Nitrogen (N) trace gas emission pulses produced after wetting dry soils may be important pathways of ecosystem N loss. However, the rates and mechanisms controlling these emissions remain unclear. We tested whether changes in microbial community structure and increased rates of atmospheric N deposition could explain N emissions at two desert sites differing in atmospheric N deposition by ~ six fold. We measured peak NO x (sum of nitric oxide and nitrogen dioxide) emissions 12 h post-wetting. NO x emissions remained elevated over 24 h and increased after adding N. In contrast, we measured the highest nitrous oxide (N 2 O) emissions within only 15 min post-wetting. N 2 O emissions decreased within 12 h, were insensitive to adding N, and were among the highest reported globally. Microbial communities at the high N deposition site were less diverse with higher 16S nitrifier and bacterial amoA gene abundances relative to the low N deposition site, suggesting an increased capacity for nitrification. Nevertheless, N emissions were lower at the high N deposition site. While microbial communities changed after wetting, these changes were not correlated with N emissions. We conclude that desert soils can produce substantial NO x and N 2 O emission pulses, but that these emissions do not appear directly governed by changing microbial community characteristics or higher atmospheric N inputs. These findings highlight the importance of gaseous N loss pathways from dryland ecosystems that may contribute to sustained N limitation, with implications for atmospheric chemistry and Earth’s climate.

中文翻译：

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来自沙漠土壤和相关微生物组的大量氮氧化物排放脉冲

湿润干燥土壤后产生的氮 (N) 痕量气体排放脉冲可能是生态系统 N 损失的重要途径。然而，控制这些排放的速率和机制仍不清楚。我们测试了微生物群落结构的变化和大气 N 沉积速率的增加是否可以解释大气 N 沉积差异约 6 倍的两个沙漠地点的 N 排放。我们测量了润湿后 12 小时的峰值 NOx（一氧化氮和二氧化氮的总和）排放量。NO x 排放量在 24 小时内保持升高，并在添加 N 后增加。相比之下，我们在润湿后仅 15 分钟内测量到最高的一氧化二氮 (N 2 O) 排放量。N 2 O 排放量在 12 小时内下降，对添加 N 不敏感，是全球报告的最高水平之一。与低氮沉积位点相比，高氮沉积位点的微生物群落多样性较低，具有更高的 16S 硝化菌和细菌 amoA 基因丰度，表明硝化能力增加。尽管如此，高氮沉积地点的氮排放量较低。虽然润湿后微生物群落发生了变化，但这些变化与 N 排放无关。我们得出结论，沙漠土壤可以产生大量的 NO x 和 N 2 O 排放脉冲，但这些排放似乎不受微生物群落特征变化或更高的大气 N 输入的直接控制。这些发现强调了来自旱地生态系统的气态氮损失途径的重要性，这可能导致持续的氮限制，对大气化学和地球气候产生影响。