Collaborative Research: MRA: Climate legacies and timescales of influence on carbon cycle processes in drylands

地球的气候正在发生变化，干旱和热浪等极端气候正变得越来越普遍。这些变化正在影响植被生产力、碳循环和水循环，尤其是在美国西部的干旱地区。研究表明，极端气候事件不仅在发生时影响生态系统，而且影响在事件发生后很长一段时间内仍会持续。这种极端气候的持续影响，尤其是干旱事件，通常被称为气候或干旱的“遗产”。研究还表明，过去的条件，无论是否极端，在它们发生后继续影响生态系统，因此生态系统对过去的条件有“记忆”。这些遗产和记忆的重要性可能对理解持续的气候变化将如何影响地球的生态系统和碳平衡至关重要。该项目将研究气候变量（如降水、干旱和温度）对美国西部树木生长、森林生产力和生态系统碳通量的影响。研究人员将分析大量不同类型的数据，包括年树木生长、碳变化和植被生产，并将使用计算机模拟来预测未来的趋势。这项工作的结果将增加对植物和生态系统如何受到气候变率和极端气候事件影响的理解，这可能有助于减轻气候变化的影响。博士后研究人员、研究生和本科生将参与研究。该项目将通过与专业河流向导、州和联邦机构以及对干旱对植被、生态系统和碳循环的影响感兴趣的科学家和土地管理者的合作，与当地和区域社区分享从这项研究中获得的知识。本研究试图在美国西部旱地的一系列时空尺度上，量化气候相关驱动因素对关键c循环成分的遗留（极端事件的长期影响）和记忆（影响的时间尺度，无论极端与否）。本研究将(1)量化气候（如干旱）对碳通量的影响程度和持续时间；(2)评估气候记忆和气候驱动因素影响碳通量的时间尺度；(3)确定美国西部旱地的遗产和记忆响应如何变化；(4)评估遗产和记忆对C循环的重要性。为了解决这些问题，本研究将采用现代统计方法（小波分析、机器学习、贝叶斯模型）来整合不同时空覆盖和分辨率的不同数据集，包括多个树轮网络、地面通量塔、卫星数据产品、模型数据融合产品和生物圈模型输出。这项研究将提供对气候-c循环遗产的规模和持续时间的见解，这些遗产如何在空间上变化，以及产生这些遗产的潜在机制。核心项目团队（8名研究人员）包括3名早期职业科学家，以及多名其他参与者（博士后、博士生、本科生）。该项目包括针对科学界、土地和资源管理者、机构利益相关者和公众的各种培训和外联活动。活动包括组织科学会议，一个以“干旱遗产和地球c循环”为重点的研讨会，通过与国家综合干旱信息系统合作促进机构间的交流，与科罗拉多高原地区的专业指导项目合作向公众传播知识，并为弗拉格斯塔夫科学节开发实践教育材料。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。

Earth’s climate is changing, and climate extremes such as droughts and heat waves are becoming more common. Such changes are impacting vegetation productivity, the carbon cycle, and the water cycle, especially in drier regions in the western United States. Studies are showing that not only do extreme climate events affect ecosystems when those events occur, but the effects continue long after the events themselves. This lingering effect of climate extremes, especially drought events, is often referred to as a climate or drought “legacy.” Studies also suggest that past conditions, regardless of whether extreme or not, continue to affect ecosystems after they have occurred, such that ecosystems have “memory” of those past conditions. The importance of such legacies and memory may be critical to understanding how continued climate change will impact Earth’s ecosystems and carbon balance. This project will study the legacies and memory of climate variables — such as precipitation, drought, and temperature — on tree growth, forest productivity, and ecosystem carbon fluxes in the western US. Researchers will analyze a huge volume of data of different types, including annual tree growth, carbon variability, and vegetation production, and will use computer simulations to predict future trends. Results from this work will increase understanding of how plants and ecosystems are impacted by climate variability and extreme climate events, which may be useful for mitigating the impacts of climate change. Post-doctoral researchers, graduate students, and undergraduate trainees will participate in the research. The project will share knowledge gained from this research with local and regional communities via collaborations with professional river guides, state and federal agencies, and scientists and land managers interested in understanding the impacts of drought on vegetation, ecosystems, and the carbon cycle.This study seeks to quantify legacies (prolonged impacts of an extreme event) and memory (timescales of influence, whether extreme or not) of climate-related drivers on key C-cycle components, over a range of spatial and temporal scales across drylands in the western US. This study will (1) quantify the magnitude and duration of climate (e.g., drought) legacies on C fluxes; (2) evaluate climatic memory and the timescales over which climate drivers impact C fluxes; (3) determine how legacy and memory responses vary across drylands in the western US; and (4) evaluate the importance of legacies and memory for the C cycle. To address these, this study will employ modern statistical methods (wavelet analyses, machine learning, Bayesian models) to integrate diverse datasets varying in temporal and spatial coverage and resolution, including multiple tree-ring networks, ground-based flux towers, satellite data products, model-data fusion products, and biospheric model outputs. This study will provide insights into the magnitude and duration of climate-C-cycle legacies, how these legacies vary across space, and the potential mechanisms giving rise to such legacies. The core project team (8 researchers) includes 3 early career scientists, and multiple additional participants (postdocs, PhD students, undergraduates). The project includes a variety of training and outreach activities aimed at the scientific community, land and resource managers, agency stakeholders, and the public. Activities include organizing sessions for scientific meetings, a workshop focused on “Drought Legacies and Terrestrial C-cycling,” facilitating interagency communication via collaborations with the National Integrated Drought Information System, working with professional guide programs in the Colorado Plateau region to disseminate knowledge to the public, and developing hands-on educational materials for the Flagstaff Festival of Science.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.