Collaborative Research: Thresholds and mechanisms of net ecosystem production (NEP) resilience following moderate disturbance: Why does one ecosystem recover and another one crash?

合作研究：中度干扰后生态系统净生产（NEP）恢复力的阈值和机制：为什么一个生态系统恢复而另一个生态系统崩溃？

• 批准号: 1655095
• 负责人: Christopher Gough
• 金额: $ 80万
• 依托单位: Virginia Commonwealth University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-08-15 至 2023-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1655095&HistoricalAwards=false
• 关键词: Collaborative; Research; Thresholds; mechanisms; net

Forests of the United States are primary sources of food, fiber and energy. They play a fundamental role in the earth's climate system by sequestering in plant biomass carbon that might otherwise form the molecular backbone of atmospheric greenhouse gases such as carbon dioxide. Forests' capacity to capture atmospheric carbon dioxide and build biomass may change substantially with age and disturbance. Scientists have long theorized a decline in growth and carbon uptake as forests age. New observations, however, suggest that low levels of disturbance, such as those originating from insect pests, fungal pathogens, and extreme weather, in aging forests may, counter-intuitively, sustain or even increase forest carbon sequestration and growth. The mechanisms underlying these higher-than-expected rates of forest carbon sequestration are unknown. This study seeks to identify the mechanisms underpinning forest growth resilience to disturbance, and their thresholds. The researchers will also evaluate if, how, and why different computer simulations, critical to predicting future forest carbon storage and growth and yield, fail to replicate this resilience. Furthermore, they will determine whether evergreen forests in the western United States and deciduous forests in the East, with different prevailing disturbance regimes and climates, follow unique age-forest growth trajectories. The benefits of this project to society, forest and land managers, grade school educators, university students, and forest scientists are far-reaching. By combining biologically-informed field and simulation experiments with a synthesis of North American forests, this study will significantly advance our ecological thinking about forest disturbance, while producing results immediately relevant and accessible to ecosystem and earth system simulations, and to forest managers working to maximize carbon storage, growth, and timber production in increasingly disturbed forest landscapes. The project will produce openly available instructional materials for grade school teachers, train several graduate and undergraduate students, provide open and transparent sources of data and computer code to scientists and land managers, and form a student training partnership between a United States Department of Energy laboratory and an academic institution.  The future terrestrial carbon sink is uncertain as forests of the United States upper Midwest and east broadly advance from early to middle forest succession. With this transition, early successional canopy dominants are senescing and giving way to more biologically and structurally complex forests that are increasingly subject to moderate severity disturbance. Recent studies suggest that net primary production may be sustained in such forests at higher-than-expected rates, but the limits of and mechanisms behind such functional resilience cannot be predicted from present knowledge, which is derived almost entirely from studies of severe, stand-replacing disturbance dynamics in recently disturbed forests. Ecosystem and global models, developed from the same intellectual foundations, also have trouble reproducing the effects of moderate disturbances. The three core research objectives of this work are to: 1) identify mechanisms supporting net primary production resilience to disturbance, and their thresholds; understand if, how, and why different forest models fail to replicate this NPP resilience; and 3) elucidate whether temperate deciduous and coniferous forests, with different disturbance regimes and climates, follow unique age-production trajectories. The project uses a 3-pronged approach of field experiments, model testing, and large-scale data synthesis to transform understanding of how resilient the carbon cycle will be to a range of moderate disturbance intensities in aging forests, elucidating the underlying mechanisms that determine the threshold between net primary production resilience and decline. The field component uses a fully replicated gradient of disturbance severity, from 0 to 85 % defoliation, to systematically determine how and why the carbon cycle shifts in response to rising disturbance levels. The PIs will employ a suite of carbon and nitrogen cycling measurements, focusing on canopy structure, leaf physiology, and canopy nitrogen reallocation, to identify the mechanisms that cause rapid net primary production resilience or decline following disturbance. The modeling component of the project uses data assimilation experiments, running two very different ecophysiological models within an open source, NSF-supported ecoinformatics toolbox, to identify the processes most responsible for the models' hypothesized failure to simulate net primary production resilience to disturbance, and iteratively inform the next field season's sampling priorities. Finally, a data synthesis component uses newly available observations to characterize disturbance effects on age-net ecosystem production trajectories for North American's temperate forests.

美国的森林是食物，纤维和能量的主要来源。它们通过隔离植物生物量碳中的含量，在地球的气候系统中起着基本作用，否则可能构成大气温室气体（例如二氧化碳）的分子骨干。森林捕获大气二氧化碳和建造生物质的能力可能会随着年龄和灾难而发生重大变化。随着森林年龄的增长，科学家长期以来一直将生长和碳吸收下降。然而，新的观察结果表明，在衰老的森林中，造成害虫，真菌病原体和极端天气的灾难水平较低，可能会违反直觉，甚至可以维持甚至增加森林碳螯合和生长。这些高于预期的森林碳固存的机制尚不清楚。这项研究旨在确定森林生长抗障碍及其阈值的基础的机制。研究人员还将评估是否，如何以及为什么不同的计算机模拟对于预测未来的森林碳储存，生长和产量至关重要，无法复制这种弹性。此外，他们将确定在美国西部的常绿森林和东方的决定森林是否具有不同的灾难制度和气候，并遵循独特的年龄增长轨迹。该项目对社会，森林和土地经理，小学教育者，大学生和森林科学家的好处是深远的。通过将生物知识的现场和模拟实验与北美森林的合成结合，这项研究将大大提高我们对森林灾难的生态思维，同时产生与生态系统和地球系统模拟的立即相关且可访问的结果，以及致力于最大程度地吸收碳储存，增长和木材的森林经理，在日益激烈的森林景观中产生碳的生产和木材。该项目将为小学教师提供公开可用的教学材料，培训几名研究生和本科生，向科学家和土地管理者提供开放透明的数据和计算机代码来源，并在美国能源实验室和学术机构之间建立学生培训合作伙伴关系。随着美国上西部和东部的森林从早期到中森林的成功，未来未来的地面碳水槽不确定。通过这种过渡，早期的成功冠层优势正在感知并让位于更加生物学和结构上复杂的森林，这些森林越来越多地遭受中等严重性的灾难。最近的研究表明，在此类森林中，净初级产量可能以高于预期的速度来维持，但是这种功能弹性背后的局限性和机制不能从当前知识中预测，这几乎完全来自最近受影响森林中严重的，替代性障碍动态的研究。从相同的智力基础开发的生态系统和全球模型也难以再现中等灾难的影响。这项工作的三个核心研究目标是：1）确定支持净生产抗灾难及其阈值的机制；了解是否，如何以及为什么不同的森林模型无法复制这种NPP的弹性； 3）阐明具有不同灾难制度和气候的温度决定和针叶林是否遵循独特的年龄生产轨迹。该项目使用现场实验，模型测试和大规模数据合成的三方面方法，以改变人们对碳循环如何弹性的理解，从而在衰老的森林中如何适应中等的灾难强度，从而阐明了确定净产生生产能力和下降之间阈值的基本机制。该田间组件使用灾难严重性的完全复制的梯度，从0到85％的落叶，以系统地确定碳周期如何以及为何响应灾难水平上升的响应。 PIS将采用一套碳和氮气循环测量值，重点关注冠层结构，叶子生理和冠层氮的重新分配，以确定在灾难后引起快速净初级生产弹性或下降的机制。该项目的建模组件使用数据同化实验，在开放源代码内运行两个非常不同的生态生理模型，即NSF支持的生态信息信息箱，以识别最大程度地负责该模型的过程，该过程对模拟净净产量生产能力模拟了灾难的抗灾能力，并迭代地将下一个现场季节告知下一个现场赛季的采样率。最后，数据合成部分使用新的可用观测值来表征北美温度森林对年龄网状生态系统生产轨迹的灾难影响。

项目成果

Collar Properties and Measurement Time Confer Minimal Bias Overall on Annual Soil Respiration Estimates in a Global Database

• DOI: 10.1029/2020jg006066
• 发表时间: 2020-11
• 期刊: Journal of Geophysical Research: Biogeosciences
• 作者: J. Jian;C. Gough;D. Sihi;A. Hopple;B. Bond‐Lamberty

Mapping Temperate Forest Phenology Using Tower, UAV, and Ground-Based Sensors

• DOI: 10.3390/drones4030056
• 发表时间: 2020-09
• 期刊: Drones
• 影响因子: 4.8
• 作者: J. Atkins;A. Stovall;Xi Yang

Inferring the effects of partial defoliation on the carbon cycle from forest structure: challenges and opportunities

从森林结构推断部分落叶对碳循环的影响：挑战与机遇

• DOI: 10.1088/1748-9326/ac46e9
• 发表时间: 2022
• 期刊: Environmental Research Letters
• 影响因子: 6.7
• 作者: Gough, Christopher M;Foster, Jane R;Bond-Lamberty, Ben;Tallant, Jason M
• 通讯作者: Tallant, Jason M

Mechanistically-grounded pathways connect remotely sensed canopy structure to soil respiration

机械接地路径将遥感冠层结构与土壤呼吸连接起来

• DOI: 10.1016/j.scitotenv.2022.158267
• 发表时间: 2022
• 期刊: Science of The Total Environment
• 影响因子: 9.8
• 作者: Hickey, Laura J.;Nave, Lucas E.;Nadelhoffer, Knute J.;Clay, Cameron;Marini, Alexandra I.;Gough, Christopher M.
• 通讯作者: Gough, Christopher M.

Structure and parameter uncertainty in centennial projections of forest community structure and carbon cycling

森林群落结构和碳循环百年预测的结构和参数不确定性

• DOI: 10.1111/gcb.15164
• 发表时间: 2020
• 期刊: Global Change Biology
• 影响因子: 11.6
• 作者: Shiklomanov, Alexey N.;Bond‐Lamberty, Ben;Atkins, Jeff W.;Gough, Christopher M.
• 通讯作者: Gough, Christopher M.