Effects of Shelter Forests on Soil Organic Carbon of Irrigated Soils in the Taklimakan Desert

An experiment was carried out to test the effects of artificial vegetation on soil organic carbon in sandy soil. The soils were collected from the Taklimakan desert highway shelter forests with different stand age (the stand ages are 5, 7, 10, 13, 16, respectively, and three shrubs named Calligonum mongolicunl , Tamarix chinensis and Haloxylon ammodendron were planted along the highway) in Xinjiang, northwest of China. The soil organic carbon stock in soil vertical layers were calculated. We measured four passive organic carbons (i.e., micro-aggregates organic carbon, humic organic carbon, acid-resistant organic carbon and antioxidant organic carbon). Furthermore, we analyzed the correlations and ratios among the different passive organic carbons. Finally, the chemical composition of humus was detected and the relative contents of C=O and CH groups were determined. The main results showed that, (1) the soil organic carbon and organic carbon stock were decreased with the increase of depth, mainly in 0–50 cm. (2) With the increase of stand age, only in Tamarix chinensis forest, the total soil organic carbon stock increased a little. (3) Total soil organic carbon had more closely correlation with contents of micro-aggregate organic carbon and humic organic carbon. (4) C=O/C-O-C increased a little after 10 years; CH/C-O-C had no obvious change with stand age; CH 2 /CH 3 did not change obviously after 13 years. The Tamarix chinensis forest is the most helpful for carbon sequestration in sandy soil and stabilization in surface layer than Calligonum mongolicunl and Haloxylon ammodendron .