The reintroduction of fire to landscapes where it was once common is considered a priority to restore historical forest dynamics, including reducing tree density and decreasing levels of woody biomass on the forest floor. However, reintroducing fire causes tree mortality that can have unintended ecological outcomes related to woody biomass, with potential impacts to fuel accumulation, carbon sequestration, subsequent fire severity, and forest management. In this study, we examine the interplay between fire and carbon dynamics by asking how reintroduced fire impacts fuel accumulation, carbon sequestration, and subsequent fire severity potential. Beginning pre-fire, and continuing 6 years post-fire, we tracked all live, dead, and fallen trees ≥ 1 cm in diameter and mapped all pieces of deadwood (downed woody debris) originating from tree boles ≥ 10 cm diameter and ≥ 1 m in length in 25.6 ha of an Abies concolor/Pinus lambertiana forest in the central Sierra Nevada, California, USA. We also tracked surface fuels along 2240 m of planar transects pre-fire, immediately post-fire, and 6 years post-fire. Six years after moderate-severity fire, deadwood ≥ 10 cm diameter was 73 Mg ha−1, comprised of 32 Mg ha−1 that persisted through fire and 41 Mg ha−1 of newly fallen wood (compared to 72 Mg ha−1 pre-fire). Woody surface fuel loading was spatially heterogeneous, with mass varying almost four orders of magnitude at the scale of 20 m × 20 m quadrats (minimum, 0.1 Mg ha−1; mean, 73 Mg ha−1; maximum, 497 Mg ha−1). Wood from large-diameter trees (≥ 60 cm diameter) comprised 57% of surface fuel in 2019, but was 75% of snag biomass, indicating high contributions to current and future fuel loading. Reintroduction of fire does not consume all large-diameter fuel and generates high levels of surface fuels ≥ 10 cm diameter within 6 years. Repeated fires are needed to reduce surface fuel loading.

中文翻译：

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再次引入大火后，大直径树木占主导地位的障碍和表面生物量

将火重新引入曾经很常见的景观，被认为是恢复历史森林动态的优先事项，包括降低树木密度和降低森林地上木质生物量的水平。但是，重新引入火势会导致树木死亡，这可能会带来与木质生物量有关的意想不到的生态后果，并对燃料积累，碳固存，随后的火势和森林管理产生潜在影响。在这项研究中，我们通过询问重新引入的火如何影响燃料积聚，碳固存和随后发生火势的可能性，研究了火与碳动力学之间的相互作用。从开火前到开火后的6年，我们一直追踪所有活着的，死亡的，以及直径≥1 cm的倒下的树木，并绘制了内华达山脉中部一个25.6公顷的艾比斯彩色/松树林中直径≥10 cm且长度≥1 m的树木的死木碎片（倒下的木屑），美国加利福尼亚。我们还跟踪了火灾前，火灾后以及火灾后6年沿2240 m平面断面的地面燃料。中度烈火后的六年，直径≥10 cm的枯木为73 Mg ha-1，包括在火中持续燃烧的32 Mg ha-1和新落木的41 Mg ha-1（相比之前为72 Mg ha-1 -火）。木质表面燃料的负载在空间上是异质的，质量在20 m×20 m方形的范围内变化了几乎四个数量级（最小0.1 Mg ha-1；平均73 Mg ha-1；最大497 Mg ha-1 ）。大直径树木（直径≥60厘米）的木材在2019年占地面燃料的57％，但占粗枝生物质的75％，这表明对当前和未来的燃料负荷贡献很大。重新引入火并不会消耗掉所有大口径燃料，并且会在6年内产生高水平的直径≥10 cm的表面燃料。需要反复起火以减少地面燃料负荷。