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.