Table 1.
Characterization of the 5 examined soilsa
| Soil parameter | Value(s) for soil |
||||
|---|---|---|---|---|---|
| P0 | P50 | P100 | P300 | P2000 | |
| Soil texture (% sand, silt, clay) | 7.4, 80.4, 12.2 | 0.4, 83.6, 16.0 | 2.0, 81.2, 16.8 | 3.4, 81.2, 15.4 | 4.0, 85.1, 10.9 |
| pH | 8.1 (0.13) a | 7.6 (0.08) b | 7.6 (0.13) b | 7.5 (0.08) b | 7.3 (0.10) c |
| TOC (%) | 0.58 (0.17) a | 1.7 (0.14) b | 1.7 (0.16) b | 2.5 (0.16) c | 3.1 (0.11) d |
| TN (%) | 0.060 (0,012) a | 0.17 (0.014) b | 0.19 (0.015) c | 0.27 (0.020) d | 0.36 (0.019) e |
| WEOC (μg g−1 dw) | 9.5 (2.8) a | 17 (5.4) b | 18 (11) ab | 21 (8.3) ab | 14 (5.3) ab |
| WEON (μg g−1 dw) | 0.43 (0.19) a | 0.46 (0.77) a | 5.5 (6.6) a | BDLb | 0.36 (0.60) a |
| Nitrate (μg N g−1 dw) | 2.1 (0.70) a | 12 (1.2) ab | 8.3 (2.9) ab | 16 (6.5) b | 2.2 (1.7) a |
| Ammonium (μg N g−1 dw) | 0.42 (0.12) a | 6.0 (3.5) a | 25 (19) a | 27 (30) a | 22 (11) a |
| Cmic (μg g−1 dw) | 150 (58) a | 720 (120) b | 1,000 (330) b | 1,800 (780) b | 5,100 (1,300) c |
| Nmic (μg g−1 dry wt) | 39 (6.8) a | 28 (18) a | 110 (55) ab | 92 (36) ab | 150 (30) b |
| DNA content (μg g−1 dry wt) | 140 (35) a | 760 (24) bc | 630 (120) b | 810 (220) bc | 1,100 (140) c |
a
Soils (tidal wetland and paddy soils cultivated for 50, 100, 300, and 2,000 years) at 0- to 20-cm depth were analyzed using different parameters: soil texture, pH value (CaCl2), total organic carbon (TOC), and total nitrogen (TN), water extractable organic carbon (WEOC) and nitrogen (WEON), nitrate and ammonium concentrations, microbial biomass C and N, and DNA content. Standard deviations are given in parentheses (n = 5). Significant differences are indicated by different letters.
b
Below detection limit of 0.2 μg g−1 soil dry weight.