Estimated Amounts and Rates of Carbon Mobilized by Landsliding in Old‐Growth Temperate Forests of SE Alaska
Estimated Amounts and Rates of Carbon Mobilized by Landsliding in Old‐Growth Temperate Forests of SE Alaska
复制标题
DOI：
10.1029/2021jg006321
复制
发表时间：
2021-11
期刊：
影响因子：
--
通讯作者：
B. Vascik;A. Booth;B. Buma;M. Berti
中科院分区：
文献类型：
--
作者：
B. Vascik;A. Booth;B. Buma;M. Berti
山体滑坡是一种森林扰动，它调动了封存在植被和土壤中的碳。被动员的碳要么沉积在山坡上，要么沉积在水中，在不同的时间尺度上从大气中吸收碳，又向大气中释放碳。阿拉斯加东南部的C -密集的古老温带森林是一个独特的地点，可以量化频繁的滑坡对C -动员率的影响，这些滑坡经常演变成饱和的移动块体，即泥石流。在这项研究中，通过将滑坡清单与模拟生物量和土壤碳图相结合，估算了泥石流在历史时间尺度上调动的碳量。我们在55年的时间里分析了阿拉斯加东南部的滑坡，总共动员了4.69±0.21 MtC，平均速度为2.5 tC km−2 yr−1。2015年8月的一次活动动员了57,651±3,266 tC，平均为63 tC km−2。沉积命运通过两种方法推断，一种是标准的河流交汇分析，另一种是基于研究区域校准的模拟泥石流沉积模型的新方法。大约60%的泥石流沉积物与河流网络相交（9%进入主河道，91%进入小支流），这与长期模拟的连通性相一致，表明泥石流可能导致全球范围内大量的C埋藏在当地峡湾沉积物中。我们的研究结果与一个新兴的共识是一致的，即在地质时期，山体滑坡扰动可能在全球碳循环中发挥重要作用，沿海温带森林是潜在碳封存的热点。
Landslides, a forest disturbance, mobilize carbon (C) sequestered in vegetation and soils. Mobilized C is deposited either onto hillslopes or into the water, sequestering C from and releasing C to the atmosphere at different time scales. The C‐dense old‐growth temperate forests of SE Alaska are a unique location to quantify C mobilization rate by frequent landslides that often evolve into saturated moving masses known as debris flows. In this study, the amount of C mobilized by debris flows over historic time scales was estimated by combining a landslide inventory with maps of modeled biomass and soil carbon. We analyzed SE Alaskan landslides over a 55‐year period where a total of 4.69 ± 0.21 MtC was mobilized, an average rate of 2.5 tC km−2 yr−1. A single event in August 2015 mobilized 57,651 ± 3,266 tC, an average of 63 tC km−2. Depositional fate was inferred using two methods, a standard stream intersection analysis and a second novel approach using simulated debris flow deposition modeling calibrated to the study area. Approximately 60% of debris flow deposits intersected the stream network (9% into mainstem channels, 91% into small tributaries), consistent with long‐term modeled connectivity, suggesting that debris flows are likely to contribute to globally significant amounts of C buried in local fjord sediments. Our results are consistent with an emerging consensus that landslide disturbances that mobilize organic carbon may play an important role in the global carbon cycle over geologic time, with coastal temperate forests being hotspots of potential carbon sequestration.