A better understanding of how dominant fuels affect fire behavior can improve predictions and comparisons of the ecological effects of fires in forests and other ecosystems. Current methods for evaluating effects of fuel characteristics on fire behavior, including maximum temperature and heating duration, range from small-scale laboratory to large-scale field experiments. Small-scale experiments often have many replicates and high measurement precision but can lack realism, while field experiments may have few replicates and lower measurement precision, thereby making comparisons across ecosystems difficult. Here, we present a method to experimentally evaluate ecological effects of fire while maintaining realism in fuel structure. We applied the method to investigate fire behavior effects of cogongrass (Imperata cylindrica), an invasive grass with a vertical growth form that is widespread across Southeast US forests. Examining the effect of fuel structure (piled vs. standing) on fire behavior for a range of fuel loads illustrated how more realistic standing fuels produced shorter heating duration (s above 100 °C), taller flame heights, and faster spread rates compared to piled fuels. Average heating duration was ~2–4 times longer and ranged more widely when fuels were piled (80–277 s) compared to standing (41–57 s). Flame heights were ~1.4 times taller when fuels were standing than piled. These differences highlight that maintaining natural fuel structure in experimental fires produces more realistic estimates of fire behavior and effects. Consequently, not maintaining realistic vertical fuel structure could lead to overestimation of potential fire impacts related to temperature (e.g., tissue damage) but underestimate potential impacts related to flame heights, such as total engulfment of tree seedlings and saplings by fire. Altogether, our method effectively maintained fuel structure, enabling assessment of more probable fire behavior and impacts of the invasive grass than if fuels were simply piled. This approach may help further bridge the gap in realism between small-scale experiments and large-scale fires, enabling comparisons of the ecological effects of fires and fire-invasion interactions across forest ecosystems.

更好地了解主要燃料如何影响着火行为可以改善对森林和其他生态系统中火的生态影响的预测和比较。当前评估燃料特性对火行为的影响的方法，包括最大温度和加热持续时间，范围从小型实验室到大型现场实验。小型实验通常具有很多重复性和较高的测量精度，但缺乏现实性，而现场实验则可能具有很少的重复性和较低的测量精度，从而使跨生态系统的比较变得困难。在这里，我们提出了一种在保持燃料结构真实性的同时，通过实验评估火的生态效应的方法。我们应用该方法研究了香茅（Imperata cylindrica）的着火行为），一种具有垂直生长形式的侵入性草，在美国东南部的森林中广泛分布。在一定范围的燃料负载下，研究燃料结构（堆放与静置）对着火行为的影响，说明与堆放相比，更现实的静置燃料如何产生较短的加热持续时间（高于100°C），更高的火焰高度和更快的扩散速度燃料。与堆放（41-57 s）相比，堆放燃料（80-277 s）时，平均加热时间长约2-4倍，范围更广。放置燃料时，火焰高度比堆积时高1.4倍。这些差异突出表明，在实验性大火中保持自然燃料结构可以对火的行为和效应做出更现实的估计。所以，不保持实际的垂直燃料结构可能会导致高估与温度相关的潜在火势影响（例如，组织损坏），但会低估与火焰高度相关的潜在影响，例如火势吞噬树木幼苗和树苗。总之，与仅堆放燃料相比，我们的方法有效地维持了燃料结构，从而能够评估更可能的火灾行为和侵入性草丛的影响。这种方法可能有助于进一步弥合小规模实验与大规模火灾之间的现实差距，从而能够比较火灾的生态效应和森林生态系统中火灾与入侵的相互作用。与仅堆放燃料相比，我们的方法有效地维持了燃料结构，从而能够评估更可能的火灾行为和入侵草丛的影响。这种方法可能有助于进一步弥合小规模实验与大规模火灾之间的现实差距，从而能够比较火灾的生态效应和森林生态系统中火灾与入侵的相互作用。与仅堆放燃料相比，我们的方法有效地维持了燃料结构，从而能够评估更可能的火灾行为和入侵草丛的影响。这种方法可能有助于进一步弥合小规模实验与大规模火灾之间的现实差距，从而能够比较火灾的生态效应和森林生态系统中火灾与入侵的相互作用。