long and detailed. For example, recent work by the California Natural Diversity Data Base on the California sycamore series required two seasons of field sampling and several months of data analysis. It was only then possible to quantitatively define and map three associations, two of which are very rare (Keeler-Wolf et al. 1994). We hope that such sampling and analysis efforts will initially focus on describing the rarest communities to help protect them.
The focus on rarity does not imply that we ignore vegetation types that are common and extensive. The only way we can understand the rare ones is in the context of all of the state's vegetation. Yet, how do we build a quantitative, data-driven classification without collecting and analyzing data from all vegetation? We have, by necessity, chosen a compromise. We established basic rules of dominance and nomenclature for the larger units of floristic composition that we call series. Based on our knowledge of the distribution of a series, distinct subdivisions can be targeted for study.
For example, we know that the Valley oak series is widespread. Although clearing of oak woodland for agriculture and urban development has reduced acreage over the past 150 years, there is still a considerable area dominated by valley oaks. However, acreage of closed-canopy valley oak forest in the riparian zone is very small today. It has been reduced substantially by agricultural clearing, gravel mining, and other stream bed alterations. Because this subtype of Valley oak series is visually distinct, it has been treated as a distinct vegetation type called Great Valley valley oak riparian forest (Holland 1986). By targeting stands dominated by valley oak and others not dominated by it in the riparian zone for sampling and analysis, we are able to ascertain if valley oak riparian forest is a unique vegetation type. If it is, we are able to offer a quantitative description of it, map its extent, and definitively distinguish it from other types of vegetation.
Our Views of Dominance, Existing Vegetation and Refinement of this Classification
Although the general rules of dominance and cover (see how to use this manual) apply to all series in this manual, there are many cases where a series is not yet quantitatively derived through sampling and analysis. Dominance can be visually estimated and in many cases it is an obvious enough trait to make detailed sampling and analysis to prove the point unnecessary. In some cases you will see series named by a dominant species, while in other cases you will see them named by a dominant genus. This has been done in the case where species in the genus have similar ecological requirements. This practice is in keeping with the way series have been defined in earlier efforts (Parker & Matayas 1979, Paysen et al. 1982).
Series are defined using the dominance rule. Vegetation ecologists have found that certain species other than the dominant upper layer species may be informative in defining ecological groupings of vegetation types. These species are described as "representative", "diagnostic", and "characteristic" (Mueller-Dombois & Ellenberg 1974, Kent & Coker 1992). Types that have the same characteristic species are described as belonging to an "alliance" rather than to a series (The Nature Conservancy 1994). A few of the series in this manual, the Woollyleaf manzanita series for example, are defined in terms of characteristic species rather than the dominant ones.
Our classification views vegetation in terms of what exists today. There is no presupposition on our part that stands of one series will naturally always stay in a series or be replaced by another one. The vegetation dynamics are currently being worked out for a number of forest types in the state, but our principal focus in this manual is to identify any vegetation type that currently exists as a visually distinct entity. At the same time, we recognize that vegetation change and development are real, and that there is value in understanding vegetational states of a particular area. Understanding allows for wise resource management, including that of endangered species requiring special habitat conditions.
In comparison, most of the quantitative classifications developed for California by the Forest Service (e.g., Fites 1993, Jimerson 1994) are based on the concept of a "potential natural community," not on one of the existing community or vegetation. A potential natural community is one "that would be established if all successional sequences of its ecosystem were completed without human-caused disturbance, under present environment conditions" (Forest Service Manual). We cannot provide a uniform view of such a potential for the state's series. We also believe that other concepts of stand dynamics and state-transition concepts may afford a better way of understanding much of California's vegetation.
Conservation and Management in the Present and Future
How Description of Vegetation Can Help with Conservation and Ecosystem Management
Those who have spent time in California have heard it described by superlatives in comparison to other states in the country – highest and lowest points, greatest number of plant species, greatest number of endemic plant taxa, greatest number of climatic zones, most complex geology, greatest number of endangered species (an unfortunate superlative), the list continues. California also contains the most diverse and complicated patterning of vegetation of any area of comparable size in North America. The combination of complex geology, climatic conditions, natural disturbance regimes, and topography, coupled with its high plant species diversity, has created an extremely diverse hodgepodge of vegetation types.
Classifiers of California vegetation are faced with an urgent task. Its seriousness is underscored because CNPS believes that many of the rare and endangered communities in California are being destroyed. Yet, without quantitative descriptions of California's vegetation types, we cannot distinguish the rare or endangered series from other more common ones. Further, we cannot justify their protection in terms of CEQA if we cannot clearly define them.
As we encounter economic pressures that alter and destroy our vegetation, the amount of time to distinguish its many forms appears frighteningly short. The California Natural Diversity Data Base (NDDB) has determined that 135 out of the 280 vegetation types listed as end points in the Holland (1986) classification are rare enough to warrant concern and some level of protection. At least 50 of these are so rare that it is believed that there are fewer than 2000 acres of high quality habitat for each of them.
We are at a crossroad. The federal and state endangered species acts are undergoing more scrutiny and challenge than ever before. The legal tools for conservation of biodiversity were not explicitly developed for conservation of vegetation types and ecosystems. There are only vague inferences and brief intent language that address conservation of habitats and ecosystems in CEQA legislation. Yet, conservationists recognize that to sustain the natural values of California there must be something more useful and comprehensive than single species-based conservation. CNPS hopes eventually to secure explicit legislative protection for rare and endangered vegetation types, but we recognize that we must now focus on seeking protection through existing mechanisms. These include CEQA, NEPA, and a number of innovative programs. Recently, some programs based on vegetation types have begun. These efforts pertain to southern California's coastal sage scrub, a pilot project initiated by the 1991 Natural Communities Conservation Planning Act (NCCPA), and multispecies conservation plans for the Sacramento Valley, San Joaquin Valley, western Mojave Desert, and other areas.
Conceptually, these programs have the advantage of establishing habitat reserves for key portions of an ecological region, while allowing areas of lesser ecological importance to be modified or developed, satisfying both the conservationist and developer. However, these programs are scientifically compromised by the lack of information. These programs have, by default, focused on individual threatened or endangered indicator species within broadly conceived ecosystems. Chief among the reasons for this compromise is insufficient information on the vegetational building blocks of these areas. CNPS believes that by developing quantitative vegetation descriptions, critical habitat for numerous targeted rare species can be better defined.
As an example, not all areas within the zone described for the NCCPA activities are prime habitat for the California gnatcatcher, the bird species motivating much of the conservation work in southern California. Classification of vegetation can play an important role in resolving conflicts. Broad conceptual views of coastal sage scrub and chaparral in the vein of the Munz & Keck (1949, 1950) or Holland (1986) classification may under or overestimate the value of areas to gnatcatcher habitat. In all likelihood, the bird is responding to distinct mixes of plant species composition with special structure, as recently pointed out by Read (1994) and White (1994). Only a detailed, quantitatively based vegetation classification can specify such important resource differences.
Using carefully crafted quantitative vegetation descriptions can aid to multispecies conservation. There are, however, vegetation types that are in and of themselves rare. These may occur within areas not slated for broad scale habitat planning, and may exist without containing a single threatened or endangered species. Yet, we recognize the uniqueness of the vegetation type and the threats to its existence. If we want to develop a framework for the protection of these types, we need to develop defensible definitions for them.
The conservation-based Holland classification currently used by NDDB is insufficient to answer repeated questions about the relevance of many of its vegetation types because of the lack of quantitative data. Does the southern maritime chaparral differ significantly from adjacent chamise chaparral or southern mixed chaparral? How can we differentiate sycamore alluvial woodland from southern sycamore-alder riparian woodland? Such questions arise because NDDB has identified some communities as rare and endangered. Therefore, landowners and resource managers want to know how to identify and protect, or more skeptically, how to demonstrate or discredit the uniqueness of these vegetation types. Rigorous definitions and mapping remain a problem because until very recently we have not chosen to quantify salient components of these types.
We treat Holland (1986) high priority communities in various ways as they are translated into series. The following list identifies some of the Holland "rare" communities in need of precise sampling, and their relationships to the new system.
|Holland communities represented by several series||Coastal sage scrub, Coastal dune scrub, Freshwater swamps, Great Basin grassland, Great Valley riparian forest, Maritime chaparral, Native coastal grassland, Sitka spruce-grand fir forest, Southern riparian forest.|
|Holland rare communities considered as associations||Gabbroic northern mixed chaparral, Great Valley chenopod scrub, Maritime coast range ponderosa pine forest, North Coast black cottonwood riparian forest, Sycamore alluvial woodland.|
|Holland communities considered as series||California walnut forest and woodland, Ione manzanita chaparral, Washoe pine-fir forest, Western hemlock forest.|
|Holland communities treated as stands in which a species, not the community, is of interest||Cherry forest, Island ironwood forest, Torrey pine forest.|
How the CNPS Classification Fits into a National Vegetation Classification
The enormity of the task of vegetation classification in California is multiplied several times when we consider classifying the vegetation of the entire country. Yet, an integrated and complete classification of vegetation for our country would afford the most comprehensive approach to conservation and management of our nation's natural ecosystems. The need has been long recognized. Classification efforts have proceeded in two ways: from the top down in the form of physiognomically based classifications, and from the bottom up in the form of small regional systems that may be pieced together to form an as yet incomplete, fine-scale national classification quilt.
The top-down physiognomic hierarchies of Driscoll et al. (1984) and Bailey (1994) are frameworks that have been built upon by projects, for example, the USDA Forest Service current (ECOMAP 1993) effort, which nationally describes a hierarchy of regional to landscape levels of physiognomically defined vegetation and ecosystems. However, the lower floristically defined building blocks are far from completely described.
The most extensive integration of the floristic vegetation units at the national level is being conducted by The Nature Conservancy (TNC) Heritage Task Force ecologists. By integrating existing floristic-level classifications from the USDA Forest Service and thousands of other agency and individual studies much progress has been made on assembling a national system. However, due to the somewhat inconsistent methods of classification, certain regions of the country are less well integrated than others. The most successfully organized region is the western United States, where quantitative definition of vegetation associations has been most complete. TNC's heritage ecologists have recently produced a preliminary classification of the western United States (Bourgeron & Engelking 1994). This work relates the quantitatively defined associations to alliances. It does not include California at this time, a situation that this CNPS effort will change due to the comparability of approaches.
That conservation and resource management classifications are now speaking the same language is an important step forward. Specificity is important in both a practical manager's and an idealistic conservationist's lexicon. The work that the Forest Service and other land management agencies have done to attain this level of understanding is of direct value to conservation.
In 1994, TNC western heritage ecologists and members of CNPS Plant Community Committee met and agreed that the time was right to meld the California and western United States classifications. The first collaborative effort was recently published (Grossman et al. 1994). This initial survey of rare plant communities of the conterminous United States was possible because the classifications are at compatible scales. In addition, the efforts were able to use comparable ranking criteria for rarity.
Recently Michael Barbour, on behalf of the Ecological Society of America (ESA), has agreed to chair a special subcommittee on vegetation classification. Its principal charge is to develop a united system for use in the nation (Barbour 1994).
Conservation of Vegetation in the Future
Beyond the level of quantitative definition of series and associations, serious questions may arise about the basic premise of the CNPS plant communities program: to identify and to protect rare plant communities in California. As more and more associations are defined, we may be faced with an enormous number of rare plant associations. How can we justify protecting them in the political, social, and economic climate where it is becoming nearly impossible even to legally "list" strongly substantiated rare species? Can we effectively justify supporting legal protection for potentially hundreds of rare assemblages of plants? In addition to the refinement of classification, there must come a refinement of concepts of threat, endangerment, and different levels of biodiversity value for vegetation. Two points may serve as examples of the complexity of issues involved.
We already know that several quantitatively defined associations of Blue oak series in the southern Coast Ranges are restricted to just a few sites of limited acreage (Borchert et al. 1993). However, they have no rare species associated with them. Instead they are uncommon assemblages of widespread species limited by topographic position and soil type. Are these limited assemblages as important as plant associations that are dominated by or contain a mixture of rare species that occur nowhere else? To evaluate such situations, might we not incorporate wildlife values, watershed protection values, and other non-vegetation traits into our assessment and deliberations?
Secondly, as a result of direct human disturbances, including livestock grazing and invasion by exotic plants, excellent examples of common vegetation types are rare in themselves. Do we need to become more interested in identifying and quantifying the best remaining examples of some of our more common plant assemblages? Ranking and prioritizing sites based directly on human disturbances underscores another need for quantitative assessment that goes beyond standard vegetation sampling techniques.
Conservation strategies will surely arise that we do not fully comprehend at this time. They may enable us to view more clearly the value of individual vegetation associations in terms of larger watersheds and landscapes. We may be able to envision and sustain a set of vegetational states and a patchwork of ecosystems that enables us to foster the processes necessary to maintain biodiversity without the legal protection of any specific plant associations. In the interim, the least we can do is be committed to analysis and study of vegetation so we can provide some of the scientific building blocks for these larger goals.
The History of Vegetation Classification in California
The early explorers left records describing California's vegetation in the broadest of terms. In the late 1800s, descriptions by Brewer (in Farquahr 1966), Sudworth (1908), Kellogg and Greene (1889) and others mentioned oak woodlands, grasslands, chaparral, and conifer forests, but these accounts lacked precision.
In the early 1900s many vegetation classification systems in the United States were associated with Clements' concept of stratifying the world's vegetation into large-scaled climatic zones (Clements 1916, 1920, Weaver & Clements 1938). Cooper (1922) was interested in characterizing California's communities dominated by plants with relatively stiff thick leaves with a waxy cuticle (the so-called sclerophylls) occurring in its Mediterranean-type climate. Within the two main sclerophyll groups, the California chaparral formation and the Broad sclerophyll forest formation, he made further divisions into units representing distinctive categories. These units he called associations (or consociations, if the unit was dominated by a single species). Because it is a useful way of accounting for vegetation without the need to know the identity of the smallest units, Cooper's approach has been followed and extended over the years. This approach can be naturally extended to mapping and is seen in the system developed by Wieslander in his Vegetation Type Map (VTM) Survey of California (Wieslander 1935, Critchfield 1971).
The Wieslander mapping effort was a remarkable achievement. Between 1928 and 1940 almost half of the state (about 40 million acres) was mapped by USDA Forest Service field crews who combed California using a specific protocol. Because this project was initiated before the widespread availability of aerial photos, the crews worked from the prominent peaks and ridges to gain the perspective needed to draw and label the individual patches of vegetation. In addition to sketching these types, the VTM survey collected data from thousands of individual plots which further characterized and documented this dominance-based system. These data, in many cases over 60 years old, have provided a valuable resource for further studies of the relationships of vegetation in cismontane California. Recent work by Allen et al. (1990) has taken advantage of the VTM vegetation plots to develop classification systems of California's oak and other hardwood rangelands. Griffin & Critchfield (1976) used the species identifications of the VTM survey and the succeeding Soil-Vegetation Survey maps (another USDA Forest Service project with less detail on species composition) to develop an atlas for forest trees in California. Minnich et al. (1994) showed the effects of 60 years of fire suppression on mixed coniferous forests in southern California by resampling plots established in the 1930s by the VTM crews.
The multifaceted values of the mapping project data were clearly envisioned by Wieslander (1935). He states, in his description of the project, that the maps of broadly defined plant associations (his larger hierarchical units) are useful to engineers, foresters, and others charged with the management of wildlands. They represent an attempt to group subtypes having similar fire hazard characteristics and qualities of economic importance. Wieslander considered his more detailed subtype units as providing basic information on vegetation cover desired by the research worker in various fields of botany, ecology, or forestry.
Despite the great effort involved, no systematic attempt was made to synthesize the Wieslander vegetation units into a classification that also described the mapping units. In 1980, Glen Holstein, the first ecologist with the California Natural Diversity Data Base, catalogued the vegetation polygons on the VTM maps and came up with about 1800 individual cover types. Because of the large number of types, the incomplete total coverage, the somewhat inconsistent listing of subdominant species, and the lumping of some vegetation mosaics into larger polygons, it has proved difficult to synthesize the mapping data in a bottom-up hierarchy meaningful for the state. The ancillary plot data have proven much more useful in this regard (see Allen et al. 1990, Allen-Diaz & Holzman 1991), although limitations of geographic coverage and lack of detailed understory species composition pose constraints.
Jensen (1947) developed a methodology for classifying California's vegetation in several ways based on the VTM survey. Jensen presents three classifications useful for different purposes. The first section is a vegetation cover and land status classification including 12 categories, such as chaparral, commercial conifers, bare ground, and cultivated areas. The second section is a system of the "species units", including single species, mixed species, or "mosaic mixtures" where two or more elements are involved. These species units are analogous to the mapping units in the original VTM survey. The third section is a synthesis of the first two, grouping the 32 main types, including commercial conifer, non-commercial conifer, hardwood, and non-tree types. This latter synthesis was developed into a statewide vegetation map (Wieslander & Jensen 1946). Both Wieslander and the Jensen efforts were based on maps of a certain scale (15' USGS 1:62,500), thus limiting the size of the vegetation units depicted to no less than about 40 acres (Jensen 1947).
In contrast to the map-based efforts of Jensen and Wieslander, the next California vegetation classification developed was based on broad climatically inferred plant communities (Munz & Keck 1949, 1950). It was meant to aid in the discussion of habitat and distribution of species in the book, A California Flora (Munz 1959). This was another Clementsian-based classification that created 29 plant communities within 11 vegetation types, distributed among five biotic provinces. The names, familiar to many contemporary botanists, use names of dominant species (red fir, redwood, and bristlecone pine forests) while others invoke habitat characteristics or physiognomy (foothill woodland, valley grassland, coastal strand, and alkali sinks). Although the Munz and Keck plant communities form a useful tool for understanding the statewide distribution of plants, the system omits numerous ecologically distinctive habitat types.
In the 1970s, heightened interest in vegetation within California resulted in two books (Barbour & Major 1977, Ornduff 1974), a number of descriptions of local vegetation (e.g., Hanes 1976, Minnich 1976, Sawyer & Thornburgh 1977, Vogl 1976), and two statewide classification systems that refined the Munz and Keck approach to finer levels and developed many new types (Cheatham & Haller 1975, Thorne 1976). The two books describe California's vegetation on various scales of knowledge and were not intended as a formal classification.
Thorne's system was published by CNPS for purposes of plant conservation. Cheatham and Haller's system was never published and was specifically designed for the identification of University of California natural reserves. The Thorne system is more detailed than Munz and Keck's, but is more general than Cheatham and Haller's. Both divide broad habitats, including dunes, scrub, and chaparral, bogs and marshes, riparian, woodlands, and forests into finer divisions based on species composition and geographic location.
Arising directly from the Cheatham and Haller system was the classification used by the California Natural Diversity Data Base (NDDB) to identify rare natural communities. The unpublished Holland (1986) classification, a refined version of the NDDB system, is structurally identical with Cheatham and Haller, but it defines more types and, for the first time, assigns rarity ranks and conservation status to units of the hierarchy.
An advantage of the Cheatham and Haller and Holland classifications is that they are specific and differentiate among similar, but geographically isolated types. A disadvantage lies in the lack of uniform criteria in distinguishing units. Some are defined by location, some by structure, others by specific taxa. Although descriptions of most types indicate dominant and characteristic species and distribution, the accounts are general and tend to overlap. Although the Holland system is hierarchically arranged, it is of uneven resolution with coarse as well as fine scales of vegetation defined at the lowest units of the system (Keeler-Wolf 1993).
Another concern with classifications, as those of Cheatham and Haller and Holland, arises with the increasing importance of vegetation units as indicators of ecosystems. We need to unequivocally define these units, and to relate them to similar units across state boundaries so that a broad network of ecosystem conservation may become established. We also need to ratify and validate these units so that they gain acceptance in scientific and land management circles. This situation requires quantitatively defensible definitions for vegetation types as the most important units of conservation.
A system to classify California wildlife habitats was developed in the early 1980s (Mayer & Laudenslayer 1988). This is the California Wildlife Habitat Relationships System (WHR), and it consists of about 50 types intermediate in scale and definition between Munz and Keck's and Thorne's community types. The WHR system also consists of some non-native vegetation types, including eucalyptus groves and several types of agricultural and developed habitats not treated in other classifications.
The WHR system was developed primarily to classify and predict habitat value for the vertebrate animals. It is one of the few systems that identifies structural stages in various tree, shrub, and herb-dominated types. Because cover class rules and size rules are established, the system has use in predicting habitat value based on management practices.
WHR has been less successful in differentiating between vegetation types. Because the habitat types are inconsistently defined, a broad familiarity of its detailed descriptions is needed to differentiate among types of similar structure. Although mappers have constructed rules for discriminating among types, difficulties still remain because species dominance varies substantially within some types and broad overlaps in dominant plants occur among types. Other problems arise due to the small number of classes and the inconsistencies in scale among them.
At approximately the same time that Thorne's and Cheatham and Haller's classifications were introduced, the USDA Forest Service was coming to grips with the need to manage their California lands in a way that would sustain natural resources and underscore the potential of different environments to support timber removal, grazing, recreational use, and other human activities. To accomplish this goal they recognized that classification of ecosystems was a high priority. Much of their effort in the 1970s and 1980s was directed towards classification (Allen 1987, Hunter & Paysen 1986, Paysen 1982, Parker & Matayas 1979, Paysen et al. 1980, 1982).
The purpose of these efforts was to develop a land classification that could be applied to research and management activities. Their approach differs fundamentally from earlier classifications of California's vegetation because it relies on field samples (plots) of the vegetation to build the bottom layers of the hierarchy. Consequently the basic taxonomic units of the system were not identified by arbitrarily assigning a name to what is generally perceived as a unique type. Instead, the basic units are defined after a number of plots are analyzed over a large area. This classification is quantitative and driven by the availability of data, rather than qualitative and anecdotal.
California has lagged behind Oregon, Washington, Idaho, and Montana in developing data-driven vegetation classifications. Efforts of Daubenmire (1952), Daubenmire & Daubenmire (1968), Franklin et al. (1971), Pfister & Arno (1980), and others set the standards for the USDA Forest Service, Pacific Southwest Region classification of forests and chaparral in California. The California data, however, can be added to a standardized system that can be related to a national land use system (Driscoll et al. 1984, ECOMAP 1993).
The larger floristic units of these efforts became known as series and the smaller basic units as associations. Series were identified by the dominant plants in the overstory, while the associations were identified by characteristic species in the understory layers. There is an ecological basis for grouping associations into a series. For example, although there are many associations of white fir forest in the Sierra Nevada, all occupy sites that are warmer than the red fir-dominated forests. Red fir typically occurs at higher elevations or on cooler exposures, so the dominant overstory species reflect broadscale environmental differences. The presence of certain understory species reflect more localized differences related to microclimate and soil.
The framework of the classification produced by the USDA Forest Service in California is described by Allen (1987). This project entails several Forest Service zone ecologists developing classifications of targeted areas. The work includes extensive sampling of the vegetation, soils, and other environmental characteristics.
Classifications are completed for Port Orford-cedar forests (Jimerson 1994) in the North Coast and Klamath regions, for blue oak woodlands (Borchert et al. 1993) and redwood forests (Borchert et al. 1988) in the Central Coast region, for mixed conifer forests (Fites 1994) and red fir forests (Potter (1994) of the Sierra Nevada, for eastside pine forests of the Cascade Range, Modoc Plateau, and Sierra Nevada (Smith 1994), and for chaparral types of the Transverse and Peninsular Ranges (Gordon & White 1994).
In the past few years there have been many local and regional vegetation mapping efforts. A number of land management and resource agencies have been funding these projects, including the California Department of Forestry and Fire Protection, the USDA Forest Service, the USDI Fish and Wildlife Service, the USDI Bureau of Land Management, and various individual county governments. Most of these recent efforts have relied on sophisticated state-of-the-art mapping techniques based on computer-assisted interpretation of satellite images and aerial photos. Computerized Geographic Information Systems (GIS) are used to associate detailed information with each mapping unit and allow easy updating of products. These projects have used various vegetation classifications.
The most prominent and extensive of these recent mapping projects is the California Gap Analysis Project (GAP) (Scott et al. 1993). This is part of a national effort by the Fish and Wildlife Service to identify gaps in the preservation of species and habitats. The distribution of species and known significant natural areas are overlain on a map of land ownership. Significant elements of biodiversity that are not protected within nature reserves, parks, or other preserves are then identified and targeted for protection. The underlying rationale for GAP is to gain a fuller understanding of the current mosaic of vegetation types. Since an up-to-date vegetation map for California does not exist, the project is developing one. The team members are currently piecing together a map on a region-by-region basis using the 10 main floristic provinces in The Jepson Manual (Hickman 1993) as a guide. Currently the South Coast, Colorado Desert, and Mojave Desert are completed and other regions are in varying stages of completion. The classification is based on the CALVEG series-level classification (Parker and Matayas 1979). In many cases the mapping effort is flexible enough to translate to Holland (1986), WHR, and other systems. This flexibility is afforded by decision rules incorporating species dominance as a translator among classifications. The principal problem with the GAP map is one of scale. The mapping is based on a scale of 1:100,000 [1 cm2 on the map, 100 ha on the ground] with a minimum polygon size of 100 ha (240 acres). Consequently it is insufficient to depict small vegetation units.
The Difference Between a Vegetation Classification and a Vegetation Map
Vegetation mapping units (the individual patches depicted on a map) and vegetation classification units (the vegetation type described at a given hierarchical level of a classification) are not necessarily one and the same. A vegetation map is a symbolic representation of visually distinct groupings of plants. A classification can afford to be much more detailed and descriptive. It can involve more floristic and structural details than that perceptible on aerial photographs or easily depicted in maps.
Another important difference between a map and a classification is that a map is limited by scale, while a classification need not have this restriction. The development of a quantitative classification system allows the user to benefit from the knowledge that all the pieces of vegetation can be arranged from the smallest identified units to the largest. In a system that starts with stands of vegetation, the classes at a given level in the hierarchy are grouped according to prescribed similarities to form classes at the next level. This approach affords a consistent interpretation that is driven by the known framework. For example, if the classification is based on species cover, rules to that effect can be established and consistently followed. Conversely, in a vegetation map, the matter of scale will always compromise a dominance-based system. Naturally occurring types smaller than the minimum mapping unit will not be represented and must be included within other often unrelated, but more extensive types. In addition, species that are visually similar to one another may need to be lumped as a single map unit, obliterating important ecological differences.
The best vegetation maps are presented in the context of a classification. The mapping units are often elegantly presented in categories of increasing generalized classes. Each class in the hierarchy can be consistently described in detail in a text that accompanies the map.
How to Use this Manual
California's vegetation is classified into a set of series. Keys allow quick access to the individual series descriptions, which are alphabetically arranged after each key.
Some vegetation cannot be classified using series rules. Some vegetation is better thought of as unique stands because they are found in only one occurrence, are defined by the presence of a rare plant, or are structurally distinctive. Some vegetation types are better defined by habitats. Vernal pools offer a special challenge in that they are defined as much by physical conditions as by plants. These categories are treated separately in sections following series descriptions.
The body of the Manual is arranged into six sections.
How to Use the Keys
The keys are written as if the user were located in a stand and wanted to identify the series to which it belongs. To do that, read both opposing couplet statements with the same number. The statements pick one character (a given species, for example) of the stand. Each character has various states (whether a species is dominant, important, common, rare). Pick the state that best matches the condition in the stand. Continue this process until you reach a series name.
Read the series description before you decide whether you have correctly keyed out the stand. If you have, the stand's structure,
species composition, habitat, and location should agree with the description. If they do not match, try the key again, remembering that series-level vegetation types vary, and that some stands are transitional to other series. Some series may be missing from this classification, as well.
The key primarily asks the user whether a species is dominant or important in the layer with the greatest amount of cover: the tree layer in forests and woodlands, the shrub layer in shrublands, and the ground layer in herbaceous vegetation. The words dominate and dominant refer to the extent to which plant crowns of a species or all species in a genus spread over (cover) the area, and how often the species or genus is encountered in the stand. It would be ideal to furnish cover values for each species listed in a series description, but few of California's plant vegetation types have sufficient data to assign average values. This is why these terms are not quantitatively defined here.
If the crown cover of a species spreads over much of the stand and individual plants are often encountered, the species dominates or is a dominant. Species that are not dominant have much lower cover and occurrence. In some series two or three species have comparably high cover and occurrence; they are described as important. Species that are not important have much lower cover. In some cases the user is asked whether a species is present or absent. The existence of the species in the stand is sufficient to answer "present". Such species are often called a "character" or "characteristic" species. In these instances whether a species is dominant, important, or rare is not necessary in identifying the series.
We Present Three Keys.
Key 2: Series dominated by shrubs (page 91)
Key 3: Series dominated by trees (page 214)
The shrub and tree keys are long and involved, so they are separated into subkeys to make use easier. After a few tries, the user can quickly jump directly to subkeys. The same series can occur several times in these keys.
To shorten the key, we avoided obvious strings of "yes or no" steps by establishing groups with informal names such as needlegrass grasslands. These terms do not imply hierarchical relationships, but are only meant as convenient groupings. Many series are not easily placed in common categories: desert scrub, chaparral, coastal scrub, or many kinds of forests and woodlands. For example, is the Chamise-white sage series better placed in chaparral or coastal scrub? For this reason, these terms are not given formal status.
Series descriptions follow the keys and are arranged alphabetically within the three key groups: Series dominated by herbaceous plants, Series dominated by shrubs, and Series dominated by trees. In a few cases genera and subspecies are diagnostic of a series.
Terms Used in the Keys:
Abundant: a species that is very likely to be encountered; it need not be dominant.
Chaparral: a shrubland dominated by species having evergreen, leathery leaves such as chamise, manzanita, or scrub oaks.
Chenopod scrub:a shrubland dominated by species which are members of the Chenopodiaceae, such as greasewood, iodine bush, or saltbush.
Coastal scrub [= coastal sage scrub]: a shrubland dominated by species having evergreen or deciduous, non-leathery leaves, such as California buckwheat, California sagebrush, coyote brush, or sages.
Desert scrub: a shrubland of Colorado or Mojave Desert taxa other than chenopod scrub.
Dominant [dominance]: an abundant species with high crown cover, especially in relation to other species in the stand.
Exotic [= alien, introduced]: a species that is judged to be a non-native member of the California flora.
Herb [herbaceous]: Plant lacking woody stems above ground; may be annual or perennial. Includes aquatics, forbs, and grasses.
Important [importance]: two or more species with similar abundance and crown cover in relation to other species in the stand.
Shrub: a woody plant with a short ulitmate height, commonly with 2+ stems from the base.
Shrublands: areas where shrubs dominate, including chaparrals, chenopod scrubs, coastal scrubs, and desert scrubs.
Similarity: used with term "important" to indicate species with equal abundance and crown cover in a stand.
Stand: an actual piece of California's vegetation in which plant composition and structure are uniform.
Subshrub: a plant with woody lower stems and herbaceous upper stems that die back seasonally.
Tree: a woody plant with a tall final height; commonly with one stem [trunk] from the base.
Format of Vegetation Type Descriptions
Format [refer to a series description such as the Purple needlegrass series]
The first paragraph describes the compositional and structural features of a series, unique stand, habitat, or vernal pool type. The first sentence specifies the composition of the most continuous layer by listing the sole, dominant, and important species before a semi-colon. This phrase defines the type. The alphabetically listed species following the semi-colon are commonly present as well, but they may be absent with other species present due to habitat and regional variation. They are listed to describe the type, but are not part of the definition. The remaining sentences summarize the structure of lower layers; presence, degree of canopy closure, and height. Species are not included for the secondary layers, except for typical emergent plants, those that are taller than plants of the most continuous layer.
The words sole, dominant, and important refer to the extent to which the plant crowns of a species or all species in a genus spread over (cover) the area, and how often the species or life form is encountered (frequency) in the stand. If crowns of a species spread over all or much of the stand and individuals are often encountered, then the species is a sole or a dominant. Species that do not dominate have low cover and are less frequent.
The second paragraph relates habitat factors of the type: topography, soil, and other characteristics of the environment. Wetland and upland settings for the type are characterized as well.
The third paragraph summarizes the geographic range and elevation. Provinces and regions are detailed in the California geography section. If the type occurs outside the state, its range is indicated by listing state names by two-letter codes. The range of a type in these states is not described. In some cases, we use more extensive terms such as "inter-West" or "Asia".
The sections below the line in each type description include supporting information.
The NDDB/Holland type and status section catalog the California Department of Fish and Game Natural Diversity Data Base (NDDB) element code(s) and Heritage Program status (see next page).
The Other types section lists synonymy categories in other vegetation classifications. The General references section lists commonly available treatments in the literature.
The Comments section is distinctive to a type, so format varies. We do not attempt to exhaustively review the ecology of the type at this time. Relationships among types are suggested in some cases. Botanical names generally conform to nomenclature of The Jepson Manual. We use the following alternate names:
|Alaska yellow-cedar||Chamaecyparis nootkatensis.|
|Bluebunch wheatgrass||Elymus spicatus.|
|Cuyamaca cypress||Cupressus stephensonii.|
|Desert needlegrass||Stipa speciosa.|
|Foothill needlegrass||Stipa lepida.|
|Indian ricegrass||Oryzopsis hymemoides.|
|Nodding needlegrass||Stipa cernua.|
|Port Orford-cedar||Chamaecyparis lawsoniana.|
|Purple needlegrass||Stipa pulchra.|
|Western wheatgrass||Elymus smithii.|
The paragraph of Plot-based descriptions catalog associations included in the type. The author of the association is cited after the association name. For example, the Cordgrass series contains a Dense-flowered cordgrass association described in Eicher (1987).
Synonymy is presented if two or more authors describe the same vegetation type. The earlier publication is given priority. For example, in the Native dunegrass series, Paker described a Native dunegrass-sea rocket association (1974) and LaBanca also characterized a Elymus mollis association (1993). The data presented by the authors suggest that the investigators sampled the same association.
Kinds of plot-derived data other than association definitions exist in the literature. Many times authors describe stand composition and structure without intent to classify; instead they present stand attributes as species present and their density, cover, or frequency. Some authors report specific detailed measurements for the most continuous layer as tree density, basal area, and frequency for forests. These papers are reported in this section along with association names.
The Nature Conservancy Heritage Program
G1: Fewer than 6 viable occurrences worldwide and/or 2000 acres
G2: 6-20 viable occurrences worldwide and/or 2000-10,000 acres
G3: 21-100 viable occurrences worldwide and/or 10,000-50,000 acres
G4: Greater than 100 viable occurrences worldwide and/or greater than 50,000 acres
G5: Community demonstrably secure due to worldwide abundance
S1: Fewer than 6 viable occurrences statewide and/or less than 2000 acres
S2: 6-20 viable occurrences statewide and/or 2000-10,000 acres
S3: 21-100 viable occurrences statewide and/or 10,000-50,000 acres
S4: Greater than 100 viable occurrences statewide and/or greater than 50,000 acres
S5: Community demonstrably secure statewide
0.1: Very threatened
0.3: No current threats known
We have reviewed the Forest Service Research Natural Area references with the coordinator for accuracy.
The shaded box titled Species mentioned in text lists the species mentioned in the text. Botanical equivalents for the common names are given there. The Comments section reports both names if the one used in the box differs from the name in The Jepson Manual.
References: We use the following labels for commonly cited references in series descriptions. Most are other vegetation classifications mentioned in the Other types section.
Barry type: A hierarchical vegetation classification system with emphasis on California plant communities by W.J. Barry, 1989.
Brown Lowe Pase type: A digitized systematic classification of ecosystems with an illustrated summary of the natural vegetation of North America by D.E. Brown et al., 1980.
Cheatham & Haller type: An annotated list of California habitat types, by N.D. Cheatham and J. R. Haller, 1975.
Cowardin class: Classification of wetlands and deepwater habitats of the United States, by L.M. Cowardin et al., 1979.
Holland type: Preliminary descriptions of the terrestrial natural communities of California, by R. F. Holland, 1986.
Jones & Stokes type: Methods used to survey the vegetation of Orange County parks and open space areas and the Irvine Company property, by Jones and Stokes, 1993.
PSW-45 type: A vegetation classification system applied to Southern California, by T.E. Paysen et al., 1980.
Rangeland type: Rangeland cover types of the United States, by T.N. Shiflet, 1994.
Thorne type: The vascular plant communities of California by R.F. Thorne in Plant communities of southern California, 1976.
The Jepson Manual: The Jepson Manual edited by J.C. Hickman, 1993.
WHR type: A guide to wildlife habitats of California, by K.E. Mayer and W.F. Laudenslayer, Jr., 1988.
Plant names: We chose to use common names for type and their description at the recommendation of the Plant Communities Committee. Those who disagreed suggested that common names were inconsistent in their application to scientific names; others argued that common names were more stable. Some sentiment may be in response to the different treatments in A California Flora and The Jepson Manual.
We realize that a single species may have many common names and that none is correct. In most cases, we used the most commonly used names in the ecological literature. In some cases, personal bias is no doubt involved.
Once a name is chosen, the form that it takes varies greatly in the literature as well. Capitalization, endings, separating words, and use of a hyphen are common differences. Birchleaf mountain-mahogany offers an example:
Why not Birchleaf Mountain Mahogany? In the botanical literature the more common rule is not to capitalize common names unless they refer to a person. Douglas-fir is preferred over douglas-fir.
The birchleaf part of the name can take several forms as birch-leaf, birchleaved or birch-leaved. We use the shorter "leaf" form over "leaved" and combine terms.
The name mountain-mahogany follows a customary rule that certain common names are associated with certain genera. Douglas-fir is not a member of the genus Abies, the firs, as indicated by the hyphen. Cercocarpus is not a member of the genus of commercial mahogany.
Should the possessive form be used for those involving people's names? The common name is most often Douglas-fir not Douglas'-fir. For some reason, tree names generally lack the possessive ending: Jeffrey pine, McNab cypress, etc. Yet the ending is used for shrubs, and especially herbs: Brewer's sedge, Davidson's penstemon, and King's ricegrass. For consistency, the possessive is not used for common names throughout the Manual.
The combining of two words is another place where inconsistences abound. Is black bush better than blackbush? In this case, literature also offers black brush and blackbrush, as well. In this manual, the most commonly used form is generally chosen.
Variation in species composition among stands can occur in a series. Tree canopies may have a consistent makeup among stands, but the shrub layer and ground layer composition may vary. This variation may be related to habitat as well. For example, a stand with a dense shrub layer and few ferns and herbs on the ground layer may occur at the top of a hill. At the bottom of a hill, a stand may have few shrubs and a luxuriant ground layer of herbs and ferns. Both stands have tree canopies of Douglas-fir.
This variation can be handled by considering the series to be composed of several vegetation types called associations. This approach is equivalent to thinking of a plant family as being composed of a set of genera, or a genus being a collection of species. In the earlier example, the Douglas-fir tree canopy is consistent. Variation in understory species defines the associations of the series.The convention of listing members of two layers easily separates series and association-level names. The Douglas-fir forest series includes Douglas-fir/huckleberry and Douglas-fir/sword fern associations. This "/" convention will be used for associations with more than one layer. If only one layer exists, then a hyphen will be used to separate important species. In some chaparral series, parentheses are used to distinguish associations where series names involve more than one species.
Associations found in the literature are based on the dominance rules used to define series. The association's name, author, and citation are listed in the plot-data descriptions section. In some cases, an association is assigned to more than one series, and the association's name is changed to conform with our conventions.
Geography of California
The geographical regions used to describe the locations of series in this manual are similar to those used in The Jepson Manual. However, because this is a manual of vegetation and not of flora, we choose to emphasize and recognize certain geographic areas as regions rather than subregions. For example, the Channel Islands, Peninsular Ranges, South Coast, and Transverse Ranges are treated as separate regions rather than being lumped as part of a Southwest California Region (Hickman 1993).
Lands west of the Cascade-Sierra Nevada-Peninsular range crest are designated cismontane California [Cis-CA], and are comparable to the California Floristic Province in The Jepson Manual. The area to the east is called transmontane California [Trans-CA], and it is equal to the Great Basin and Desert provinces in The Jepson Manual. The word "eastside" is also used to make this distinction in many papers on California vegetation.
We divide the Cis-CA into northern California [Nor-CA] and southern California [So-CA] subprovinces; Trans-CA into the Great Basin [GB] and Desert [DES] subprovinces.
The four subprovinces are divided into the physiographic regions or subregions used in The Jepson Manual. Six regions occur in Nor-CA, and four in So-CA.
Nor-CA includes five mountain regions surrounding the Central Valley [CenV]. The Klamath Ranges [KlaR] separates the coastal North Coast [NorCo] and Central Coast [CenCo] from the inland Cascade Range [CasR] and Sierra Nevada [SN].
So-CA includes two mountain regions, the Transverse Ranges [TraR] and Peninsular Ranges [PenR], and two low elevation regions, the South Coast [SoCo] and Channel Islands [ChaI].
Subdivisions of NorCo, CenCo, TraR, SoCo recognize climatic and vegetational differences between coastal or outer [o-] and inner [i-] locations.
Where mountains are high enough to show vegetation zonation, the following zones are possible: foothills [f-] surrounding CenV, low elevation [l-] canyons and valleys, montane [m-], subalpine [su-], and alpine [a-] zones.
We recognize in CenV the delta [d-CenV], Sacramento Valley [sac-CenV], and San Joaquin Valley [sj-CenV].
In GB, the area east of the Cascade Range [trans-CASR] distinguishes from that east of the Sierra Nevada [trans-SN], and in DES, the Mojave Desert [Moj-D] is differentiated from the Colorado Desert [Col-D]. Trans-CAS and trans-SN, and Moj-D each have two regions, while Col-D has one. In trans-CASR, we recognize the Modoc Plateau [ModP] with its Warner Range [WarR]. The trans-SN, involves the White, Inyo, and Sweetwater Ranges [WIS] and the valleys to their west plus the eastside of the Sierra Nevada [TraSN].
DES includes the Mojave Desert as a region [Moj-D] with the desert floor [MojD] and its Desert Ranges [DesR]. The Colorado Desert as a region [Col-D] has one area [ColD].
Modifiers indicating the northern [n.] central [c.], southern [s.], western [w.], and eastern [e.] parts of a region may be used.
IA Cis-CA Cismontane California
A0 Nor-CA Northern California
1a NorCo North Coast
a0 o-NorCo outer North Coast
b0 i-NorCo inner North Coast
c0 m-NorCo montane North Coast Ranges
2a CenCo Central Coast
a0 o-CenCo outer Central Coast
b0 i-CenCo inner Central Coast
c0 m-CenCo montane Central Coast Ranges
3a CenV Central Valley
a0 d-CenV Delta
b0 sac-CenV Sacramento Valley
c0 sj-CenV San Joaquin Valley
4a KlaR Klamath Ranges
a0 l-KlaR low elevations of the Klamath Ranges
b0 f-KlaR Klamath foothills
c0 m-KlaR montane Klamath Ranges
d0 su-KlaR subalpine Klamath Ranges
5a CasR Cascade Range
a0 f-CasR Cascade Range foothills
b0 m-CasR montane Cascade Range
c0 su-CasR subalpine Cascade Range
d0 a-CasR alpine Cascade Range
6a SN Sierra Nevada
a0 f-SN Sierra Nevada foothills
b0 m-SN montane Sierra Nevada
c0 su-SN subalpine Sierra Nevada
d0 a-SN alpine Sierra Nevada
B0 So-CA Southern California
1a SoCo South Coast
a0 o-SoCo outer South Coast
b0 i-SoSo inner South Coast
2a TraR Transverse Ranges
a0 o. TraR outer Transverse Ranges
(1) o. l-TraR Lowelevation Transverse Ranges
(2) o. m-TraR outer montane Transverse Ranges
(3) o. su-TraR outer subalpine Transverse Ranges
b0 i. TraR inner Transverse Ranges
(1) i. m-TraR inner montane Transverse Ranges
(2) i. su-TraR inner subalpine Transverse Ranges
(3) i. a-TraR inner alpine Transverse Ranges
3. PenR Peninsular Ranges
a. m-PenR montane Peninsular Ranges
b. su-PenR subalpine Peninsular Ranges
c. a-PenR alpine Peninsular Ranges
4. ChaI Channel Islands
II. Trans-CA Transmontane California
A0 GB Great Basin
1a trans-CASR Transmontane Cascade Range
a0 ModP Modoc Plateau
b0 WarR Warner Range
(1) m-WarR montane Warner Range
(2) su-WarR subalpine Warner Range
2a trans-SN Transmontane Sierra Nevada
a0 TraSN eastside Sierra and valleys
b0 WIS White, Inyo, Sweetwater Ranges
(1) m-WIS montane White, Inyo, Sweetwater Ranges
(2a su-WIS subalpine White, Inyo, Sweetwater Ranges
(3a a-WIS alpine White, Inyo, Sweetwater Ranges
B. DES Deserts
1. Moj-D Mojave Desert area
a. MojD Mojave Desert
b. DesR Desert Ranges
(1a m-DesR montane Desert Ranges
(2a su-DesR subalpine Desert Ranges
2. Col-D Colorado Desert area
a. ColD Colorado Desert
Modifiers for any region: n. northern part, c. central part, s. southern part, w. western part, e. eastern part. Other geographical areas: States are referred to by the postal codes, inter-West = intermountain West as defined in the Intermountain Flora (Cronquist et al. 1989).
© CNPS 1997