The biogeochemical cycles of carbon (C) and nitrogen (N) are inextricably linked for a range of reactions. For coupled reactions such as denitrification to occur, however, solutes must be found together in space and time. Using the framework of concentration-discharge (c-Q) relationships, we examine the frequency of synchronous C and N export (i.e. identical c-Q behavior) across a river network using > 5 years of high-frequency sensor data. We demonstrate that across space and time the export of C and N to a river network is asynchronous 57% of the time. The probability of simultaneous export in largely forested watersheds demonstrates little temporal structure, while in more human-impacted watersheds, we observe the highest frequency of asynchronous c-Q behavior. We discuss the implications of synchronous c-Q behavior for solute flux estimation models and develop a theoretical framework for predicting where within a landscape we expect the probability of coupled C and N reactions to be greatest. By simultaneously comparing the variability in C and N c-Q relationships we develop an integrated framework for predicting synchronous export of solutes.

中文翻译：

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量化同步向河网输出碳氮的频率

碳 (C) 和氮 (N) 的生物地球化学循环在一系列反应中密不可分。然而，为了发生反硝化等耦合反应，溶质必须在空间和时间上一起被发现。使用浓度-排放 (cQ) 关系的框架，我们使用 > 5 年的高频传感器数据检查跨河网同步 C 和 N 输出（即相同的 cQ 行为）的频率。我们证明了跨空间和时间向河流网络的 C 和 N 输出在 57% 的时间是异步的。在大部分森林覆盖的流域中同时出口的概率显示出很少的时间结构，而在更多受人类影响的流域中，我们观察到异步 cQ 行为的最高频率。我们讨论了同步 cQ 行为对溶质通量估计模型的影响，并开发了一个理论框架来预测在景观中我们预计耦合 C 和 N 反应的概率最大的位置。通过同时比较 C 和 N cQ 关系的可变性，我们开发了一个用于预测溶质同步输出的集成框架。