OPP-PRF: Investigating Fire-Biotic Disturbance Interactions and Their Sensitivity to Climate in the North American Boreal Biome

北方森林很重要，因为它们储存了大量的碳。几乎30%的森林碳储存在这个生物群系中。随着气候变化，森林火灾、害虫、食草动物和疾病等干扰的频率正在增加。更频繁的火灾在北方黑云杉森林的森林地面上燃烧碳，这可以阻止云杉重新生长。火灾后，当黑云杉不能再长出来时，落叶树种如桦树、白杨或柳树就会长出来。新的昆虫爆发和疾病正在北美北方森林出现，威胁到许多这些落叶树的死亡。然而，对于这些新爆发的原因和影响，以及它们如何继续影响北方森林的碳储存，人们知之甚少。这项研究将使用计算机模拟来更好地了解(1)阿拉斯加北方森林中新害虫、食草动物和疾病的程度、影响和潜在威胁；(2)新爆发的害虫、食草动物和疾病如何与火灾和气候相互作用，从而改变北方森林储存碳的方式。北方生物群落是全球重要的陆地碳汇：大约30%的陆地碳储存在北方森林及其下面的土壤和永久冻土中。然而，北方碳的未来命运取决于气候变化对多种干扰及其相互作用的影响。北方森林火灾对气候很敏感，并且在频率、规模和严重程度上都在增加。越来越多的短间隔火灾燃烧黑云杉林分表面有机层的遗留碳，并驱动火灾后物种更新从云杉向阔叶为主转变。短间隔火灾后改变的森林再生产生了排放脉冲，导致碳储量从地下转移到地上，并改变了随后碳积累的脆弱性。新的生物干扰同时出现在北美北方森林中，可能导致广泛的阔叶树死亡，并威胁到阔叶树生物量中积累的碳的释放。然而，对于这些新出现的生物干扰的原因和后果，以及它们如何进一步改变北方碳储量，人们知之甚少。该项目将使用基于过程的森林建模(1)来开发一个基于系统的框架，利用现有的和新兴的数据来模拟生物干扰及其相互作用的新影响，综合目前对这些新威胁的理解；(2)将该框架应用于一系列气候和生物因子情景，在当前和未来条件下，在景观尺度上测试火-气候-生物相互作用对生态系统碳和演替轨迹的影响。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。

Boreal forests are important because they store large amounts of carbon. Almost 30% of all forest carbon is stored in this biome. The frequency of disturbances, such as forest fires, pests, herbivores, and diseases, are increasing with climate change. More frequent fires combust carbon on the forest floor of boreal black spruce forests, which can prevent spruce from growing back. When black spruce trees fail to grow back after fire, deciduous species such as birch, aspen or willow grow instead. New insect outbreaks and diseases are showing up in the North American boreal forest, which threaten to kill many of these deciduous trees. However, little is known about the causes and effects of these new outbreaks, and how they may continue to affect carbon storage in boreal forests. This research will use computer simulations to better understand (1) the extent, impact and potential threats of new pests, herbivores, and diseases in Alaskan boreal forests; (2) how new outbreaks of pests, herbivores, and diseases may interact with fire and climate to alter how boreal forests store carbon.The boreal biome is a globally important terrestrial carbon sink: Approximately 30% of all terrestrial carbon is stored within boreal forests and the soils and permafrost (frozen soil) underneath. However, the future fate of boreal carbon depends on the impact of climate change on multiple disturbances and their interactions. Boreal forest fires are sensitive to climate and are increasing in frequency, size, and severity. Increasing short-interval fires combust legacy carbon in surface organic layers of black spruce stands and drive transitions in post-fire species regeneration from spruce to broadleaf dominance. Altered forest regeneration following short-interval fires creates a pulse of emissions, causes shifts in carbon stocks from below to aboveground and alters the vulnerability of subsequent carbon accumulation. New biotic disturbances are concurrently emerging in the North American boreal forest that could cause widespread broadleaf tree mortality and threaten to release the carbon accumulated in broadleaf biomass. However, little is known about the causes and consequences of these emerging biotic disturbances, and how they may further alter boreal carbon storage. This project will use process-based forest modeling (1) to develop a systems-based framework leveraging available and emerging data to model new impacts of biotic disturbances and their interactions, synthesizing current understanding of these emerging threats; and (2) apply that framework to a suite of climatic and biotic agent scenarios, testing the impact of fire-climate-biotic interactions on ecosystem carbon and successional trajectories at landscape scales under current and future conditions.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.