Turnover and Retention of Nitrogen in an Arctic Watershed: Links to Organic Matter Accumulation and Response to Climate

在过去的25年里，许多研究表明，冻原氮循环的特征在控制冻原碳循环对气候变化和干扰的响应方面起着重要作用。这项研究将确定氮循环的特点如何影响碳积累和损失在1至10年的时间尺度在北极阿拉斯加流域。 PI将（1）测量N输入和输出，如大气沉积，固定和河流中的损失，（2）执行15 N标记实验，以确定主要的N汇，量化其周转率，并跟踪下坡N通量，（3）模拟C-N相互作用，重点是N限制作为C循环变化的约束。 研究人员打算使用开发的模型来比较北极苔原与其他生态系统类型的C-N相互作用。 这项研究很重要，因为氮是大多数陆地生态系统（包括北极苔原）碳循环的关键调节剂，但在流域尺度上对C-N相互作用的研究相对较少。 了解碳氮相互作用是了解生态系统对气候变化的长期响应的关键。 由于人类活动，全球氮的年周转率翻了一番，流域氮的周转和保留也是关键的生态系统服务。

Over the past quarter-century, many studies have shown that the characteristics of tundra nitrogen cycles play a major role in controlling the response of tundra carbon cycles to climate change and disturbance. This research will determine how the characteristics of nitrogen cycling influence carbon accumulation and loss at 1- to 10-year time scales in an arctic Alaska watershed. The PIs will (1) measure N inputs and outputs such as atmospheric deposition, fixation, and losses in streams, (2) perform a 15N -labeling experiment to identify major N sinks, quantify their turnover rates, and trace downslope N fluxes, and (3) model C-N interactions, focusing on N limitation as a constraint on change in the C cycle. The investigators intend to use the models that are developed to compare C-N interactions in arctic tundra with other ecosystem types. The research is important because nitrogen is a key regulator of carbon cycling in most terrestrial ecosystems, including arctic tundras, but relatively little work on C-N interactions has been done at the watershed scale. Understanding C-N interactions is key to understanding long-term responses of ecosystems to climate change. Turnover and retention of nitrogen in watersheds are also key ecosystem services in a world where the annual nitrogen turnover rate has doubled globally due to human activity.