Distribution of Values for
Omernik Level III Ecoregion (ECOREGION)
| Code | Definition | Number of Accessions |
| 8.1.2 | Lake Erie Lowland | 1 |
| 8.1.4 | North Central Hardwood Forests | 1 |
| 8.2.3 | Central Corn Belt Plains | 5 |
| 8.2.4 | Eastern Corn Belt Plains | 3 |
| 8.3.2 | Interior River Valley and Hills | 5 |
| 8.3.3 | Interior Plateau | 7 |
| 8.3.4 | Piedmont | 6 |
| 8.3.5 | Southeastern Plains | 2 |
| 8.3.7 | South Central Plains | 21 |
| 8.4.1 | Ridge and Valley | 5 |
| 8.4.3 | Western Allegheny Plateau | 1 |
| 8.4.4 | Blue Ridge | 6 |
| 8.4.5 | Ozark Highlands | 34 |
| 9.2.3 | Western Corn Belt Plains | 30 |
| 9.2.4 | Central Irregular Plains | 13 |
| 9.3.3 | Northwestern Great Plains | 17 |
| 9.4.2 | Central Great Plains | 7 |
| 9.4.3 | Southwestern Tablelands | 2 |
| 9.4.4 | Flint Hills | 3 |
| 9.4.5 | Cross Timbers | 16 |