Increased occurrence, size, and intensity of fire result in significant but variable changes to hydrology and material retention in watersheds with concomitant effects on stream biogeochemistry. In arid regions, seasonal and episodic precipitation results in intermittency in flows connecting watersheds to recipient streams that can delay the effects of fire on stream chemistry. We investigated how the spatial extent of fire within watersheds interacts with variability in amount and timing of precipitation to influence stream chemistry of three forested, montane watersheds in a monsoonal climate and four coastal, chaparral watersheds in a Mediterranean climate. We applied state-space models to estimate effects of precipitation, fire, and their interaction on stream chemistry up to five years following fire using 15 + years of monthly observations. Precipitation alone diluted specific conductance and flushed nitrate and phosphate to Mediterranean streams. Fire had positive and negative effects on specific conductance in both climates, whereas ammonium and nitrate concentrations increased following fire in Mediterranean streams. Fire and precipitation had positive interactive effects on specific conductance in monsoonal streams and on ammonium in Mediterranean streams. In most cases, the effects of fire and its interaction with precipitation persisted or were lagged 2–5 years. These results suggest that precipitation influences the timing and intensity of the effects of fire on stream solute dynamics in aridland watersheds, but these responses vary by climate, solute, and watershed characteristics. Time series models were applied to data from long-term monitoring that included observations before and after fire, yielding estimated effects of fire on aridland stream chemistry. This statistical approach captured effects of local-scale temporal variation, including delayed responses to fire, and may be used to reduce uncertainty in predicted responses of water quality under changing fire and precipitation regimes of arid lands.

火灾发生率、规模和强度的增加导致流域水文和物质滞留发生显着但可变的变化，同时对河流生物地球化学产生影响。在干旱地区，季节性和间歇性降水会导致连接流域和受纳河流的水流出现间歇性，从而延迟火灾对河流化学的影响。我们研究了流域内火灾的空间范围如何与降水量和时间的变化相互作用，从而影响季风气候下三个森林山地流域和地中海气候下四个沿海丛林流域的河流化学。我们应用状态空间模型，利用 15 年以上的月度观测来估计降水、火灾及其相互作用对火灾发生后五年内河流化学的影响。仅降水就稀释了比电导，并将硝酸盐和磷酸盐冲入地中海溪流。火灾对两种气候下的电导率都有积极和消极的影响，而地中海河流中的铵和硝酸盐浓度在火灾后增加。火灾和降水对季风溪流的比电导率和地中海溪流的铵具有积极的交互作用。在大多数情况下，火灾及其与降水的相互作用的影响持续存在或滞后 2-5 年。这些结果表明，降水影响干旱地区流域火灾对河流溶质动力学影响的时间和强度，但这些响应因气候、溶质和流域特征而异。 时间序列模型应用于长期监测数据，包括火灾前后的观察，从而估计火灾对干旱地区河流化学的影响。这种统计方法捕捉了局部尺度时间变化的影响，包括对火灾的延迟响应，并可用于减少干旱地区不断变化的火灾和降水状况下水质预测响应的不确定性。