Table 1. List of geological, climatic, environmental and anthropogenic variables used in the multivariate regression.
| Variables | Description | Resolution | Type | Source |
|---|---|---|---|---|
| r.maxage_geol | GLiM age attribute (Myrs) | 1 km | D | [13, 45] |
| r.minage_geol | GLiM age attribute (Myrs) | 1 km | D | [13, 45] |
| r.meanage_geol | GLiM age attribute (Myrs) | 1 km | D | [13, 45] |
| r.age | Terrane age attribute (Myrs) | 1 km | D | [46] |
| r.ssaw | Multi-models average sea salt wet deposition (kg.ha-1.yr-1) | 1°×1° | C | [47] |
| r.ssa | Multi-models average Sea salt wet+dry deposition (kg.ha-1.yr-1) |
1°×1° | C | [47] |
| r.dust | Multi-models average (g.m-2.yr-1) | 1°×1° | C | [48] |
| r.elevation | SRTM (m) | 90 m | C | [49] |
| r.cec | Cation Exchange Capacity | 250 m | C | [50] |
| r.ph | Soil pH in H2O solution (x10) | 250 m | C | [50] |
| r.phkcl | Soil pH in KCl solution (x10) | 250 m | C | [50] |
| r.clay | Clay (weight %) | 250 m | C | [50] |
| r.orc | Soil organic carbon (weight %) | 250 m | C | [50] |
| r.bulk | Bulk density (kg m−3) | 250 m | C | [50] |
| r.bouguer | WGM2012_Bouguer (mGal) | 2 min | C | [51] |
| r.map | Mean annual precipitation (mm.yr-1) | 30-arc sec | C | [52] |
| r.mat | Mean annual temperature (°C) | 30-arc sec | C | [52] |
| r.distance | Distance to the coast (km) | 30-arc sec | C | This study |
D: Discrete; C: Continuous; GLiM: Global Lithological Map; CCSM.3: CommunityClimate System Model 3; SRTM: Shuttle Radar Topography Mission.