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: 2124824
• 负责人: Benjamin Gaglioti
• 金额: $ 16.76万
• 依托单位: University of Alaska Fairbanks Campus
• 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=2124824&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.

北极的迅速变暖预计将对北方森林造成重大变化。虽然气候变暖可能会导致受短而冷的生长季节限制的森林增长增加，但气候变化也可能导致意外。一个例子是过去几十年来发现的北方森林树木的温度变化和年生长率之间的脱钩。这种“分歧问题”表明，在某些北极森林系统中，树木的生长不再受温度的限制。其原因尚不清楚，并且由于其他影响生长的因素，如气候变暖导致的干旱，很难进行测试。该项目将测试北美北方森林线的差异，特别是在阿拉斯加和加拿大西北部迅速变暖的地区。研究人员将使用从古树木材中获得的树木年轮记录，结合数学方法和建模以及木材解剖分析，以更好地了解与分歧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反馈，新的测量方法至关重要。该项目将通过利用跨越北方许多地点的树木年轮来估计气候与森林生长之间的关系，从而促进这一认识。该项目为学生、美洲原住民和教师提供资金，让他们参与北极研究。北极的迅速变暖预计将对北方森林系统产生深远影响。虽然气候变暖可能会导致森林生产力的提高和增长，但通常受到短而冷的生长季节的限制，气候变化的速度和幅度也可能导致意外。一个例子是自二十世纪中期以来在森林地点发现的北方森林树木的温度变化和年生长率之间的脱钩。这一现象被称为“分歧问题”，表明在某些北极森林系统中，树木的生长不再主要受温度的限制。其原因尚不清楚，并且由于可能影响最近树木生长的共同变化的生物，生理和环境因素而难以测试。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。 另一种假说是“全球变暗”，即大气气溶胶的增加减少了光合作用所需的太阳辐射量。该项目将评估目前在北美北方的林木线森林的分歧假设，强调迅速变暖的阿拉斯加和加拿大西北部地区，这似乎是关键领域的分歧型的影响。该项目将利用一个新的，大量的树木年轮数据汇编（已经在手）和更新的关键地点，已经显示出早期的证据，不寻常的增长下降，尽管最近变暖。检测最近的变化，生长参数将使用一种新的，综合的统计技术，定量木材解剖方法和树木生长建模的结合，制定一个详细的评估的程度，原因和碳循环的分歧。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相互作用以及耦合的地球系统域之间的反馈至关重要。该项目将通过对气候/生长相互作用进行定量估计，从每日到百年的时间尺度和从细胞到大陆的空间尺度，为北方森林的环境变化和生产力建模提供有价值的新数据，从而促进对这一问题的理解。该项目为研究生提供三年的支持，为高中课程开发和本地教育环境中的课程提供资金，并为教师提供实地考察的机会，让他们参与北极研究。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。