The impact from humans on soils, particularly in terms of intensive agriculture, has been most noticeable in the last 200 years. Intensive agricultural activities have caused soil organic carbon (SOC) to decline in many parts of the world. However, there is a dearth of approaches that can spatially estimate the change of SOC due to human influence. Here, we used the concept of Pedogenon to stratify the landscape into soil classes called Pedogenons. Within each Pedogenon, we sampled representative soils under native vegetation and soils under intensive human management. We surveyed the lower Namoi Valley area, NSW, Australia (1700 km²), comprising 13 Pedogenons (soil classes) and analysed SOC on 99 soil cores. Using Digital Soil Mapping techniques, the SOC data were used for mapping SOC every 10 cm down to 1 m using environmental covariates. Sampling points under native vegetation were used to map SOC under the native state, and all data were used for mapping SOC current state. By comparing the SOC maps at two states (native and current), we assessed SOC change. The results show that the SOC loss in irrigated cropping areas was the largest, with surface SOC content decreased by 38%, followed by non-irrigated cropping (30% loss), and pasture (19% loss). All cropping areas show a decrease in SOC stock content at least 5 t C ha⁻¹. SOC loss was greatest in the surface soils and decreased exponentially with depth. We further demonstrate that each Pedogenon can be used to define SOC sequestration potential. Understanding SOC change can provide information on areas under SOC loss threat and require immediate remediation.

人类对土壤的影响，特别是集约化农业的影响，在过去 200 年中最为明显。集约化农业活动导致世界许多地区土壤有机碳（SOC）下降。然而，缺乏能够在空间上估计由于人类影响而造成的 SOC 变化的方法。在这里，我们使用 Pedogenon 的概念将景观分层为称为 Pedogenon 的土壤类别。在每个 Pedogenon 中，我们对原生植被下的代表性土壤和人类密集管理下的土壤进行了采样。我们调查了澳大利亚新南威尔士州纳莫伊谷下游地区（1700 公里²），包括 13 个 Pedogenons（土壤类别），并分析了 99 个土壤核心的 SOC。使用数字土壤测绘技术，利用环境协变量将 SOC 数据用于每 10 cm 至 1 m 绘制 SOC。利用原生植被下的采样点绘制原生状态下的SOC，所有数据用于绘制SOC当前状态。通过比较两种状态（原始状态和当前状态）的 SOC 图，我们评估了 SOC 变化。结果表明，灌溉农作区SOC损失最大，地表SOC含量下降38%，其次是非灌溉作物（损失30%）和牧草（损失19%）。所有种植区的 SOC 库含量均减少至少 5 t C ha ⁻¹。表层土壤的 SOC 损失最大，并随深度呈指数下降。我们进一步证明每个 Pedogenon 都可以用来定义 SOC 封存潜力。了解 SOC 变化可以提供有关 SOC 损失威胁区域的信息，并需要立即采取补救措施。