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，这些昆虫会使树木落叶，并经常杀死树木。该项目使用田间实验和计算机模型来研究由钻木虫引起的不同程度的树木死亡对森林生长和碳吸收的影响。具体地说，这项研究研究了受干扰后森林生长和碳固存的初始变化是否可以用来预测对森林和土地管理者有意义的时间尺度上的较长期反应；哪些生物和物理特征使森林能够从干扰中恢复；以及需要在计算机模型中包括哪些信息来预测森林将如何对虫害做出反应。该项目吸引了不同的本科生、学士后和研究生团队，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，项目数据和实地实验本身--位于密歇根州的一个野外站点--作为公开共享的资源，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。该项目使用2018年在密歇根大学生物站建立的森林弹性阈值实验(FOTE)来研究森林碳循环过程将如何以及为什么对虫害和病原体造成的一系列干扰严重做出反应。重复的8公顷试验包括零(对照)、45%、65%和85%的总落叶水平，并包括两种干扰类型。利用Forte的干扰严重程度、场地生产力和植被组成的扩展轴，该项目使用观测来询问：(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，森林组成、结构和净初级生产力在多大程度上相关联，以及(3)需要多大程度的模型复杂性来模拟整个干扰响应周期中观察到的碳循环稳定性？这项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，以前几乎只适用于人口和社区，以评估碳循环对干扰严重程度和类型的响应。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.