Soil organic carbon (SOC) is closely tied to soil health. However, additional biological indicators may also provide insight about C dynamics and microbial activity. We used SOC and the other C indicators (potential C mineralization, permanganate oxidizable C, water extractable organic C, and β-glucosidase enzyme activity) from the North American Project to Evaluate Soil Health Measurements to examine the continental-scale drivers of these indicators, the relationships among indicators, and the effects of soil health practices on indicator values. All indicators had greater values at cooler temperatures, and most were greater with increased precipitation and clay content. The indicators were strongly correlated with each other at the site-level, with the strongest relationship between SOC and permanganate oxidizable C. The indicator values responded positively to decreased tillage, inclusion of cover crops, application of organic nutrients, and retention of crop residue, but not the number of harvested crops in a rotation. The effect of decreased tillage on the C indicators was generally greater at sites with higher precipitation. The magnitude and direction of the response to soil health practices was consistent across indicators within a site but measuring at least two indicators would provide additional confidence of the effects of management, especially for tillage. All C indicators responded to management, an essential criterion for evaluating soil health. Balancing the cost, sensitivity, interpretability, and availability at commercial labs, a 24-hr potential C mineralization assay could deliver the most benefit to measure in conjunction with SOC.

土壤有机碳 (SOC) 与土壤健康密切相关。然而，额外的生物指标也可以提供有关 C 动力学和微生物活动的见解。我们使用北美项目评估土壤健康测量的 SOC 和其他 C 指标（潜在 C 矿化、高锰酸盐可氧化 C、水可提取有机 C 和 β-葡萄糖苷酶活性）来检查这些指标的大陆尺度驱动因素，指标之间的关系，以及土壤健康实践对指标值的影响。所有指标在较冷的温度下都有较大的值，并且随着降水和粘土含量的增加，大多数指标都较大。各指标在位点水平上具有很强的相关性，其中 SOC 与高锰酸盐可氧化 C 之间的相关性最强。指标值对减少耕作、覆盖作物、有机养分的施用和作物残留物的保留作出积极反应，但对轮作中收获的作物数量没有积极反应。在降水量较高的地点，减少耕作对 C 指标的影响通常更大。对土壤健康实践的反应幅度和方向在一个场地内的各个指标上是一致的，但测量至少两个指标将提供对管理效果的额外信心，特别是对于耕作。所有 C 指标都对管理作出反应，管理是评估土壤健康的基本标准。平衡商业实验室的成本、灵敏度、可解释性和可用性，24 小时潜在 C 矿化分析可以提供与 SOC 结合测量的最大好处。