The multidimensionality of forest carbon cycling and structure in response to disturbance

森林提供食物、燃料、木材、娱乐和野生动物栖息地，并储存大量的碳。然而，这些有价值的商品和服务的可持续性受到昆虫的威胁，这些昆虫会落叶并经常杀死树木。该项目利用实地试验和计算机模型来调查木材蛀虫造成的树木死亡率变化对森林生长和碳吸收的影响。具体而言，该研究研究了扰动后森林生长和碳固存的初始变化是否可用于预测对森林和土地管理者有意义的时间尺度上的长期响应；哪些生物和物理特征使森林能够从干扰中恢复；计算机模型需要包括哪些信息来预测森林对害虫的反应。该项目有一个由本科生、学士后和研究生组成的多元化团队，提供适用于森林和保护管理、环境科学和政策、数据管理、计算机编码和模型模拟等职业的培训。该项目还为高级大学教师、专业生态学家、土地管理人员和商业林农提供免费的教育资源。此外，项目数据和现场实验本身——位于密歇根州的一个现场站——每年为数百名学生、研究人员、教育工作者和社区成员提供现场教育和研究培训的公开共享资源。该项目使用森林恢复阈值实验（FoRTE），该实验于2018年在密歇根大学生物站成立，旨在研究森林碳循环过程如何以及为什么会对害虫和病原体引起的一系列严重干扰做出反应。重复的8公顷试验包括零（对照）、45%、65%和85%的总落叶水平，并包含两种干扰类型。利用FoRTE的干扰严重程度、场地生产力和植被组成的扩展轴，该项目利用观测结果来提出以下问题：(1)碳循环稳定性的维度之间是否存在权衡；(2)在干扰响应期间，森林成分、结构和净初级产量之间存在多大程度的联系；(3)在整个干扰-响应周期中，模拟观测到的碳循环稳定性需要多大程度的模型复杂性？本研究通过实验和计算模拟了新出现的扰动模式的碳循环后果。该实验采用了一种新的稳定性理论框架来评估碳循环对干扰程度和类型的响应，该框架以前几乎只适用于种群和社区。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Forests provide food, fuel, timber, recreation and wildlife habitat, and store large amounts of carbon. However, the sustainability of these valuable goods and services is threatened by insects that defoliate and often kill trees. This project uses field experiments and computer models to investigate how forest growth and carbon uptake are affected by variable levels of tree mortality caused by wood boring insects. Specifically, the research studies whether initial changes in forest growth and carbon sequestration following disturbance can be used to predict longer-term responses at timescales meaningful to forest and land managers; what biological and physical characteristics enable forests to recover from disturbance; and what information needs to be included in computer models to predict how forests will respond to insect pests. The project engages a diverse team of undergraduate, post-baccalaureate, and graduate students, providing training that is applicable to careers in forest and conservation management, environmental science and policy, data management, and computer coding and model simulation. The project also produces freely available educational resources for upper-level college instructors, professional ecologists, land managers, and commercial foresters. Moreover, project data and the field experiment itself- located at a field station in Michigan- serve as openly shared resources for onsite education and research training for hundreds of students, researchers, educators, and community members annually. This project uses the Forest Resilience Threshold Experiment (FoRTE), which was established in 2018 at the University of Michigan Biological Station to examine how and why forest carbon cycling processes will respond to a range of disturbance severities caused by insect pests and pathogens. The replicated, 8-hectare experiment includes zero (control), 45%, 65%, and 85 % levels of gross defoliation and incorporates two disturbance types. Leveraging FoRTE’s expansive axes of disturbance severity, site productivity, and vegetation composition, the project uses observations to ask: (1) Do trade-offs exist between dimensions of carbon cycling stability, (2) To what extent are forest composition, structure, and net primary production linked during disturbance response, and (3) What degree of model complexity is required to simulate observed carbon cycling stability across the full disturbance-response cycle? This study experimentally and computationally simulates the carbon cycling consequences of newly emerging disturbance patterns. The experiment adopts a novel stability theoretical framework, previously applied almost exclusively to populations and communities, to assess carbon cycling responses to disturbance severity and type.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.