Table 1. Soil characteristics and environmental variables.
| Soils | Location | Order | Sample Year | Horizon | depth (cm) | Clay (%) | pH | Total C (%) | avg T (°C) | GWC | MAT (°C) | MAP (mm) |
| Arctic 1 | Fairbanks, AK | Gelisol | Dec-10 | Active | 0–30 | 13 | 7.03 | 2.54 | −12.0 | 0.362 | −2.9 | 572 |
| Permafrost | 50–75 | 13 | 8.05 | 1.82 | 0.453 | −2.9 | 572 | |||||
| Subarctic 1 | Krýsuvík, Iceland | Andisol | July-11 | A | 0–15 | 12 | 5.84 | 8.49 | 8.6 | 0.775 | 5.0 | 1600 |
| B | 35–55 | 10 | 6.13 | 8.14 | 1.053 | 5.0 | 1600 | |||||
| Temperate 1 | Kane, IL | Mollisol | July-11 | A | 0–15 | 35 | 6.70 | 3.72 | 19.9 | 0.354 | 11.3 | 996 |
| B | 55–70 | 26 | 6.80 | 1.66 | 0.291 | 11.3 | 996 | |||||
| Temperate 2 | Gibson, TN | Alfisol | April-11 | A | 0–15 | 29 | 5.50 | 1.06 | 12.2 | 0.217 | 16.9 | 1381 |
| B | 50–75 | 32 | 5.80 | 0.52 | 0.12 | 16.9 | 1381 | |||||
| Temperate 3 | Blount, TN | Ultisol | May-11 | A | 0–10 | 25 | 6.17 | 1.97 | 16.6 | 0.239 | 14.7 | 1225 |
| B | 40–60 | 45 | 5.11 | 0.26 | 0.203 | 14.7 | 1225 | |||||
| Tropical 1 | Lavras, Brazil | Oxisol | March-11 | A | 0–12 | 67 | 4.42 | 5.85 | 24.0 | 0.299 | 19.3 | 1343.3 |
| B | 42–65 | 79 | 4.68 | 2.33 | 0.272 | 19.3 | 1343.3 | |||||
| Tropical 2 | Lavras, Brazil | Ultisol | March-11 | A | 0–10 | 45 | 5.42 | 3.17 | 24.0 | 0.24 | 19.3 | 1343.3 |
| B | 37–50 | 42 | 5.17 | 1.07 | 0.227 | 19.3 | 1343.3 |
Total C = total carbon, avg T = average air temperature (°C) for the month preceding sampling, GWC = gravimetric water content, MAT = mean annual temperature, MAP = mean annual precipitation.