The effect of ash on runoff and erosion after a severe forest wildfire, Montana, USA
The effect of ash on runoff and erosion after a severe forest wildfire, Montana, USA
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美国蒙大拿州严重森林野火后灰烬对径流和侵蚀的影响
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
V. Balfour
中科院分区：
文献类型：
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作者：
S. Woods;V. Balfour
植被燃烧形成的灰烬以及枯枝落叶层可能会影响野火发生后不久的径流和侵蚀率，但只有少数研究专门测量了其影响。 2005 年蒙大拿州西部塔基奥火灾发生后大约 1 个月，我们对烧毁严重且表面有连续 1 厘米至 3.5 厘米火山灰层的六对 0.5 平方米地块进行了 1 小时的模拟降雨，平均强度为 7.5 cm h–1。灰烬保留在每对一个地块中，并用细刷子从另一块地去除。灰层提供了额外 1.5 厘米的储水能力，并保护下面的矿质土壤免受表面密封，因此，与无灰地相比，灰覆盖地块的积水时间延长了 12 ± 10 分钟，最终径流量降低了 2.1 ± 0.4 cm h–1，总入渗量高了 2.0 ± 1.2 cm。与没有灰烬覆盖的地块相比，被灰烬覆盖的地块径流减少，加上雨水溅落减少，导致沉积物产量减少 74%。火灾九个月后，灰烬呈斑片状，厚度只有几毫米，第二组模拟显示，有和没有灰烬的地块之间的积水时间、最终径流率、总渗透或沉积量没有显着差异。火灾后不久，灰烬可能会显着减少严重烧毁地区的径流和侵蚀。因此，最大的火后水文地貌灾害将发生在火山灰层被风和水侵蚀去除之后，但在大量植被再生之前。
Ash formed by the combustion of vegetation and the litter and duff layers may affect runoff and erosion rates in the period immediately following wildfires, but only a handful of studies have specifically measured its effect. Approximately 1 month after the 2005 Tarkio Fire in western Montana, we applied simulated rainfall for 1 h at a mean intensity of 7.5 cm h–1 to six pairs of 0.5-m2 plots in an area burned at high severity and with a continuous 1-cm to 3.5-cm ash layer on the surface. The ash was retained in one plot per pair and removed from the other plot with a fine brush. The ash layer provided an additional 1.5 cm of water storage capacity and protected the underlying mineral soil from surface sealing, so that the time of ponding in the ash-covered plots was 12 ± 10 min longer, the final runoff rate was 2.1 ± 0.4 cm h–1 lower and the total infiltration was 2.0 ± 1.2 cm higher than in the plots without ash. The reduced runoff from the ash-covered plots in combination with reduced rainsplash detachment resulted in a 74% reduction in sediment yield relative to the plots without ash. Nine months after the fire, the ash was patchy and just a few millimetres thick, and a second set of simulations showed no significant differences in the time of ponding, final runoff rate, total infiltration or sediment yield between plots with and without ash. Ash may significantly reduce the runoff and erosion from severely burned areas in the period shortly after a fire. Consequently, the largest post-fire hydrogeomorphic hazard will occur after the ash layer has been removed by wind and water erosion, but before there has been substantial vegetative regrowth.