5. Conclusion
Desert soil organic carbon contents ranged from 0.54 to 24.34 g/kg with high variation coefficient around 81.14% in Qaidam Basin. Mean and median value of SOC contents were approximate 4.86 and 3.80 g/kg.
Cluster analysis revealed that soils organic carbon contents were divided into four groups by multivariate regression trees. The largest group was around 3.32 g/kg (145 samples), when precipitation was lower than 371.5 mm, air temperature and altitude were higher than 1.49oC and 2793 m.
All TN and pH and precipitation were main driven factors on SOC by structural equation model with R2 of 0.87. Affected coefficients were 0.99 and −0.21 and −0.16, separately (P<0.001). Furthermore, air temperature significantly affected soil pH (P<0.05). With nitrogen deposition increasing, deserts soil organic carbon contents would increase significantly in Qaidam basin.