Collaborative Research: Understanding the impacts of an ongoing megadrought: Synthesizing the role of soil moisture in driving ecosystem fluxes from site to regional scales

美国西部旱地目前正处于长达23年的“特大干旱”之中，这是过去1200年来最干旱的时期。这一特大干旱是一场持续的气候危机，严重影响着自然生态系统、森林管理、农业系统和人类水资源。尽管后果如此严重，我们对超级干旱的了解还是相当有限。具体来说，研究界缺乏对特大干旱如何影响土壤湿度的全面了解，特别是对植被健康至关重要的深层水分库。在过去的23年里，人们对碳和水循环是如何变化的理解也很有限；调节全球气候反馈的生态系统功能的重要指标。这项研究增强了我们对干旱如何影响旱地的生态学理解，这为对未来气候变化影响的更预测性理解奠定了基础。这一知识可用于其他旱地和非旱地生物群系，因为预计未来几十年全球此类特大干旱的频率和严重程度将增加。为了实现这些目标，该研究将数百个长期土壤水分深度剖面与遥感估计的浅层土壤水分、深水可用性和地下水结合起来。这些数据使我们能够评估特大干旱对植物可用水分的影响，并作为这些遥感产品用于干旱监测的关键验证。利用21个涡动相关塔的数据与经验模拟生态系统通量的网格化数据相结合，揭示了旱地生态系统功能的驱动因素，并在高时空分辨率上量化了特大干旱对碳水通量的影响。通过综合这些数据源，利用它们的独特优势；利用原位数据解决详细的机制问题，并利用建模和遥感数据研究碳-水循环的广泛趋势。该项目由生态系统科学和促进竞争研究的既定计划（EPSCoR）共同资助。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Drylands in the American West are currently in the grips of a 23-year long ‘megadrought’, constituting the driest period of the last 1,200 years. This megadrought is an ongoing climate crisis that is severely impacting natural ecosystems, managed forests, agricultural systems, and human water resources. Despite such serious consequences, our understanding of the megadrought is quite limited. Specifically, the research community lacks a comprehensive understanding of how the megadrought has impacted soil moisture, particularly the deeper moisture pools that are critical for vegetation health. There is also a limited understanding of how carbon and water cycling have changed over the last 23 years; an important indicator of ecosystem function that mediates global climate feedbacks. This research enhances our ecological understanding of how drylands have been impacted by the megadrought, which sets the stage for a more predictive understanding of future climate change impacts. This knowledge is transferable to other dryland and non-dryland biomes, as such megadroughts are projected to increase in frequency and severity globally in the coming decades. To accomplish these aims, the research combines hundreds of long-running soil moisture depth profiles with remotely-sensed estimates of shallow soil moisture, deep water availability, and groundwater. These data allow us to assess the impacts of the megadrought on plant-available water, and serve as a crucial validation of these remotely-sensed products for drought monitoring. Data from 21 eddy covariance towers are paired with a new gridded dataset of empirically-modeled ecosystem fluxes to uncover the drivers of dryland ecosystem function, and quantify the impact of the megadrought on carbon-water fluxes at high spatial and temporal resolutions. By synthesizing these data sources their unique strengths are leveraged; addressing detailed mechanistic questions with in situ data, and examining broad trends in carbon-water cycling using modeled and remotely-sensed data. This project is jointly funded by Ecosystem Science and the Established Program to Stimulate Competitive Research (EPSCoR).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.