USDA Forest Service
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Calveg System

Hierarchical Classification

The USDA Forest Service Region 5 employs the Calveg system and its standards to classify "existing vegetation" in contrast to the classification of "potential natural vegetation", which employs other classification systems. Calveg is a dynamic system that is updated by R5 and maintains strict standards for classification and naming conventions that are consistent across California.

Historical to Present

The CALVEG ("Classification and Assessment with Landsat of Visible Ecological Groupings") system was initiated in January 1978 by the Region 5 Ecology Group of the U.S. Forest Service with headquarters in San Francisco. The Calveg team's mission was to classify California existing vegetation communities for use in statewide resource planning considerations. This was originally accomplished with the use of color infrared satellite imagery and field verification of types by current soil-vegetation mapping efforts as well as professional guidance through a network of contacts throughout the state. It is a hierarchical classification originally based on "formation" categories: forest, woodland, chaparral, shrubs and herbaceous in addition to non-vegetated units. They were originally identified by distinctions calculated among canopy reflectance values used in the LANDSAT satellite. Since then, the classification has been expanded from an initial 129 types occurring throughout the eight regions of the state to the current 213 occurring in nine regions, and image resolution has been enhanced. Recent Calveg expansions include identifying:

  • new types in sites consisting of mixed species, such as mixtures of alkaline shrubs rather than dominants
  • combinations of conifer and hardwood mixtures in the canopy that are mapped as two primary Calveg alliances
  • types that are not widespread across the state, such as various species of Cupressus or Cercocarpus but are suitable for mapping at the current scale of resolution

More info: Vegetation Classification & Mapping

Crosswalks to Other Systems

At the state level, the Calveg system crosswalks easily to types in the California Wildlife Habitat Relationships System (Meyer and Laudenslayer, 1988 ¹) and it's later versions. Additionally, efforts are underway to finalize crosswalks with vegetation types defined in the revision of the Manual of California Vegetation (Sawyer and Keeler-Wolf, in process ²).

Calveg is also consistent with the non-floristic guidelines of the National Vegetation Classification System (NVCS) supported and approved by the Federal Geographic Data Committee Vegetation Subcommittee since 1997 (pdf 167Kb). The USDA Forest Service is a lead agency on this Subcommittee and has recently clarified these standards in a technical guide ("Existing Vegetation Classification and Mapping Technical Guide") designed for classification and vegetation community mapping uses in our agency. The "Floristic 1" level of the NVCS equates to Calveg's Alliances. They are considered to be provisional alliances in the sense that, although they have been verified in the field, they are not usually determined by sets of plot data that meet NVCS standards for collection and analysis. Under the current floristic standards, which have not yet been approved by the Federal Geographic Data Committee, the analysis of plot data is required to determine plant associations, the lowest level of the system ("Floristic 2") prior to determining alliances. For many USDA Forest Service projects, this approach to classification is not practical for larger-scale or rapid mapping and classification projects. Calveg Alliances are also defined as "Dominance Types" for the purpose of mapping vegetation in accordance with the Tech. Guide's mapping standards.

Identification of Calveg Types

Types are defined in the field with the aid of a set of descriptions and dichotomous keys, one for each of the Calveg regions of California. The provisional alliance descriptions are based on types that have been mapped in each region, indicating environmental conditions, site locations, and species composition.

¹ Meyer, K. E. and W. F. Laudenslayer. 1988. A guide to wildlife habitats of California. 1988. Sacramento: California Dept. of Fish and Game.

² Sawyer, J. and T. Keeler-Wolf. Revision to Manual of California Vegetation. In process.

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