Wildfire alters hydrologic and geomorphic systems, promoting increases in runoff and erosion relative to unburned areas. As a result, pyrogenic carbon (PyC) produced by wildfires can experience substantial lateral redistribution from overland flow. Since landscape position helps to determine the fate of PyC, it is critical to understand the geomorphic factors that govern its lateral redistribution as well as the sensitivity of those factors to soil burn severity, which controls the magnitude of many wildfire-induced hydrologic and geomorphic changes. In this study, we quantified the spatial distribution of near-surface (0–5 cm) PyC on three hillslopes roughly 1 year after the 2018 Buzzard Fire in the Gila National Forest, New Mexico, USA. We then use hydrologic monitoring data, terrain analysis, and rainfall-runoff modeling to explain the observed spatial distribution of PyC. Near-surface PyC concentrations decreased from averages of roughly 12–8 g/kg as slope and unit stream power increased by factors of ∼2 and 4, respectively, on a hillslope burned at low severity. This suggests that susceptibility to runoff-driven erosion was a dominant control on the redistribution of PyC. In contrast, the spatial distribution of PyC in areas burned at moderate to high severity was independent of slope and unit stream power. We attribute this pattern to intense runoff and lack of canopy cover, which promoted erosion of PyC regardless of slope and landscape position. Results demonstrate that how wildfire-induced hydrogeomorphic changes can modulate the importance of terrain attributes in controlling the spatial distribution of PyC in upland landscapes.

中文翻译：

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山火一年后山坡近地表热解碳空间分布控制

野火改变了水文和地貌系统，促进了相对于未燃烧区域的径流和侵蚀增加。因此，野火产生的热解碳 (PyC) 可能会从地表水流中经历大量的横向再分布。由于景观位置有助于确定 PyC 的命运，因此了解控制其横向再分布的地貌因素以及这些因素对土壤燃烧严重程度的敏感性至关重要，这控制着许多野火引起的水文和地貌变化的幅度. 在这项研究中，我们量化了美国新墨西哥州吉拉国家森林 2018 年秃鹰大火后大约 1 年三个山坡上近地表（0-5 厘米）PyC 的空间分布。然后我们使用水文监测数据，地形分析，和降雨径流模型来解释观察到的 PyC 空间分布。近地表 PyC 浓度从大约 12-8 g/kg 的平均值下降，因为坡度和单位流功率分别增加了约 2 和 4 倍，在低严重度燃烧的山坡上。这表明对径流驱动侵蚀的敏感性是对 PyC 重新分布的主要控制。相比之下，PyC 在中度至高度燃烧区域的空间分布与坡度和单位流功率无关。我们将这种模式归因于强烈的径流和缺乏冠层覆盖，无论坡度和景观位置如何，这都会促进 PyC 的侵蚀。结果表明，野火引起的水文地貌变化如何调节地形属性在控制高地景观中 PyC 空间分布方面的重要性。