Organic mulching is an effective forest management technique that provides carbon and nutrient sources to soil ecosystems, thereby improving the soil environment and promoting plant growth. Although the importance of rhizosphere microbiomes in plant and soil ecosystem functions has been widely recognised, the effect of organic mulching on rhizosphere microorganisms and the underlying mechanisms are unclear. We performed a field experiment in a 15-year-old Ligustrum lucidum forest of urban green space. The diversity and composition of the rhizosphere bacterial and fungal communities following organic mulching were assessed by combining 16S ribosomal RNA and internal transcribed spacer amplicon sequencing. The correlations between microbial diversity, composition, and fine-root traits, as well as rhizosphere soil properties, were also analysed. The results showed that organic mulching did not significantly affect the diversity of the rhizosphere bacterial or fungal communities on the whole, but it increased the bacterial diversity after 6 months, with a 20-cm-thick mulch layer showing a greater effect than 5- or 10-cm layers. Organic mulching significantly altered the rhizosphere bacterial and fungal community composition; after 6 months of mulching, the community compositions were significantly associated with fine-root traits (specific root length, nitrogen, and phosphorus concentration) and enzyme (urease and dehydrogenase) activity. Moreover, alterations in the bacterial and fungal communities occurred at the order level within each mulching stage. Bacterial diversity is affected by fungal diversity and rhizosphere soil properties (water content and organic carbon) in time-dependent manners. Hence, organic mulching appears to directly affect the fungal composition while indirectly affecting the bacterial composition via influencing rhizosphere soil properties (dissolved organic carbon and peroxidase activity). Our study suggests that organic mulching affects the rhizosphere bacterial and fungal community composition through different pathways; however, the underlying mechanisms, including the effects of time and soil layers, require further exploration combined with multi-index measurements and long-term dynamic monitoring.

有机覆盖是一种有效的森林管理技术，可为土壤生态系统提供碳源和营养源，从而改善土壤环境，促进植物生长。尽管根际微生物组在植物和土壤生态系统功能中的重要性已得到广泛认可，但有机覆盖对根际微生物的影响及其潜在机制尚不清楚。我们在 15 岁的女贞子中进行了田间试验城市绿地森林。通过结合 16S 核糖体 RNA 和内部转录间隔扩增子测序，评估了有机覆盖后根际细菌和真菌群落的多样性和组成。还分析了微生物多样性、组成和细根性状以及根际土壤特性之间的相关性。结果表明，有机覆盖总体上对根际细菌或真菌群落的多样性没有显着影响，但在 6 个月后增加了细菌多样性，20 厘米厚的覆盖层比 5 或10 厘米层。有机覆盖显着改变了根际细菌和真菌群落组成；经过6个月的覆盖，群落组成与细根性状（特定根长、氮和磷浓度）和酶（脲酶和脱氢酶）活性显着相关。此外，细菌和真菌群落的改变发生在每个覆盖阶段的有序水平上。细菌多样性受真菌多样性和根际土壤特性（含水量和有机碳）的影响随时间变化。因此，有机覆盖似乎直接影响真菌组成，同时通过影响根际土壤特性（溶解有机碳和过氧化物酶活性）间接影响细菌组成。我们的研究表明，有机覆盖通过不同途径影响根际细菌和真菌群落组成；然而，潜在的机制，