Due to the rapidly growing population in tropical Africa, a substantial rise in food demand is predicted in upcoming decades, which will result in higher pressure on soil resources. However, there is limited knowledge on soil redistribution dynamics following land conversion into arable land in tropical Africa that is partly caused by infrastructure limitations for long-term landscape-scale monitoring. In this study, fallout radionuclides ^239+240Pu are used to assess soil redistribution along topographic gradients at two cropland sites and at three nearby pristine forest sites located in the DR Congo, Uganda and Rwanda. In the study area, a ^239+240Pu baseline inventory is found that is higher than typically expected for tropical regions (mean forest inventory 41 Bq m⁻²). Pristine forests show no indication of soil redistribution based on ^239+240Pu along topographical gradients. In contrast, soil erosion and sedimentation on cropland reached up to 37 cm (81 Mg ha⁻¹ yr⁻¹) and 40 cm (87 Mg ha⁻¹ yr⁻¹) within the last 55 years, respectively. Cropland sites show high intra-slope variability with locations showing severe soil erosion located in direct proximity to sedimentation sites. This study shows the applicability of a valuable method to assess tropical soil redistribution and provides insight into soil degradation rates and patterns in one of the most socio-economically and ecologically vulnerable regions of the world.

中文翻译：

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使用^239+240 Pufallout 放射性核素评估潮湿热带非洲森林和农田场地的土壤重新分布

由于热带非洲人口迅速增长，预计未来几十年粮食需求将大幅增加，这将对土壤资源造成更大压力。然而，关于热带非洲土地转变为耕地后土壤再分配动态的知识有限，部分原因是长期景观尺度监测的基础设施限制。在这项研究中，放射性核素^239+240 Pu 用于评估沿地形梯度在刚果民主共和国、乌干达和卢旺达的两个农田地点和三个附近原始森林地点的土壤重新分布。在研究区域， 发现^239+240 Pu 基线清单高于热带地区的通常预期（平均森林清单 41 Bq m ^-2）。基于^239+240 Pu 沿地形梯度，原始森林没有显示土壤重新分布的迹象。相比之下，在过去的 55 年中，农田上的土壤侵蚀和沉积分别达到 37 cm (81 Mg ha ^-1  yr ^-1 ) 和 40 cm (87 Mg ha ^-1  yr ^-1 )。农田地点显示出高度的斜坡内变异性，其中直接靠近沉积地点的地点显示出严重的土壤侵蚀。这项研究展示了一种评估热带土壤重新分布的宝贵方法的适用性，并提供了对世界上社会经济和生态最脆弱地区之一的土壤退化率和模式的深入了解。