Hydrology Controls Dissolved Organic Carbon and Nitrogen Export and Post‐Storm Recovery in Two Arctic Headwaters
Hydrology Controls Dissolved Organic Carbon and Nitrogen Export and Post‐Storm Recovery in Two Arctic Headwaters
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DOI：
10.1029/2023jg007583
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发表时间：
2024-02
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通讯作者：
Arial J. Shogren;J. Zarnetske;Benjamin W. Abbott;Amelia L. Grose;Abigail F. Rec;Jansen Nipko;Chao Song;J. O’Donnell;William B. Bowden
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作者：
Arial J. Shogren;J. Zarnetske;Benjamin W. Abbott;Amelia L. Grose;Abigail F. Rec;Jansen Nipko;Chao Song;J. O’Donnell;William B. Bowden
气候变化正在迅速改变水文过程，从而改变北极生态系统的结构和功能。预测这些变化将如何影响河流的生物地球化学反应仍然是一个重大挑战。我们连续测量了两个北极流域的[C]碳和[N]氮浓度，以评估尚未充分研究的事件尺度C和N浓度-排放（C - Q）行为和事件后化学计量条件的恢复。流域代表了阿拉斯加北坡布鲁克斯山脉东部典型的低梯度苔原景观，是北极长期生态研究地点的一部分：库帕鲁克河和奥克斯鲁库伊克河。在这两个流域，我们部署了高频光学传感器，测量了连续五个解冻季节（2017-2021）的溶解有机碳（DOC）、硝酸盐（NO3 - ${{\text{NO}}_{3}}^{-}$）和总溶解氮（TDN）。我们的分析显示，在水文扰动后，DOC: NO3 - ${\text{NO}}_{3}}^{-}$的化学计量恢复存在滞后性：虽然DOC在高流量后持续升高，但NO3 - ${{\text{NO}}_{3}}^{-}$在降雨事件中被稀释，因此，事件后浓度的恢复被延迟。相反，高流量时TDN的共富集，即使是在需要量相对较高的流域，也代表了水文有效有机氮向下游生态系统的潜在“泄漏”。我们使用高频、长期光学传感器提供了一种改进的方法来估计碳和养分预算以及跨事件和季节时间尺度的化学计量恢复行为，从而对北极变化提供了新的见解和概念，例如评估跨多个时间尺度的生态系统干扰和恢复。
Climate change is rapidly altering hydrological processes and consequently the structure and functioning of Arctic ecosystems. Predicting how these alterations will shape biogeochemical responses in rivers remains a major challenge. We measured [C]arbon and [N]itrogen concentrations continuously from two Arctic watersheds capturing a wide range of flow conditions to assess understudied event‐scale C and N concentration‐discharge (C‐Q) behavior and post‐event recovery of stoichiometric conditions. The watersheds represent low‐gradient, tundra landscapes typical of the eastern Brooks Range on the North Slope of Alaska and are part of the Arctic Long‐Term Ecological Research sites: the Kuparuk River and Oksrukuyik Creek. In both watersheds, we deployed high‐frequency optical sensors to measure dissolved organic carbon (DOC), nitrate ( NO3− ${{\text{NO}}_{3}}^{-}$ ), and total dissolved nitrogen (TDN) for five consecutive thaw seasons (2017–2021). Our analyses revealed a lag in DOC: NO3− ${{\text{NO}}_{3}}^{-}$ stoichiometric recovery after a hydrologic perturbation: while DOC was consistently elevated after high flows, NO3− ${{\text{NO}}_{3}}^{-}$ diluted during rainfall events and consequently, recovery in post‐event concentration was delayed. Conversely, the co‐enrichment of TDN at high flows, even in watersheds with relatively high N‐demand, represents a potential “leak” of hydrologically available organic N to downstream ecosystems. Our use of high‐frequency, long‐term optical sensors provides an improved method to estimate carbon and nutrient budgets and stoichiometric recovery behavior across event and seasonal timescales, enabling new insights and conceptualizations of a changing Arctic, such as assessing ecosystem disturbance and recovery across multiple timescales.