Microbial Community Imbalance Drives Nitrous Oxide Emissions from Strongly Acidic Soil—Insights from a Laboratory Experiment with Microbial Inhibitors

Nitrous oxide (N₂O) is a potent greenhouse gas with intensive emissions from acidic soil. This study explored the impact of the disruption of the microbial balance from microbial inhibitors (streptomycin and cycloheximide) on soil's N₂O emission and nitrogen (N) dynamics. Under all the conditions examined, biotic processes accounted for 96-98% of total N₂O emissions. High concentrations of streptomycin (6 and 10 mg g^-1) reduced N₂O emissions from 2.24 μg kg^-1 h^-1 to 1.93 μg kg^-1 h^-1 and 2.12 μg kg^-1 h^-1, respectively, whereas lower concentrations (2 and 4.5 mg g^-1) increased emissions from 2.24 μg kg^-1 h^-1 to 2.95 μg kg^-1 h^-1 and 3.27 μg kg^-1 h^-1, respectively. Lower cycloheximide (2 and 4.5 mg g^-1) significantly enhanced N₂O emissions, reaching 9.15 μg kg^-1 h^-1 and 5.68 μg kg^-1 h^-1, respectively, whereas higher dosages (6 mg g^-1 and 10 mg g^-1) inhibited N₂O emissions, reducing them to 5.55 μg kg^-1 h^-1 and 4.84 μg kg^-1 h^-1, respectively. Carbon dioxide (CO₂) emissions generally decreased with increasing inhibitor dosages but significantly increased at 2 mg g^-1 and 4.5 mg g^-1 streptomycin. The inhibitors also altered soil N and carbon (C) dynamics, increasing ammonium (NH₄⁺-N), dissolved organic nitrogen (DON), and dissolved organic carbon (DOC) levels. Pearson correlation analysis indicated that N₂O emission was negatively correlated with cycloheximide dosage (R = -0.68, <i>p</i> < 0.001), NH₄⁺-N (R = -0.31, <i>p</i> < 0.001) and DOC content (R = -0.57, <i>p</i> < 0.05). These findings highlight the consequences of microbial disruption on N₂O emission and the complex microbial interactions in acidic soils. High concentrations of microbial inhibitors effectively reduce N₂O emissions by suppressing key microbial groups in nitrification and denitrification. Conversely, lower concentrations may prompt compensatory responses from surviving microorganisms, resulting in increased N₂O production. Future research should focus on sustainable management strategies to mitigate N₂O emissions while preserving the soil's microbial community.