目前关于农田耕作管理措施下，cbbL细菌对不同水平土壤碳饱和亏缺（SCSD）的响应机制仍不清楚。因此我们研究了长期免耕秸秆还田（NT）和常规耕作（CT）措施下，SCSD对cbbL细菌丰度和多样性的影响。结果表明，相比于CT，NT降低了SCSD，降低了cbbL细菌的丰度和香农指数，改变了cbbL细菌的群落结构。另外，土壤碳饱和和cbbL基因数量存在显著正相关关系，但是与cbbL基因多样性之间不存在相关关系。综上，低SCSD限制了cbbL细菌的丰度，但是对cbbL细菌的多样性没有影响。因此，关于cbbL细菌固碳速率和能力的研究，应该建立在耕作措施对cbbL细菌丰度和多样性影响的基础上。我们的研究揭示了土壤固定CO₂过程中生物机制和物理化学机制之间存在的关系，对于CO₂的固定机制研究具有重要意义。

Nitrification inhibitors, such as dicyandiamide (DCD), have been shown to decrease leaching from urea- and ammonium- based fertilizers in agricultural soils. The effect of nitrification inhibitors on nitrifier and denitrifier in short- and long-term intensive vegetable cultivation soils was poorly understood. In this study, the pot trial was conducted to investigate the differential responses of nitrifier (amoA-containing bacteria) and denitrifier (nirK-containing bacteria) to DCD in short-(soil S) and long-term (soil L) intensive vegetable cultivation soils. Quantitative polymerase chain reaction (qPCR) and terminal restriction fragment length polymorphism (T-RFLP) were employed to detect the abundance and composition of amoA- and nirK-containing communities. The results indicated that application of DCD led to a consistently higher NH4 +-N concentration during the whole incubation in soil L, while it was quickly decreased in soil S after 21 days. Furthermore, DCD induced more severe decrease of the abundance of amoA-containing bacteria in soil L than in soil S. However, the abundance of the nirKcontaining community was not significantly affected by DCD in both soils. Long-term vegetable cultivation resulted in a super-dominant amoA-containing bacteria group and less divergence in soil L compared with soil S, and DCD did not cause obvious shifts of the composition of ammonia-oxidising bacteria (AOB). On the contrary, both amoA- and nirK-containing bacterial compositions were influenced by DCD in soil S. The results suggested that long-term intensive vegetable cultivation with heavy nitrogen fertilization resulted in significant shifts of AOB community, and this community was sensitive to DCD, but denitrifiers were not clearly affected by DCD.