The soil organic carbon (SOC) mineralization rate in sandy soil plays an important role in improving soil quality, and a research is needed to determine management practices that optimize the mineralization rate. When sandy soil is improved by adding soft rock, the specific promotion process of bacterium to SOC mineralization remain unclear. To investigate these mechanisms, we selected four treatments with soft rock to sand volume ratios of 0:1 (CK), 1:5 (C1), 1:2 (C2) and 1:1 (C3) to study. The mineralization rate of organic carbon was measured using the lye absorption method. High-throughput sequencing and scanning electron microscopy were used to determine the bacterial community structure and soil microstructure, respectively. The results showed that the organic carbon content of the sandy soil increased significantly (182.22–276.43%) after using the soft rock treatments. The SOC mineralization rate could be divided into two stages: a rapid decline during days 1–8 and a slow decline during days 8–60. With increased incubation time, the intensity of the cumulative release of organic carbon gradually weakened. Compared with the CK treatment, the SOC mineralization accumulation (Ct) and the potential mineralizable organic carbon content (C₀) in the C1, C2, and C3 treatments increased significantly, by 106.98–225.94% and 112.22–254.08%, respectively. The cumulative mineralization rate (Cr) was 18.11% and 21.38% smaller with treatments C2 and C3, respectively. The SOC mineralization rate constant (k) decreased significantly after the addition of soft rock, while the half-turnover period (Th) changed inversely with k. Compared with the CK treatment, the number of gene copies of the soil bacteria increased by 15.38–272.53% after adding soft rock, with the most significant increase in treatment C3. The bacterial diversity index also increased significantly under treatment C3. The three dominant bacteria were Proteobacteria, Actinobacteria, and Chloroflexi. The correlation between C_r and one of the non-dominant bacteria, Firmicutes, was large, and the bacteria had a significant positive correlation with k. At the same time, the abundance of Firmicutes under treatments C2 and C3 was small. As the proportion of soft rock increased, the soil particles changed from point contact to surface contact, and the adhesion on the surface of the particles gradually increased. Results from this study show that the retention time of SOC can be increased and the carbon sequestration effect is better when the ratio of soft rock to sand is set to 1:2.

中文翻译：

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软岩-砂复合土壤细菌多样性与有机碳矿化的关系。

沙质土壤中的有机碳（SOC）矿化率在改善土壤质量方面起着重要作用，需要进行研究以确定优化矿化率的管理措施。当通过添加软岩来改善沙质土壤时，细菌促进SOC矿化的具体过程仍不清楚。为了研究这些机理，我们选择了四种软岩砂体积比为0：1（CK），1：5（C1），1：2（C2）和1：1（C3）的处理方法进行研究。使用碱液吸收法测量有机碳的矿化率。高通量测序和扫描电镜分别用于确定细菌群落结构和土壤显微结构。结果表明，沙质土壤中的有机碳含量显着增加（182.22–276。43％）。SOC的矿化率可以分为两个阶段：第1-8天迅速下降，第8-60天缓慢下降。随着孵育时间的增加，有机碳累积释放的强度逐渐减弱。与CK处理相比，SOC矿化累积量（Ct）和潜在的可矿化有机碳含量（C₀）在C1，C2和C3处理中分别显着增加，分别增加了106.98–225.94％和112.22–254.08％。处理C2和C3的累积矿化率（Cr）分别降低18.11％和21.38％。添加软岩后，SOC矿化速率常数（k）显着降低，而半周转期（Th）与k成反比。与CK处理相比，添加软岩后土壤细菌的基因拷贝数增加了15.38–272.53％，其中处理C3的增加最为明显。在处理C3下，细菌多样性指数也显着增加。三种主要细菌是Proteobacteria，Actinobacteria和Chloroflexi。C _r之间的相关性非优势细菌之一Firmicutes很大，并且该细菌与k呈显着正相关。同时，在处理C2和C3下的沙门氏菌的丰度很小。随着软岩比例的增加，土壤颗粒从点接触变为表面接触，颗粒表面的附着力逐渐增加。这项研究的结果表明，当软岩与砂的比例设定为1：2时，SOC的保留时间会增加，碳固存效果会更好。