Purpose

Ascertaining soil and associated soil organic carbon (SOC) redistribution induced by erosion and deposition processes is of critical importance to explore SOC dynamics on the landscape. The relationship between landscape scale erosion and deposition and SOC dynamics still has to be clearly described in fragile karst region.

Methods

The soil profiles of 40-cm depth in relation to different land use types (e.g., grassland, forests, shrubland, and farmland) at the eroding and depositional landform positions were chosen. The profile patterns of SOC and its isotopic signatures were analyzed. The source and decomposition of SOC in profiles were investigated subsequently.

Results

The mean SOC concentration in soil profiles decreased in the following order: shrubland > grassland > artificial forest > farmland at the eroding sites and grassland > artificial forest > shrubland > farmland at the depositional sites. The main sources of SOC in profiles at both landform positions were from C3 plants, while the proportional contribution of C4 plants increased along the depth. Although a higher concentration of SOC at the depositional sites was found relative to upland soils, there was higher decomposition rate of SOC at the depositional sites than that at the eroding sites, particularly under the farmlands.

Conclusions

Our findings imply that the conversion of farmland to natural forests or grassland could be feasible for enhancing SOC sequestration potential; meanwhile, the soil redistribution process has significant effect on dynamics of eroded SOC in fragile systems, especially in the karst region.

中文翻译：

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喀斯特流域土地利用变化与土壤再分布对土壤有机碳动态的影响。

目的

确定由侵蚀和沉积过程引起的土壤及相关土壤有机碳（SOC）的重新分布对于探索景观上SOC的动态至关重要。在脆弱的喀斯特地区，仍然必须清楚地描述景观尺度侵蚀与沉积和SOC动态之间的关系。

方法

选择了在侵蚀和沉积地貌位置上与不同土地利用类型（例如，草地，森林，灌木丛和农田）相关的40厘米深度的土壤剖面。分析了SOC的剖面模式及其同位素特征。随后研究了剖面中SOC的来源和分解。

结果

土壤剖面中的平均SOC浓度按以下顺序降低：灌木丛>草地>人工林>侵蚀点的农田和草地>人工林>灌木丛>沉积点的农田。在两个地貌位置，剖面中SOC的主要来源均来自C3植物，而C4植物的比例贡献则沿深度增加。尽管相对于旱地土壤，沉积位点的SOC浓度更高，但沉积位点的SOC分解速率比侵蚀位点的高，尤其是在农田下。

结论

我们的研究结果表明，将农田转变为天然林或草地对于增强SOC封存潜力是可行的。同时，土壤的重新分配过程对脆弱系统（尤其是喀斯特地区）中的SOC侵蚀动力学具有显着影响。