*MAT: mean annual temperature, MTCQ: mean temperature of the coldest quarter, solar_rad: solar radiation, PET: potential evapotranspiration, MAP: mean annual precipitation, AI: aridity index, WD: water deficit; calculated as the difference between PET and the actual evapotranspiration (AET) (Francis and Currie 2003). TS: temperature seasonality, PS: precipitation seasonality. ELER-SD: standard deviation of elevation, ELER: elevation range, CLY: clay fraction, CRF: coarse fragments, SLT: silt fraction, SND: sand fraction. AW: available water, AN: available nitrogen, AP: available phosphorus, C_stock: organic carbon stock, C_content: organic carbon content, C/N_ratio: carbon/nitrogen ratio, CEC: cation exchange capacity.

Table 2. The best combinations of variables for each conifer species group in South-western China evaluated using stepwise regression and their coefficients of determination (R²). The best models for each group were selected from 1344 models based on the lowest Akaike information criterion (AIC). Numbers in parentheses are coefficients of respective variables. The variance inflation factors (VIF) for all predictors were less than 5 indicating insignificant multicollinearity.