Collaborative Research: Regional impacts of increasing fire frequency on carbon dynamics and species composition in the boreal forest

合作研究：火灾频率增加对北方森林碳动态和物种组成的区域影响

• 批准号: 1737166
• 负责人: Vladimir Romanovsky
• 金额: $ 15.02万
• 依托单位: University of Alaska Fairbanks Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1737166&HistoricalAwards=false
• 关键词: Collaborative; Research; Regional; impacts; increasing

The Arctic is warming faster than any other area of the world and its boreal forests have experienced dramatic increases in the size and frequency of fires. The fast pace of these changes has prompted concern because boreal forests make up about a third of all forests worldwide, contain almost half of the world's stored carbon, and have been historically stable with black spruce dominating this landscape for the past 6,000 years. Warming of 2-8 °C is projected by the end of the century and the emergence of a new fire regime threatens to disrupt this forest ecosystem. For example, in some regions of interior Alaska, the fire return interval has decreased to 10-50 years, causing shifts from black spruce to deciduous trees and grasses. Changes in the climate and fire regime are also expected to affect global carbon cycling since fires and thawing of frozen soils (permafrost) may release large amounts of carbon into the atmosphere. This research will incorporate field studies and computer simulations to determine how fire frequency and climate change affect shifts between vegetation types (e.g. switch from conifer to grasses) and long term carbon storage in this vast and under-studied region. The study will train graduate students and involve Native American high school students from the Rural Alaska Honors Institute (RAHI) in field work. The investigators will collaborate with Your World Rocks (YWR), a nonprofit organization of female scientists and engineers dedicated to promoting science education in elementary schools. They will develop hands-on activities focusing on climate change, forests, and fire and conduct free hands-on activities in elementary schools in the greater Portland/Vancouver metro area, with a particular focus on underserved Title 1 schools. The fast pace of climate warming and an increase in fire frequency over the past few decades in northern latitudes has raised concerns about major shifts in vegetation and the long-term ability of ecosystems to capture and store carbon. Boreal forest ecosystems account for about 33% of all forests worldwide and contain about 45% of the world's carbon stocks, with the majority (~85%) stored belowground. For the past 6,000 years, black spruce (Picea mariana (Mill.) B.S.P.) has been the dominant species over a large proportion of this landscape, exhibiting substantial resilience to changes in climate. However, unprecedented warming (causing earlier snowmelt, permafrost thawing, and longer growing seasons) and the emergence of a new fire regime over the past 60 years threatens to disrupt the existing dominance by black spruce and release globally significant amounts of carbon into the atmosphere. The goal of this research is to quantify the potential for large-scale changes in carbon (C) sink strength, C stocks, and vegetation in boreal forests due to climate change and repeated wildfires by integrating mechanistic field and lab work with dynamic, spatially explicit landscape modeling. Working in central Alaska, the investigators will: 1) determine how fire frequency and climate change affect successional trajectories and above- and belowground C cycling, and 2) assess how the mechanisms that cause tipping points between vegetation types (i.e. conifer, hardwood, graminoid) and C sequestration (i.e. sink, source) vary spatially and temporally. To achieve these objectives, the investiagors will empirically measure above- and belowground C stocks, productivity, heterotrophic respiration, soil temperature and moisture content, and active layer thickness in the field and quantify C mineralization using laboratory soil incubations. They will also develop and validate a physically based permafrost/hydrology module for a widely-used, high resolution landscape simulation model (LANDIS-II) to forecast long-term dynamics of species composition and C source/sink status given projected changes in climate (including thawing permafrost) and fire. The work will improve our understanding of how C cycling and species composition in boreal forests will respond to climate change and disturbances at the fine spatial scales critical to accurately project the future of the boreal forest.

北极的变暖比世界上任何其他地区都要快，其北方森林的大小和火灾频率急剧增加。这些变化的快速步伐引起了人们的关注，因为北方森林约占全球所有森林的三分之一，其中几乎含有世界上储存的碳，并且历史上一直稳定，在过去的6000年中，黑云杉占据了这一景观。 2-8°C的变暖预测到本世纪末，新的火灾制度的出现可能会破坏这个森林生态系统。例如，在阿拉斯加室内的某些地区，火回流间隔已减少到10 - 50年，从而导致从黑云杉转向决定的树木和草。由于火灾和冻结土壤（Permafrost）的融化，气候和火灾状况的变化也会影响全球碳循环。研究将结合现场研究和计算机模拟，以确定火灾频率和气候变化如何影响植被类型之间的变化（例如，从针叶树转换为草）和在这个庞大且研究不足的地区的长期碳存储。这项研究将培训研究生，并参与来自阿拉斯加农村荣誉研究所（RAHI）的美国原住民高中生。调查人员将与您的世界岩石（YWR）合作，该组织由女性科学家和工程师组织，致力于促进小学的科学教育。他们将开展针对气候变化，森林和火灾的动手活动，并在大波特兰/温哥华都会区的小学进行免费的动手活动，特别关注服务不足的标题1学校。在过去的几十年中，北部纬度的气候变暖和火灾频率的提高速度引起了人们对植被的重大变化以及生态系统捕获和存储碳的长期能力的担忧。北方森林生态系统约占全球所有森林的33％，约有45％的碳股，其中大多数（约85％）存储在下面。在过去的6，000年中，黑云杉（Picea Mariana（Mill。）B.S.P.）一直是这种景观的主要物种，具有对气候变化的实质性韧性。然而，前所未有的变暖（导致较早的融雪，永久冻结融化和更长的生长季节），并且在过去60年中新的火灾制度的出现可能会破坏黑色云杉的现有优势，并释放出全球范围内的大量碳。这项研究的目的是量化由于气候变化而导致的碳强度，C种和植被的大规模变化的潜力，并通过将机械场和实验室与动态，空间明显的景观建模进行整合，并重复进行野火。研究人员将在阿拉斯加中部工作：1）确定火灾频率和气候变化如何影响成功的轨迹以及高于C循环的轨迹，以及2）评估如何在植被类型之间引起倾斜点的机制（即对针叶，硬木，graminoid）（即固执）和cececteration（即经常和临时）。为了实现这些目标，研究人员将紧急测量地下和地下C种群，生产率，异养呼吸，土壤温度和水分含量以及现场的活跃层厚度，并使用实验室土壤孵育来量化C矿化。他们还将开发并验证一个基于物理的多年冻土/水文学模块，用于广泛使用的高分辨率景观仿真模型（Landis-II），以预测物种组成的长期动态和C源/水槽状态，并给定气候预测的变化（包括Permafrost Thawing Permafrost）和Fire。这项工作将提高我们对北方森林中C骑自行车和物种成分的理解，以应对气候变化和灾难的良好空间尺度至关重要的灾难，以准确地预测北方森林的未来。