Vegetation maps are a valuable resource for those interested in vegetation status and change. A map is a static baseline, but distributions frozen in time provide guidance on relationships between species and topography, geologic substrate, surface hydrology, and climate; vegetation maps in time-series can be used to document vegetation change. This atlas comprises maps of 82 tree species in California south of San Francisco and the peninsula of Baja California Mexico, interpreted using Google EarthTM. Species were identified based on morphological properties, including stature, crown bases, perimeters and apices, foliage color, branching habit, shadows and phenology. Imagery is comprehensively examined by manual rastor scanning such that their presence was both “ruled in” and “ruled out.” Maps of tree species were digitized one at a time to assure focus on individual properties. Forest “communities” can be created by overlay of individual species coverages, and distribution properties can be assessed by overlap of polygons with digital elevation models, geologic maps and other data. The contributions of this research are (1) unprecedented high resolution maps, including the first maps of 25 species mostly in the Baja California peninsula and the Mojave Desert. (2) range expansions of 30 species. (3) to make vegetation maps an evolutionary product using the Google Earth platform in which maps can be revised for error, omission, and as a time-slice for documentation of vegetation change.

The goal of this research is to produce an electronic book and a community on-line atlas with species maps shown as an overlay to Google Earth imagery, i.e., the map analysis is shown with the original tree data on imagery, and can also operate as a “primer” for aerial photograph interpretation. An on-line atlas permits the use of maps both in the lab and in the field. Additional information is given for each species on the Cenozoic fossil record, critical identification criteria, the role of disturbance in short-term vegetation change, and the fossil record since the Late Glacial Maximum (20 ka).

Prof. Richard Minnich