Soil carbon (C) stability is an important consideration for management that aims to increase long-term C storage. The fraction of soil C allocated to physico-chemically protected mineral-associated organic matter (MAOM) is a common soil C stability benchmark. However, the reality of soil C persistence is more complex than MAOM content alone—particularly in ecosystems such as meadows with high rates of belowground C inputs that can stimulate MAOM decomposition. Here, we combined three metrics of soil C persistence to characterize soil C stability across a meadow restoration chronosequence averaging belowground C gains of 330 g C m⁻² y⁻¹ for ~20 y. The metrics were: (1) the fraction of soil C in MAOM and particulate organic matter (POM), (2) the susceptibility of soil C to decomposition under varying temperatures, and (3) the utilization of MAOM-C by microbes. Two metrics suggested soil C stability may increase following montane meadow restoration. As soil C concentration increased with restoration, C storage in MAOM, but not POM, increased (metric 1). The susceptibility of MAOM-C to decomposition (microbial respiration relative to MAOM-C) decreased with increasing soil C concentration across temperatures (metric 2). Stable isotope results could not definitively determine the source of carbon dioxide efflux (metric 3) but generate hypotheses for future research to address. We posit that C sequestered following montane meadow restoration could be stable, with implications for regional C storage objectives. Further, our data point toward complex mineral-associated C dynamics including the potential importance of plant inputs for MAOM formation in meadow soils.

土壤碳 (C) 稳定性是旨在增加长期碳储存的管理的一个重要考虑因素。分配给受物理化学保护的矿物相关有机物 (MAOM) 的土壤碳比例是常见的土壤碳稳定性基准。然而，土壤碳持久性的实际情况比单独的 MAOM 含量更复杂，特别是在草地等生态系统中，地下碳输入率高，可以刺激 MAOM 分解。在这里，我们结合了土壤碳持久性的三个指标来表征整个草甸恢复时间序列的土壤碳稳定性，​​平均地下碳增益为 330 g C m ⁻² y ⁻¹ 约 20 年。指标为：(1) MAOM 和颗粒有机物 (POM) 中土壤碳的比例，(2) 土壤碳在不同温度下分解的敏感性，以及 (3) 微生物对 MAOM-C 的利用。两项指标表明，山地草甸恢复后土壤碳稳定性可能会增加。随着土壤碳浓度随着恢复而增加，MAOM（而非 POM）中的碳储存量增加（指标 1）。 MAOM-C 分解的敏感性（相对于 MAOM-C 的微生物呼吸）随着不同温度下土壤 C 浓度的增加而降低（指标 2）。稳定同位素结果无法明确确定二氧化碳流出的来源（指标 3），但可以为未来的研究提供假设以供解决。我们假设山地草甸恢复后固存的碳可能是稳定的，这对区域碳储存目标有影响。此外，我们的数据指出了与矿物相关的复杂碳动态，包括植物输入对草甸土壤中 MAOM 形成的潜在重要性。