Vegetation communities of San Diego County

The file has been refined (to include more detailed vegetation information, where available), expanded (to include vegetation data outside of the MSCP/MHCP study areas), and updated to reflect vegetation conditions in 1995. The update consisted of using multi-date panchromatic satellite image change detection techniques to alter habitat information in areas that have converted to agricultural, rural, or urban uses. The technology used in the update procedure did not support the identification of successional vegetation changes or other more subtle changes in vegetation. The intent of the update was to re-code habitat areas that have been converted to some other use.

The Holland vegetation classification system is used in the San Diego region. The Holland codes use a hierarchical classification system, providing flexibility in the level of vegetation detail which can be mapped. For example; 37000 is the code for chaparral, and 37120 and 37130 are subcategories of chaparral; southern and northern mixed chaparral, respectively. The northern and southern mixed chaparral types can be further broken down into granitic and mafic versions, 37121, 37122 and 37131, 37132, respectively. Usually finer levels of vegetation can be mapped at larger scales; i.e., project or site level; than can be mapped from small-scale air photo interpretation. More detailed vegetation mapping generally requires more detailed source data and more extensive fieldwork.

The vegetation file contains a mixed level of vegetation information. Some areas contain more detailed vegetation information (both categorical and positional) obtained from digital project-level vegetation surveys. Other areas contain more generalized vegetation information, as was collected as part of the MSCP and MHCP. In areas where more detailed vegetation information was incorporated into the vegetation file, care was taken to edge-match (where possible) the vegetation inside the project with areas outside the project, thus creating an apparently seamless database. This edge-matching effort provided both positional and categorical consistency across project boundaries.

The location of vernal pools and vernal pool complexes are not contained in the vegetation layer, even though there are Holland codes for them in the Holland Classification system. Because vernal pools tend to small and seasonal, their locations are contained in a separate layer.

There are a number of attributes on the file to assist users in determining the level of information within specific areas. The following attribute information should help to explain how to use this database.

The coverage is in double precision. This is necessary in order to preserve and maintain the data integrity, particularly in areas with a finer level of classification and more detailed scale of vegetation information.

Comments: Users should be aware of the level of vegetation information represented in specific areas of interest when mapping, tabulating, and analyzing this data. Vegetation information should generally be reported and/or portrayed for the least common denominator for the study area. If necessary, please contact Sue Carnevale of SANDAG staff (619) 699-6981 or sca@sandag.org for more information.

Complete description of vegetation codes can be found at: http://www.sandag.org/resources/maps_and_gis/gis_