RAPID: Effects of changing wildfire regimes on soil carbon fluxes during and following fire

RAPID：改变野火状况对火灾期间和火灾后土壤碳通量的影响

• 批准号: 2420420
• 负责人: Thea Whitman
• 金额: $ 19.99万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-06-01 至 2025-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2420420&HistoricalAwards=false
• 关键词: RAPID; Effects; changing; wildfire; regimes

The soil of northern forests holds massive reservoirs of carbon (C). This carbon is at risk of being lost to the atmosphere and contributing to climate change, due to recent patterns of wildfire that are also related to climate change. Determining how wildfires affect C stored in the soil is difficult, because it is rare that researchers know where a wildfire will take place before it happens, so there are not often measurements of C content from before the wildfire. In addition to assessing how much C is lost to the atmosphere when organic matter is combusted during a wildfire, fires can change how the remaining soil C is transformed, as remaining organic matter decomposes and returns C to the atmosphere. For this RAPID project, the extensive wildfire season in Canada in 2023 offers this team a unique chance to measure fire-induced soil C losses at their previously studied sites and to compare the size of C emissions derived from combustion during the fire vs. decomposition afterwards. In this project, the researchers will test pre-fire samples and return to to obtain and test post-fire samples in order to determine how fires affected carbon cycling. This research offers a critical opportunity to leverage rare pre-fire data to investigate pressing questions about wildfire effects on soil C content in a globally-relevant ecosystem. The findings will inform understanding of post-wildfire ecology and interactions between fire severity and C cycling. In addition, junior researchers will be trained, and the project team will develop new outreach materials to engage the public on the topic of fires and soils.As part of sampling campaigns in 2019 and 2022 in Wood Buffalo National Park (WBNP), AB and NWT, Canada, and the surrounding region, the research group collected a large number of soil samples from sites that had not experienced fire for at least 30 years. They characterized pre-burn soil C and N concentrations, pH, microbial community composition, and respiration (decomposition). The 2023 WBNP fire complex burned 32 out of 70 of the previously sampled sites, representing a range of soil types, including organic-rich peatlands and sandy acidic soils, and dominant tree species. In this project, researchers are pairing post-burn sampling with the existing pre-burn samples to answer two questions: (1) How does fire severity relate to post-burn soil C decomposition rates? (2) How does the relative importance of C losses due to combustion vs. changes in C decomposition rates change over time with increasing fire severity? At each site, researchers will estimate C losses due to wildfire, collect soil cores and quantify soil C, and measure potential decomposition using soil incubations. They will use simple biogeochemical models to extrapolate potential net C losses through decomposition, to quantify the relative magnitude of these two major C loss pathways – direct losses through combustion vs. changes in C decomposition rates after the wildfires. Further leveraging this dataset, researchers will collect and preserve subsamples of soil for future efforts to characterize microbial community composition. These samples will be compared with pre-burn (and lab-burned) microbial communities from previous sampling campaigns – another opportunity to take advantage of these unusual pre-fire datasets. Samples will also be preserved for further chemical characterization supported by future proposals, in order to explore the potential role that organic matter chemistry plays in determining post-fire soil C decomposition rates. The research project will provide training for a graduate student, undergraduate field assistants, and a research technician, as well as enhance wildfire and climate change public education.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.

北森林的土壤占有巨大的碳（C）。由于最近与气候变化有关的野火模式，该碳有可能失去大气并导致气候变化的风险。很难确定野火如何影响土壤中的c，因为很少有研究人员知道野火在发生之前会发生在哪里，因此通常不会在野火之前对C含量进行测量。除了评估在野火期间有机物燃烧时大气中损失多少C外，火灾还可以改变其余土壤C的变化方式，因为剩余的有机物分解并返回C回到大气中。对于这个快速项目，2023年加拿大在加拿大的广泛野火季节为这支球队提供了一个独特的机会，可以在其先前研究的地点衡量火引起的土壤C损失，并比较在火灾与分解过程中从组合中得出的C排放大小。在该项目中，研究人员将测试火前样品并返回以获取和测试火灾后样品，以确定火灾如何影响碳循环。这项研究提供了一个关键的机会，以利用罕见的火灾前数据来调查有关与全球相关的生态系统中土壤C含量影响的紧迫问题。这些发现将为野火后的生态学以及火灾严重性与C骑自行车之间的相互作用提供理解。此外，将对初级研究人员进行培训，项目团队将开发新的外展材料，使公众讨论火灾和土壤的主题。作为2019年和2022年在伍德布法罗国家公园（WBNP），AB和NWT，加拿大和NWT，加拿大和周边地区的采样活动的一部分，研究小组从未从30年中收集过30年的土地，从而从30年中收集了大量的土壤。他们表征了烧焦的土壤C和N浓度，pH，微生物群落组成和呼吸（分解）。 2023 WBNP火灾综合体在70个先前采样的地点中燃烧了32个，代表了一系列土壤类型，包括有机富含有机的山峰和沙质酸性土壤以及主要的树种。在该项目中，研究人员将燃烧后抽样与现有的燃烧前样品配对，以回答两个问题：（1）火灾严重性与燃烧后的土壤C分解率有何关系？ （2）由于燃烧和C分解速率变化而导致的C损失的相对重要性随着时间的流逝而随着火灾严重程度的增加而变化？在每个地点，研究人员将估计由于野火，收集土壤核心并量化土壤C的C损失，并使用土壤孵化来测量潜在的分解。他们将使用简单的生物地球化学模型通过分解来推断潜在的净C损失，以量化这两种主要C损失途径的相对大小 - 野火后C的直接损失与C分解速率的变化。进一步利用该数据集，研究人员将收集并保留土壤子样本，以供将来的微生物社区组成的努力。这些样本将与以前的采样活动中的预燃烧（和实验室燃烧的）微生物群落进行比较，这是利用这些不寻常的火灾前数据集的另一个机会。还将保留样品以供未来建议支持的进一步化学表征，以探讨有机物化学在确定火后土壤c分解速率中所发挥的潜在作用。该研究项目将为研究生，本科野外助理和研究技术人员提供培训，并增强野火和气候变化公共教育。该奖项反映了NSF的法定任务，并通过使用基金会的知识分子优点和更广泛的影响来评估NSF的法定任务。