黄土高原小流域不同地形下土壤有机碳分布特征

研究了黄土高原小流域尺度塬面、坡地、沟道和梯田4种地形条件下土壤有机碳总量和活性组分的分布、储量及碳库管理指数的差异.结果表明,小流域土壤有机碳和不同活性有机碳的变异系数介于32％-70％之间,表现出中到高度的变异特征.4种地形下各组分有机碳含量和储量以塬面土壤最高,沟道土壤最低,并随土层深度的增加而降低,降低程度随有机碳活性增强而增加.以塬面土壤为对照所获得的碳库管理指数可灵敏指示有机碳对地形条件的响应特征,中活性有机碳库管理指数的指示效果最好.研究结果可部分解释黄土高原土壤有机碳地带性分布特征.

The distribution of soil organic carbon as affected by landforms in a small watershed of gully region of the Loess Plateau

Soil organic carbon plays important role in soil quality changes and terrestrial carbon cycling. However, the relationships between soil organic carbon distribution and landscape positions were not well understood, which are essential for the precisely predication of the spatial distribution of soil organic carbon and for the rational management of soil organic carbon, as well as for the assessment of the dynamics of soil organic carbon at different landscape positions at different landscape scales. China's Loess Plateau is a major region for agricultural production, and an ecological ecotone in northwest China, which suffers serious land degradation and ecologically economic problems due to the soil erosion in the region. The distribution and cycling of soil organic carbon were related not only with the maintaining and improving of soil quality in the region, but also with the response and adaptation of soil ecosystems to the future global climate change, and thus should be carefully assessed. In this study, we investigated the distribution of soil organic carbon and labile organic carbon at various landforms, that is, plateau land, sloping land, gully bottom and terrace land. We also anlyzed the differences of carbon management index at various landscape positions. The objectives were to establish the relationships between soil organic carbon and the landscape positions in a gully watershed of the Loess Plateau, and to understand how the labile organic carbon and carbon pool management index respond to the landscape positions. The results showed that soil organic carbon and labile organic carbon in the small watershed of the Loess Plateau have variance coefficients ranging from 32% to 70%, indicating medium to high variation. The highest and lowest of total and labile organic carbon were observed in plateau land and gully bottom, respectively. Additionally, total and labile organic carbon decreased with soil depth and the most decrease was tested in high labile organic carbon fraction. The carbon management index in this study can sensitively indicate the response of soil organic carbon to landforms. Among the 3 labile organic carbon fractions, the middle labile organic carbon based carbon management index present the best indication for carbon along soil profile. Our results indicate that the effects of landform on soil organic carbon can partly explain the regional distribution of soil organic carbon in the Loess Plateau.