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.

北极的快速变暖预计将导致北部森林发生重大变化，虽然变暖可能导致森林生长受到短暂而寒冷的生长季节的限制，但气候变化也可能导致意外的发生，其中一个例子是温度变化与森林之间的脱钩。过去几十年来发现的北方森林树木的年生长率表明，一些北极森林系统的树木生长不再受到温度的限制，其原因尚不清楚，也很难测试。由于其他因素影响增长，例如由于气候变暖导致的干旱，该项目将测试北美北部的林线森林的差异，特别是在阿拉斯加和加拿大西北部快速变暖的地区。调查人员将使用从古树的木材中获得的树木年轮记录，数学方法和建模以及木材解剖分析的结合，以更好地了解与差异相关的森林生长模式：如果我们要了解北方森林如何与大气相互作用以及与全球其他特征的反馈，新的测量至关重要。该项目将通过以下方式促进这种理解。利用跨越许多北部地区的树木年轮来估计气候与森林生长之间的关系 该项目为学生、美洲原住民和教师参与北极研究提供资金。北极的迅速变暖预计将对北部产生深远的影响。森林系统的变暖可能会导致森林生产力的提高和生长速度的提高，而森林的生长通常受到短暂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令人惊讶的情况，例如北方地区的温度变化与年增长率之间的脱钩。自此以来在森林地点发现的森林树木二十世纪中叶，这种被称为“分歧问题”的现象表明，一些北极森林系统的树木生长不再主要受到温度的限制。共同变化的生物、生理和环境因素可能影响近期树木的生长。一种假设是，一旦变暖超过生理阈值，干旱胁迫就会限制生长。另一种假设是“全球变暗”，即大气气溶胶的增加会减少树木的生长。太阳辐射可用于该项目将评估北美北部林线森林当前的分歧假设，重点关注阿拉斯加和加拿大西北部的快速变暖地区，这些地区似乎是分歧型效应的关键地区。树木年轮数据（已在手）并更新已显示出尽管最近变暖但生长异常下降的早期证据的关键位置，将使用统计技术、定量木材解剖方法和技术的新颖综合组合来检测生长参数的近期变化。树木生长建模对差异的范围、原因和碳循环影响进行详细评估：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的地球系统域之间的反馈至关重要。通过对每天到百年的时间尺度和从细胞到大陆的空间尺度的气候/生长相互作用的定量估计，为这种理解做出贡献，为北方森林的环境变化和生产力建模提供了有价值的、新颖的数据。研究生，资助高中课程开发和本土教育环境中的课程，以及为教师提供参与实践北极研究的基于实地考察的机会。该奖项是 NSF 的法定使命，并通过使用基金会的智力优势和更广泛的评估进行评估，被认为值得支持影响审查标准。

项目成果

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

公元 1809 年不明火山喷发后北美西北部极端寒冷的时空评估

• DOI: 10.1029/2022pa004581
• 发表时间: 2023-05
• 期刊: Paleoceanography and Paleoclimatology
• 影响因子: 3.5
• 作者: Leland, C.;D’Arrigo, R.;Davi, N.;Anchukaitis, K. J.;Andreu‐Hayles, L.;Porter, T. J.;Galloway, T.;Mant, M.;Wiles, G.;Wilson, R.;et al
• 通讯作者: et al