Collaborative Research: Tracking Divergent Warming and Tree Growth at Arctic Treeline

合作研究：追踪北极林线的不同变暖和树木生长

• 批准号: 2124889
• 负责人: Kevin Anchukaitis
• 金额: $ 20.4万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-03-01 至 2025-02-28
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2124889&HistoricalAwards=false
• 关键词: Collaborative; Research; Tracking; Divergent; Warming

The rapid warming of the Arctic is expected to cause major changes to northern forests. While warming may lead to increased growth in forests limited by short, cold growing seasons, climate change could also lead to surprises. One example is a decoupling between temperature variability and annual growth rates in boreal forest trees that has been detected over the past few decades. This ‘divergence problem’ suggests that tree growth in some arctic forest systems is no longer limited by temperature. The causes are not well understood and can be hard to test due to other factors impacting growth, such as drought due to the warming climate. This project will test for divergence across the treeline forests of northern North America, especially in rapidly warming regions of Alaska and northwestern Canada. The investigators will use tree-ring records obtained from the wood of ancient trees, a combination of mathematical methods and modeling, and wood anatomy analysis, to better understand forest growth patterns related to divergence. Broader Impacts: New measurements are critical if we are to understand how boreal forests interact with the atmosphere and feedback with other features of the global environment. This project will contribute to this understanding by estimating relationships between climate and forest growth using tree rings at sites spanning many northern locations. The project provides funding for students, Native American citizens, and for teachers to take part in Arctic research.The rapid warming of the Arctic is expected to impact profoundly northern forest systems. While warming may lead to greater productivity and growth in forests typically limited by short, cold growing seasons, the speed and magnitude of climate change could also lead to surprises. One example is a decoupling between temperature variability and annual growth rates in boreal forest trees that has been detected at forest sites since the middle of the twentieth century. This phenomenon, known as the ‘divergence problem’, suggests that tree growth in some Arctic forest systems is no longer primarily limited by temperature. The causes are not well understood and have been difficult to test due to the co-varying biological, physiological, and environmental factors potentially impacting recent tree growth. One hypothesis is that once warming has surpassed a physiological threshold, drought stress limits growth. Another hypothesis is ‘global dimming’, in which increased atmospheric aerosols decrease the amount of solar radiation available for photosynthesis. This project will assess current divergence hypotheses across the treeline forests of northern North America, emphasizing rapidly warming regions of Alaska and northwestern Canada, which appear to be key areas for divergence-type effects. The project will leverage a new, large compilation of tree-ring data (already in hand) and update key locations that have shown early evidence of unusual growth decline despite recent warming. Detection of recent changes in growth parameters will use a novel, integrated combination of statistical techniques, quantitative wood anatomy methods, and tree growth modeling to develop a detailed assessment of the extent, causes, and carbon cycle implications of divergence. Broader Impacts: New measurements of boreal forest dynamics are critical for understanding how boreal systems interact with the changing atmosphere and the feedbacks between coupled earth system domains. This project will contribute to this understanding by developing quantitative estimates of climate/growth interactions at daily to centennial time scales and spatial scales from cellular to continental, yielding valuable, novel data for modeling of environmental change and productivity in northern forests. The project provides three years of support for a graduate student, funding for high school curricular development and courses in native educational settings, and fieldwork-based opportunities for a teacher to take part in hands-on Arctic research.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.

预计北极的快速变暖会导致北森林的重大变化。虽然变暖可能会导致森林的增长受到短而寒冷的生长季节的限制，但气候变化也可能导致惊喜。一个例子是在过去几十年中检测到的北方林木中温度可变性和年增长率之间的脱钩。这个“差异问题”表明，某些北极森林系统中的树木生长不再受温度的限制。原因不充分理解，由于其他影响生长的因素，例如由于气候变暖而难以测试。该项目将测试北美林线森林的分歧，尤其是在阿拉斯加和加拿大西北部的快速变暖地区。研究人员将使用从古老树木的木头获得的树木记录，数学方法和建模以及木材解剖学分析的结合，以更好地理解与差异有关的森林生长模式。更广泛的影响：如果我们要了解北方森林如何与大气相互作用并与全球环境的其他特征相互作用，那么新的测量值至关重要。该项目将通过在许多北部地区使用树环估算气候与森林增长之间的关系来有助于这种理解。该项目为学生，美国原住民公民和教师参与北极研究提供资金。北极的快速变暖有望影响北方森林系统。虽然变暖可能会导致森林的生产率和增长通常受到短而寒冷的生长季节的限制，但气候变化的速度和幅度也可能导致惊喜。一个例子是自20世纪中叶以来在森林地点发现的北方林木中温度变化和年增长率之间的脱钩。这种现象被称为“发散问题”，表明某些北极森林系统中的树木生长不再受温度的限制。由于共同变化的生物学，生理和环境因素可能会影响最近的树木生长，因此这些原因尚未得到充分的理解，并且很难测试。一个假设是，一旦变暖幸存下来，就有身体阈值，干旱应力限制了生长。另一个假设是“全球变暗”，其中增加的大气气溶胶减少了可用于光合作用的太阳辐射量。该项目将评估当前北美林线森林的当前差异假设，强调阿拉斯加和加拿大西北部的快速变暖地区，这似乎是分歧型影响的关键领域。该项目将利用新的大量汇编树木数据（已经在手头上），并更新关键位置，这些位置已显示出早期的证据表明，最近变暖了。最新生长参数变化的检测将使用统计技术，定量解剖方法和树木生长模型的新颖，整合的组合，以对差异的程度，原因和碳循环含义进行详细评估。更广泛的影响：北方森林动态的新测量对于了解北方系统如何与变化的大气以及耦合地球系统域之间的反馈相互作用至关重要。该项目将通过开发每天从细胞到连续的百年纪化时间尺度和空间量表的定量估计来促进这种理解，从而产生北部森林中环境变化和生产力的新颖数据。该项目为研究生提供了三年的支持，用于高中课程发展的资金和本地教育环境中的课程，以及基于现场工作的机会，使教师有机会参加北极研究的动手研究。这项奖项反映了NSF的法定任务，并通过使用该基金会的知识分子和更广泛的影响来评估NSF的法定任务，并被认为是珍贵的支持。

项目成果

A Spatiotemporal Assessment of Extreme Cold in Northwestern North America Following the Unidentified 1809 CE Volcanic Eruption

• DOI: 10.1029/2022pa004581
• 发表时间: 2023-04
• 期刊: Paleoceanography and Paleoclimatology
• 影响因子: 3.5
• 作者: C. Leland;R. D’Arrigo;N. Davi;K. J. Anchukaitis;L. Andreu‐Hayles;T. Porter;T. Galloway;M. Mant;G. Wiles;R. Wilson;S. Beaulieu;R. Oelkers;B. Gaglioti;M. Rao;E. Reid;T. Nixon