Existing studies suggest that biochar application can reduce soil nitrous oxide (N
2O) emissions, mainly based on short-term results. However, it remains unclear what the effects (i.e., legacy effects) and underlying mechanisms are on N
2O emissions after many years of a single application of biochar. Here, we collected intact soil columns from plots without and with biochar application in a subtropical tea plantation 7 years ago for an incubation experiment. We used the N
2O isotopocule analysis combined with ammonia oxidizer-specific inhibitors and molecular biology approaches to investigate how the legacy effect of biochar affected soil N
2O emissions. Results showed that the soil in the presence of biochar had lower N
2O emissions than the control albeit statistically insignificant. The legacy effect of biochar in decreasing N
2O emissions may be attributed to the reduced effectiveness of the soil substrate, nitrification and denitrification activities, and the promotion of the further reduction of N
2O. The legacy effect of biochar reduced the relative contribution of nitrifier denitrification/bacterial denitrification, nitrification-related N
2O production, and the relative abundance of several microorganisms involved in the nitrogen cycle. Our global meta-analysis also showed that the reduction of N
2O by biochar increased with increasing application rate but diminished and possibly even reversed with increasing experimental time. In conclusion, our findings suggest that the abatement capacity of biochar on soil N
2O emissions may weaken over time after biochar application, but this remains under further investigation.
相似文献