This paper presents the digitized edition of the Wieslander Vegetation Type Maps (VTMs). The VTMs were part of the first statewide systematic survey of California's vegetation, conducted 1928–1939. Under the direction of Albert Wieslander, crews recorded the patterns of vegetation that they observed from vantage points across the state. The survey covers 176,901 km2 including border and lake polygons and 165,652 km2 of landscapes that we describe in more detail. There are 251,541 polygons in the full extent of the maps, with 249,630 in the analysis extent. These polygons are annotated with codes indicating the dominant plant species, for which voucher specimens were collected. The maps contain 655 species codes, representing 535 species or sub-species in 229 genera, including 34 Arctostaphylos Adans. and 16 Quercus L. species. The 249,630 polygons contain 26,013 unique combinations of species and levels of disturbance. These can be classified into 525 vegetation alliances or provisional alliances using the 2009 edition of the Manual of California Vegetation, or into 53 of the simpler California Wildlife Habitat Relationships (WHR) classes. The most extensive WHR types in the VTMs are Annual grasslands (25,733 km2) Chamise-redshank chaparral (14,771 km2), Mixed chaparral (9314 km2), and Coastal Scrub (7088 km2). California's Southwestern ecoregion is the most completely surveyed, with 93% of the area mapped, followed by the Central Western ecoregion (88.2%, including the Bay Area), the Sierra Nevada (71.6%), and the Great Valley (39.7%). The VTMs in these ecoregions provide a baseline for assessment of landcover change across large areas, and are an important legacy of the biogeographic patterns of plants and vegetation in California. This paper provides the methods used to digitize the collection and suggestions about how the data may be properly used in future studies.
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Vol. 63 • No. 4