Table 1 Soil N concentrations, δ15N values, C concentrations, δ13C in the Oa+e horizon and mineral horizon (0–20 cm) in four treatments
Soil horizons | Soil properties | N addition treatments | |||
|---|---|---|---|---|---|
CK | LN | MN | HN | ||
Oa+e horizons | Total N (g kg−1) | 1.65 ± 0.12b | 1.77 ± 0.07b | 1.85 ± 0.32a | 1.96 ± 0.10a |
δ15N (‰) | − 1.47 ± 0.52b | − 0.89 ± 0.19ab | − 0.25 ± 0.58a | − 0.48 ± 0.10a | |
Total C (g kg−1) | 39.92 ± 4.21a | 42.64 ± 1.90a | 39.12 ± 6.21a | 42.60 ± 1.12a | |
δ13C (‰) | − 29.13 ± 0.11a | − 28.96 ± 0.28a | − 29.16 ± 0.28a | − 29.15 ± 0.20a | |
NH4+–N (mg kg−1) | 45.54 ± 12.39b | 85.12 ± 15.99ab | 186.28 ± 85.75a | 166.32 ± 85.43a | |
NO3−–N (mg kg−1) | 9.88 ± 0.90b | 9.66 ± 0.54b | 17.52 ± 3.21a | 14.11 ± 3.46ab | |
Mineral horizons | Total N (g kg−1) | 0.19 ± 0.03b | 0.21 ± 0.03b | 0.29 ± 0.04a | 0.26 ± 0.04ab |
0–10 cm | δ15N (‰) | 5.54 ± 0.93a | 4.77 ± 0.69a | 5.03 ± 0.70a | 4.47 ± 0.55a |
Total C (g kg−1) | 5.15 ± 1.29a | 4.07 ± 1.61a | 4.02 ± 1.13a | 5.13 ± 2.67a | |
δ13C (‰) | − 26.54 ± 0.30a | − 26.75 ± 0.25a | − 26.28 ± 0.19a | − 26.70 ± 0.17a | |
NH4+–N (mg kg−1) | 6.14 ± 0.72b | 8.01 ± 3.01b | 13.47 ± 3.47a | 12.64 ± 2.19a | |
NO3−–N (mg kg−1) | 1.70 ± 0.21c | 2.74 ± 0.16bc | 3.14 ± 0.42b | 5.02 ± 2.06a | |
10–20 cm | Total N (g kg−1) | 0.08 ± 0.01a | 0.08 ± 0.03a | 0.08 ± 0.02a | 0.09 ± 0.04a |
δ15N (‰) | 5.93 ± 0.36a | 5.90 ± 0.87a | 5.87 ± 0.72a | 5.13 ± 0.52a | |
Total C (g kg−1) | 1.41 ± 0.71a | 1.26 ± 0.07a | 1.18 ± 0.48a | 1.18 ± 0.44a | |
δ13C (‰) | − 26.00 ± 0.44a | − 25.98 ± 0.03a | − 26.11 ± 0.38a | − 26.12 ± 0.25a | |
NH4+–N (mg kg−1) | 3.52 ± 1.59a | 4.05 ± 1.46a | 4.78 ± 0.73a | 4.54 ± 1.52a | |
NO3−–N (mg kg−1) | 2.23 ± 0.75a | 2.47 ± 0.41a | 2.78 ± 0.52a | 2.37 ± 0.45a | |