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、人类健康与福祉中发挥着关键作用，且与气候变化密切相关。植物会影响野火行为，预测该反馈机制是当前的重点研究课题。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同时对（i）单叶可燃性，以及（ii）装填于燃料床（fuel bed）中的多叶可燃性具有重要影响。基于某一概念框架，我们提出了如下假说：燃料床的装填特性可通过限制气流，抵消单叶形态与化学性状的影响。为验证该假说，我们对比了两项实验的结果：其一聚焦澳大利亚东部25个多年生植物物种的单叶可燃性，其二则针对其单物种燃料床可燃性。在所有物种中，燃料床装填比与容重均与火蔓延速率呈负相关，与最高温度及燃烧时长呈正相关。叶片更为卷曲、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，可加快燃料床内的火蔓延速率。我们发现，单叶引燃时间更短的物种，其所在燃料床的火蔓延速率更快、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（例如比叶面积），即使在叶片被装填为燃料床后，仍会发挥相应作用。尽管此前的研究多聚焦于单个植物颗粒的可燃性或燃料床内的野火行为，但本研究首次针对大范围物种，全面结合了这两类研究方法。本研究的发现基于叶片形态与部分化学性状的种间变异，为理解燃料床可燃性提供了更深入的视角。这或将成为连接叶片性状与野外野火行为的重要开端。