Data from: Scaling up flammability from individual leaves to fuel beds

Wildfires play an important role in vegetation composition and structure, nutrient fluxes, human health and wealth, and are interlinked with climate change. Plants have an influence on wildfire behaviour and predicting this feedback is a high research priority. For upscaling from leaf traits to wildfire behaviour we need to know if the same leaf traits are important for the flammability of (i) individual leaves, and (ii) multiple leaves packed in fuel beds. Based on a conceptual framework, we hypothesised that fuel packing properties, through airflow limitation, would overrule the effects of individual leaf morphology and chemistry. To test this hypothesis we compared the results of two experiments, respectively addressing individual leaf flammability and monospecific fuel bed flammability of 25 perennial species from eastern Australia. Across species, fuel bed packing ratio and bulk density scaled negatively with fire spread and positively with maximum temperature and burning time. Species with “curlier” leaves, higher specific leaf area, lower tannin concentrations and lower tissue density promoted faster fire spread through fuel beds. We found that species with shorter individual leaf ignition times had a faster fire spread, shorter burning times and lower temperatures in fuel beds. Leaf traits that affect the flammability of individual leaves (e.g. specific leaf area), continue to do so even when packed in fuel beds. While previous studies have focused on either flammability of individual plant particles or fire behaviour in fuel beds, this is the first time that an overarching combination of the two approaches was made for a wide range of species. Our findings provide a better understanding of fuel bed flammability based on interspecific variation in morphological and some chemical leaf traits. This can be a first step in linking leaf traits to fire behaviour in the field.野火（Wildfire）对植被组成与结构、养分通量、人类健康与福祉均具有重要作用，且与气候变化密切相关。植物可影响野火行为，因此预测二者间的反馈关系是当前的重点研究方向。从叶片性状（leaf trait）尺度上推至野火行为，我们需要明确：相同的叶片性状是否对（i）单叶可燃性以及（ii）填充于燃料床（fuel bed）中的多叶可燃物的可燃性均具有重要影响。基于概念框架，我们提出假设：通过限制气流的燃料填充特性，将抵消单叶形态与化学性质的影响。为验证该假设，我们对比了两项实验的结果：分别针对澳大利亚东部25种多年生植物的单叶可燃性与单物种燃料床可燃性开展测试。在物种水平上，燃料床填充率与容重与火蔓延速率呈负相关，与最高温度及燃烧时长呈正相关。叶片更卷曲、比叶面积（specific leaf area）更高、单宁（tannin）浓度更低且组织密度（tissue density）更低的物种，可加快燃料床内的火蔓延速率。我们发现：单叶点火时长更短的物种，其燃料床内的火蔓延速率更快、燃烧时长更短且峰值温度更低。影响单叶可燃性的叶片性状（如比叶面积（specific leaf area）），在叶片被填充至燃料床后仍会发挥同等作用。尽管以往研究要么聚焦于单植物颗粒的可燃性，要么关注燃料床内的野火行为，但本研究首次针对大量物种，将两种研究方法进行了系统性整合。本研究结果基于叶片形态与部分化学性状的种间差异，增进了我们对燃料床可燃性的认知。这或将成为连接叶片性状与野外野火行为的首个研究步骤。