Surface fuel loadings are some of the most important factors contributing to fire intensity and fire spread. In old-growth forests where fire has been long excluded, surface fuel loadings can be high and can include woody debris ≥100 cm in diameter. We assessed surface fuel loadings in a long-unburned old-growth mixed-conifer forest in Yosemite National Park, California, USA, and assessed fuel consumption from a management-ignited fire set to control the progression of the 2013 Rim Fire. Specifically, we characterized the distribution and heterogeneity of pre-fire fuel loadings, both along transects and contained in duff mounds around large trees. We compared surface fuel consumption to that predicted by the standard First Order Fire Effects Model (FOFEM) based on pre-fire fuel loadings and fuel moistures. We also assessed the relationship between tree basal area—calculated for two different spatial neighborhood scales—and pre-fire fuel loadings. Pre-fire total surface fuel loading averaged 192 Mg ha−1 and was reduced by 79% by the fire to 41 Mg ha−1 immediately after fire. Most fuel components were reduced by 87% to 90% by the fire, with the exception of coarse woody debris (CWD), which was reduced by 60%. Litter depth in duff mounds were within 1 SD of plot means, but duff biomass for the largest trees (>150 cm diameter at breast height [DBH]) exceeded plot background levels. Overstory basal area generally had significant positive relationships with pre-fire fuel loadings of litter, duff, 1-hour, and 10-hour fuels, but the strength of the relationships differed between overstory components (live, dead, all [live and dead], species), and negative relationships were observed between live Pinus lambertiana Douglas basal area and CWD. FOFEM over-predicted rotten CWD consumption and under-predicted duff consumption. Surface fuel loadings were characterized by heterogeneity and the presence of large pieces. This heterogeneity likely contributed to differential fire behavior at small scales and heterogeneity in the post-fire environment. The reductions in fuel loadings at our research site were in line with ecological restoration objectives; thus, ecologically restorative burning during fire suppression is possible.

中文翻译：

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重新生长的内华达山脉混合针叶林大火后的燃料动态

地表燃料负荷是造成火势和火势蔓延的一些最重要因素。在长期没有生火的老树林中，地表燃料负荷可能很高，并且可能包含直径≥100 cm的木屑。我们评估了美国加利福尼亚州优胜美地国家公园一个长时间未燃烧的旧针叶混交林的地表燃料负荷，并评估了一种由管理层点燃的大火控制2013 Rim Fire的进展，从而消耗了燃料。具体来说，我们描述了沿样线以及包含在大树周围的达芙丘中的预燃燃料负荷的分布和非均质性。我们将表面燃料消耗与标准一阶火灾效应模型（FOFEM）根据火灾前燃料负荷和燃料水分预测的燃料消耗进行了比较。我们还评估了根据两个不同的空间邻域比例计算得出的树基面积与火灾前燃料负荷之间的关系。火灾前的总表面燃料平均负载为192 Mg ha-1，火灾后立即减少了79％，降至41 Mg ha-1。大火将大多数燃料成分减少了87％至90％，但粗木屑（CWD）减少了60％。达芙丘的凋落物深度在样地平均值的1 SD之内，但最大树木（胸高[DBH]处直径大于150厘米]的达芙生物量超过了样地背景水平。楼上基础区域通常与火前垃圾，垃圾，1小时和10小时燃料的装载量之间具有显着的正相关关系，但楼上基础部分之间的关​​系强度不同（生，死，所有[生和死]） ，种类），松材线虫活产基面积与CWD之间存在负相关关系。FOFEM高估了腐烂的CWD消耗量和低估了达芙的消耗量。表面燃料负荷的特征是异质性和大块的存在。这种异质性可能导致小规模的火灾行为不同，并且在后燃环境中产生异质性。我们研究地点的燃料装载量减少符合生态恢复目标；因此，在灭火过程中可以进行生态恢复性燃烧。这种异质性可能会导致小规模火灾行为的差异以及后火环境中的异质性。我们研究地点的燃料装载量减少符合生态恢复目标；因此，在灭火过程中可以进行生态恢复性燃烧。这种异质性可能会导致小规模火灾行为的差异以及后火环境中的异质性。我们研究地点的燃料装载量减少符合生态恢复目标；因此，在灭火过程中可以进行生态恢复性燃烧。