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Moisture absorption and drying alter nonadditive litter flammability in a mixed conifer forest
Journal of Ecology ( IF 5.5 ) Pub Date : 2020-07-15 , DOI: 10.1111/1365-2745.13467
Rita Quinones Magalhães 1 , Dylan W. Schwilk 1
Affiliation  

  1. Moisture content is a strong determinant of forest fuel flammability. However, little is known about the mechanisms by which species‐specific litter traits influence litter moisture absorption and retention. Characterizing how litter fuels retain moisture through time and how fuels from multiple species interact are key steps to adding taxon‐specific information to fire behaviour prediction.
  2. To fill these gaps in knowledge, we determined moisture absorption and retention characteristics of the litter from multiple tree species, investigated what litter traits influenced these processes and tested for nonadditive moisture dynamics and nonadditive flammability in multi‐species mixtures. The litter from eight tree species of a mixed conifer forest was saturated and allowed to dry to determine moisture absorption capacity and drying rates. Burn trials were performed in litter beds of single species and of mixtures to establish flammability response to the dry‐down process and to species interactions.
  3. Litter mixtures exhibited nonadditivity in flame spread rate and in fuel consumption. This nonadditivity became more positive with fuel drying.
  4. Moisture dynamics varied across species with higher specific leaf area being associated with higher maximum absorption and lower litter bulk density being associated with faster drying rates. We found that these differing moisture dynamics resulted in time since wetting having strongly differing effects on flammability across the major litter types typified by different tree taxa.
  5. Synthesis. This study is the first to examine ecologically relevant drying rates and their interaction with nonadditive mixture effects on flammability. We find that taxon specific patterns of moisture absorption and drying change flammability rankings under moist compared with dry fuels because traits that increase flame spread rate increase water absorption. Litter mixtures generally burn with fire behaviour more similar to that of the most flammable constituent species and this effect increases as fuels dry.


中文翻译:

水分吸收和干燥改变了针叶树混交林中非附加凋落物的可燃性

  1. 水分含量是森林燃料可燃性的重要决定因素。但是,对于物种特定的垫料性状影响垫料水分吸收和保留的机制知之甚少。表征垃圾燃料如何随时间保持水分以及来自多种物种的燃料如何相互作用是将特定分类信息添加到火灾行为预测中的关键步骤。
  2. 为了填补这些知识上的空白,我们确定了多种树种凋落物的水分吸收和保留特性,调查了哪些凋落物性状影响了这些过程,并测试了多种树种混合物中非加性水分动力学和非加性可燃性。将来自混合针叶林的八种树的凋落物饱和,然后干燥以确定吸湿量和干燥速率。在单一物种和混合物的垫料床上进行燃烧试验,以建立对干燥过程和物种相互作用的可燃性响应。
  3. 垃圾混合物在火焰蔓延速率和燃料消耗方面显示出非可加性。随着燃料干燥,这种非可加性变得更加积极。
  4. 水分动态因物种而异,较高的比叶面积与较高的最大吸收有关,而较低的垫料堆积密度与较快的干燥速度有关。我们发现,这些不同的水分动力学导致了时间,因为在以不同树种为代表的主要凋落物类型中,润湿对可燃性具有显着不同的影响。
  5. 综合。这项研究是第一个研究与生态有关的干燥速率及其与非添加剂混合物对可燃性的相互作用的研究。我们发现,与干燃料相比,在湿润下,分类单元特定的水分吸收和干燥模式会改变易燃性等级,因为增加火焰传播速度的特性会增加水分吸收。垃圾混合物的燃烧行为通常与大多数易燃成分的燃烧行为相似,并且这种影响随着燃料的干燥而增加。
更新日期:2020-07-15
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