Wildfires produce pyrogenic carbon (PyC) through the incomplete combustion of organic matter, and its chemical characterization is critical to understanding carbon (C) budgets and ecosystem functions in forests. Across western North American forests, fires are burning through landscapes with substantial tree mortality from insect outbreaks, often referred to as short-interval disturbances. These short-interval disturbances often result in beetle-killed snags (snags that subsequently burn) that are heavily charred, while their fire-killed (alive at time of fire) counterparts are lightly charred. We investigated whether the chemical signature of PyC on heavily charred beetle-killed snags differs from lightly charred fire-killed snags. We evaluated differences in PyC chemical concentrations and condensation on beetle-killed (n = 3) and fire-killed snags (n = 3) with the benzene polycarboxylic acid (BPCA) molecular marker method. Beetle-killed snags exhibited over five times the grams of BPCA per kilogram of C, and over seven times the grams of BPCA per kilogram of material compared to fire-killed snags, indicating higher concentrations of PyC. PyC concentrations were greater in samples from beetle-killed snags compared to fire-killed snags, pointing to an important compound effect from the interaction of beetle outbreak and wildfire in forest ecosystems. While this study was limited to a single fire event and sampling in individual trees, it provides insight into PyC on snags with different disturbance histories. The abundance of heavily charred snags from a fire burning through landscapes with high levels of existing mortality from drought, insect outbreaks, and previous wildfire events is becoming a more common legacy for contemporary western North American forests. Accordingly, the distinct wood-based PyC legacy could influence ecosystem functions: C sequestration, water purification, soil nutrient supply, and resources for wildlife.

中文翻译：

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当野火烧毁火灾前死亡率高的森林时，热解碳的增加

野火通过有机物质的不完全燃烧产生热解碳（PyC），其化学特性对于理解森林中的碳（C）预算和生态系统功能至关重要。在整个北美西部的森林中，大火肆虐，虫害引起树木大量死亡，通常被称为短间隔干扰。这些短间隔的干扰通常会导致严重烧死甲虫杀死的细枝（随后燃烧的细枝），而杀死火苗（在生火时存活）的细枝则被轻度烧焦。我们调查了PyC在严重烧焦的甲虫杀虫物上的化学特征是否与轻度烧焦的火除虫剂不同。我们使用苯多元羧酸（BPCA）分子标记法评估了在甲虫杀死（n = 3）和火杀死的钩枝（n = 3）上PyC化学浓度和缩合的差异。甲虫杀死的障碍物表现出的每公斤碳BPCA克含量是其的五倍以上，每千克物质所产生的BPCA克数则超过七倍，这表明PyC的浓度更高。甲虫杀死的钩虫样品中的PyC浓度高于火杀死的钩虫样品，表明甲虫暴发和森林生态系统中的野火相互作用具有重要的复合作用。虽然这项研究仅限于单个火灾事件并在单独的树木中取样，但它可以深入了解具有不同干扰历史的障碍物上的PyC。火灾烧毁的景观中有大量烧焦的残渣，这些景观因干旱，虫害暴发和先前的野火事件而导致很高的现有死亡率，这已成为当代北美西部森林更为普遍的遗产。因此，基于木材的PyC遗留物可能会影响生态系统功能：固碳，水净化，土壤养分供应和野生动植物资源。