In 1926, the U.S. National Forest Service began a natural vegetation survey of California and those portions of Region 5 National Forests and adjacent areas that extended into Nevada and Oregon. The initial purpose was to provide data in support of statewide land use and fire protection policy development.
The California survey was headed by A.E. Wieslander, Associate Silviculturist with the USFS California (now Pacific Southwest) Forest and Range Experiment Station. The project became known as the Wieslander Vegetation Type Map (VTM) Survey. This Survey mapped the vegetation of 113 15-minute USGS quadrangles, and generated a number of products and data, as well as the maps. Data types included Forest Resource Maps, Supplementary Maps, approximately 13,000 Vegetation Sample Plot data sets, Site Index Maps, Herbarium Specimens, Stand Photographs, a Field Manual of data collection, a Species Symbology and Growth Form List for plant taxa, and Field Journals and Monthly Progess Reports.
In the late 1920s and early 1930s Albert Everett Wieslander and several others, in a project of the newly formed California Forest Experiment Station, explored much of California's wildland sampling vegetation, taking photographs, collecting specimens, and drawing exquisitely detailed maps of what they found. The marvelously preserved collection is now known as the Wieslander Vegetation Type Mapping (VTM) collection. The entire survey encompassed nearly seventy million acres of the state, covering most of the wild areas excluding the deserts and the larger agricultural areas. These data constitute an invaluable resource for ecological studies.
The VTM collection consists of five main components:
1. Plot Data
About 13,000 sample plots were located in the central and southern coastal ranges and in the Sierra across a gradient of vegetation types. Records contain data on tree stand structure, percent cover of dominant overstory, and understory vegetation by species, soil type, parent material, leaf litter, and environmental elements for each site.
2. Plot Maps
The original plot locations were stamped in red ink on USGS topographic maps that had been cut into sections, mounted on canvas, and folded to facilitate use. The plot map collection comprises about 150 15-minute (1:62500 scale) and 30-minute (1:125000 scale) U.S. Geological Survey quadrangles. Unfortunately, the resulting maps were not dimensionally stable and 80 years of use, temperature changes, and other factors have warped many of the maps.
3. Vegetation Maps
Vegetation type maps showing hand drawn polygons of forest type and associated species were drawn in the field by direct observation and by "sketching from ridges, peaks, and other vantage points". Some areas have"zoomed-in" maps drawn on 6- and 7.5-minute USGS quads. The major vegetation types were subdivided into pure and mixed stands with notation on species composition and grouped by fire hazard characteristics, use, or economic importance. There are about 350 of these detailed and beautiful maps in the collection. Only some of these have previously been published.
4. Photographs and Associated Data
There are approximately 3,100 black and white photographs taken during 1920-1941, with their photo points and floristic associates noted. In addition there are approximately 100 topographic maps. The photographs document the typical and atypical subtype, species, timber stand conditions, range of variation, consequence of land use and cultivation, grazing, logging, mining and fire. Wieslander was the main photographer with a second series photographed by Richard C. Wilson (Class of 1934, past Director, California Dept. Forestry and Fire Protection), C. Raymond Clar (Class of 1927, past Chief Deputy State Forester), and others.
5. Herbarium Specimens
Herbarium specimens were collected for every species recorded on the vegetation maps or in the sample plots. Many of the samples collected during the original VTM surveys now reside in the UC Berkeley Jepson Herbarium.
The VTM Digitization Project, a large effort to digitally reunite the VTM datasets, was a collaboration of teams at UC Berkeley and UC Davis, funded by the US Forest Service and USDA CSREES. The digitization project is described in this paper: Digitization of a Historic Dataset: The Wieslander California Vegetation Type Mapping Project (2005).
You can see results of the digitization efforts on the VTM website.