5 Conclusion
This study demonstrated that 20 years of IM practice using MCM (combined inorganic fertilizer and manure application) in Moso bamboo plantation enhanced the content of SOC and available soil N, P, and K, although fluctuations were observed. Soil pH was generally stable with values between 5.0 and 5.5, indicating little acidification occurred. Soil CO2 and N2 fixing bacteria responded strongly to IM strongly in the short term and then gradually recovered over time, indicating an inherent resilience. The abundance of CO2-fixing bacteria eventually returned to their original levels but their communities did not. In contrast, the communities of N2-fixing bacteria recovered to their initial state while their abundances did over after 20 years of IM. The diversity of both groups of bacteria had a turning point after 10 years of IM, as reflected by higher values for Shannon and Evenness indices but lower values for the Simpson index compared with the remaining treatments. Both CO2 and N2 fixation bacterial groups had similar dominant species, but these differed in their relative abundances among the treatments and also exhibited different patterns in response to IM duration. The results indicated that relationships between potential environmental drivers and measures of abundance and community composition for both CO2- and N2- fixing bacteria are complex. Nevertheless, IM practice using MCM in Moso bamboo plantation appeared to have an overall positive effect on these bacterial groups as well as on associated soil properties.