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

在过去的四分之一个世纪里，许多研究表明，冻土带氮循环的特征在控制冻土带碳循环对气候变化和干扰的响应方面发挥着重要作用。这项研究将确定北极圈阿拉斯加分水岭的氮循环特征如何在1到10年的时间尺度上影响碳的积累和损失。PIs将(1)测量N的输入和输出，如大气沉积、固定和溪流损失，(2)进行15N标记实验，以确定主要的N汇，量化它们的周转率，并追踪下坡N通量，(3)建立C-N相互作用模型，重点关注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冻土带与其他生态系统类型的碳-氮相互作用。这项研究很重要，因为在包括北极苔原在内的大多数陆地生态系统中，氮是碳循环的关键调节因素，但在分水岭尺度上，关于碳-氮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反应的关键。在人类活动导致全球氮年周转率翻了一番的世界里，流域中氮素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.