Mechanical mastication is a fuels treatment that shreds midstorey trees and shrubs into a compacted woody fuel layer to abate fire hazards in fire-prone ecosystems. Increased surface fuel loading from mastication may, however, lead to undesirable fire intensity, long-duration flaming or smouldering, and undesirable residual tree mortality. Two major questions facing fuels managers are: how long do masticated fuels persist, and how does the composition of masticated fuelbeds change over time? To evaluate these changes, we measured 25 masticated sites with a range of vegetation, species masticated and time since treatment (1–16 years) in the western US. Seven of the 25 sites were sampled nearly a decade earlier, providing a unique opportunity to document fuelbed changes. Woody fuel loading ranged from 12.1 to 91.9 Mg ha−1 across sites and was negatively related to time since treatment. At remeasured sites, woody fuel loads declined by 20%, with the greatest losses in 1- and 10-h woody fuels (69 and 33% reductions in mass respectively). Reductions were due to declines in number of particles and reduced specific gravity. Mastication treatments that generate greater proportions of smaller-diameter fuels may result in faster decomposition and potentially be more effective at mitigating fire hazard.

中文翻译：

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美国加利福尼亚州北部和俄勒冈州南部咀嚼木质燃料床的长期变化

机械咀嚼是一种燃料处理，可将中层树木和灌木切碎成压实的木质燃料层，以减少易发生火灾的生态系统中的火灾危险。然而，由于咀嚼而增加的表面燃料负荷可能导致不希望的火灾强度、长时间的燃烧或阴燃，以及不希望的残余树木死亡。燃料管理者面临的两个主要问题是：咀嚼燃料持续多久，以及咀嚼燃料床的组成如何随时间变化？为了评估这些变化，我们测量了美国西部的 25 个咀嚼点，其中包含一系列植被、咀嚼物种和处理后的时间（1-16 年）。近十年前对 25 个站点中的 7 个进行了采样，为记录燃料床变化提供了独特的机会。木质燃料装载量从 12.1 到 91 不等。9 Mg ha-1 跨位点，与治疗后的时间呈负相关。在重新测量的地点，木质燃料负荷下降了 20%，其中 1 小时和 10 小时木质燃料的损失最大（质量分别减少了 69% 和 33%）。减少是由于颗粒数量的减少和比重的降低。产生更大比例的小直径燃料的咀嚼处理可能会导致更快的分解，并可能更有效地减轻火灾危险。