Region
United States
27
West (U.S.)
13
Southern States
6
Northeastern States
4
Rocky Mountains
4
Mexico
2
Northwest, Pacific
2
Southwestern States
2
Tropics
2
Arizona
1
Asia
1
Asia, Central
1
Belize
1
British Columbia
1
California
1
Canada
1
Colorado
1
Developing countries
1
Fort Valley Experimental Forest (Ariz.)
1
Fraser Experimental Forest (Colo.)
1
Great Plains
1
Guadalupe Mountains (N.M. and Tex.)
1
Guatemala
1
Hawaii
1
High Plains (U.S.)
1
Madrean Archipelago
1
Mexican-American Border Region
1
Middle East
1
North America
1
Rocky Mountains Region
1
South Atlantic Bight
1