Permafrost Landscape History Shapes Fluvial Chemistry, Ecosystem Carbon Balance, and Potential Trajectories of Future Change
Permafrost Landscape History Shapes Fluvial Chemistry, Ecosystem Carbon Balance, and Potential Trajectories of Future Change
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DOI：
10.1029/2022gb007403
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发表时间：
2022-08
影响因子：
5.2
通讯作者：
S. Zolkos;S. Tank;S. Kokelj;R. Striegl;S. Shakil;C. Voigt;O. Sonnentag;W. Quinton;E. Schuur
中科院分区：
文献类型：
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作者：
S. Zolkos;S. Tank;S. Kokelj;R. Striegl;S. Shakil;C. Voigt;O. Sonnentag;W. Quinton;E. Schuur
永久冻土融化加剧，通过将大量陆地基质动员到水生生态系统中，改变了碳循环。然而，很少有研究测量了北极异质景观中水生碳通量和生态系统碳平衡的约束驱动因素。在这里，我们描述了水化学和景观对河流碳循环的控制，量化了河流碳通量，并估计了河流对加拿大北极西部连续多年冻土带4个生态区33个流域的生态系统碳平衡的贡献：无冰川高地、富含冰的冰碛、富含有机的低地和耕作平原。主要离子、稳定同位素、碳形态和通量揭示了由地形起伏和有机物聚集所定义的生态区域的碳循环模式。在以前没有冰川覆盖的山地流域，由于基岩的化学风化作用，碳酸氢盐主导了碳输出（占总量的70%）。在土壤有机碳储量最大的低地流域，溶解有机碳的横向运输（50%）和生物CO2的外排（25%）占主导地位。在受融化引起的大量浪费影响的流域，富冰垄的侵蚀增强了化学风化作用，并使颗粒碳通量增加了两个数量级。从生态系统碳平衡的角度来看，不受融化引起的浪费影响的流域河流碳输出平均相当于估计净生态系统交换（NEE）的6%-16%。在受融化损耗影响的流域，河流碳输出接近新能源经济的60%。由于未来热岩溶活动的加剧将扩大河流碳输出，因此确定不同北方景观中碳的命运是限制永久冻土区生态系统碳平衡轨迹的优先事项。
Intensifying permafrost thaw alters carbon cycling by mobilizing large amounts of terrestrial substrate into aquatic ecosystems. Yet, few studies have measured aquatic carbon fluxes and constrained drivers of ecosystem carbon balance across heterogeneous Arctic landscapes. Here, we characterized hydrochemical and landscape controls on fluvial carbon cycling, quantified fluvial carbon fluxes, and estimated fluvial contributions to ecosystem carbon balance across 33 watersheds in four ecoregions in the continuous permafrost zone of the western Canadian Arctic: unglaciated uplands, ice‐rich moraine, and organic‐rich lowlands and till plains. Major ions, stable isotopes, and carbon speciation and fluxes revealed patterns in carbon cycling across ecoregions defined by terrain relief and accumulation of organics. In previously unglaciated mountainous watersheds, bicarbonate dominated carbon export (70% of total) due to chemical weathering of bedrock. In lowland watersheds, where soil organic carbon stores were largest, lateral transport of dissolved organic carbon (50%) and efflux of biotic CO2 (25%) dominated. In watersheds affected by thaw‐induced mass wasting, erosion of ice‐rich tills enhanced chemical weathering and increased particulate carbon fluxes by two orders of magnitude. From an ecosystem carbon balance perspective, fluvial carbon export in watersheds not affected by thaw‐induced wasting was, on average, equivalent to 6%–16% of estimated net ecosystem exchange (NEE). In watersheds affected by thaw‐induced wasting, fluvial carbon export approached 60% of NEE. Because future intensification of thermokarst activity will amplify fluvial carbon export, determining the fate of carbon across diverse northern landscapes is a priority for constraining trajectories of permafrost region ecosystem carbon balance.