Wildfire is a major driver of nitrogen (N) cycling and export from terrestrial to aquatic systems. While fire is a natural process in many watersheds, it can still degrade water quality by rapidly flushing N to streams. This can be particularly problematic in watersheds that experience high levels of N deposition or where climate change is promoting larger and more severe fires. The extent and duration of postfire N export, and the potential consequences for downstream water quality, depend on how N inputs, internal cycling, and outputs vary before, during, and after fire. Here we review the major factors controlling N cycling and retention in forests and adjacent shrublands, and how fire modifies these controls. We connect burned slopes to streams to describe how fire exports N to aquatic environments. We also consider the implications for municipal watersheds and water resources management. We close by identifying critical knowledge gaps in projecting how fire will affect watershed N cycling and retention in the future.

野火是氮 (N) 循环和从陆地系统向水生系统输出的主要驱动力。虽然火灾是许多流域的自然过程，但它仍然会通过将 N 快速冲入溪流而降低水质。这在经历高水平氮沉降或气候变化导致更大和更严重火灾的流域尤其成问题。火灾后氮输出的范围和持续时间，以及对下游水质的潜在后果，取决于氮输入、内部循环和输出在火灾前、期间和之后如何变化。在这里，我们回顾了控制森林和邻近灌木丛中氮循环和保留的主要因素，以及火灾如何改变这些控制。我们将燃烧的斜坡连接到溪流，以描述火如何将 N 输出到水生环境。我们还考虑了对市政流域和水资源管理的影响。我们通过确定未来火灾将如何影响流域氮循环和保留的关键知识差距来结束。