The response of soil microorganisms to elevated atmospheric CO₂ (eCO₂) has the potential to alter the regulation of soil biogeochemical processes including carbon and nutrient cycling. A mechanistic understanding of this microbial response in agricultural systems is essential due to the potential impact on soil quality. This study used an eight-year free-air-CO₂ enrichment (SoilFACE) experiment to assess the microbial response to eCO₂ in three major agricultural soils (Chromosol, Vertosol, and Calcarosol) planted annually with grain crops. Elevated CO₂ increased the number of operational taxonomic unit (OTU) by 14.3%, 13.3% and 4.1% and the Shannon diversity by 3.7%, 4.4%, and 2.6% in the top 5-cm soil layer of the Chromosol, Calcarosol and Vertosol, respectively. The relative abundance of the oligotroph Acidobacteriaceae Subgroup 1 in the top 5-cm soil of the Chromosol and Vertosol was significantly increased by eCO₂. Elevated CO₂ did not affect community diversity in the 5–10 cm soil layer. The functional attribute analysis of the bacterial communities showed that eCO₂ increased pectin and benzene degradation, the pentose phosphate pathway and the production of phytase-6 in the top 5-cm soil of the Chromosol. These results suggest that eCO₂ increases the presence of oligotrophs in the bacterial community and overall mineralization of soil organic carbon (SOC) in surface soils with high SOC. Changes in microbial function due to eCO₂ likely impact the stability of SOC and, consequently, the quality of farming soils for sustainable crop production.

土壤微生物对升高的大气CO ₂（eCO ₂）的响应具有改变土壤生物地球化学过程（包括碳和养分循环）的调控的潜力。由于对土壤质量的潜在影响，因此对农业系统中微生物响应的机械理解至关重要。这项研究使用了一项为期八年的自由空气CO ₂富集（SoilFACE）实验，以评估每年种植谷物作物的三种主要农业土壤（Chromosol，Vertosol和Calcarosol）对微生物对eCO _2的响应。升高的CO ₂在Chromosol，Calcarosol和Vertosol的最上面5厘米土壤层中，分别将操作分类单位（OTU）的数量增加了14.3％，13.3％和4.1％，并将Shannon多样性增加了3.7％，4.4％和2.6％。 。eCO ₂显着提高了嗜铬菌科亚群1的贫营养，其色浆和Vertosol顶部5厘米土壤的相对丰度。升高的CO ₂不会影响5-10 cm土壤层的群落多样性。细菌群落的功能属性分析表明，eCO ₂增加了果胶溶胶顶部5 cm土壤中的果胶和苯降解，磷酸戊糖途径和植酸酶6的产生。这些结果表明，eCO ₂会在细菌群落中增加寡营养菌的存在，并增加高SOC土壤表层土壤中有机碳（SOC）的总体矿化度。由eCO ₂引起的微生物功能变化可能会影响SOC的稳定性，进而影响可持续作物生产的耕作土壤质量。