[揽瓜阁精读] 320. 森林大火

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We present data from a study of early conifer regeneration and fuel loads after the 2002 Biscuit Fire, Oregon, USA, with and without postfire logging. Natural conifer regeneration was abundant after the high-severity fire. Postfire logging reduced median regeneration density by 71%, significantly increased downed woody fuels, and thus increased short-term fire risk. Additional reduction of fuels is necessary for effective mitigation of fire risk. Postfire logging can be counterproductive to the goals of forest regenration and fuel reduction.

Recent increases in wildfire activity in the United States have intensified controversies surrounding the management of public forests after large fires. The view that postfire (salvage) logging diminishes fire risk via fuel reduction and that forests will not adequately regenerate without intervention, including logging and planting, is widely held and commonly cited. An alternate view maintains that postfire logging is detrimental to long-term forest development, wildlife habitat, and other ecosystem functions. Scientific data directly informing this debate are lacking.

Here we present data from a study of early conifer regeneration and fuel loads after the 2002 Biscuit Fire, Oregon, USA, with and without postfire logging. Because of the fire's size (∼200,000 ha), historic reforestation difficulties in the region, and an ambitious postfire logging proposal, the Biscuit Fire has become a national icon of postfire management issues. We used a spatially nested design of logged and unlogged plots replicated across the fire area and sampled before (2004) and after (2005) logging.

Natural conifer regeneration on sites that experienced high-severity fire was variable but generally abundant, with a median stocking density of 767 seedlings per hectare, primarily of Douglas fir (Pseudotsuga menziesii). Such density exceeds the regional standards for fully stocked sites, suggesting that active reforestation efforts may be unnecessary. Postfire logging subsequently reduced regeneration by 71% to 224 seedlings per hectare (Fig. 1A) due to soil disturbance and physical burial by woody material during logging operations. Thus, if postfire logging is conducted in part to facilitate reforestation, replanting could result in no net gain in early conifer establishment.

Postfire logging significantly increased both fine and coarse downed woody fuel loads. This wood was composed of unmerchantable material (e.g., branches), and far exceeded expectations for fuel loads generated by postfire logging. In terms of short-term fire risk, a reburn in logged stands would likely exhibit elevated rates of fire spread, fireline intensity, and soil heating impacts.

Postfire logging alone was notably incongruent with fuel reduction goals. Fuel reduction treatments (prescribed burning or mechanical removal) are frequently intended after postfire logging, including in the Biscuit plan, but resources to complete them are often limited. Our study underscores that, after logging, the mitigation of short-term fire risk is not possible without subsequent fuel reduction treatments. However, implementing these treatments is also problematic. Mechanical removal is generally precluded by its expense, leaving prescribed burning as the most feasible method. This will result in additional seedling mortality and potentially severe soil impacts caused by long-duration combustion of logging-generated fuel loads. Therefore, the lowest fire risk strategy may be to leave dead trees standing as long as possible (where they are less available to surface flames), allowing for aerial decay and slow, episodic input to surface fuel loads over decades.

Our data show that postfire logging, by removing naturally seeded conifers and increasing surface fuel loads, can be counterproductive to goals of forest regeneration and fuel reduction. In addition, forest regeneration is not necessarily in crisis across all burned forest landscapes.

Maxxiemoo00

P1 数据调研：灾后是否伐木，对于松叶树的影响。火灾后松树自然再生很快，伐木减少了再生密度，大大增加了燃料，增加了火灾风险，需要把燃木减少。

【提出观点】伐木和森林再生和燃木减少相背。



P2 火灾频发加剧大火后森林管理的争议。灾后是否伐木，观点1减少了森林大火风险，也不会毫无干预野蛮再生，伐木种木普世观点。观点2，伐木对长期森林发展，野外生物生态系统不利。没有数据可以参考。


P3：以B这个icon案例，研究伐木与否两块地方，再04、05年伐木前后的对比


P4：论据：【经历大火的再生密度大，不必伐木】伐木导致的土壤和材质变化减少了70%再生，如果伐木是为了再生，早期的种植就无利可图。伐木大大增加了燃木数量，没有商业价值的树枝组成，远超过灾后伐木所产生的燃料。复燃更快传播，火线密度造成土壤更大影响。

P5 论据：【灾后伐木达不到减少燃料目的】减少燃料在灾后伐木之后很常见，但是资源受限。伐木以后，没有减少燃料的动作就不可能减少火灾概率。但是！处理起来也很困难，不如直接烧了，但是又会带来额外损伤，土壤损耗。所以（亮出结论）让枯木自然腐烂最好。

P6 作者观点：数据证明，灾后伐木不利于重建，树木再生不必要。

草舟逐波

Mark一下！               

筱雅Jane510

Thanks

橙子咿呀哟

第一段：火后伐木导致自然再生密度下降，增加可燃物，提升了短期风险。
第二段：最近的野外灾情使得大众对大火后的管理讨论变多。
    观点一：大众认为火后伐木可以通过减少可燃物降低风险，森林在未干预的情况下不能足够的再生。
    替代的观点：火后伐木对长期森林管理有害，包括野生动物栖息地和生态系统。
    这些观点都没有科学数据支撑。
第三段：引入案例：2002 biscuit fire 。因为火灾的规模、历史自然再生的难度和极具野心的火后伐木提案，这个案例变成了当地灾后管理的典范。样本数据是2004和2005年伐木前后的数据。
第四段：自然再生不必要。伐木的过程中造成的土壤破坏和掩埋使得自然再生的密度下降。
第五段：火后伐木增加了木质可燃物，导致火灾的蔓延。
第六段：减少木质可燃物的资源是有限的。持续减少的燃料可以帮助降低短期的火灾风险。
第七段：机械的去除燃料可能会造成长期的土壤的影响。因此让这些树留着，自然的腐烂可能是最好的控制风险的措施。
第八段：总结：火后伐木可能无法达到燃料和再生的目标，而且再生也不一定是必须的。

darcyzhx

P1: 抢救性伐木引发争论，其功能有哪些，好处与坏处；P2：两种观点的对比；P3-P4：提供2002美国火灾的样本研究说明抢救性火灾可能没有必要；P5-P6：抢救性采伐在短期内会增加火灾风险因为增加了燃料负荷，与减少燃料的目标不一致，机械去除费用昂贵，最有效的方法是树木自然腐烂。P7结论：数据显示，抢救性采伐会对森林再生和减少燃料产生反作用。

Ashely默默

记录阅读时间、总结时间、总时间
6 min,  30 min

1. 主题
伐木和森林大火之间的关系
2.分论点
Para1：火灾后伐木降低森林密度，增加火灾风险，伐木与森林再生和燃料减少的目的背道而驰
Para 2：大家对是否应该火灾后伐木各执一词，没有数据支持二者之间辩论
Para 3：选取了2004年前和2005年后的样本数据进行观察。
Para 4：火灾后伐木对于重造森林没有没要
Para 5：火灾后伐木增加了远超预期的燃料负荷，增加了短期火灾的蔓延率
Para 6：火灾后伐木和燃料减少的目标是不一致的，
Para 7：数据表明，火灾后伐木可能与森林再生和减少燃料的目标会适得其反，对于被烧毁的森林而言再造森林也不是必须的
3.摘抄印象深刻或者觉得优美的句子
4.总结文章中的生词
mitigation 缓解
counterproductive 适得其反，反作用
be notably incongruent with  与…显著不一致
Preclude  排除
mortality 死亡率
Combustion 燃烧
episodic 事件，偶发

Blair1001

看一下

Timothyboss

感谢分享！               

Glimmer09

320.
1)  2002年美国俄勒冈州Biscuit大火 → 火后采伐：森林再生↓，燃料↑ → 短期火灾风险↑ （-）
2) 火后伐木的争议（正：火灾风险↓ 再生可能↑，反：森林功能恢复↓），但没科学依据。（=）
3) Biscuit火灾后对火后采伐和未采伐地块的采样数据。（=）
4) 对3)分析，以Douglas fir为例 → 火后伐木 + 造林 = 再生↓（-）
5) 火后伐木 = 燃料↑ → 火灾↑ （-）
6)  火后伐木 ≠ 燃料↓ = 燃料↑ + 清理费用↑ / 持续烧+幼苗↓ ⇒ 火灾↓ = 保留树木 （-）
7) 总结：火后伐木 = 燃料↑ = 再生↓ ，火后森林大部分再生↑（-）