| Code | Definition | Number of Accessions |
| 8.1.2 | Lake Erie Lowland | 1 |
| 8.1.4 | North Central Hardwood Forests | 1 |
| 8.1.5 | Driftless Area | 1 |
| 8.1.6 | S. Michigan/N. Indiana Drift Plains | 7 |
| 8.2.1 | Southeastern Wisconsin Till Plains | 1 |
| 8.2.3 | Central Corn Belt Plains | 6 |
| 8.2.4 | Eastern Corn Belt Plains | 6 |
| 8.3.2 | Interior River Valley and Hills | 9 |
| 8.3.3 | Interior Plateau | 7 |
| 8.3.6 | Mississippi Valley Loess Plains | 1 |
| 8.4.3 | Western Allegheny Plateau | 1 |
| 8.4.5 | Ozark Highlands | 6 |
| 8.4.7 | Arkansas Valley | 1 |
| 8.4.8 | Ouachita Mountains | 1 |
| 9.2.3 | Western Corn Belt Plains | 11 |
| 9.2.4 | Central Irregular Plains | 8 |
| 9.4.2 | Central Great Plains | 13 |
| 9.4.3 | Southwestern Tablelands | 2 |
| 9.4.4 | Flint Hills | 2 |
| 9.4.5 | Cross Timbers | 3 |