We examined the relative effects of long-term (25 years) intensive management on abundance and diversity of soil CO₂-assimilating bacteria in a Phyllostachys pubescens (moso bamboo) forest. Soil samples in moso bamboo stands receiving 0 (control; CK), 10, 15, 20, and 25 years of intensive management were collected from the topsoil (0-20 cm) and subsoil (20-40 cm) layers separately and analyzed using quantitative PCR (q-PCR), terminal restriction fragment length polymorphism (T-RFLP), and a clone library of the cbbL gene. Differences in the community structure of CO₂-assimilating bacteria over time and its relationship with soil properties were detected using redundancy analysis (RDA). We found that long-term intensive management significantly increased soil nutrient content but decreased soil pH. Among the soil parameters measured, N content influenced cbbL abundance, but soil organic carbon (SOC) did not. During the intensive management process, the bacterial cbbL abundance in topsoil increased in the first 10 years and then decreased, and it correlated positively with nitrogen levels (P < 0.05); conversely, in subsoil, cbbL abundance decreased linearly with time and showed a positive correlation with C:N ratio (P < 0.05). Intensive management of P. pubescens altered the community structure of CO₂-assimilating bacteria in both topsoil and subsoil, and induced a decline in the species diversity indices of CO₂-assimilating bacteria in topsoil. The results for the cbbL clone library indicated that uncultured bacteria accounted for up to 56% of the species present. The dominant species in the soil were facultative autotrophic bacteria such as Proteobacteria and Actinobacteria. RDA indicated that the changes in community structure and diversity of CO₂-assimilating bacteria resulted from soil acidification and nutrient accumulation.