Collaborative Research: RAPID: A perfect storm: will the double-impact of 2023/24 El Nino drought and forest degradation induce a local tipping-point onset in the eastern Amazon?

合作研究：RAPID：一场完美风暴：2023/24厄尔尼诺干旱和森林退化的双重影响是否会导致亚马逊东部地区出现局部临界点？

• 批准号: 2403883
• 负责人: Scott Saleska
• 金额: $ 10.38万
• 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: 2024
• 资助国家: 美国
• 起止时间: 2024-02-15 至 2025-01-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2403883&HistoricalAwards=false
• 关键词: Collaborative; Research; RAPID; perfect; storm

The Amazon rainforest sustains itself by recycling rainfall: trees pump water from the soil and release it from their leaves as vapor, which can be recondensed in the atmosphere and fall as rain again. The potential for drought and forest degradation to break this forest-sustaining recycling system, pushing the Amazon rainforest past a point of collapse into a degraded or even savanna state, has received much recent attention in the media and scientific literature. However, exactly how the so-called ‘tipping point’ occurs in any given forest site is unclear. This project investigates two possible causes of tipping points, both of which are predicted to become more common in the future: severe drought linked to El Niño climate conditions, and forest degradation caused by increasingly frequent strong storms and winds. This award capitalizes on a fleeting opportunity to observe how the ongoing drought, amplified by previous forest degradation, shuts down the capacity of trees to transfer water from the soil to the atmosphere, and thereby breaks the water pump that sustains rainfall recycling throughout the Amazon. The knowledge produced will help scientists predict when and how Amazon-wide tipping points might occur, which would importantly affect weather patterns, water resources, and economic stability in South America, as well as global climate. This study has broad impacts on education, through training of graduate students at public universities and through a custom-designed high school educational program that connects U.S. students with Amazon researchers and real scientific data from trees of the world’s most famous tropical forest.This study focuses on whole-forest and leaf-level observations of transpiration–the transport of water by trees from soil to atmosphere during photosynthesis–through drought and initial recovery. It tests three key hypotheses at the heart of the Amazon forest tipping-point paradigm. H1) Whole-forest drought sensitivity is heightened by the legacy of previous droughts. H1 is tested by comparing eddy-flux-tower measured 2023/24 drought response to those of previous droughts, notably the extreme El Niño of 2015/16. H2) Whole-forest drought sensitivity emerges from individual trees’ differing ecophysiological strategies for drought response. These strategies contribute to ecosystem-scale drought sensitivity and structure the tipping point onset. H2 is tested by observing responses across six dominant species, providing a foundation for individual-to-ecosystem trait-based scaling. H3) Forest drought sensitivity is heightened by disturbance-induced forest degradation. H3, widely postulated but never directly tested, explores the tipping point mechanisms relating increased drought sensitivity to altered energy balance from forest cover loss. H3 is tested by comparing tree ecohydrology and microenvironments between forest interior and large windthrow gaps. This research will provide new, hard-to-observe datasets that will allow critical tests (and subsequent improvement) of models of forest drought response and ecohydrologic tipping pointsThis 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.

The Amazon rainforest sustains itself by recycling rainfall: trees pump water from the soil and release it from their leaves as vapor, which can be recondensed in the atmosphere and fall as rain again. The potential for drought and forest degradation to break this forest-sustaining recycling system, pushing the Amazon rainforest past a point of collapse into a degraded or even savanna state, has received much recent attention in the media and scientific literature.但是，确切地说，在任何给定的森林地点，所谓的“临界点”的发生方式尚不清楚。 This project investigates two possible causes of tipping points, both of which are predicted to become more common in the future: severe drought linked to El Niño climate conditions, and forest degradation caused by increasingly frequently strong storms and winds. This award capitalizes on a fleeting opportunity to observe how the ongoing drought, amplified by previous forest degradation, shuts down the capacity of trees to transfer water from the soil to the atmosphere, and thereby breaks the water pump that maintains rainfall recycling throughout the Amazon. The knowledge produced will help scientists predict when and how Amazon-wide tipping points might occur, which would importantly affect weather patterns, water resources, and economic stability in South America, as well as global climate. This study has broad impacts on education, through training of graduate Students at public universities and through a custom-designed high school educational program that connects U.S. students with Amazon researchers and real scientific data from trees of the world’s most famous tropical forest.This study focuses on whole-forest and leaf-level observations of transmission–the transport of water by trees from soil to atmosphere during photosynthesis–through drought and initial recovery.它在亚马逊森林临界点范式的中心测试了三个关键假设。 H1）先前干旱的遗产提高了全林干旱的敏感性。 H1 is tested by comparing eddy-flux-tower measured 2023/24 drought response to those of previous droughts, notably the extreme El Niño of 2015/16. H2）各个树木的不同生态生理策略以干旱反应而产生全林干旱敏感性。这些策略有助于生态系统规模的干旱敏感性，并构建临界点的发作。 H2通过观察六个主要物种的响应来测试，为基于个体的基于生态系统性状的缩放为基础提供了基础。 H3）森林干旱的敏感性通过干扰引起的森林退化提高。 H3, widely posted but never directly tested, explores the tipping point mechanisms relating increased drought sensitivity to altered energy balance from forest cover loss.通过比较森林内部和大风间隙之间的树生态干旱和微环境来测试H3。 This research will provide new, hard-to-observe datasets that will allow critical tests (and subsequent improvement) of models of forest drought response and ecological tipping points This award reflects NSF's statutory mission and has been deemed precious of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.