Soil organic carbon (SOC) is important for soil quality and fertility in forest ecosystems. Labile SOC fractions are sensitive to environmental changes, which reflect the impact of short-term internal and external management measures on the soil carbon pool. Organic mulching (OM) alters the soil environment and promotes plant growth. However, little is known about the responses of SOC fractions in rhizosphere or bulk soil to OM in urban forests and its correlation with carbon composition in plants. A one-year field experiment with four treatments (OM at 0, 5, 10, and 20 cm thicknesses) was conducted in a 15-year-old Ligustrum lucidum plantation. Changes in the SOC fractions in the rhizosphere and bulk soil; the carbon content in the plant fine roots, leaves, and organic mulch; and several soil physicochemical properties were measured. The relationships between SOC fractions and the measured variables were analysed. The OM treatments had no significant effect on the SOC fractions, except for the dissolved organic carbon (DOC). OM promoted the movement of SOC to deeper soil because of the increased carbon content in fine roots of subsoil. There were significant correlations between DOC and microbial biomass carbon and SOC and easily oxidised organic carbon. The OM had a greater effect on organic carbon fractions in the bulk soil than in the rhizosphere. The thinnest (5 cm) mulching layers showed the most rapid carbon decomposition over time. The time after OM had the greatest effect on the SOC fractions, followed by soil layer. The frequent addition of small amounts of organic mulch increased SOC accumulation in the present study. OM is a potential management model to enhance soil organic matter storage for maintaining urban forest productivity.

中文翻译：

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有机覆盖促进了城市人工林中土壤有机碳积累到土壤深层

土壤有机碳（SOC）对于森林生态系统的土壤质量和肥力至关重要。不稳定的SOC组分对环境变化敏感，这反映了短期内部和外部管理措施对土壤碳库的影响。有机覆盖（OM）可以改变土壤环境并促进植物生长。然而，关于城市森林中根际或块状土壤中SOC组分对OM的响应及其与植物碳组成的相关性知之甚少。在具有15年历史的女贞子人工林中进行了为期一年的野外试验，其中进行了四种处理（厚度分别为0、5、10和20厘米的OM）。根际和块状土壤中SOC含量的变化；植物细根，叶片和有机覆盖物中的碳含量；并测定了几种土壤理化特性。分析了SOC分数与测量变量之间的关系。除溶解的有机碳（DOC）外，OM处理对SOC分数无显着影响。由于底土细根中碳含量的增加，OM促进了SOC向更深土壤的移动。DOC与微生物生物量碳和SOC与易氧化有机碳之间存在显着相关性。OM对块状土壤中有机碳组分的影响要大于根际。随着时间的推移，最薄的覆盖层（5厘米）显示出最快的碳分解速度。OM处理后的时间对SOC的影响最大，其次是土壤层。在本研究中，频繁添加少量有机覆盖物会增加SOC的积累。