不同地形条件下青藏高原农田土壤有机碳的分布特征

Soil organic carbon in croplands across different terrains in the Qinghai-Tibet Plateau

西北高寒地区农田土壤有机碳(SOC)储量的变化研究,可为东部农田SOC对气候和管理措施的响应提供预警信息。针对西部高原县域尺度上典型的地貌类型和土壤类型,对其耕层和剖面SOC进行了分析。结果表明,青海省乐都县农田耕层(0—20 cm)SOC的变化范围为4.38 g/kg～20.81 g/kg,均值为11.29 g/kg,且不同土壤类型上表现出黑钙土(16.15 g/kg)>栗钙土(10.53 g/kg)>灰钙土(9.50 g/kg)的趋势。地形对耕层(0—20 cm)SOC含量没有显著影响,但深层(20—100 cm)SOC因地形存在显著差异,在峁坡上,黑钙土、栗钙土和灰钙土的深层(20—100 cm)SOC分别比同种土壤类型的谷底深层土壤提高了111.5%、62.5%和66.3%。农田SOC的垂直分布也因地形存在差异,同一种土壤类型在谷底其耕层(0—20 cm)SOC含量均比深层(20—100 cm)高,峁坡上其深层(20—100 cm)比耕层(0—20 cm)高,黑钙土、栗钙土和灰钙土在谷底其耕层(0—20 cm)SOC含量分别比同一土壤类型的深层(20—100 cm)土壤提高18.7%、24.3%和153.5%,黑钙土、栗钙土和灰钙土在峁坡上其深层(20—100cm)SOC含量分别比同一土壤类型耕层(0—20 cm)提高46.9%、8.0%和1.0%。这一结果可为准确估算青藏高原农田SOC的变化提供参考。

Northwest alpinecold region is an important part of China＇s agricultural production. Understanding soil organic carbon （SOC） storage and its influencing factors in northwest alpinecold region contributes to accurately evaluate change of national soil organic carbon storage, and also may provide early warning information on response of SOC to climate and management measures in croplands with same latitude or lowaltitude. Based on two landform types （slope and bottom） and three soil types （chernozem, kastanozem and sierozem）, soil samples from seventyfive sites were collected for investigating distribution characteristics of cropland SOC contents and the relationship with terrains in Ledu county of Qinghai province. The cropland surface （0 -20 cm） SOC contents range from 4.38 g/kg to 20.81 g/kg with the average of 11.29 g/kg in Ledu county, and the SOC contents in the three soil types follow the decreasing order as： chernozem〉kastanozem〉sierozem. There are no significant differences of surface SOC contents （0-20 cm） in different terrains, however, there are significant differences in the subsoil SOC contents （20-100 cm）. Compared with the three soil types in bottom, the subsoil SOC contents of the same soil type in the slope are increased by 111.5%、 62.5% and 66.3%. The SOC contents in the vertical layers have differences in different terrains. The surface SOC contents （0-20 cm） are higher than those of the subsoil （20-100 cm） in the bottom in the same soil type, and the SOC contents in the subsoil （20-100 cm） are higher than those of the surface soil in the slope in the same soil type. Compared with the subsoil （20-100 cm） SOC contents of the three soil types in the bottom, the surface （0-20 cm） SOC contents are increased by 18.7%, 24.3% and 153.5%. Compared with the surface （0-20 cm） SOC contents of the three soil types in the slope, the subsoil （20-100 cm） SOC contents are increased by 46.9%, 8.0% and 1.0%. These results are contribution to the study of accurately estimating the cropland SOC in the Qinghai Tibet Plateau.