第二次青藏高原综合科学考察研究(2019QZKK0307)； 国家自然科学基金项目“水蚀和耕作侵蚀交互作用对紫色土坡耕地微地貌变化的影响”(41401313)； 国家重点研发计划“金沙江干热河谷坝区生态综合治理及农业产业发展技术试验示范”(2017YFC0505102)联合资助。
[目的] 查明青藏高原东南部地区坡耕地土壤侵蚀空间分布格局及其对土壤有机碳(SOC)和全氮(TN)顺坡迁移过程的影响，为该区土地资源利用及土壤资源保护提供科学依据。[方法] 利用137Cs核素示踪技术，结合现场调查，研究藏东南地区梯田系列和复合坡耕地土壤侵蚀空间分布格局差异；采用相关分析，探明坡面土壤137Cs面积浓度与同样深度(30 cm) SOC、TN面积浓度之间的相关性。[结果] ①在整个梯田系列内，土壤137Cs面积浓度从坡顶到坡脚呈离散分布格局，上部梯田下坡部位土壤137Cs面积浓度明显高于紧邻的下部梯田上坡土壤，且上坡梯田表现为土壤侵蚀，而下坡和坡脚梯田则表现为土壤沉积；在单个梯田景观内，土壤侵蚀速率主要呈上部坡位高，下部坡位低的趋势； ②复合坡坡耕地土壤侵蚀速率表现为先波动减少，然后逐渐增加的趋势，即坡顶部位土壤侵蚀速率相对较高，顺坡向下逐渐变小，在坡中部和下部表现为沉积，在坡脚部位土壤侵蚀速率又逐渐增加； ③梯田系列和坡耕地土壤137Cs面积浓度与SOC，TN面积浓度之间均具有显著的相关关系(p＜0.05)。[结论] 在藏东南地区，梯田有效地改变了该区的土壤侵蚀空间分布格局，土壤137Cs示踪技术可以较好地示踪该区坡耕地土壤、SOC和TN顺坡迁移和空间再分布状况，防控耕作侵蚀的危害也应当得到与水蚀同样的重视。
[Objective] The impacts of soil erosion on the spatial distribution of soil organic carbon (SOC) and total nitrogen (TN) in the sloping farmland of the Southeast Tibet Plateau were determined in order to provide a scientific basis for land resource utilization and soil resource conservation. [Methods] Spatial patterns of soil erosion were investigated using the 137Cs tracer method combined with field investigation. Correlations between 137Cs inventories and inventories of SOC and TN were determined using correlation analysis. [Results] For the terraced toposequence, discrete patterns of 137Cs inventories were found, and an abrupt increase in 137Cs inventories was observed between lower slope positions of the upper terrace and the upper slope position of an adjacent lower terrace. A fluctuating increasing trend in 137Cs inventories was observed from the upper terrace to the lower terrace. A gradual increasing trend in 137Cs inventories appeared within a terrace, indicating that soil loss occurred at the upper slope positions and soil deposition appeared at the lower slope positions. For sloping farmland, increasing and decreasing trends in 137Cs inventories appeared along the slope transects, accompanied by decreasing and increasing trends in the soil erosion rate. Low 137Cs inventories were observed at the summit and toe slope positions of sloping farmland, and the highest 137Cs inventories were found at the middle slope positions. ③ Inventories of SOC and TN showed similar spatial patterns to those observed for 137Cs inventories, and a linear relationship was found between137Cs inventories and SOC and TN inventories (p＜0.05). [Conclusion] Soil erosion was one of the most important driving forces affecting SOC and TN transport along a slope transect. Overall, the spatial patterns of 137Cs can be used to trace spatial patterns of SOC and TN in the sloping farmland of the Southeast Tibet Plateau. The 137Cs tracing method was a useful tool to elucidate the redistribution and migration of soil and nutrients on a slope. Furthermore, tillage erosion should be given the same attention as water erosion in order to prevent and control soil erosion in this area.