| Sensitivity classes | Critical load range (meq∙m−2∙yr−1) | |
| Lower range | Upper range | |
| 1 | 0 - 25 | 25 - 50 |
| 2 | 25 - 50 | 50 - 100 |
| 3 | 50 - 100 | 100 - 200 |
| 4 | 100 - 200 | 200 - 400 |
| 5 | >200 (there is not a critical load) | >400 (there is not a critical load) |