The perhumid coastal temperate rainforest (PCTR) of northwestern North America is projected to become warmer and wetter in coming decades, with largely unquantified implications for the magnitude and speciation of riverine nitrogen (N) and phosphorus (P) export from PCTR ecosystems. We collected streamwater at weekly to monthly intervals for a year and intensively during two multi-day storms (one each in summer and the autumn rainy season) from streams draining three of the most common landcover types in southeast Alaska (poor fen, forested wetland and upland forest). Our goal was to investigate how seasonal and episodic (stormflows) changes in runoff influence the magnitude and species of dissolved N and P exported from PCTR watersheds. Riverine yields of total dissolved N and P ranged from 238 to 406 kg km2 year− 1 for N and 11 to 17 kg km2 year− 1 for P and were dominated by organic nutrient forms. Yields of N and P showed a varied response to runoff, with both hydrologic transport and source limitation of nutrient yields observed across the landcover types. During stormflows, log transformed ratios of dissolved inorganic N to soluble reactive P decreased from prestorm levels of ~ 1.0 to 1.5 to less than 0.3 during peak flow at all sites, illustrating that storms induce ephemeral changes in inorganic nutrient export and stoichiometry. Our findings highlight the pulsed nature of dissolved N and P export from PCTR watersheds suggesting that future changes in the seasonality and intensity of precipitation may influence the flow of terrestrial nutrients to marine ecosystems.

中文翻译：

---

流量变化控制着阿拉斯加沿海温带雨林流域的氮和磷的输出和物种形成

预计未来几十年，北美西北部的高湿沿海温带雨林 (PCTR) 将变得更加温暖和湿润，对 PCTR 生态系统中河流氮 (N) 和磷 (P) 输出的数量和形态的影响很大程度上未量化。我们在一年中每周到每月一次收集溪水，并在两次多日风暴（夏季和秋季雨季各一次）期间从阿拉斯加东南部三种最常见的土地覆盖类型（贫瘠、森林湿地和高地森林）。我们的目标是研究径流的季节性和偶发性（风暴流）变化如何影响从 PCTR 流域输出的溶解氮和磷的量级和种类。河流中总溶解氮和磷的产量范围为 238 至 406 kg km2 year− 1 的 N 和 11 到 17 kg km2 year− 1 的 P 并且以有机养分形式为主。N 和 P 的产量对径流表现出不同的响应，在整个土地覆盖类型中观察到水文运输和养分产量的来源限制。在风暴流期间，溶解无机氮与可溶性活性磷的对数转换比从风暴前水平的 ~ 1.0 降至 1.5，在所有地点的峰值流量期间降至小于 0.3，说明风暴导致无机养分输出和化学计量的短暂变化。我们的研究结果强调了 PCTR 流域溶解的 N 和 P 输出的脉冲性质，这表明未来降水的季节性和强度的变化可能会影响陆地养分向海洋生态系统的流动。