Post-agricultural natural restoration is a worldwide strategy for eco-environmental sustainability. However, it is unclear how it affects soil organic carbon (SOC) pools and composition among soil types across climate gradient. Here, we investigated 23-year post-agricultural restorations of SOC in three soils: Luvic Phaeozem, Calcaric Cambisol and Ferralic Cambisol typical for mid-temperate, warm-temperate and subtropical zones, respectively. Six SOC fractions with different protection mechanisms (non-protected, physically, chemically, biochemically, physico-chemically and physico-biochemically) were separated. Compared with pre-restoration in 1990, post-agricultural restoration rebuilt SOC similarly (+68–+91%) among the three soils despite of different SOC background. Compared with continuous cultivation, post-agricultural restoration increased total SOC pools in all the three soils (+33–+60%) mainly because of the increments of non-protected pool (coarse particulate organic C, cPOC). However, the pure physically, chemically, and biochemically protected SOC fractions were less sensitive to post-agricultural restoration. The physico-biochemically protected SOC was hampered by restoration in the two temperate soils but remained stable in the subtropical soil, suggesting a divergent self-restoring trend. Positive correlations of the total SOC and most fractions with wetness (precipitation/temperature ratio) demonstrated the climate dependency of SOC. In conclusion, post-agricultural natural restoration builds up SOC pool mainly due to the cPOC increment and shifts SOC composition towards more easily available C in three soils across the climatic gradient.

农业后自然恢复是生态环境可持续性的全球战略。然而，目前尚不清楚它如何影响气候梯度下土壤有机碳（SOC）库和土壤类型的组成。在这里，我们调查了三种土壤的SOC的23年农业后恢复情况：Luvic Phaeozem，Calcaric Cambisol和Ferralic Cambisol分别用于中温带，暖温带和亚热带地区。分离了具有不同保护机制（未保护，物理，化学，生物化学，物理化学和物理生物化学）的六个SOC馏分。与1990年的恢复相比，尽管不同的SOC背景，但在三种土壤中，农业后的恢复重建SOC相似（+ 68– + 91％）。与连续栽培相比 农业后的恢复增加了所有三种土壤的总SOC库（+ 33– + 60％），这主要是由于未保护的库（粗粒有机碳，cPOC）的增加所致。但是，纯的物理，化学和生物化学保护的SOC馏分对农业后的恢复较不敏感。在两个温带土壤中，受物理生化保护的SOC受阻，但在亚热带土壤中仍保持稳定，表明存在不同的自我恢复趋势。总SOC和大部分水分含量与湿度（降水/温度比）呈正相关，证明了SOC的气候依赖性。结论，