Tree Species Distribution Shapefiles
The following link contains shapefiles for download containing native range/distribution areas for various North American trees and plants.
“Maps of the ranges of tree species in North America compiled by Elbert Little, of the U.S. Department of Agriculture, Forest Service, and others (see references below) were digitized for use in USGS’ vegetation-climate modeling studies. These digital map files are available here for download.”
http://esp.cr.usgs.gov/data/atlas/little/
