Abstract River corridors play an important role in the carbon cycle as sites of carbon transport, storage, and transformation. Floodplain soil organic carbon (OC) and dead, downed large wood (LW) are two of the largest OC stocks in rivers. Human modifications of river corridors, such as damming and floodplain land-use change, have likely modified floodplain OC storage and retention through removal of LW and potential reduction of OC concentrations in soils. However, the effect of human alterations on floodplain OC storage is poorly understood. We measured floodplain soil OC and downed LW loads on three rivers in northern Sweden that display a gradient in the degree of human alteration. The Muddus River is located in a national park and is unaltered. The Vindel River is free-flowing but has been modified via logging and other land-use changes within the floodplain. The Ume River is dammed along its length and has also experienced floodplain logging and land-use change. We used statistical models to determine which factors are associated with differences in mineral soil OC and LW among rivers with different degrees of human alteration. We find the highest mineral soil OC concentrations on the unaltered Muddus River (mean ± standard error (SE) = 3.70 ± 0.59%; median = 3.81%), with lower soil OC along the Vindel (mean ± SE = 1.44 ± 0.22%; median = 0.72%) and Ume (mean ± SE = 2.47 ± 0.44%; median = 1.12%) Rivers. The Muddus River also has the highest downed LW loads (mean ± SE = 22.25 ± 6.99 m3 ha−1) compared to the Vindel (mean ± SE = 3.10 ± 1.26 m3 ha−1) and Ume (mean ± SE = 7.26 ± 3.53 m3 ha−1) Rivers. Variations in soil OC and downed large wood loads indicate that damming may reduce floodplain OC in these boreal systems through reducing lateral channel-floodplain connectivity and longitudinal connectivity. Logging and other land-use changes likely reduce OC inputs to the floodplain surface through removal of organic matter and LW. Further research is needed to elucidate the impact of human modifications on floodplain OC across diverse regions and to inform river restoration efforts to enhance floodplain OC storage.

中文翻译：

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评估跨越北方地区人类变化梯度的漫滩有机碳

摘要 河流廊道作为碳运输、储存和转化的场所，在碳循环中发挥着重要作用。洪泛区土壤有机碳 (OC) 和枯死、倒下的大木 (LW) 是河流中最大的两种有机碳储量。人类对河流走廊的改造，例如筑坝和洪泛区土地利用变化，可能通过去除 LW 和潜在降低土壤中 OC 浓度来改变洪泛区 OC 的储存和保留。然而，人类改变对洪泛区 OC 储存的影响知之甚少。我们在瑞典北部的三条河流上测量了漫滩土壤 OC 和下降的 LW 载荷，这些河流显示了人类改变程度的梯度。穆杜斯河位于国家公园内，未曾改变。Vindel 河是自由流动的，但已经通过伐木和泛滥平原内的其他土地利用变化进行了修改。梅河沿途筑坝，还经历了洪泛区砍伐和土地利用变化。我们使用统计模型来确定哪些因素与人类改变程度不同的河流中矿质土壤 OC 和 LW 的差异有关。我们发现未改变的 Muddus 河上矿质土壤 OC 浓度最高（平均值 ± 标准误差 (SE) = 3.70 ± 0.59%；中值 = 3.81%），沿 Vindel 的土壤 OC 较低（平均值 ± SE = 1.44 ± 0.22%；中值 = 0.72%) 和 Ume（平均值 ± SE = 2.47 ± 0.44%；中值 = 1.12%）河流。与 Vindel（平均值 ± SE = 3.10 ± 1.26 m3 ha-1）和 Ume（平均值 ± SE = 7.26 ± 3）相比，Muddus 河的下降 LW 负荷也最高（平均值 ± SE = 22.25 ± 6.99 m3 ha-1） . 53 m3 ha−1) 河流。土壤有机碳的变化和大量木材负载的下降表明，筑坝可能会通过减少横向渠道 - 漫滩连通性和纵向连通性来减少这些北方系统中的漫滩有机碳。伐木和其他土地利用变化可能会通过去除有机物质和 LW 来减少对洪泛区表面的 OC 输入。需要进一步的研究来阐明人类改造对不同地区泛滥平原有机碳的影响，并为河流恢复工作提供信息，以增强泛滥平原有机碳的储存。伐木和其他土地利用变化可能会通过去除有机物质和 LW 来减少对洪泛区表面的 OC 输入。需要进一步的研究来阐明人类改造对不同地区泛滥平原有机碳的影响，并为河流恢复工作提供信息，以增强泛滥平原有机碳的储存。伐木和其他土地利用变化可能会通过去除有机物质和 LW 来减少对洪泛区表面的 OC 输入。需要进一步的研究来阐明人类改造对不同地区泛滥平原有机碳的影响，并为河流恢复工作提供信息，以增强泛滥平原有机碳的储存。