Table 2.
Fractions of soil P in an age sequence of soil crusts under plantations (mg kg−1).
| MS | BSC-8 | BSC-20 | BSC-35 | ANOVA in response to plantation age | ||||
|---|---|---|---|---|---|---|---|---|
| Regress equation | R 2 | F | P | |||||
| H2O-Pi | 2.585 ± 0.169 | 0.805 ± 0.150 | 2.920 ± 0.540 | 2.835 ± 0.678 | - | 0.164 | 1.955 | 0.192 |
| NaHCO3-Pi (0.5 mol L−1) | 3.870 ± 0.098 | 7.010 ± 1.129 | 10.35 ± 1.043 | 12.51 ± 2.645 | y = 0.243x + 4.605 | 0.835 | 50.715 | <0.001 |
| NaHCO3-Po (0.5 mol L−1) | 56.13 ± 7.969 | 71.99 ± 10.23 | 65.66 ± 5.505 | 68.49 ± 2.115 | - | 0.127 | 1.449 | 0.256 |
| NaOH-Pi (0.1 mol L−1) | 4.435 ± 0.369 | 8.010 ± 0.781 | 12.76 ± 1.783 | 12.80 ± 0.717 | y = 0.242x + 5.688 | 0.780 | 35.507 | <0.001 |
| NaOH-Po (0.1 mol L−1) | 72.57 ± 1.559 | 82.99 ± 27.09 | 92.24 ± 18.03 | 83.20 ± 20.47 | - | 0.052 | 0.553 | 0.474 |
| HCl-Pi (1.0 mol L−1) | 3.990 ± 0.234 | 19.56 ± 0.788 | 16.42 ± 1.157 | 16.65 ± 2.307 | - | 0.298 | 4.246 | 0.066 |
| HCl-Po (1.0 mol L−1) | 94.01 ± 4.809 | 97.44 ± 3.471 | 112.6 ± 2.263 | 105.6 ± 3.608 | y = 0.389x + 96.226 | 0.433 | 7.640 | 0.020 |
| NaOH-Pi (0.5 mol L−1) | 4.200 ± 0.398 | 8.695 ± 0.345 | 9.160 ± 1.435 | 9.290 ± 0.162 | y = 0.121x + 5.932 | 0.525 | 11.043 | 0.008 |
| NaOH-Po (0.5 mol L−1) | 78.80 ± 9.563 | 66.31 ± 9.236 | 83.84 ± 8.069 | 81.71 ± 22.64 | - | 0.063 | 0.677 | 0.430 |
| Residual-P | 84.33 ± 0.389 | 86.90 ± 6.301 | 85.10 ± 1.126 | 94.62 ± 5.732 | y = 0.260x + 83.639 | 0.407 | 6.868 | 0.026 |
| General-P | 404.9 ± 13.78 | 457.7 ± 29.99 | 511.0 ± 15.95 | 522.5 ± 22.47 | y = 3.307x + 421.934 | 0.763 | 32.193 | <0.001 |
Values are means ± SD. MS, moving sand dune (0-year); BSC-8, 8-year soil crust; BSC-20, 20-year soil crust; and BSC-35, 35-year soil crust.