Regulation of Soil Nitrogen Turnover and N2O Emissions by Silicon in Intensively Managed Phyllostachys edulis (Carrière) J.Houz. Forests

Intensive nitrogen (N) fertilization in Phyllostachys edulis (Carrière) J.Houz. forests increases productivity but also accelerates nitrous oxide (N2O) emissions, posing a challenge to balancing forest yield with environmental sustainability. Silicon (Si), a beneficial element for bamboo, has emerged as a potential regulator of soil nitrogen (N) cycling, but its role in controlling N2O emissions in forest ecosystems is not fully understood. In this study, we conducted a factorial pot experiment using P. edulis forest soil, with data collected over two years, but only the second-year results were analyzed, with controlled N (0, 80, and 160 mg kg−1) and Si (0, 25, and 50 mg kg−1) additions. The experiment lasted two years, but only the second-year data were used for analysis. We investigated how Si affected soil inorganic N dynamics, enzyme activities, plant growth, and cumulative N2O emissions. Si addition significantly reduced N-induced N2O emissions by up to 53%, with the strongest mitigation observed under moderate N input (p < 0.05, two-way ANOVA). This effect was associated with lower activities of AMO, NaR, and NiR, together with reduced availability of oxidized N substrates, indicating that Si mitigated N2O emissions mainly by constraining upstream N transformation processes rather than by directly suppressing N2O fluxes. Si addition also tended to promote plant biomass accumulation. These findings suggest that integrating Si fertilization into bamboo forest management may help improve nutrient use efficiency while mitigating greenhouse gas emissions.