A Manual of California Vegetation Online
1. What is A Manual of California Vegetation?
A Manual of California Vegetation (MCV) (Sawyer et. al 2009) is a prominent scientific publication distributed by the California Native Plant Society (CNPS) in collaboration with the California Department of Fish and Wildlife (CDFW); it has been adopted as the standard for vegetation classification and description by state and federal agencies. The book and this website contain detailed descriptions of vegetation alliances, which are vegetation types identified by dominant and/or characteristic species. The alliance descriptions include membership rules, ecology notes about dominant species, fire characteristics, regional status and variation, and management considerations.
The MCV has been endorsed by the California Vegetation MOU Committee as a standard for mapping classification units and the quantitative alliance definitions can be directly applied to the testable accuracy of map units.
The web-based version of this book provides query tools, will allow regular quarterly updates, and provides means for distributing new information such as range maps and photographs of each of the alliances.
2. What are these complicated vegetation names?
The names are based upon the national and state classification, which is hierarchical and allows analysis at varying spatial scales. Names at the higher levels are based on physiognomy (life form) and ecological drivers (e.g., climate, regionalism); the lower levels are based on floristics (species composition).
Names follow US National Vegetation Classification (USNVC) standards. An example is below:
3. What can I do with the MCV?
Since the MCV is a classification of plant communities in California, it allows users to identify a plant community from their area, compare their communities to the statewide and nationwide classification, and translate to other existing classifications including the California Wildlife Habitat Relationships (CWHR) and Holland system (Holland 1986).
You also are able to use the MCV in many applied ways: a) to discover relationships between specific plant species (including rare species) and vegetation as habitat, b) to develop a better understanding of the predominant plant species and the habitats in your region of California, c) to explore relationships between vegetation and fire or other natural processes based on the fire and life history information tables (e.g., find out which dominant plants have low flammability and are fire-wise), d) to establish local plant palettes for your garden using a plant community perspective, e) to add to the knowledge base by contributing information from a specific locale or to help define a new type.
4. How does the MCV relate to other California classifications, including California Wildlife Habitat Relations (CWHR), CALVEG, GAP and the Holland system, as well as the national vegetation classification?
The first three of these California systems generally have a coarser classification resolution than the MCV. Crosswalks are available between the MCV and these three other commonly-used systems. MCV field data collection protocols include much of the structural data required to determine CWHR type. Robert Holland’s “Preliminary descriptions of the terrestrial natural communities of California” is the basis for the existing rare community elements in the California Natural Diversity Database (CNDDB). However, this system is not quantitative and does not have definitive rules for typing vegetation; types vary in resolution with equivalency to the Association, Alliance or Group level; and a direct crosswalk to the MCV is not possible for all types. The Holland system is no longer supported by CDFW; in the future, rare MCV types may be incorporated into CNDDB. The MCV meets the US National Vegetation Classification (USNVC) standards. These standards were developed by the Federal Geographic Data Committee and peer-reviewed by the Ecological Society of America’s Vegetation Panel.
5. How are rare vegetation types defined and how can they be addressed in environmental review?
Vegetation types in regions of the state that are already classified, or types with basic levels of identification have been assigned Global and State Rankings based on the NatureServe’s Network Core Methodology. Rare types (S1-S3) should be evaluated for compliance with the state’s wetlands and riparian policies and codes, as certain vegetation types are restricted to wetlands or riparian settings; with the Native Plant Protection Act and the state and federal Endangered Species Acts, as some vegetation types either support rare species or are defined by the dominance or presence of such species; with CEQA Guidelines Section 15065(a)(1), which mandates completion of an EIR if a project would threaten to eliminate a plant community; and with local regional plans, regulations, or ordinances that call for consideration of impacts to rare plant communities or vegetation types.
If the vegetation type does not appear to be currently recognized and described, plot data can be collected following standardized protocols and submitted to the CNPS Vegetation Program and CDFW Vegetation Classification and Mapping Program(VegCAMP) for review. A provisional state ranking could be assigned, and final ranking would be assigned after an ecoregional vegetation map is completed, which currently depends on the availability of funding. VegCAMP and/or CNPS can provide assistance and a both a template field sample database and map geodatabase, including a standard set of map attributes, for use in new classification and mapping projects.
6. What if I can’t find my vegetation type in the MCV?
The MCV is not yet complete; it contains descriptions of most known community types but vegetation patterns may be encountered in local areas that are not yet described. Where new types are found, you are encouraged to collect field data and submit datasheets for inclusion within the statewide vegetation database. This will allow future classification analyses to include the full variation of vegetation types, allowing us to update the existing statewide classification, to identify and update range-wide distributions for all vegetation types, and to make defensible definitions of vegetation.
You also are welcome to join us for training sessions through the CNPS Plant Science Workshops or help us to coordinate a local CNPS chapter workshops, and we encourage you to provide us general user feedback about alliances through the website.
7. What about weedy vegetation?
Vegetation strongly dominated by non-native plants that have become naturalized in the state are designated as semi-natural types. However, a non-native species may be included in the name of an association dominated by native species (e.g. Baccharis salicifolia-Tamarix ramosissima Shrubland Association). Semi-natural vegetation is sometimes the result of prior intensive human land use, but also includes areas dominated by spontaneously growing vegetation that requires no human input for its maintenance. Some of these areas dominated by non-native plants still provide intrinsic habitat for species, especially the golden rolling hills of California that offer habitat for hosts of wildlife species.
8. What are membership rules?
Membership rules are quantitative definitions used to assign field samples to vegetation types based on data analysis. A simple example of a membership rule is: “a stand of vegetation belongs to the Baccharis salicifolia Shrubland Alliance if Baccharis salicifolia is > 50% relative cover in the shrub canopy.”The rules are developed from the analysis of data collected for particular projects and can include species constancy, cover values, and the presence of indicator species (Klein et al. 2007). Membership rules are relative to the specific analysis of data cited, and may not apply to the full range of variation within an alliance across the state. Documenting the membership rules assigned within individual projects makes it easier to understand analogous or similar vegetation types from other studies, and they can also help users determine if additional membership rules need to be defined.
9. Is the MCV appropriate for mapping?
Yes. The California Vegetation MOU Committee has endorsed the use of the MCV for map classification. It has also defined map unit standards for the state, which meet the Federal Geographic Data Standards. The Committee has established a set of attributes for maps and data sets, including consistent categories for vegetation mapping units, overstory vegetation cover, understory cover, overstory height, and site quality measures. The quantitative and testable definitions developed for the MCV can be directly related to the testable accuracy of map units. This encourages thematically accurate and repeatable mapping products.
Mapping units are based on vegetation classification units, which come from field plots. Therefore, vegetation maps using the MCV should be defined from local field data collected and analyzed by vegetation ecologists. Because vegetation maps are often developed by the interpretation of aerial or satellite imagery, they are constrained by the quality and resolution of the imagery and by the scale of the map being developed. The use of the US NVC classification hierarchy in conjunction with the MCV can allow flexibility in assigning a more general classification unit, if necessary, for vegetation that is seasonally variable or difficult to discern at the alliance and/or association level. For example, mapping classifications (or Mapping Units) sometimes use the Group or Macrogroup classification level.
10. Is this classification system likely to change?
It is highly unlikely that the underlying principles of the classification will change. The upper levels of the national hierarchy and the Group level may shift as more comparative information over broader geographic regions becomes available. Alliances and associations may be added as more data are collected, but the existing alliances are based on analyzed data and are likely to persist.
11. How can I contribute to the MCV?
There are three specific ways to contribute to the MCV.
A. Collect plot data based on the standards. The best classifications come from analyzing plot data, and thus the more representative plot data, the better. Often classifications are limited by too few plots (such is the case with the provisional alliances) or have been delineated within too small of an area. In addition, plot data are collected and analyzed in a variety of ways. By collecting plot data using the protocols outlined by CNPS/CDFW, and analyzing such data with standard methods (Jennings et al. 2009; Peet and Roberts 2013), a complete plot-based classification of California will be realized.
B. Submit your vegetation data to CNPS/CDFW. By submitting your field data, CDFW and CNPS can add this information to the statewide database that we jointly maintain and will allow analyses of greater community variability and spatial breadth. Ultimately, all California vegetation types should be supported by plot data.
C. Propose changes to Alliances or add a new Alliance. The MCV is a dynamic classification because our knowledge remains incomplete and vegetation is dynamic. Proposals to change vegetation at any level are always welcome and will go through a professional review process. Proposals can be based on analysis of new plot data or current literature review. Proposals may either modify existing concepts (e.g., some alliances may be merged or split) or put forth entirely new concepts. If the proposal is accepted, the changes will be published in on-line proceedings with historical documentation of the change. As with species taxonomy, synonymies of previous concept names will be maintained.
12. Why do some alliances seem to occur outside of their expected range in the maps?
The MCV alliance range maps are based upon the USDA Ecoregions in California (including 19 ecological sections and 221 subsections). When an alliance occurs within a subsection, the range map highlights the entire subsection, which may overemphasize the actual range of an alliance. For instance, the majority of the Quercus douglasii Woodland Alliance occurs west of the Sierra Nevada, though a few stands occur in a subsection (M261Er) that wraps around the east side. While these stands are at the very southern end of that subsection (e.g., in the Piute Mountains of Kern Canyon), the entire subsection is highlighted to include these occurrences.
An ecoregion-based range map gives viewers a general sense of where a vegetation type occurs, but it is not a precise map of all known locations. Its scale is similar to having a map that highlights an entire county even if a single occurrence of the vegetation type is documented there, though an ecoregion is defined by geographic, climatic, and floristic patterns rather than by politics. If you have additional information on vegetation occurrences within a certain subsection or section, please send us your specific observations to update these range maps.
13. Where can I access detailed vegetation map data in California that support alliance range maps?
Maps that are based on the actual distributions of vegetation types are definitely more accurate and useful for a variety of purposes. Fine-scale range information can only be accomplished through detailed vegetation sampling and mapping, which currently has been completed across one-third of the state. While Phase 2 of the MCV Database project will include tools to view and query these detailed maps and supporting field data, you can currently view and download fine-scale vegetation mapping data from different regions of California here.
14. Am I free to use your images, and are they copyrighted?
The use of images requires acknowledgement under all circumstances; the photos may be freely used for personal or academic purposes without prior permission under the Fair Use provisions of US copyright law as long as you provide credit to the photographer and the MCV online edition. The conditions of use vary as follows:
Copyrighted images: Please see the contact information for the copyright holder or designated contact person to communicate with them directly regarding any use of copyrighted images. Regardless of how you use the image, you must acknowledge the source of the image as shown below.
Acknowledgement: Use of any image requires proper credit to the photographer, copyright holder, institution, and the CNPS MCV online edition. Here are two examples of appropriate acknowledgment:
©R. Parker @ CNPS MCV online edition
Julie Evens @ CNPS MCV online edition
15. How do I cite the MCV?
Sawyer, J.O., T. Keeler-Wolf, and J.M. Evens. 2009. A Manual of California Vegetation, Second Edition. California Native Plant Society, Sacramento, CA. 1300 pp.
CNPS. [Year of online search]. A Manual of California Vegetation, Online Edition. http://www.cnps.org/cnps/vegetation/; searched on [Day, Month, Year]. California Native Plant Society, Sacramento, CA.
16. How is the MCV financed?
The MCV online project was achieved through the very generous support from numerous grantors and private donors, who are recognized on our home page. We also gratefully acknowledge the continuing in-kind support from the California Department of Fish & Wildlife.
17. How can I help improve the capacity of the online MCV database?
Additional donations are necessary to support the next phase of the MCV online, which will include querying and display of statewide plot data and fine-scale vegetation maps. If this capacity is important to you, please consider donating to our efforts. Contact CNPS via email at jevens@cnps.org.
18. How often is the site updated, and can I see what changes have been made?
Changes are being made quarterly. Specific revisions can be viewed in the Change Log, and newly described alliances can be searched for by year on the Custom Search page.
Literature Cited:
FGDC [Federal Geographic Data Committee]. 2008. National Vegetation Classification Standard (Version 2.0). FGDC Document Number FGDC‑STD‑005‑2008. Vegetation Subcommittee, Federal Geographic Data Committee, Reston, VA. 126 pp.
Holland, R. 1986. Preliminary list of terrestrial natural communities of California. Department of Fish and Game, Sacramento, CA.
Jennings M.D., D. Faber-Langendoen, O.L. Loucks, R.K. Peet, and D. Roberts. 2009. Characterizing Associations and Alliances of the U.S. National Vegetation Classification. Ecological Monographs 79 173-199.
Klein, A., J. Crawford, J. Evens, D. Hickson, and T. Keeler-Wolf. 2007. Classification of the vegetation alliances and associations of the northern Sierra Nevada foothills, California. California Native Plant Society and California Department of Fish and Game, Sacramento, CA. 176 pp.
Peet, R.K., and D.W. Roberts. 2013. Classification of natural and semi-natural vegetation. Pages 28-70 in: E. van der Maarel and J. Franklin, editors. Vegetation Ecology, Second Edition. John Wiley & Sons, Ltd, Oxford, UK.
Sawyer, J.O., T. Keeler-Wolf, and J. M. Evens. 2009. A Manual of California Vegetation, Second Edition. California NativePlantSociety,Sacramento,CA. 1300 pp.