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Existing Vegetation / Mid Level

Revised National and Region 5 Standards

Existing vegetation GIS maps are comprehensive vegetation databases that meets regional and national vegetation mapping standards. A mapping methodology has been developed to capture forest vegetation characteristics using automated, systematic procedures, remote sensing classification, photo editing and field based observations that efficiently and cost-effectively map large areas with minimal bias. Map attributes consist of land use Anderson 1, life form cover type, FGDC physiognomic order, class and subclass, vegetation types using the CALVEG classification system and forest structural characteristics. Forest productivity is determined by CALVEG type. Integration of other data sources for water features and re-forestation origin dates are implemented where available. For more information on the mapping process go to Remote Sensing Lab, Ecosystem Planning - Mapping .

The CALVEG classification is a provisional system that meets the floristically based level of the National Vegetation Classification Standard hierarchy. These vegetation alliances were originally developed by the Region's Ecology Program in 1978. (USDA Forest Service. 1981. CALVEG: A Classification of California Vegetation. Pacific Southwest Region, Regional Ecology Group, San Francisco CA. 168 pp.) The descriptions and keys are being maintained and updated by the Pacific Southwest Region. The system currently consists of 178 distinct vegetation and land use types. For more information on the CALVEG classification system go to Remote Sensing Lab, Ecosystem Planning – Classification.

The following are the general mapping and classification rules for the existing vegetation layer.

Vegetation Mapping Criteria:

• Minimum Mapping Size
  • 2.5 acres for contrasting vegetation conditions based on cover type, vegetation type, tree cover from above classes and overstory tree diameter classes
  • No minimum mapping unit for lakes and conifer plantations
  
  
• Life Forms are initially generated from classification of Landsat Thematic Mapper imagery into the following hierarchical classes:
  • Conifer - greater than 10 percent conifer cover as the dominant type
  • Mix - greater than 10 percent tree cover and 20 to 90 percent hardwood cover
  • Hardwood - greater than 10 percent hardwood cover as the dominant type
  • Shrub - greater than 10 percent shrub cover as the dominant type
  • Grass - greater than 10 percent grass cover as the dominant type
  • Barren - less than 10 percent cover of any natural vegetation
  • Agriculture
  • Urban
  • Ice/snow
  • Water
  
  
• Subsequently, the following items are mapped within Life Form classes:
  • Vegetation Dominance Type (CALVEG): Rules have been developed by Vegetation Zone for setting parameters for CALVEG mapping. For complete CALVEG mapping keys and detailed alliance descriptions go to Remote Sensing Lab, Ecosystem Planning – Classification.
  • Physiognomic Division, Order and Class as well as SAF and SRM types are derived from a crosswalk from cover type and CALVEG type. Total tree cover is also used for deriving Physiognomic Subclass along with cover type and CALVEG type.
  • Tree Cover from Above: Conifer and hardwood tree cover is mapped as a function of canopy closure in ten- percent classes. In conifer/hardwood mixtures, relative density of each is mapped as well as total tree canopy closure, with conifer tree cover stored in item CON CFA, hardwood tree cover stored in HDW CFA and total tree cover mid level class stored in Tree CFA 1.
  • Overstory Tree Diameter: Overstory tree sizes are mapped as a function of crown diameters of overstory trees as interpreted from aerial photography and satellite imagery. Conifer seedling and sapling sizes are modeled based on planting origin dates where available from agency records. Fire history and change detection are also inputs to determine small tree sizes when not directly observable on image sources. The plurality size condition of the predominant, dominant, and co-dominant trees in a stand is assigned and stored in OS Tree Diameter Class 1. For Mixed tree types, conifer size in stored in OS Tree Diameter Class 1, and hardwood size is stored in OS Tree Diameter Class 2.

Additional Fields:

• Ecological Tile: The basic units used to store existing vegetation layers within a statewide existing vegetation library. Source is from Goudey and Smith (1994), Ecological Units of California-Subsections (map), USDA Forest Service, Pacific Southwest Region, San Francisco, CA. Scale 1:1,000,000. Calveg Zone, Ecological Domain, Division, Province, Section and Subsection lines are retained from this source.
• WHR Type, Size, Density, and Range: Corresponding parameters from the California Wildlife Habitat Relationships classification system. WHR type is derived primarily from CALVEG type and relative cover of conifer and hardwood trees for various mixed conditions. WHR tree size class is a mapped attribute. WHR tree density is calculated from conifer and hardwood cover from the above values. For more information about this logic, go to http://www.fs.fed.us/r5/rsl/projects/classification/system.shtml#xwalk.
• Northwest Structure: Structural attributes specific to monitoring requirements for the Northwest Forest Plan and not present in Forest vegetation layers outside the Klamath Province.
• Feature level metadata is captured for mapping sources, source dates and update causes.
• Map Tile: A tiling system currently being used to tile the existing vegetation dataset and to serve out logical portions of vegetation data for use in land management issues such as forest-wide planning efforts, wildlife habitat mapping and fire risk assessment.

Key to row colors:

Updated page content 10/06/10

USDA Forest Service · Pacific Southwest Region