Table 3 The coefficients and associated p-values of the variables correlated with aboveground carbon storage using both forward and backward selection procedures
Variable (where appropriate, units are given in brackets) | Group | Forward | Backward | ||
|---|---|---|---|---|---|
Coefficient | p-value | Coefficient | p-value | ||
(Intercept) | n/a | -1.21E + 03 | 3.14E-03 | -2.80E + 00 | 7.55E-01 |
Natural logarithm of the population pressure with decay constant of 12.5 km | Anthropogenic | 1.06E + 00 | 1.06E-05 | 1.42E + 00 | 2.27E-06 |
Natural logarithm of the population pressure with decay constant of 16.7 km | Anthropogenic | n/a | n/a | 1.42E + 00 | 2.27E-06 |
Distance to roads (km) | Anthropogenic | 1.15E-04 | 1.09E-03 | 1.78E-04 | 1.30E-05 |
Historical logging – Partially logged (no logging/partially logged) | Anthropogenic | -2.10E + 00 | 1.09E-03 | -3.83E + 00 | 4.97E-07 |
Cost distance to Dar es Salaam | Anthropogenic | 3.41E-05 | 2.00E-03 | 2.58E + 00 | 5.46E-03 |
Natural logarithm of the cost distance to market towns | Anthropogenic | -6.05E-01 | 5.24E-02 | -9.85E-01 | 1.89E-02 |
Governance – local (national/local/joint/unknown) | Anthropogenic | 4.24E + 00 | 9.29E-03 | n/a | n/a |
Governance – national (national/local/joint/unknown) | Anthropogenic | -7.95E-03 | 9.78E-01 | n/a | n/a |
Governance – unknown (national/local/joint/unknown) | Anthropogenic | 6.26E-01 | 7.10E-01 | n/a | n/a |
Mean annual monthly temperature range (°C) | Climatic | -9.79E-01 | 2.00E-16 | -1.15E + 00 | 1.98E-13 |
Mean annual minimum monthly temperature (°C) | Climatic | n/a | n/a | 1.09E + 00 | 3.07E-16 |
Mean annual maximum monthly temperature (°C) | Climatic | n/a | n/a | -1.15E + 00 | 1.98E-13 |
Mean number of dry months annually | Climatic | -2.28E-01 | 2.57E-02 | -3.09E-01 | 5.58E-03 |
Total available water capacity of the soil (vol. %, -33 to -1500 kPA conforming to USDA standards) | Edaphic | -3.75E-01 | 1.16E-05 | -8.59E-01 | 3.05E-05 |
Total nitrogen content of the soil (g kg-1) | Edaphic | n/a | n/a | -4.13E-01 | 2.50E-03 |
Total carbon content of the soil (g kg-1) | Edaphic | n/a | n/a | 6.18E + 00 | 1.15E-03 |
pH of the soil (pH) | Edaphic | n/a | n/a | 1.73E + 00 | 2.96E-02 |
Spatial autocorrelation term 5 | Spatial | 6.45E + 01 | 3.15E-03 | 6.60E + 00 | 1.18E-01 |
Spatial autocorrelation term 7 | Spatial | -8.48E-01 | 3.57E-03 | -1.71E-01 | 1.45E-01 |
Spatial autocorrelation term 4 | Spatial | n/a | n/a | 6.60E + 00 | 1.18E-01 |
Spatial autocorrelation term 3 | Spatial | n/a | n/a | -1.71E-01 | 1.45E-01 |