Abstract. Simulation models are potentially useful tools to test our understanding of the processes involved in the turnover of soil organic carbon (SOC) and to evaluate the role of management practices in maintaining stocks of SOC. We describe here a simple model of SOC turnover at the soil profile scale that accounts for two key processes determining SOC persistence (i.e. microbial energy limitation and physical protection due to soil aggregation). We tested the model and evaluated the identifiability of key parameters using topsoil SOC contents measured in three treatments with contrasting organic matter inputs (i.e. fallow, mineral fertilized and cropped, with and without straw addition) in a long-term field trial. The estimated total input of organic matter (OM) in the treatment with straw added was roughly three times that of the treatment without straw addition, but only 12 % of the additional OM input remained in the soil after 54 years. By taking microbial energy limitation and enhanced physical protection of root residues into account, the model could explain the differences in C persistence among the three treatments, whilst also accurately matching the time-courses of SOC contents using the same set of model parameters. Models that do not explicitly consider microbial energy limitation and physical protection would need to adjust their parameter values (either decomposition rate constants or the retention coefficient) to match this data. We also performed a sensitivity analysis to identify the most influential parameters in the model determining soil profile stocks of OM at steady-state. Input distributions for soil and crop parameters in the model were defined for the agricultural production area of PO4 (east-central Sweden), which includes Uppsala. The resulting model predictions compared well with aggregated soil survey data for the PO4 region. This analysis showed that model parameters affecting SOC decomposition rates, including the rate constant for microbial-processed SOC and the parameters regulating physical protection and microbial energy limitation, are more sensitive than parameters determining OM inputs. Thus, the development of pedotransfer approaches to estimate SOC decomposition rates from soil properties would help to support predictive applications of the model at larger spatial scales.

中文翻译：

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土壤剖面中有机碳周转的简单模型：模型检验、参数识别和敏感性


摘要。模拟模型可能是有用的工具，可以测试我们对土壤有机碳 （SOC） 周转所涉及的过程的理解，并评估管理实践在维持土壤有机碳库存中的作用。我们在这里描述了一个土壤剖面尺度上 SOC 周转的简单模型，该模型解释了决定 SOC 持久性的两个关键过程（即微生物能量限制和土壤聚集引起的物理保护）。我们在一项长期田间试验中，使用三种处理中测量的表层土壤有机碳含量（即休耕、矿物施肥和种植，添加和不添加秸秆）测试模型并评估关键参数的可识别性。在添加秸秆的处理中，有机质 （OM） 的估计总输入量大约是不添加秸秆的处理的三倍，但 54 年后，只有 12% 的额外 OM 输入留在土壤中。通过考虑微生物能量限制和加强对根残基的物理保护，该模型可以解释三种处理之间 C 持久性的差异，同时还可以使用同一组模型参数准确匹配 SOC 含量的时间进程。未明确考虑微生物能量限制和物理保护的模型需要调整其参数值（分解速率常数或保留系数）以匹配这些数据。我们还进行了敏感性分析，以确定确定稳态 OM 土壤剖面储量的模型中最具影响力的参数。 模型中土壤和作物参数的输入分布是针对 PO4（瑞典中东部）的农业生产区定义的，其中包括乌普萨拉。所得模型预测与 PO4 区域的聚合土壤调查数据进行了很好的比较。该分析表明，影响 SOC 分解速率的模型参数，包括微生物加工 SOC 的速率常数以及调节物理保护和微生物能量限制的参数，比决定 OM 输入的参数更敏感。因此，开发从土壤特性估计 SOC 分解速率的 pedotransfer 方法将有助于支持模型在更大空间尺度上的预测应用。