Category Archives: Soils

Historic 'Soil-Veg' Maps Available for Northern Sonoma Cty.

We are very excited to announce the availability of a set of historic vegetation maps for the northern portion of Sonoma County.  The maps are the 'Soil-Veg' maps published in collaboration by California's Department of Forestry (now CalFire), the University of California, and the U.S.D.A. Forest Service between 1947 and 1980.  The maps contain detailed information about soils, dominant vegetation (listed by species in descending order of dominance), and timber site quality index.

If you use these maps, please remember that they are very old and reflect the state of landscape between 40 and 70 years ago (date varies by 7.5 minute U.S.G.S. quad - see index map below).  Also bear in mind that the maps were created at a small scale (1:31,680) and with far less advanced methods than those used in today's digital age.

Kass Green and Gene Forsburg (part of the Sonoma Veg Map team) were familiar with these maps and - when they realized the maps had probably never been scanned and georeferenced - asked Dr. Maggi Kelly (a Sonoma Veg Map advisor) at UC Berkeley's Geospatial Innovation Facility (GIF) about them.  Dr. Kelly tracked down the old maps, finding them at the Biosciences & Natural Resources Library and the Earth Sciences and Map Library.  Through a generous gift from Kass and Gene to the GIF, UC Berkeley scanned and georeferenced the Soil-Veg map quads for Sonoma County. Thanks to these U.C. Berkeley Libraries for taking good care of the maps for all of these years so that we can share them with you today!

Even though the 'Soil-Veg' maps are small-scale and old, they provide a key to species distribution for our team in areas where access is impossible. The 20th century veg. mappers were able to access broad areas of the county and used field visits in conjunction with photo interpretation of stereo pairs of aerial photography to make the maps.

We are very excited because we know these maps have been helpful to us, and we think that they will be useful to others, especially those interested in the state of the landscape in the second half of the last century.

The maps are packed with information.  The graphic below shows part of a polygon and provides a rudimentary decoding of the information on the maps. Refer to the list of resources at the end of this post for more detailed information about the maps.

Explanation of Soil-Veg Map Polygon Labels

Explanation of Soil-Veg Map Polygon Labels

The 'Soil-Veg' maps were created by 7.5 minute U.S.G.S. quad. The GIF scanned and georeferenced each of the individual quads (see map below) and then mosaiced them without their collars into a single TIF image. The TIF is available for download, and the mosaic has also been published as a tile service (see below for links).

Area of Availability Soil-Veg Maps

Soil-Veg Map Availability and Dates When Mapping Occurred for Each Area

Here's how to get the 'Soil-Veg' maps and related information:

  • Check out this story map!
  • Work with the maps in ArcMap by downloading this TIF image of the maps (2 GBs)
  • Download the list of species abbreviations (you'll need this!)
  • Download an legend/user's guide (for one of the individual Sonoma County quads)
  • Download a product description that includes info about the 'Soil-Veg' maps
  • Use the quad index grid for the 'Soil-Veg' maps, which includes in its attributes the years of field work and mapping for each U.S.G.S. quad (these are the quad polygons shown in the map above)
  • View this blog post from Dr. Kelly, which includes estimated horizontal error for each scanned and georeferenced 'Soil-Veg' map quad

Sonoma County Serpentine

Serpentine communities occur in scattered areas across Sonoma County. These communities support a number of rare and endangered plant species.  From a vegetation mapping perspective, these are important areas.  Because thesy are small, geographically isolated, and occur uncommonly across the County's landscape, it will be important to clearly identify these areas and compile existing field data for them before our mapping work begins.  Serpentine areas on the North Coast have been studied significantly in the past 75 years, and much is known about their composition. In the April, 2009 issue of the Journal Fremontia (California Native Plant Society), Roger Raiche provides a great botanical profile of the Cedars, the county's largest serpentine area.

The serpentine areas of Sonoma County are associated with several soil types.  Among these are soils from the Henneke Series, soils from the Montara  series, and soils from the Huse series.

The interactive map below shows the 1997 Soil Survey Geographic (SSURGO) soils data overlaid on Bing aerial imagery.  Pan and zoom to move around on the map.  Access the "Bookmarks" to navigate to the major serpentine areas in the county.  If you click "View Larger Map," a larger map will open in with more functionality.  This map's default extent is an area of serpentine soils (mainly the Henneke series) and vegetation north of Occidental near the Bohemian Highway.

View Larger Map