| Arctic |
| Caribbean |
| Central Interior and Appalachian |
| Eastern Great Plains |
| Gulf and Atlantic Coastal Plain |
| Hawaiian Highlands |
| Ice Cap |
| Inter-Mountain Basins |
| Laurentian and Acadean |
| Madrean Semidesert |
| Mediterranean California |
| Montane Arctic |
| Montane Boreal |
| North American Pacific Maritime |
| North American Pacific Warm Continental |
| North American Warm Desert |
| Rocky Mountain |
| Western Great Plains |