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.

野火在植被组成与结构、养分通量、人类健康与福祉方面发挥着重要作用，且与气候变化紧密相关。植物会影响野火行为，预测这一反馈关系是当前的高优先级研究方向。若要实现从叶片性状到野火行为的尺度上推，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）装填于燃料床（fuel beds）中的多叶混合物的可燃性均具有重要影响。基于某一概念框架，我们提出假说：通过气流限制作用，燃料床的装填特性将凌驾于单叶形态与化学组成的影响之上。为验证该假说，我们对比了两项实验的结果：分别针对澳大利亚东部25个多年生物种的单叶可燃性，以及单物种燃料床可燃性展开测试。跨物种分析显示，燃料床装填比率与堆积密度与火蔓延速率呈负相关，与最高火温及燃烧时长呈正相关。叶片更卷曲、比叶面积（specific leaf area）更高、单宁浓度更低且组织密度更低的物种，可促进燃料床内的火蔓延速率提升。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、燃烧时长更短且火温更低。影响单叶可燃性的叶片性状（例如比叶面积），在叶片被装填为燃料床后，依然会对整体可燃性产生影响。尽管此前的研究要么聚焦于单个植物颗粒的可燃性，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，将这两种研究路径进行了系统性结合。本研究的发现基于叶片形态与部分化学性状的种间变异，增进了我们对燃料床可燃性的理解。这可为后续将叶片性状与野外野火行为建立关联迈出第一步。