Clarifying the responses of different N₂O production pathways to pH change is helpful to better understand the effect of pH on N₂O emission from soils. A¹⁵N tracing study was carried out on subtropical forest (SF) and cropland (SC) soil in 30-day pH manipulation treatments to quantify the effect of pH on autotrophic nitrification, heterotrophic nitrification and denitrification-derived N₂O. Gene abundances of autotrophic nitrification (AOA-amoA, AOB-amoA) and denitrification (nirK, nirS, nosZ) -related N₂O production were determined to identify the microbial mechanism behind the pH effect on N₂O production. The results showed that the total N₂O production rate (N₂O_t) of the SF soil was 4.56 and 4.86 μg N kg⁻¹ day⁻¹ at pH 3.5 and 4.5, respectively, which was significantly higher than the other treatments. Similarly, the highest N₂O_t of the SC soil was also observed in pH 3.5 treatment (7.15 μg N kg⁻¹ day⁻¹). Both N₂O production rate via denitrification (N₂O_d) and heterotrophic nitrification (N₂O_h) markedly increased, while the N₂O production rate via autotrophic nitrification (N₂O_a) markedly decreased by decreasing pH in both the SF and SC soil. Thus, denitrification and heterotrophic nitrification were responsible for the high N₂O production under strongly acidic conditions. The abundance of nosZ gene was significantly and negatively correlated with N₂O_d (P < 0.05), and the abundance of AOB-amoA was significantly and positively correlated with N₂O_a (P < 0.01). The results of the structural equation modeling (SEM) analysis revealed that soil pH generated a more direct effect on the denitrifying and ammonia-oxidizing gene abundance, in turn, affected N₂O_d and N₂O_a, respectively. In addition, soil pH exerted a significant effect on both the bacterial 16S rRNA and fungal ITS rDNA gene abundance (P < 0.05). However, the role of soil fungi and bacteria on N₂O_h could not be determined in this study.

阐明不同N ₂ O 生产途径对pH 变化的响应有助于更好地了解pH 对土壤N ₂ O 排放的影响。对亚热带森林 (SF) 和农田 (SC) 土壤进行了为期 30 天的 pH 操纵处理的¹⁵ N 示踪研究，以量化 pH 对自养硝化、异养硝化和反硝化衍生的 N ₂ O 的影响。自养硝化 (AOA- amoA , AOB- amoA ) 和反硝化 ( nirK , nirS , nosZ ) 相关的 N ₂确定 O 产量是为了确定 pH 值对 N ₂ O 产量的影响背后的微生物机制。结果表明， 在pH 3.5和4.5下，SF土壤的总N ₂ O产生率（N ₂ O _t）分别为4.56和4.86 μg N kg ^-1 day ^-1，显着高于其他处理。类似地，在pH 3.5 处理（7.15 μg N kg ^-1天^-1）中也观察到SC 土壤的最高N ₂ O _t。均为N ₂通过反硝化（N 2 O生成率₂ ö _d）和异养硝化（N₂ O _h ) 显着增加，而通过自养硝化作用 (N ₂ O _a )产生的 N ₂ O 的生成率随着 SF 和 SC 土壤中 pH 值的降低而显着降低。因此，反硝化作用和异养硝化作用是在强酸性条件下产生高 N ₂ O 的原因。nosZ基因丰度与N ₂ O _d显着负相关（P  < 0.05），AOB- amoA丰度与N ₂ O _a显着正相关（P < 0.01)。结构方程模型（SEM）分析结果表明，土壤pH值对反硝化和氨氧化基因丰度产生更直接的影响，进而分别影响N ₂ O _d和N ₂ O _a。此外，土壤pH值对细菌16S rRNA和真菌ITS rDNA基因丰度均有显着影响（P  < 0.05）。然而，本研究无法确定土壤真菌和细菌对 N ₂ O _h的作用。