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、纤维和能源的主要来源。 它们通过在植物生物质中封存碳而在地球气候系统中发挥着重要作用，否则这些碳可能形成大气温室气体（例如二氧化碳）的分子骨架。森林捕获大气二氧化碳和产生生物量的能力可能会随着年龄和干扰而发生巨大变化。 科学家长期以来一直认为，随着森林老化，生长和碳吸收量会下降。然而，新的观察结果表明，老化森林中的低水平干扰，例如源自害虫、真菌病原体和极端天气的干扰，可能与直觉相反，维持甚至增加森林碳固存和生长。森林固碳率高于预期的背后机制尚不清楚。本研究旨在确定森林生长对干扰的恢复能力的机制及其阈值。研究人员还将评估对于预测未来森林碳储存、生长和产量至关重要的不同计算机模拟是否、如何以及为何无法复制这种弹性。此外，他们还将确定美国西部的常绿森林和东部的落叶森林，在不同的普遍干扰模式和气候下，是否遵循独特的年龄森林生长轨迹。该项目对社会、森林和土地管理者、小学教育工作者、大学生和森林科学家的好处是深远的。通过将生物信息实地和模拟实验与北美森林的综合相结合，这项研究将显着推进我们对森林干扰的生态思考，同时产生与生态系统和地球系统模拟直接相关且可获取的结果，并为致力于在日益受到干扰的森林景观中最大化碳储存、生长和木材生产的森林管理者提供直接相关和可获取的结果。该项目将为小学教师制作公开的教学材料，培训多名研究生和本科生，向科学家和土地管理者提供开放透明的数据源和计算机代码，并在美国能源部实验室和学术机构之间建立学生培训合作伙伴关系。  由于美国中西部北部和东部的森林从早期森林演替到中期演替，未来的陆地碳汇是不确定的。随着这一转变，早期演替的冠层优势植物正在衰老，并让位给生物和结构更加复杂的森林，这些森林越来越受到中度严重的干扰。最近的研究表明，这些森林的净初级生产力可能会以高于预期的速度持续存在，但这种功能恢复力的局限性和背后的机制无法从现有知识中预测出来，而现有知识几乎完全来自对最近受干扰森林中严重的林分替代干扰动态的研究。从相同的知识基础发展而来的生态系统和全球模型也难以再现适度干扰的影响。这项工作的三个核心研究目标是：1）确定支持净初级生产对干扰的恢复能力的机制及其阈值；了解不同的森林模型是否、如何以及为何无法复制这种核电厂复原力； 3）阐明具有不同干扰机制和气候的温带落叶林和针叶林是否遵循独特的年龄生产轨迹。该项目采用实地实验、模型测试和大规模数据合成三管齐下的方法，以转变人们对碳循环对老化森林中一系列中等干扰强度的恢复能力的理解，阐明决定净初级生产恢复力和衰退之间阈值的根本机制。现场组件使用完全复制的干扰严重程度梯度（从 0% 到 85% 落叶）来系统地确定碳循环如何以及为何随着干扰水平的上升而变化。 PI将采用一套碳和氮循环测量，重点关注冠层结构、叶片生理学和冠层氮重新分配，以确定导致净初级生产力快速恢复或干扰后下降的机制。该项目的建模部分使用数据同化实验，在 NSF 支持的开源生态信息学工具箱中运行两个截然不同的生态生理模型，以确定模型未能模拟净初级生产对干扰的恢复力的假设的最重要过程，并迭代地告知下一个田间季节的采样优先级。最后，数据合成部分使用新获得的观测结果来描述对北美温带森林年龄网生态系统生产轨迹的干扰影响。

项目成果

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

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

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

The <i>fortedata</i> R package: open-science datasets from a manipulative experiment testing forest resilience

<i>fortedata</i> R 包：来自测试森林恢复力的操作性实验的开放科学数据集

• DOI: 10.5194/essd-13-943-2021
• 发表时间: 2021
• 期刊: Earth System Science Data
• 影响因子: 11.4
• 作者: Atkins, Jeff W.;Agee, Elizabeth;Barry, Alexandra;Dahlin, Kyla M.;Dorheim, Kalyn;Grigri, Maxim S.;Haber, Lisa T.;Hickey, Laura J.;Kamoske, Aaron G.;Mathes, Kayla
• 通讯作者: Mathes, Kayla

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.