Abstract. Land restoration is of critical importance in Rwanda, where land degradation negatively impacts crop productivity, water, food and nutrition security. We implemented the Land Degradation Surveillance Framework in Kayonza and Nyagatare districts in eastern Rwanda to assess baseline status of key soil and land health indicators, including soil organic carbon (SOC) and soil erosion prevalence. We collected 300 topsoil (0–20 cm) and 281 subsoil (20–50 cm) samples from two 100 km² sites. We coupled the soil health indicators with vegetation structure, tree density and tree diversity assessments. Mean topsoil organic carbon was low overall, 20.9 g kg⁻¹ in Kayonza and 17.3 g kg⁻¹ in Nyagatare. Stable carbon isotope values (d13CV-PDB ) ranged from −15.35 to −21.34 ‰ indicating a wide range of plant communities with both C3 and C4 photosynthetic pathways. Soil carbon content decreased with increasing sand content across both sites and at both sampling depths and was lowest in croplands compared to shrubland, woodland and grasslands. Field-saturated hydraulic conductivity (K_fs) was estimated based on infiltration measurements, with a median of 76 mm h⁻¹ in Kayonza and 62 mm h⁻¹ in Nyagatare, respectively. Topsoil OC had a positive effect on K_fs, whereas pH, sand and compaction had negative effects. Soil erosion was highest in plots classified as woodland and shrubland. Maps of soil erosion and SOC at 30-m resolution were produced with high accuracy and showed high variability across the region. These data and analysis demonstrate the importance of systematically monitoring multiple indicators at multiple spatial scales to assess drivers of degradation and their impact on soil organic carbon dynamics.

中文翻译：

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评估土壤有机碳的生物地球化学和人为驱动因素，为卢旺达的恢复活动提供依据

摘要。土地恢复在卢旺达至关重要，那里的土地退化对作物生产率，水，粮食和营养安全产生不利影响。我们在卢旺达东部的Kayonza和Nyagatare地区实施了土地退化监测框架，以评估关键土壤和土地健康指标的基线状态，包括土壤有机碳（SOC）和土壤侵蚀发生率。我们从两个100 km ^2的地点收集了300个表土（0–20 cm）和281个底土（20–50 cm）样品。我们将土壤健康指标与植被结构，树木密度和树木多样性评估结合在一起。平均数表土有机碳是低的整体，20.9克千克^-1在Kayonza和17.3克千克^-1在Nyagatare。稳定的碳同位素值（d13CV-PDB）在-15.35至-21.34‰范围内，表明具有C3和C4光合作用途径的植物群落范围很广。与灌木丛，林地和草地相比，两个地点和两个采样深度的土壤碳含量都随着含沙量的增加而降低，在农田中最低。根据渗透测量值估算了田间饱和的水力传导率（K _fs），Kayonza中位数为76 mm h ^-1，Nyagatare中位数为62 mm h ^-1。表土OC对K _fs有积极影响，而pH，沙土和压实则有负面影响。在被归类为林地和灌木地的样地中，土壤侵蚀最高。以30 m的分辨率绘制的土壤侵蚀和SOC的地图具有很高的精度，并且在整个地区显示出较高的变异性。这些数据和分析表明，有必要在多个空间尺度上系统地监测多个指标，以评估退化的驱动因素及其对土壤有机碳动态的影响。