<b>Data for opposing effects</b><b> of maize straw and its biochar on soil N</b>_{<strong>2</strong>}<b>O emissions</b><b> </b><b>by mediating microbial nitrification and denitrification in a subtropical Moso bamboo forest</b>

Application of straw and biochar has been shown to significantly affect greenhouse gas emissions from soil. However, microbial mechanisms underlying the effects on soil N₂O effluxes within subtropical Moso bamboo forests remain elusive. This study aimed to assess the contrasting influences of maize straw and its derived biochar on soil N₂O emissions by meditating key functional microbial genes and communities involved in soil nitrification and denitrification within a subtropical Moso bamboo forest. Straw amendment (5 t C ha⁻¹) stimulated N₂O emission by 16–27% (P &lt; 0.05). However, biochar addition (5 t C ha⁻¹) reduced available N, i.e., 11.1–13.9% for NH₄⁺, 11.0–14.8% for NO₃⁻ and 13.8–16.6% WSON, and decreased the abundances of nitrification/denitrification genes (39.0–44.6% for AOB <i>amoA</i>, 29.5–35.5% for <i>nirK</i>, 24.4–31.8% for <i>nirS</i>) and associated genera <i>Nitrosospira</i>, <i>Mesorhizobium</i>, <i>Bradyrhizobium</i>, <i>Rhizobium</i>, <i>Pseudomonas</i>, and <i>Cupriavidus</i>. Biochar also decreased the activities of enzymes related to organic N hydrolysis (protease and urease) and denitrification (nitrate reductase and nitrite reductase); and thus decreased N₂O emissions by 17–20% (P &lt; 0.05). Furthermore, biochar enhanced the abundance of <i>nosZ </i>gene (39.9–45.9%) and its dominant genera (<i>Mesorhizobium</i>, <i>Bradyrhizobium</i>, and <i>Azospirillum</i>), which facilitated N₂O reduction. In contrast, straw inhibited growth of these dominant genera and lowered the abundance of <i>nosZ </i>gene (24.4–38.3%); thereby increasing N₂O emissions. These results highlight the varied responses of nitrification and denitrification processes and hence N₂O emission to the application of straw and biochar in soils of a subtropical Moso bamboo forest.