RAPID: Collaborative Research: Hydrologically driven export of pyrogenic carbon and nutrients in fire-impacted watersheds

整个美国西部的野火规模和频率都在增加。这些野火烧毁了植被和地表土壤，破坏了山坡的稳定，使它们更容易受到侵蚀，从而极大地改变了地球表面。这些变化加在一起，影响了降水和其他物质被输送到河流的方式。河流是将水和材料从源头向下游并最终输送到海洋的主要渠道。然而，考虑到捕捉不可预测的野火事件的挑战，缺乏对火灾发生后立即从集水区输出材料的组成、浓度和时间的了解。在运输的材料中包括烟尘和木炭(称为热源碳)和必要的营养物质，如氮。这些材料对当地生态系统功能、全球生物地球化学循环以及下游饮用水资源的水质都很重要。这项研究将收集和分析圣克拉拉单位闪电综合体火灾后烧毁的流域的水和土壤样本。这些分水岭在火灾发生前进行了测量，并提供了分析火灾前后的水文和生化数据的机会。这项研究将产生有助于了解野火对用于饮用水的水资源的影响的数据，并为缓解这些影响提供有价值的信息。本研究的目标是揭示改变的山坡水文和新燃烧景观中的径流将如何影响生态和生物地球化学关键物质的溪流储存和出口，特别是氮和热解碳。这项研究将在加利福尼亚州中部沿海的一个源头集水区进行，由于其地中海气候，该地区经历了非常年溪流。研究人员将在五个嵌套流域的出口处结合营养物质和热源碳浓度的测量，以评估以前发现的主导径流产生过程的差异如何影响观测到的物质传输。通过部署自动采样器和分光光度计，这项工作将建立一个丰富的数据集，其中包括从火灾后的第一次降水事件到夏季干涸期间的河流中热源碳和养分浓度。这对于构建受火灾影响的流域的水文和生物地球化学过程的综合观点是至关重要的。该项目将为本科生和研究生提供培训，并生成数据，向圣克拉拉河谷水区通报从烧毁的分水岭向饮用水水源出口材料的情况。该项目由地球科学部的水文科学、地球生物学和低温地球化学计划和环境生物学部的生态系统科学集群计划共同资助。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Wildfire magnitude and frequency are increasing across the western US. These wildfires are drastically altering Earth’s surface by burning vegetation and surface soils and destabilizing hillslopes, making them more prone to erosion. Together, these alterations impact how precipitation and other material is transported to rivers. Rivers are the main conduit for transferring water and materials from headwaters further downstream and ultimately to oceans. However, given the challenges of capturing unpredictable wildfire events, there is a lack of understanding of the composition, concentration, and timing of material export out of watersheds immediately following fires. Included in the material being transported is soot and charcoal (called pyrogenic carbon) and essential nutrients, such as nitrogen. These materials are important for local ecosystem function, global biogeochemical cycles, and for the water quality of downstream drinking water resources. This study will collect and analyze water and soil samples from burned watersheds following the fires of the Santa Clara Unit Lightning Complex. The watersheds were instrumented prior to the fires and provide an opportunity to analyze hydrologic and biochemical data previous to and after the fire. This study will generate data that will help to understand the impacts of wildfires on water resources used for drinking water purposes and provide valuable information for mitigation of these impacts.The goal of this research is to reveal how altered hillslope hydrology and streamflow in newly burned landscapes will impact the in-stream storage and export of ecologically and biogeochemically critical material, with specific focus on nitrogen and pyrogenic carbon. This research will be conducted in a headwater catchment in central coastal California, which experiences non-perennial streamflow due to its Mediterranean climate. Researchers will couple measurements of nutrient and pyrogenic carbon concentrations at the outlets of five nested watersheds to assess how previously identified differences in dominant streamflow generation processes influence observed material transport. Through deployment of automated samplers and a spectrophotometer, this work will develop a rich dataset of in-stream pyrogenic carbon and nutrient concentrations from the very first post-fire precipitation event to the summer dry down. This is critical for constructing an integrative view of hydrologic and biogeochemical processes in fire- impacted watersheds. The project will provide train undergraduate and graduate students and generate data that will inform the Santa Clara Valley Water District on the export of materials from burned watershed into drinking water sources. This project is jointly funded by the Hydrologic Sciences and Geobiology and Low-Temperature Geochemistry programs in the Division of Earth Sciences and the Ecosystem Science Cluster program in the Division of Environmental Biology.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.