Quantifying Postfire Aeolian Sediment Transport Using Rare Earth Element Tracers
Quantifying Postfire Aeolian Sediment Transport Using Rare Earth Element Tracers
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DOI：
10.1002/2017jg004284
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发表时间：
2016-12
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影响因子：
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通讯作者：
David Dukes;H. B. Gonzales;S. Ravi;D. Grandstaff;R. V. Van Pelt;Junran Li;Guan Wang;J. Sankey
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文献类型：
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作者：
David Dukes;H. B. Gonzales;S. Ravi;D. Grandstaff;R. V. Van Pelt;Junran Li;Guan Wang;J. Sankey
草原在世界上许多干旱和半干旱地区提供基本的生态系统服务，正在经历迅速的火灾活动，并且非常容易受到火灾后加速的土壤风蚀的影响。因此，需要对与植被变化、土壤生物地球化学循环、空气质量和景观演变相关的物理过程进行量化评估，其中包括火-风侵蚀反馈。我们研究了一种新的示踪技术-使用多种稀土元素(REE)-在美国新墨西哥州奇瓦瓦沙漠燃烧和未燃烧的灌木-草过渡带中量化土壤风运移并确定风吹沉积物的源和汇的适用性。结果表明，火灾发生后，风生泥沙的水平质量通量增加了近3倍。风生沉积物的稀土元素示踪分析表明，未焚烧地水平质量通量的来源主要来自裸露微区(88.5%)，而火烧地主要来自灌木(42.3%)和裸露(39.1%)微区。植被覆盖的微型场地主要是未烧毁地区的风沙沉淀池，在火灾后成为沉淀物来源。火烧区表现出沉积物示踪剂的空间均质性，突出了灌木入侵草原对景观异质性的潜在负反馈。虽然众所周知，火灾会增加风成沉积物的运移，但伴随着风成沉积物的源和汇的变化，可能会影响生物地球化学循环和土地退化动力学。此外，我们的实验表明，稀土元素可以作为现场风沙研究的可靠示踪剂。
Grasslands, which provide fundamental ecosystem services in many arid and semiarid regions of the world, are undergoing rapid increases in fire activity and are highly susceptible to postfire‐accelerated soil erosion by wind. A quantitative assessment of physical processes that integrates fire‐wind erosion feedbacks is therefore needed relative to vegetation change, soil biogeochemical cycling, air quality, and landscape evolution. We investigated the applicability of a novel tracer technique—the use of multiple rare earth elements (REE)—to quantify soil transport by wind and to identify sources and sinks of wind‐blown sediments in both burned and unburned shrub‐grass transition zone in the Chihuahuan Desert, NM, USA. Results indicate that the horizontal mass flux of wind‐borne sediment increased approximately threefold following the fire. The REE tracer analysis of wind‐borne sediments shows that the source of the horizontal mass flux in the unburned site was derived from bare microsites (88.5%), while in the burned site it was primarily sourced from shrub (42.3%) and bare (39.1%) microsites. Vegetated microsites which were predominantly sinks of aeolian sediments in the unburned areas became sediment sources following the fire. The burned areas showed a spatial homogenization of sediment tracers, highlighting a potential negative feedback on landscape heterogeneity induced by shrub encroachment into grasslands. Though fires are known to increase aeolian sediment transport, accompanying changes in the sources and sinks of wind‐borne sediments may influence biogeochemical cycling and land degradation dynamics. Furthermore, our experiment demonstrated that REEs can be used as reliable tracers for field‐scale aeolian studies.