Effectiveness of post‐fire salvage logging stream buffer management for hillslope erosion in the U.S. Inland Northwest Mountains
Effectiveness of post‐fire salvage logging stream buffer management for hillslope erosion in the U.S. Inland Northwest Mountains
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美国内陆西北山区山坡侵蚀的火灾后打捞伐木溪流缓冲区管理的有效性
DOI：
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发表时间：
2020
影响因子：
3.2
通讯作者：
Robert E. Brown
中科院分区：
文献类型：
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作者：
P. Robichaud;E. D. Bone;S. A. Lewis;E. Brooks;Robert E. Brown
美国西部活跃的野火季节需要评估火灾后的森林管理战略。地面打捞采伐常用于挽回被烧毁木材的经济损失。在未被烧毁的森林中，地面采伐通常遵循最佳管理实践，在称为溪流缓冲区的溪流附近留下未受干扰的区域。然而，这些缓冲器的有效性还没有在野火后的环境中进行测试。本试验采用野外模拟细沟试验的方法，利用含沙径流(25 g/L)，在均匀定时流速(50,100和150 L/分钟)下，释放超过40 分钟的径流，在火灾后2个月、10个月和22个月测量未燃烧和高、低土壤烧伤严重程度条件下的地表径流移动长度和含沙量。火灾后2个月高度严重地区的细沟长度高达100 m。随着植被的再生提供地面覆盖，细沟长度随着时间的推移而显着减少。泥沙浓度和泥沙丢失率也因土壤烧伤程度的不同而有显著差异。火后2个月泥沙含量最高为19 g/L，10个月后由于植被恢复，泥沙含量降至6.9~14 g/L。在研究期间，从水流中掉落的泥沙数量持续增加，较低的烧伤严重程度为1.15 g L−1 m−1，接近火灾后2年的未烧伤率1.29 g L−1 m−1。这些结果表明，经常使用的15 m缓冲区足以遏制地表径流并减少未燃烧地点的泥沙浓度，但高度烧伤地点的缓冲区需要在野火后立即增加8倍(120 m)，在火灾后1年增加4倍(60 m)。低烧伤严重程度区域在火灾后1年可能只需要未燃烧缓冲区(30 m)的两倍宽度，而火灾后2年这些区域可能会恢复到未燃烧宽度。
Active wildfire seasons in the western U.S. warrant the evaluation of post‐fire forest management strategies. Ground‐based salvage logging is often used to recover economic loss of burned timber. In unburned forests, ground‐based logging often follows best management practices by leaving undisturbed areas near streams called stream buffers. However, the effectiveness of these buffers has not been tested in a post‐wildfire setting. This experiment tested buffer width effectiveness with a novel field‐simulated rill experiment using sediment‐laden runoff (25 g/L) released over 40 min at evenly timed flow rates (50, 100 and 150 L/min) to measure surface runoff travel length and sediment concentration under unburned and high and low soil burn severity conditions at 2‐, 10‐ and 22‐month post‐fire. High severity areas 2‐month post‐fire had rill lengths of up to 100 m. Rill length significantly decreased over time as vegetation regrowth provided ground cover. Sediment concentration and sediment dropout rate also varied significantly by soil burn severity. Sediment concentrations were 19 g/L for the highest flow 2‐month post‐fire and reduced to 6.9–14 g/L 10‐month post‐fire due to abundant vegetation recovery. The amount of sediment dropping out of the flow consistently increased over the study period with the low burn severity rate of 1.15 g L−1 m−1 approaching the unburned rate of 1.29 g L−1 m−1 by 2‐year post‐fire. These results suggest that an often‐used standard, 15 m buffer, was sufficient to contain surface runoff and reduce sediment concentration on unburned sites, however buffers on high burn severity sites need to be eight times greater (120 m) immediately after wildfire and four times greater (60 m) 1‐year post‐fire. Low burn severity areas 1‐year post‐fire may need to be only twice the width of an unburned buffer (30 m), and 2‐year post‐fire these could return to unburned widths.