Fire‐produced coarse woody debris and its role in sediment storage on hillslopes
Fire‐produced coarse woody debris and its role in sediment storage on hillslopes
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火灾——产生粗木屑及其在山坡沉积物储存中的作用
DOI：
10.1002/esp.5573
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发表时间：
2023
影响因子：
3.3
通讯作者：
McWethy, Dave
中科院分区：
文献类型：
--
作者：
Adams, Kailey V.;Dixon, Jean L.;Wilcox, Andrew C.;McWethy, Dave
火后景观中植被和沉积物之间的相互作用对沉积物的连通性起着关键作用。以往的研究主要集中在从山坡上移走植被的影响，但对火灾后添加到森林地面的粗木质碎屑的影响关注较少。我们研究了火灾后CWD对山坡泥沙储存的影响。首先，我们提出了一个新的概念模型，确定了泥沙被困在原木等火灾产生的碎片的上坡的“主动”存储情景，以及额外的“被动”存储情景，包括由于烧焦的树根和折断的树干而降低扔树的效率。其次，我们利用倾斜台试验来检验对泥沙蓄积能力的控制。物理模拟表明，储存量随着对数方向和坡度的变化而非线性变化，在高泥沙通量系统中，原木屏障的最大储能可能超过假设简单沉积物堆积几何形状的估计。最后，我们结合高分辨率地形数据和航空影像中5000多个倒下的原木的数字化，计算了蒙大拿州西南部一个被烧毁的集水区的山坡沉积物储存量。我们估计，从3500-14 ，000,000 m~3的沉积物可能储存在原木的上游。这些估计假设所有倒下的原木都储存了沉积物，随着存储容量随着CWD的衰退而演变，这一过程可能是暂时动态的。我们的结果强调了CWD在限制最近烧毁的系统中的快速泥沙运动方面所起的作用。在一定的潜在土壤生产力范围内(50-100 mm/Ky)，CWD将缓冲整个景观中产生的约35-280 年的土壤向下迁移，这表明火灾产生的CWD可能是流域泥沙不连通性的一个重要来源。这些结果表明，扰动事件以前没有解释过增加山坡沉积物储存的机制，这些机制应该纳入沉积物连通性模型。
Interactions between vegetation and sediment in post‐fire landscapes play a critical role in sediment connectivity. Prior research has focused on the effects of vegetation removal from hillslopes, but little attention has been paid to the effects of coarse woody debris (CWD) added to the forest floor following fires. We investigate the impacts of CWD on hillslope sediment storage in post‐fire environments. First, we present a new conceptual model, identifying “active” storage scenarios where sediment is trapped upslope of fire‐produced debris such as logs, and additional “passive” storage scenarios including the reduced effectiveness of tree‐throw due to burnt roots and snapped stems. Second, we use tilt table experiments to test controls on sediment storage capacity. Physical modeling suggests storage varies nonlinearly with log orientation and hillslope gradient, and the maximum storage capacity of log barriers in systems with high sediment fluxes likely exceeds estimates that assume simple sediment pile geometries. Last, we calculate hillslope sediment storage capacity in a burned catchment in southwest Montana by combining high‐resolution topographic data and digitization of over 5000 downed logs from aerial imagery. We estimate that from 3500–14 000 m3of sediment was potentially stored upslope of logs. These estimates assume that all downed logs store sediment, a process that is likely temporally dynamic as storage capacity evolves with CWD decay. Our results highlight the role that CWD plays in limiting rapid sediment movement in recently burned systems. Using a range of potential soil production rates (50–100 mm/ky), CWD would buffer the downslope transport of ~35–280 years of soil produced across the landscape, indicating that fire‐produced CWD may serve as an important source of sediment disconnectivity in catchments. These results suggest that disturbance events have previously unaccounted‐for mechanisms of increasing hillslope sediment storage that should be incorporated into models of sediment connectivity.
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