NOAA/WDS Paleoclimatology - Bale - Choccolocco Mountain - PIPA - ITRDB AL003

A predictive equation for estimating fire frequency was developed from theories and data in physical chemistry, ecosystem ecology, and climatology. We refer to this equation as the Physical Chemistry Fire Frequency Model (PC2FM). The equation was calibrated and validated with North American fire data (170 sites) prior to widespread industrial influences (before ~1850 CE) related to land use, fire suppression, and recent climate change to minimize non-climatic effects. We derived and validated the empirically based PC2FM for the purpose of estimating mean fire intervals (MFIs) from proxies of mean maximum temperature, precipitation, their interaction, and estimated reactant concentrations. Parameterization of the model uses reaction rate equations based on the concentration and physical chemistry of fuels and climate. The model was then calibrated and validated using centuries of empirical fire history data. An application of the PC2FM regression equation is presented and used to estimate historic MFI as controlled by climate. We discuss the effects of temperature, precipitation, and their interactions on fire frequency using the PC2FM concept and results. The exclusion of topographic, vegetation, and ignition variables from the PC2FM increased error at fine spatial scales, but allowed for the prediction of complex climate effects at broader temporal and spatial scales. The PC2FM equation is used to map coarse-scale historic fire frequency and assess climate impacts on landscape-scale fire regimes.

本研究基于物理化学、生态系统生态学及气候学的理论与数据，构建了用于估算火灾发生频率的预测方程。我们将该方程命名为物理化学火灾频率模型（Physical Chemistry Fire Frequency Model，PC2FM）。该方程以北美170个观测点的火灾数据为基础，在受土地利用、灭火措施、近期气候变化等广泛工业活动影响之前（约公元1850年以前）完成校准与验证，以最大限度降低非气候因素的干扰。我们基于经验推导并验证了PC2FM，旨在通过平均最高温度、降水量、二者的交互作用以及估算的反应物浓度的代用指标，估算火灾平均间隔期（mean fire intervals，MFIs）。该模型的参数化过程基于可燃物与气候的浓度特性及物理化学机制，采用反应速率方程构建。随后，研究团队利用数百年的经验火灾历史数据对该模型完成校准与验证。本研究展示了PC2FM回归方程的一项应用，并借助其估算了受气候调控的历史时期火灾平均间隔期。我们基于PC2FM的理论框架与研究结果，探讨了温度、降水量及其交互作用对火灾发生频率的影响。PC2FM未纳入地形、植被及点火源变量，虽会在精细空间尺度上增加预测误差，但却能够在更宽泛的时空尺度上预测复杂的气候影响效应。本研究利用PC2FM方程绘制了大尺度历史火灾频率分布图，并评估了气候变化对景观尺度火灾格局的影响。