Table 2.
Characteristics of Environmental Variables Used in Predicting the Distribution of STHs in Nigeria.
| Variable | Units | Spatial resolution | Data source | Accessible at |
|---|---|---|---|---|
| Elevation | M | 1 km | Shuttle Radar Topography Mission (SRTM) | http://www.diva-gis.org/gdata |
|
Bioclimatic variables (BIO 1 to BIO19) BIO1—Annual Mean Temperature BIO2—Mean Diurnal Range BIO3 – Isothermality BIO4—Temperature Seasonality BIO5—Maximum Temperature of Warmest Month BIO6—Mini Temperature of the Coldest Month BIO7—Temperature Annual Range BIO8—Mean Temperature of Wettest Quarter BIO9—Mean Temperature of Driest Quarter BIO10—Mean Temperature of Warmest Quarter BIO11—Mean Temperature of Coldest Quarter BIO12—Annual Precipitation BIO13—Precipitation of Wettest Month BIO14—Precipitation of Driest Month BIO15—Precipitation Seasonality BIO16—Precipitation of Wettest Quarter BIO17—Precipitation of Driest Quarter BIO18—Precipitation of Warmest Quarter and BIO19—Precipitation of Coldest Quarter |
Temperature (Kelvin) Precipitation (mm) |
1 km | WorldClimate | (WCD, 2004) |
| Soil organic carbon at the depth of 0–5 cm | Measure by either wet oxidation or dry combustion at 900 C in g/kg | 250 m | International Soil Reference Centre (ISRIC) | (ISRIC, 2012) |
| pH of the soil at the depth of 0–5 cm | – | 250 m | International Soil Reference Centre (ISRIC) | (ISRIC, 2012) |
| Soil clay content at the depth of 0–5 cm | Measure in g/100 g (w%) | 250 m | International Soil Reference Centre (ISRIC) | (ISRIC, 2012) |
| Root zone moisture content aggregated at 30 cm (water retention capacity) | Measured in V% | 1 km | International Soil Reference Centre (ISRIC) | (ISRIC, 2012) |