Average polygon size is approximately 3,000 ha. Based on 1995 UCSB field surveys and on comparisons with independent sources of vegetation data, the vegetation map probably overestimates the extent of conifer forest types and underestimates the extent of shrubland and mid-elevational hardwood types. The northernmost and southernmost portions of the region were field checked most extensively. The central portion was only partially covered by the VTM surveys. Field mapping was least extensive in high elevation areas and sites around the northern arms of Lake Shasta which extend north and east along the McCloud and Pit river drainages and the east slope of the southern Cascades.
Floristic information is generally more reliable on public lands than on private lands.
We call attention to three categories of poor representation and one in which types appear to be well protected. Plant community types occurring mainly on status 4 lands . This type mostly occurs in the lower elevations adjacent to the Great Central Valley. The Juniper-Oak Woodland type is composed of California juniper with shrubby blue oak. Scrub, chaparral, and herbaceous types mainly located in unprotected areas .