Google the World
Have you tried this site?
Pretty cool, you can zoom in on maine– select biology and then select forest type, and then redraw, click the key for reference of colors..Looks like GIS layered info via USGS, but still might be useful. Lots of other options as well. You may want to check data for time frame.
http://nationalatlas.gov/mapmaker
National Geographic Mapmaker
http://education.nationalgeographic.com/education/mapping/interactive-map/?ar_a=1
