Asymmetric hillslope erosion following wildfire in Fourmile Canyon, Colorado: asymetric hillslope erosion wildfire fourmile canyon
Asymmetric hillslope erosion following wildfire in Fourmile Canyon, Colorado: asymetric hillslope erosion wildfire fourmile canyon
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科罗拉多州四英里峡谷野火后的不对称山坡侵蚀：不对称山坡侵蚀野火四英里峡谷
DOI：
10.1002/esp.4348
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发表时间：
2018
影响因子：
3.3
通讯作者：
Dethier, David P.
中科院分区：
文献类型：
--
作者：
Abrahams, Edward R.;Kaste, James M.;Ouimet, William;Dethier, David P.
罕见的高震级事件导致陡峭山坡上不成比例的泥沙输运，但几乎没有定量数据可以捕捉这些过程。在这里，我们研究了野火和山坡方面对土壤侵蚀的影响，在福米尔峡谷，科罗拉多。该地区经历了2010年的Fourmile Fire，2011年和2012年的夏季强对流风暴以及2013年9月的极端洪水。我们在这些事件发生后不久对土壤进行了采样，并使用沉降物放射性核素来追踪极地和赤道面燃烧斜坡以及极地面未燃烧斜坡上的侵蚀。由于这些放射性核素集中在土壤的上层分米，土壤存量对地表径流的侵蚀很敏感。朝向极地的燃烧斜坡的铯-137（137 Cs）和铅-210（210 Pb）库存显著低于朝向极地的未燃烧斜坡或朝向赤道的燃烧斜坡（p< 0.05）。当地坡度大小似乎并不能控制野火的侵蚀反应，因为相对平缓的坡度（约20%）朝向极地的位置在燃烧最强烈的地区受到严重侵蚀。现场证据和土壤剖面分析表明，在面向极地的烧毁斜坡上有高达4厘米的局部土壤侵蚀，但放射性核素质量平衡表明，其中大部分被困在附近。使用基于137 Cs的侵蚀模型，我们发现，在一到三年的时间里，烧毁的极面斜坡的净平均泥沙流失量为2 mm（约1 kg m−2），这比该地区报告的长期侵蚀率高出一到两个数量级。在科罗拉多前山脉的这一部分，强烈的山坡不对称性控制着土壤水分和植被;面向极地的斜坡支撑着明显密集的松树和冷杉林，这助长了更强烈的野火。我们的结论是，在该地区的野火之后，面向极地的斜坡经历了最严重的表面侵蚀，这表明景观尺度的干旱可以控制山坡对野火的地貌反应。版权所有© 2018约翰威利父子有限公司
Infrequent, high‐magnitude events cause a disproportionate amount of sediment transport on steep hillslopes, but few quantitative data are available that capture these processes. Here we study the influence of wildfire and hillslope aspect on soil erosion in Fourmile Canyon, Colorado. This region experienced the Fourmile Fire of 2010, strong summer convective storms in 2011 and 2012, and extreme flooding in September 2013. We sampled soils shortly after these events and use fallout radionuclides to trace erosion on polar‐ and equatorial‐facing burned slopes and on a polar‐facing unburned slope. Because these radionuclides are concentrated in the upper decimeter of soil, soil inventories are sensitive to erosion by surface runoff. The polar‐facing burned slope had significantly lower cesium‐137 (137Cs) and lead‐210 (210Pb) inventories (p< 0.05) than either the polar‐facing unburned slope or equatorial‐facing burned slope. Local slope magnitude does not appear to control the erosional response to wildfire, as relatively gently sloping (~20%) polar‐facing positions were severely eroded in the most intensively burned area. Field evidence and soil profile analyses indicate up to 4 cm of local soil erosion on the polar‐facing burned slope, but radionuclide mass balance indicates that much of this was trapped nearby. Using a137Cs‐based erosion model, we find that the burned polar‐facing slope had a net mean sediment loss of 2 mm (~1 kg m−2) over a one to three year period, which is one to two orders of magnitude higher than longer‐term erosion rates reported for this region. In this part of the Colorado Front Range, strong hillslope asymmetry controls soil moisture and vegetation; polar‐facing slopes support significantly denser pine and fir stands, which fuels more intense wildfires. We conclude that polar‐facing slopes experience the most severe surface erosion following wildfires in this region, indicating that landscape‐scale aridity can control the geomorphic response of hillslopes to wildfires. Copyright © 2018 John Wiley & Sons, Ltd.