The effects of cropland abandonment on soil enzyme activity and soil organic carbon (SOC) stability, along with the driving factors, are poorly understood. Here, we aimed to systematically and comprehensively evaluate soil enzyme activity, SOC stability, and the associated driving factors in different vegetation zones after cropland abandonment on the Loess Plateau, China. We selected grasslands with different recovery times along a rainfall gradient encompassing the steppe zone (SZ), forest-steppe zone (FSZ), and forest zone (FZ). We measured and compared the changes in soil enzyme activity (saccharase, polyphenol oxidase, urease, phosphatase, and catalase) and SOC stability as a function of recovery time; we also evaluated the relationships between these two parameters. In SZ and FSZ, soil enzyme activity, fractions of oxidizable carbon (including very labile [C1], labile [C2], and less labile [C3]), and the carbon management index (CMI) increased with recovery time, whereas the SOC stability index (SI) decreased. Conversely, in FZ, polyphenol oxidase activity increased linearly, urease and catalase activities decreased linearly, and the change in saccharase activity was represented by a cubic equation regression. SI showed no obvious changes with recovery time, whereas C1, C2, and C3 initially decreased and then increased. Redundancy analysis showed that, in FSZ and FZ, soil enzyme activity, C1, C2, C3, and SI were influenced by vegetation diversity, coverage, and soil nutrient levels. In comparison, in SZ, these parameters were mainly influenced by soil nutrient levels. Soil enzyme activity was strongly correlated with C1 and C3 in SZ and FSZ, but not in FZ. Overall, in SZ and FSZ, soil enzyme activity increased with recovery time, whereas SOC stability decreased. In contrast, both parameters were relatively stable in FZ, which had higher mean annual precipitation and mean annual temperature.

人们对农田放弃对土壤酶活性和土壤有机碳（SOC）稳定性的影响以及驱动因素了解得很少。在此，我们旨在系统地，全面地评估黄土高原农田弃耕后不同植被区的土壤酶活性，SOC稳定性以及相关的驱动因素。我们沿着降雨梯度（草原区（SZ），森林草原区（FSZ）和森林区（FZ））选择了具有不同恢复时间的草地。我们测量并比较了土壤酶活性（蔗糖酶，多酚氧化酶，脲酶，磷酸酶和过氧化氢酶）和SOC稳定性随恢复时间的变化。我们还评估了这两个参数之间的关系。在SZ和FSZ中，土壤酶活性 可氧化碳的分数（包括非常不稳定的[C1]，不稳定的[C2]和较不稳定的[C3]）和碳管理指数（CMI）随着恢复时间的增加而增加，而SOC稳定性指数（SI）则下降。相反，在FZ中，多酚氧化酶活性呈线性增加，脲酶和过氧化氢酶活性呈线性下降，而蔗糖酶活性的变化由三次方程回归表示。SI随恢复时间显示无明显变化，而C1，C2和C3最初先下降然后上升。冗余度分析表明，在FSZ和FZ中，土壤酶活性，C1，C2，C3和SI受植被多样性，覆盖率和土壤养分水平的影响。相比之下，在深圳，这些参数主要受土壤养分水平的影响。在SZ和FSZ中，土壤酶活性与C1和C3密切相关，但不在FZ中。总体而言，在SZ和FSZ中，土壤酶活性随恢复时间而增加，而SOC稳定性下降。相反，这两个参数在FZ中相对稳定，平均年降水量和年平均温度都较高。