Table 1.
The contribution rate of environmental variables.
| Category | Abbreviation | Variable | Whether excluding | Percent contribution (%) | Suitable range |
|---|---|---|---|---|---|
| Climate | bio1 | Annual mean temperature (°C) | No | 8.3 | 4.86~15.08 |
| bio2 | Mean diurnal range (°C) | No | 1.6 | 9.41~13.50 | |
| bio3 | Isothermality (bio2/bio7) (×100) | No | 1.5 | 24.30~32.26 | |
| bio4 | Temperature seasonality | Yes | – | – | |
| bio5 | Max temperature of warmest month (°C) | Yes | – | – | |
| bio6 | Min temperature of coldest month (°C) | Yes | – | – | |
| bio7 | Temperature annual range (°C) | Yes | – | – | |
| bio8 | Mean temperature of wettest quarter (°C) | No | 0.1 | 18.29~25.22 | |
| bio9 | Mean temperature of driest quarter(°C) | Yes | – | – | |
| bio10 | Mean temperature of warmest quarter (°C) | Yes | – | – | |
| bio11 | Mean temperature of coldest quarter (°C) | Yes | – | – | |
| bio12 | Annual precipitation (mm) | No | 41.6 | 351.96~712.77 | |
| bio13 | Precipitation of wettest month (mm) | Yes | – | – | |
| bio14 | Precipitation of driest month (mm) | Yes | – | – | |
| bio15 | Precipitation seasonality | No | 8.0 | -165.68~100.23 | |
| bio16 | Precipitation of wettest quarter (mm) | Yes | – | – | |
| bio17 | Precipitation of driest quarter (mm) | Yes | – | – | |
| bio18 | Precipitation of warmest quarter (mm) | Yes | – | – | |
| bio19 | Precipitation of coldest quarter (mm) | Yes | – | – | |
| Soil | t_bs | Topsoil base saturation (%) | Yes | – | – |
| t_caco3 | Topsoil calcium carbonate (% wt.) | No | 14.8 | 2.08~16.38 | |
| t_caso4 | Topsoil Gypsum (% wt.) | No | 0 | -1.51~0.34 | |
| t_clay | Topsoil clay fraction (% wt.) | No | 0.2 | 8.00~24.67 | |
| t_ece | Topsoil salinity (dS/m) | No | 0 | 0.14~1.63 | |
| t_esp | Topsoil sodicity (%) | No | 0.3 | 0.49~4.72 | |
| t_gra | Topsoil gravel content (%vol.) | No | 0 | 2.99~9.72 | |
| t_oc | Topsoil organic carbon (% wt.) | No | 0 | -3.75~-0.91 | |
| t_ph | Topsoil pH (-log (H+)) | No | 6.0 | 7.31~9.34 | |
| t_ref | Topsoil reference bulk density (kg/dm3) | Yes | – | – | |
| t_sand | Topsoil sand fraction (% wt.) | No | 0.2 | 28.99~50.64 | |
| t_silt | Topsoil silt fraction (% wt.) | Yes | – | – | |
| t_teb | Topsoil TEB (cmol/kg) | No | 0.1 | 16.79~65.30 | |
| Topographical | d_ele | Elevation (m) | No | 15.9 | -783.10~1052.71 |
| d_asp | Aspect (rad) | No | 0.4 | 154.75~352.65 | |
| d_slo | Slope (°) | No | 1.0 | -3.24~2.05 |