Fire suppression and past selective logging of large trees have fundamentally changed frequent-fire-adapted forests in California. The culmination of these changes produced forests that are vulnerable to catastrophic change by wildfire, drought, and bark beetles, with climate change exacerbating this vulnerability. Management options available to address this problem include mechanical treatments (Mech), prescribed fire (Fire), or combinations of these treatments (Mech + Fire). We quantify changes in forest structure and composition, fuel accumulation, modeled fire behavior, intertree competition, and economics from a 20-year forest restoration study in the northern Sierra Nevada. All three active treatments (Fire, Mech, Mech + Fire) produced forest conditions that were much more resistant to wildfire than the untreated control. The treatments that included prescribed fire (Fire, Mech + Fire) produced the lowest surface and duff fuel loads and the lowest modeled wildfire hazards. Mech produced low fire hazards beginning 7 years after the initial treatment and Mech + Fire had lower tree growth than controls. The only treatment that produced intertree competition somewhat similar to historical California mixed-conifer forests was Mech + Fire, indicating that stands under this treatment would likely be more resilient to enhanced forest stressors. While Fire reduced modeled wildfire hazard and reintroduced a fundamental ecosystem process, it was done at a net cost to the landowner. Using Mech that included mastication and restoration thinning resulted in positive revenues and was also relatively strong as an investment in reducing modeled wildfire hazard. The Mech + Fire treatment represents a compromise between the desire to sustain financial feasibility and the desire to reintroduce fire. One key component to long-term forest conservation will be continued treatments to maintain or improve the conditions from forest restoration. Many Indigenous people speak of “active stewardship” as one of the key principles in land management and this aligns well with the need for increased restoration in western US forests. If we do not use the knowledge from 20+ years of forest research and the much longer tradition of Indigenous cultural practices and knowledge, frequent-fire forests will continue to be degraded and lost.

中文翻译：

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森林恢复和燃料减少工作：在内华达山脉取得成功的不同途径

灭火和过去对大树的选择性砍伐从根本上改变了加利福尼亚州经常发生火灾的森林。这些变化的最终结果是，森林很容易受到野火、干旱和树皮甲虫等灾难性变化的影响，而气候变化又加剧了这种脆弱性。可用于解决此问题的管理选项包括机械治疗（机甲）、规定火力（火力）或这些治疗方法的组合（机甲+火力）。我们通过内华达山脉北部 20 年的森林恢复研究，量化了森林结构和组成、燃料积累、模拟火灾行为、树间竞争和经济方面的变化。所有三种活性处理（火、机甲、机甲+火）所产生的森林条件比未经处理的对照更能抵抗野火。包括规定火灾（火灾、机甲+火灾）在内的处理产生了最低的表面和燃料负载以及最低的模拟野火危险。初次处理后 7 年开始，Mech 产生的火灾危险较低，并且 Mech + Fire 的树木生长速度低于对照。唯一产生与历史上加州混合针叶林相似的树间竞争的处理方法是机械+火，这表明在这种处理下的林分可能对增强的森林压力源更有弹性。虽然火灾减少了模拟野火危害并重新引入了基本的生态系统过程，但这是以土地所有者的净成本完成的。使用包括咀嚼和恢复稀疏在内的机甲带来了积极的收入，并且作为减少模拟野火危险的投资也相对强劲。机甲+火处理代表了维持财务可行性的愿望和重新引入火的愿望之间的折衷。长期森林保护的一个关键组成部分是持续进行处理，以维持或改善森林恢复的条件。许多原住民将“积极管理”视为土地管理的关键原则之一，这与加强美国西部森林恢复的需求非常吻合。如果我们不利用 20 多年的森林研究知识以及更悠久的土著文化习俗和知识传统，频繁发生火灾的森林将继续退化和消失。