Effect of land use type on the active organic carbon of wetland soil in an arid area

Wetlands is important for the carbon balance of the arid area ecosystem to clarify the characteristics and influencing factors of active organic carbon in wetland soil. In order to investigate the influence of land use type on total soil organic carbon contents, soil organic carbon (SOC), readily organic carbon (ROC), and dissolved organic carbon (DOC) contents, as well as the organic carbon density, of Chaiwopu Lake wetland soil were determined. Land use type affected SOC content, as follows: farmland reclaimed before 1983 (22.97 ± 0.85) g·kg^–1 > natural farmland (21.83 ± 1.97) g·kg^–1 > wetland farm belt (16.74 ± 6.52) g·kg^–1 > lake wetland (11.98 ± 3.67) g·kg^–1 > salinized wetland (9.86 ± 3.31) g·kg^–1.There was a significant difference in ROC content between wetland and farmland(P < 0.05).Furthermore, the DOC contents of the farmland (reclaimed after 1983) soil was highest and significantly different (P < 0.05)from that of wetland-farmland transition zone and natural farmland soils respectively. The SOC, ROC, and DOC contents decreased with increasing depth (0 – 40 cm) in the lake wetland and wetland-farmland transition zone soils, whereas the opposite trend was observed for the DOC of the salinized wetland soil. The active organic carbon contents of farmland soil did not change significantly with increasing soil depth. The organic carbon density of Chaiwopu Lake wetland soil under five different land use types was higher than the national average. Soil pH was negatively correlated with organic carbon accumulation (P < 0.01), and soil conductivity was positively correlated with both SOC and ROC contents (P < 0.01). These results revealed that the active organic carbon components of arid-area wetland soil are affected by land use type and that the active organic carbon content of farmland soil after natural or wetland transformation is higher than that of wetland soil.