3.3 Structural equation model revealed main affected factors on desert SOC and TN and pH
Desert SOC were mainly affected by TN, pH and precipitation using structural equation model with R2 of 0.87 among six factors (Figure 4). Affected coefficients of TN and pH and precipitation were 0.99 and −0.21 and −0.16, separately (P<0.001). However, total phosphorus and altitude and air temperature took weak roles in affecting SOC contents. Soil total nitrogen contents were positively driven by precipitation with effect coefficient of 0.37 (P<0.001). Both temperature and altitude took weakly negative role in soil nitrogen. Furthermore, air temperature affected positively soil pH (P<0.05).
3.4 Predictions of SOC based on climate factors by generalized additive models in Qaidam basin
This generalized additive model could accurately predict soil organic carbon contents using air temperature and precipitation and altitude data with R2 of 0.40 (P<0.001). All three factors took significant effect on soc contents (Figure 5). In addition, contribution were precipitation, temperature and altitude by turn.