| Depth | Percentage nitrogen in mg N g−1 at Kouoptamo | Percentage nitrogen in mg N g−1 at Foumbot |
| 5 - 20 years | 0.17 ± 0.11 | 0.16 ± 0.03 |
| 20 - 35 years | 0.06 ± 0.02 | 0.20 ± 0.08 |
| 35 - 50 years | 0.09 ± 0.05 | 0.17 ± 0.09 |
| 50 years and over | 0.17 ± 0.08 | 0.17 ± 0.07 |