Background on the List of Vegetation Alliances and Associations (Natural Communities List)
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Converting to the National and State Vegetation Classification System in CNDDB
Natural Communities (NCs) have been considered part of the Natural Heritage conservation triad, along with plants and animals of conservation significance, since the state inception of the Natural Heritage program in 1979. The CNDDB continues to include occurrences of rare NCs despite the fact that funding for the NC part of the program was cut in the mid-1990s. Since that time, no new occurrences of NCs have been added. However, the importance of maintaining the NC layer in the CNDDB has not diminished. Many of the 2500+ individual occurrences of the 96 NCs with occurrences in the CNDDB still have significance for conservation and their existence should be considered in the environmental review process along with occurrences of plants and animals tracked by the CNDDB.
Since 1999, the Department of Fish and Game’s Vegetation Classification and Mapping Program (VegCAMP) has undertaken the classification and mapping of vegetation throughout the state and also has assumed the role of standardizing vegetation nomenclature for California to comply with the National Vegetation Classification System (NVCS). Many vegetation types included in the current list match well with the existing CNDDB NC elements, which were based on Holland (1986). Examples include Valley Wildrye Grassland, Buck Brush Chaparral, Elephant Tree Woodland, Central California Sycamore Alluvial Woodland, and Mendocino Pygmy Cypress Forest. However, others such as Northern Claypan Vernal Pool, Southern Maritime Chaparral, and Serpentine Bunchgrass Grassland are not easily translated. The problem exists because there is a complex relationship between CNDDB NC elements and today’s view of vegetation classification — in some cases, there is a one-to-one relationship, but in most there is a many-to-one or many-to-many relationship. Furthermore, in most cases no recent surveys have been made of old CNDDB NC occurrences to ascertain the proper identity based on today’s classification standards. We think it imprudent to remove these elements from the CNDDB before assessing them and reclassifying them in terms of the currently accepted state and national standards for vegetation classification.
Work continues to refine the mapping and classification of the state’s vegetation. This will take some time. In the mean time, we continue to include those "non-standard" CNDDB NC elements in the current Natural Communities List.
Codes Used in the List Formats
California Natural Community Codes (CaCodes): The California classification is currently referenced using a series of unique codes called CaCodes. Eventually, all valid vegetation types will be replaced using a nationally standardized coding system. Until that time, CaCodes are the standard reference.
CT CodesT: Holland types originally tracked by the CNDDB are referenced with a code beginning with "CTT." These are provided as "legacy information" with the understanding that Holland CTT codes and community types are no longer supported by DFG. Instead, all new information on terrestrial natural communities should use the State’s standard nomenclature as provided in the current Natural Communities List.
Hierarchy Codes: The hierarchy coding system is described and used by The Ecological Society of America’s Vegetation Hierarchy Browser.
Rarity and Global and State Ranks: One purpose of the vegetation classification is to assist in determining the level of rarity and imperilment of vegetation types. Ranking of alliances according to their degree of imperilment (as measured by rarity, trends, and threats) follows NatureServe’s Heritage Methodology, in which all alliances are listed with a G (global) and S (state) rank. For alliances with State ranks of S1-S3, all associations within them are also considered to be highly imperiled. A question mark (?) denotes an inexact numeric rank due to insufficient samples over the full expected range of the type, but existing information points to this rank. We have not provided the G and S rank of associations in the September 2010 version of this classification. However, associations currently designated as being of S3 or rarer are indicated with an asterisk (*) located to the left of their CaCode. Holland types that may encompass, either in whole or part, rare alliances or associations are likewise asterisked.
Ranking is an ongoing process and we expect to provide association level ranks for all of the S3 or rarer entities in the future. Please note that semi-natural stands are not ranked, as these are defined and strongly dominated by non-native species.
Addressing High Priority Vegetation Types
Consulting biologists or responsible agencies encountering high priority natural community elements or vegetation types when assessing a proposed project’s environmental impacts should make project proponents and reviewers aware of their existence.
Addressing high ranking vegetation types in project review should take on the following basic outline:
- Identify all natural communities within the project footprint using the best means possible including keying them out in the Manual of California, Second Edition or in reports, many of which are available from VegCAMP.
- Refer to the current standard list of natural communities to determine if any of these types are considered of special concern (S1-S3 rank); if so, the CEQA Guidelines checklist (at IVb) should be considered.
- Ascertain if project-affected stands of these vegetation types or natural communities can be considered as high-quality occurrences of the given community. The judgment of whether a stand is high quality or not involves a flexible set of criteria such as the range of existing sustainable occurrences of this element or vegetation type based on site quality, defensibility, size, and surrounding landscapes. These criteria vary based on the type of vegetation or natural community and the range of existing occurrences known. For example, it is likely that although there are many individual stands (or occurrences) and many thousands of acres of Douglas-fir/Vine maple/Oregon grape association (*82.200.20 Pseudotsuga menziesii / Acer circinatum - Mahonia nervosa) in northwestern California, there are only a few that reflect the most exemplary qualities of natural vegetation including:
For this community, these characteristics exemplify high quality, sustainable, old growth characteristics. Thus the ranking of this association is based on the restricted high quality examples. If a project would affect a small acreage of second growth stand of this type, unless there are other plant or animal elements of significance associated with it, it is unlikely that this would constitute a significant impact. Modification of this stand would be considered less likely to be a serious threat to the existence of all high quality stands of this type.
- lack of invasive exotic species,
- no evidence of human-caused disturbance such as roads or excessive livestock grazing, or high-grade logging,
- evidence of reproduction present (sprouts, seedlings, adult individuals of reproductive age), and
- no significant insect or disease damage, etc.
- Other things to consider when assessing potential impacts to vegetation types from a project include:
- Compliance with the state’s wetlands and riparian policies and codes, as certain vegetation types are restricted to wetlands or riparian settings.
- Compliance 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.
- Compliance with CEQA Guidelines Section 15065(a), which mandates completion of an EIR if a project would threaten to eliminate a plant community.
- Compliance with local regional plans, regulations, or ordinances that call for consideration of impacts to rare plant communities or vegetation types.
- The possibility that a vegetation type in the project area has not previously been described, and could therefore be considered high priority. In this case, please contact VegCAMP (Todd Keeler-Wolf or Diana Hickson) about documenting the vegetation type.
Please see the Department's Protocols for Surveying and Evaluating Impacts to Special Status Native Plant Populations and Natural Communities (PDF) for more information.
Vegetation maps produced under the state standards do not imply regulatory jurisdictional determinations under Section 404 of the Federal Clean Water Act, Section 10 of the Rivers and Harbors Act, or Section 1600 of the California Fish and Game Code (Lake and Streambed Alteration Program), or the lack thereof. Such determinations usually require a site visit to assess the current conditions on the ground and to map boundaries at a finer scale than the state vegetation map standard. Similarly, terms such as “riparian” and “wetland” in the vegetation keys and type descriptions may inform but do not imply or assert regulatory jurisdiction or the lack thereof.
FGDC (Federal Geographic Data Committee). 2008. National Vegetation Classification Standard, Version 2. FGDC-STD-005-2008. Federal Geographic Data Committee, FGDC Secretariat, U.S. Geological Survey, Reston, VA. Web Link: National Vegetation Classification Standard, Version 2 (PDF)
Holland, R. 1986. Preliminary descriptions of the terrestrial natural communities of California. Unpublished document, California Department of Fish and Game, Natural Heritage Division. Sacramento, CA.
Jennings, M.D., D.Faber-Langendoen, O. L. Loucks, R. K. Peet, and D. Roberts. 2009. Standards for associations and alliances of the U.S. National Vegetation Classification. Ecological Monographs, 79(2), pp. 173–199. Web Link: Standards for associations and alliances of the U.S. National Vegetation Classification
Peet, R.K. 2008. A Decade of Effort by the ESA Vegetation Panel Leads to a New Federal Standard. ESA Bulletin 89(3):210–211.
Web Link: A Decade of Effort by the ESA Vegetation Panel Leads to a New Federal Standard
Sawyer, J.O., T. Keeler-Wolf, and J.M. Evens. 2009. A Manual of California Vegetation, Second Edition. California Native Plant Society, Sacramento. 1300 pp. Web Link: A Manual of California Vegetation, Second Edition