In addition to the removal of excess mineral nitrogen (N) via root uptake, trees in agroforestry systems may mitigate negative effects of high N fertilization of adjacent crops by enhancing complete denitrification of excess mineral N aside from root uptake. Presently, little is known about the potential for NO₃⁻ reduction through denitrification (conversion to greenhouse gas N₂O and subsequently to non-reactive N₂) in contrasting agroforestry systems: riparian tree buffer versus tree row of an upland alley-cropping system. Our study aimed to (1) quantify gross N₂O emissions (both N₂O + N₂ emissions) and gross N₂O uptake (N₂O reduction to N₂), and (2) determine their controlling factors. We employed the ¹⁵N₂O pool dilution technique to quantify gross N₂O fluxes from 0 to 5 cm (topsoil) and 40 to 60 cm (subsoil) depths with seasonal field measurements in 2019. The riparian tree buffer exhibited higher topsoil gross N₂O emissions and uptake than the alley-cropping tree row (P < 0.03). Gross N₂O emissions were regulated by N and carbon (C) availabilities and aeration status rather than denitrification gene abundance. Gross N₂O uptake was directly linked to available C and nirK gene abundance. In the subsoil, gross N₂O emission and uptake were low in both agroforestry systems, resulting from low mineral N contents possibly due to N uptake by deep tree roots. Nonetheless, the larger available C and soil moisture in the subsoil of riparian tree buffer than in alley-cropping tree row (P < 0.05) suggest its large potential for N₂O uptake whenever NO₃⁻ is transported to the subsoil.

除了通过根部吸收去除过量的矿质氮（N）之外，农林系统中的树木还可以通过增强根部吸收之外的过量矿质氮的完全反硝化来减轻邻近作物高氮施肥的负面影响。目前，人们对对比农林业系统中通过反硝化（转化为温室气体 N ₂ O，随后转化为非反应性 N _{2 ）减少 NO 3} ⁻的潜力知之甚少：河岸树缓冲区与高地胡同作物系统的树行。我们的研究旨在 (1) 量化 N ₂ O 总排放量（N ₂ O + N ₂排放量）和 N ₂ O 总吸收量（N ₂ O 还原为 N ₂），以及 (2) 确定其控制因素。我们采用¹⁵ N ₂ O 池稀释技术，通过 2019 年的季节性现场测量来量化 0 至 5 厘米（表土）和 40 至 60 厘米（下土）深度的总 N ₂ O 通量。河岸树木缓冲区表现出较高的表土总 N ₂ O排放量和吸收量均高于胡茬林行( P  <0.03)。 N ₂ O 总排放量受氮和碳 (C) 可用性以及通气状态而非反硝化基因丰度的调节。 N _{2 O 总吸收量与可用的 C 和}nirK基因丰度直接相关。在两个农林复合系统的底土中，N ₂ O 总排放量和吸收量均较低，这可能是由于深层树根对氮的吸收所致，矿物质氮含量较低。尽管如此，河岸树缓冲区底土中的有效碳和土壤湿度比胡同种植树行中的更大（P  < 0.05），这表明每当NO ₃ ^-被输送到底土时，其吸收N _{2 O的潜力就很大。}