Abstract. Land planning projects aiming to maximize soil organic carbon (SOC) stocks are increasing in number and scope, often in line with the objective to reach carbon neutrality by 2050. In response, a rising number of studies assesses where additional SOC could be stored over regional to global spatial scales. In order to provide realistic values transferrable beyond the scientific community, studies providing targets of SOC accrual should consider the timescales needed to reach them, taking into consideration the effects of C inputs, soil type, and depth on soil C dynamics. This research was conducted in a 320 km2 territory in north-eastern France, where eight contrasted soil types have been identified, characterized, and mapped thanks to a high density of fully described soil profiles. Continuous profiles of SOC stocks were interpolated for each soil type and land use (cropland, grassland, or forest). We defined potential targets for SOC accrual using percentile boundary lines and used a linear model of depth-dependent C dynamics to explore the C inputs necessary to reach those targets within 25 years. We also used values from the literature to model C input scenarios and provided maps of SOC stocks, maximum SOC accrual, and realistic SOC accrual over 25 years. SOC stocks and maximum SOC accrual are highly heterogenous over the region of study. Median SOC stocks range from 78–333 tC ha−1. Maximum SOC accrual varies from 19 tC ha−1 in forested Leptosols to 197 tC ha−1 in grassland Gleysols. The simulated realistic SOC accrual over 25 years in the whole region of study was one-fifth of the the maximum SOC accrual. Further consideration of depth-dependent SOC dynamics in different soil types is therefore needed to provide targets of SOC storage over timescales relevant to public policies aiming to approach carbon neutrality by 2050.

中文翻译：

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2050 年碳中和目标对不同土壤类型土壤有机碳额外封存能力的深度依赖性


摘要。旨在最大限度地提高土壤有机碳 （SOC） 储量的土地规划项目在数量和范围上都在增加，这通常与到 2050 年实现碳中和的目标一致。作为回应，越来越多的研究评估了在区域到全球空间尺度上可以存储额外 SOC 的位置。为了提供可在科学界之外转移的现实值，提供 SOC 应计目标的研究应考虑实现这些目标所需的时间尺度，同时考虑到 C 输入、土壤类型和深度对土壤 C 动态的影响。这项研究是在法国东北部 320 平方公里的领土上进行的，由于高密度的完全描述的土壤剖面，在那里已经确定、表征和绘制了八种对比鲜明的土壤类型。针对每种土壤类型和土地利用（农田、草地或森林）对 SOC 储量的连续剖面进行了插值。我们使用百分位边界线定义了 SOC 应计的潜在目标，并使用深度依赖性 C 动力学的线性模型来探索在 25 年内实现这些目标所需的 C 输入。我们还使用文献中的值对 C 输入情景进行建模，并提供了 25 年 SOC 存量、最大 SOC 应计和实际 SOC 应计的地图。SOC 库存和最大 SOC 应计在研究区域内具有高度异质性。SOC 储量中位数为 78–333 tC ha-1。最大 SOC 累积量从森林 Leptosols 的 19 tC ha-1 到草原 Gleysols 的 197 tC ha-1 不等。在整个研究区域 25 年内模拟的实际 SOC 应计是最大 SOC 应计的五分之一。 因此，需要进一步考虑不同土壤类型中深度依赖性土壤有机碳动态，以提供与旨在到 2050 年实现碳中和的公共政策相关的时间尺度上的土壤有机碳储存目标。