Table 3 Location, sampling, host, climatic and soil characteristics of the study sites on the Loess Plateau.
Sites | QJ1 | QJ2 | YC1 | YC2 | YA | HL |
|---|---|---|---|---|---|---|
Location | Qingjian County | Qingjian County | Yanchuan County | Yanchuan County | Yan’an City | Huanglong County |
Latitude/ longitude | 37°07′ N/110°04′ E | 37°06′ N/110°17′ E | 36°53′ N/110°06′ E | 36°49′ N/110°14′ E | 36°37′ N/109°27′ E | 35°45′ N/109°54′ E |
Vegetation zone | Forest-steppe | Forest-steppe | Forest-stepp | Forest-steppe | Forest-steppe transitional region | Forest |
Vegetation type (tree ages) | Natural secondary poplar forest patch (40–50 years) | Natural secondary poplar forest patch (40–50 years) | Natural secondary poplar forest patch (40–50 years) | Artificial pine forest patch (40–45 years) | Artificial pine forest patch (40–45 years) | Natural secondary pure pine stand (30–40 years) |
DBH (cm)a | 11.5–35.6 (22.3) | 10.2–37.2 (20.2) | 11.3–34.7 (20.8) | 10.4–18.5 (14.2) | 11.0–33.1 (20.6) | 16.8–35.5 (26.2) |
Altitude (m) | 940–1026 | 855–937 | 845–984 | 744–827 | 1014–1068 | 1481–1524 |
Precipitation (mm) | 500 | 500 | 500 | 500 | 514 | 612 |
MAT (°C) | 9.6 | 9.6 | 10.8 | 10.8 | 7.0 | 8.6 |
Soil characteristics b | ||||||
 pH | 8.04 ± 0.13b | 8.47 ± 0.14d | 8.24 ± 0.08c | 8.37 ± 0.12cd | 7.88 ± 0.20ab | 7.76 ± 0.23a |
 EC (μS/cm) | 209.51 ± 56.80b | 133.91 ± 30.83a | 131.34 ± 15.24a | 109.41 ± 24.49a | 146.85 ± 49.96a | 191.23 ± 47.67b |
 SOM (g/kg) | 12.73 ± 2.88a | 13.71 ± 4.46a | 15.85 ± 4.87a | 15.17 ± 4.82a | 10.23 ± 1.71a | 66.69 ± 27.54b |
 TN (mg/kg) | 714.68 ± 199.14a | 735.01 ± 269.45a | 887.53 ± 262.22a | 760.50 ± 356.48a | 435.65 ± 115.35a | 3174.43 ± 1285.35b |
 TP (mg/kg) | 523.13 ± 59.18c | 499.77 ± 48.83bc | 498.83 ± 29.96bc | 463.69 ± 51.68b | 404.04 ± 83.02a | 467.96 ± 57.92b |
