The flow of organic matter (OM) along rivers and retention within floodplains contributes significantly to terrestrial carbon storage and ecosystem function. The storage and cycling of OM largely depend upon hydrogeomorphic characteristics of streams and valleys, including channel geometry and the connectivity of water across and within the floodplain. To examine the role of river morphology on carbon dynamics in mountain streams, we (a) quantify organic carbon (OC) storage in fine sediment, litter, and wood along 24 forested gravel‐bed stream reaches in the Rocky Mountains of CO, USA, (b) examine morphological factors that regulate sediment and OC storage (e.g., channel width, slope, logjams), and (c) utilize fluorescence spectroscopy to examine how the composition of fluorescent dissolved OM in surface water and floodplain fine sediment are influenced by channel morphology. Multivariate regression of the study reaches, which have varying degrees of confinement, slope, and elevation, indicates that OC storage per area is higher in less confined valleys, in lower gradient stream reaches, and at higher elevations. Within unconfined valleys, limited storage of fine sediment and greater microbial transformation of OM in multithread channel reaches decreases OC storage per area (252 ± 39 Mg C ha⁻¹) relative to single‐thread channel reaches (346 ± 177 Mg C ha⁻¹). Positive feedbacks between channel morphology and persistent channel‐spanning logjams that divert flow into multiple channels may limit the aggradation of floodplain fine sediment. Although multithread stream reaches are less effective OC reservoirs, they are hotspots for OM decomposition and provide critical resources to downstream food webs.

中文翻译：

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堵塞和河道形态影响沉积物的存储，有机质的转化以及山间小溪走廊内的碳存储

沿河流的有机物（OM）流动和洪泛区中的滞留作用显着促进了陆地碳存储和生态系统功能。OM的存储和循环在很大程度上取决于河流和山谷的水文地貌特征，包括河道的几何形状以及洪泛区之间和洪泛区内的水的连通性。为了研究河流形态对山区溪流碳动态的作用，我们（a）量化了美国落基山脉中24条森林碎石床溪流中细沉积物，凋落物和木材中有机碳（OC）的存储量， （b）检查可调节沉积物和OC储存的形态学因素（例如，河道宽度，坡度，对数堵塞），（c）利用荧光光谱法检查地表水和洪泛区细小沉积物中的荧光溶解性有机物的组成如何受到通道形态的影响。研究河段的多变量回归具有不同程度的限制，坡度和海拔高度，表明在较少限制的谷地，在较低的坡度河段和在较高的海拔处，每面积的OC储存量较高。在无限制的山谷中，细颗粒沉积物的有限存储和多线程通道中OM的更大微生物转化达到降低了每面积OC的存储量（252±39 Mg C ha 和更高的海拔。在无限制的山谷中，细沉积物的有限存储和多线程通道中OM的较大微生物转化达到降低了单位面积的OC存储（252±39 Mg C ha 和更高的海拔。在无限制的山谷中，细沉积物的有限存储和多线程通道中OM的较大微生物转化达到降低了单位面积的OC存储（252±39 Mg C ha^-1）相对于单线程通道达到（346±177 Mg C ha ^-1）。河道形态与持续的跨河道堵塞之间的正反馈（将流量分流到多个河道）可能会限制漫滩平原细沙的聚集。尽管多线程河段的OC储层效率较低，但它们是OM分解的热点，并为下游食物网提供了关键资源。