Table 2. The proportions of NMR C functional groups of humic acids in surface soil (0–10cm) per vegetation type ± standard error (n = 3).
| Vegetation | Carbon functional groups (%) |
A/O-A ratio | aromaticity | ||||
|---|---|---|---|---|---|---|---|
| Alkyl-C | O-alkyl-C | Di-O-alkyl-C | Aromatic-C | Carboxyl-C | |||
| Litter | |||||||
| Japanese cedar | 24.0 ± 0.34 a | 45.3 ± 0.71 b | 9.85 ± 0.32 b | 16.1 ± 0.56 a | 4.82 ± 0.16 | 0.43 ± 0.01 a | 16.9 ± 0.61 a |
| Transition | 22.4 ± 0.59 a | 46.3 ± 0.76 b | 9.88 ± 0.25 b | 16.5 ± 0.50 a | 4.99 ± 0.10 | 0.40 ± 0.02 a | 17.3 ± 0.51 a |
| Bamboo | 13.2 ± 0.33 b | 56.5 ± 0.53 a | 12.9 ± 0.17 a | 12.6 ± 0.52 b | 4.83 ± 0.19 | 0.19 ± 0.00 b | 13.2 ± 0.57 b |
| p-value | <0.001 | <0.001 | <0.001 | 0.004 | 0.690 | <0.001 | 0.004 |
| Soil | |||||||
| Japanese cedar | 36.6 ± 0.70 | 29.7 ± 0.73 b | 6.01 ± 0.22 | 18.2 ± 0.35 a | 9.51 ± 0.01 b | 1.03 ± 0.05 | 20.1 ± 0.39 a |
| Transition | 35.8 ± 1.12 | 31.1 ± 0.55 ab | 5.84 ± 0.15 | 16.2 ± 0.33 b | 11.0 ± 0.29 a | 0.97 ± 0.05 | 18.3 ± 0.43 b |
| Bamboo | 33.8 ± 0.41 | 33.3 0.04 a | 5.84 ± 0.03 | 16.2 ± 0.38 b | 10.9 ± 0.18 a | 0.86 ± 0.01 | 18.1 ± 0.42 b |
| p-value | 0.105 | 0.008 | 0.679 | 0.011 | 0.003 | 0.063 | 0.026 |
The different letters indicate significant differences per variable between the vegetation types according to Tukey’s HSD comparisons at p = 0.05, and the bottom row represents the p-value of the one-way ANOVA results.