ECO-CBET: Collaborative Research: Effect of surface-fuel attributes and forest-thinning patterns on wildfire, carbon storage, and advancing forest restoration

2318717 (Cobian)。近年来，高度严重的野火严重破坏了森林山区流域，这些流域储存碳，供应西部各州的水，并提供许多附带效益。虽然周期性的低到中等严重程度的野火是美国西部森林的自然组成部分，但由于燃料负荷过多和气候变暖，该地区的大部分地区正在以高严重程度燃烧。因此，森林管理的一个关键目标往往是采用旨在减少严重火灾风险的做法。这些做法统称为森林恢复，包括对不耐火、较小的树木进行疏伐、移除或修剪，同时留下较大、间距更广的树木。一种常见的恢复方法是采用机械疏林，然后进行咀嚼，这改变了森林冠层结构和表面燃料的负荷和特征。虽然已知通过咀嚼改变树木和其他植被的排列和密度会影响火灾行为，但缺乏对咀嚼燃料属性如何影响随后火灾严重程度的定量理解。该项目的目标是在一定的空间和时间尺度上制定燃料处理对火灾行为影响的指标。该项目将有助于更好地了解由管理决策产生的地表燃料属性如何影响火灾行为和严重程度，从而影响森林生物量碳储量。机械间伐后的咀嚼改变了森林冠层结构和地表燃料的负荷和特征。虽然这些变化可以显著影响火的行为，但它们对咀嚼类型和程度的敏感性尚不清楚。该研究的三个主要目标是：(1)确定异质和多尺度表面燃料的负荷和属性，在机械燃料处理之后，对这些燃料燃烧时的温度、火焰长度和火势蔓延的重要性；(2)在不同燃料属性和不同微气象条件下，开发和评估森林野火严重程度和蔓延的预测工具；(3)展示旨在减少高严重性野火发生和影响的不同燃料处理的碳储存和相关效益。这项研究将使用实验尺度的燃烧实验，包括在混合针叶林的稀薄和经过改良的林分上进行控制燃烧的实地测量，以及对荒地火灾和碳储存的建模。实验、建模和现场规模控制燃烧评估的结果将用于确定地面燃料减薄后火灾严重程度的关键驱动因素。该研究的主要贡献将是提高对管理决策产生的表面燃料属性如何影响火灾行为和严重程度以及森林生物量碳储量的理解。结果将改进火焰长度、火势蔓延和凋落物、矿物土壤和更深的风化层中的碳平衡和储存的建模。这项研究将使决策者和利益相关者与正在推进景观恢复的组织建立伙伴关系，为他们的投资如何影响野火严重程度的预测提供急需的改进。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。

2318717 (Cobian). In recent years, high-severity wildfires have severely damaged forested mountain watersheds that store carbon, supply western-states’ water, and provide many co-benefits. While periodic low- to medium-severity wildfires are a natural part of western U.S. forests, too much of the area is burning at high severity owing to excessive fuel loads and a warming climate. Therefore, a critical goal of forest management is often the introduction of practices designed to reduce the risk of high severity fires. These practices, known collectively as forest restoration, involve thinning and removing or masticating the less-fire-resistant, smaller trees, while leaving larger, more widely spaced trees. A common restoration approach is applying mechanical thinning followed by mastication which changes the forest-canopy structure and surface-fuel loading and characteristics. While it is known that changing the arrangement and density of trees and other vegetation through mastication affects fire behavior, there is a lack a quantitative understanding of how attributes of masticated fuels affect subsequent fire severity. The goal of this project is to develop metrics of the impact of fuel treatments on fire behavior across a range of spatial and temporal scales. This project will contribute to improved understanding of how surface-fuel attributes, resulting from management decisions, influence fire behavior and severity and thus forest biomass carbon storage.Mechanical thinning followed by mastication changes the forest-canopy structure and surface-fuel loading and characteristics. While these changes can impact fire behavior significantly, their sensitivities to the type and degree of mastication are not well understood. The three main goals of the study are: (1) To establish the importance of heterogeneous and multiscale surface-fuel loadings and attributes, following mechanical fuel treatments, on the temperature, flame length, and spread of fire as these fuels burn; (2) To develop and assess predictive tools for wildfire severity and spread in the forest given these different fuel attributes, under contrasting micro-meteorological conditions; and (3) To demonstrate carbon-storage and related benefits from different fuel treatments designed to reduce the occurrence and impacts of high-severity wildfires. The study will use bench-scale combustion experiments, field measurements involving controlled burns in thinned and masticated stands in a mixed-conifer forest, and modeling of wildland fire and carbon storage. Results from experiments, modeling, and assessment of field-scale control burns will be used to identify key drivers of fire severity in ground fuels following thinning. Primary contributions of the study will be improved understanding of how surface-fuel attributes, resulting from management decisions, influence fire behavior and severity and thus forest biomass carbon storage. Results will improve modeling of flame length, fire spread and carbon balance and storage in the litter, mineral soil, and deeper regolith. This research will engage decision maker and stakeholder partnerships with organizations that are advancing landscape restoration, providing much-needed improvements in projection of how their investments may affect wildfire severity.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.