Promoting ecological resilience to increasing disturbance activity is a key management priority under warming climate. Across the Northern Hemisphere, tree mortality from widespread bark beetle outbreaks raises concerns for how forest management can foster resilience to future outbreaks. Density reduction (i.e., thinning) treatments can increase vigor of remaining trees, but the longevity of treatment efficacy for reducing susceptibility to future disturbance remains a key knowledge gap. Using one of the longest-running replicated experiments in old-growth subalpine forests, we measured stand structure following a recent (early 2000s) severe mountain pine beetle (MPB; Dendroctonus ponderosae) outbreak to examine the legacy of historical (1940s) thinning treatments on two components of resilience. We asked: ‘How did historical thinning intensity affect (1) tree-scale survival probability and stand-scale survival proportion (collectively “resistance” to outbreak) for susceptible trees (lodgepole pine [Pinus contorta] ≥ 12 cm diameter) and (2) post-outbreak stand successional trajectories?’ Overall outbreak severity was high (MPB killed 59% of susceptible individuals and 78% of susceptible basal area), and historical thinning had little effect on tree-scale and stand-scale resistance. Tree-scale survival probability decreased sharply with increasing tree diameter and did not differ from the control (uncut stands) in the historical thinning treatments. Stand-scale proportion of surviving susceptible trees and basal area did not differ from the control in historically thinned stands, except for treatments that removed nearly all susceptible trees, in which survival proportion approximately doubled. Despite limited effects on resistance to MPB outbreak, the legacy of historical treatments shifted dominance from large-diameter to small-diameter lodgepole pine by the time of outbreak, resulting in historically thinned stands with ~2× greater post-outbreak live basal area than control stands. MPB-driven mortality of large-diameter lodgepole pine in control stands and density-dependent mortality of small-diameter trees in historically thinned stands led to convergence in post-outbreak live tree stand structure. One exception was the heaviest historical thinning treatments (59–77% basal area removed), for which sapling dominance of shade-tolerant, unsusceptible conifers was lower than control stands. After six decades, thinning treatments have had minimal effect on resistance to bark beetle outbreaks, but leave persistent legacies in shaping post-outbreak successional trajectories.

中文翻译：

---

历史间伐处理的遗产是否促进了亚高山森林中树皮甲虫爆发的恢复力？

在气候变暖的情况下，促进生态对干扰活动增加的复原力是一个关键的管理优先事项。在整个北半球，广泛的树皮甲虫爆发造成的树木死亡引发了人们对森林管理如何促进对未来爆发的复原力的担忧。降低密度（即间伐）处理可以增加剩余树木的活力，但用于减少对未来干扰的敏感性的处理效果的寿命仍然是一个关键的知识差距。使用在古老的亚高山森林中运行时间最长的重复实验之一，我们测量了最近（2000 年代初）严重山松甲虫（MPB；Dendroctonusponderosae) 爆发以检查历史（1940 年代）细化处理对弹性的两个组成部分的影响。我们询问：'历史间伐强度如何影响（1）易感树木（山楂松 [ Pinus contorta] ≥ 12 cm 直径）和（2）爆发后的演替轨迹？总体暴发严重程度较高（MPB 杀死了 59% 的易感个体和 78% 的易感基区），历史间伐对树木规模和林分规模的抗性影响不大。树木规模的存活概率随着树木直径的增加而急剧下降，并且在历史间伐处理中与对照（未砍伐的林分）没有区别。存活易感树木的林分比例和基面积与历史间伐林分的对照没有差异，除了几乎去除所有易感树木的处理外，存活比例大约增加了一倍。尽管对 MPB 爆发的抵抗作用有限，到爆发时，历史处理的遗产将主导地位从大直径黑松转移到小直径黑松，导致历史上变薄的林分与对照林分相比，爆发后活基面积大 2 倍。MPB 驱动的对照林分中大直径黑松的死亡率和历史上间伐林分中小直径树木的密度依赖性死亡率导致爆发后活树林分结构的趋同。一个例外是历史上最严重的间伐处理（去除了 59-77% 的基础面积），为此，耐阴、不敏感的针叶树的树苗优势低于对照林分。六年后，间伐处理对树皮甲虫爆发的抵抗力影响微乎其微，但在塑造爆发后的演替轨迹方面留下了持久的遗产。导致历史上变薄的林分比对照林分大约 2 倍的爆发后活基面积。MPB 驱动的对照林分中大直径黑松的死亡率和历史上间伐林分中小直径树木的密度依赖性死亡率导致爆发后活树林分结构的趋同。一个例外是历史上最严重的间伐处理（去除了 59-77% 的基础面积），为此，耐阴、不敏感的针叶树的树苗优势低于对照林分。六年后，间伐处理对树皮甲虫爆发的抵抗力影响微乎其微，但在塑造爆发后的演替轨迹方面留下了持久的遗产。导致历史上变薄的林分比对照林分大约 2 倍的爆发后活基面积。MPB 驱动的对照林分中大直径黑松的死亡率和历史上间伐林分中小直径树木的密度依赖性死亡率导致爆发后活树林分结构的趋同。一个例外是历史上最严重的间伐处理（去除了 59-77% 的基础面积），为此，耐阴、不敏感的针叶树的树苗优势低于对照林分。六年后，间伐处理对树皮甲虫爆发的抵抗力影响微乎其微，但在塑造爆发后的演替轨迹方面留下了持久的遗产。MPB 驱动的对照林分中大直径黑松的死亡率和历史上间伐林分中小直径树木的密度依赖性死亡率导致爆发后活树林分结构的趋同。一个例外是历史上最严重的间伐处理（去除了 59-77% 的基础面积），为此，耐阴、不敏感的针叶树的树苗优势低于对照林分。六年后，间伐处理对树皮甲虫爆发的抵抗力影响微乎其微，但在塑造爆发后的演替轨迹方面留下了持久的遗产。MPB 驱动的对照林分中大直径黑松的死亡率和历史上间伐林分中小直径树木的密度依赖性死亡率导致爆发后活树林分结构的趋同。一个例外是历史上最严重的间伐处理（去除了 59-77% 的基础面积），为此，耐阴、不敏感的针叶树的树苗优势低于对照林分。六年后，间伐处理对树皮甲虫爆发的抵抗力影响微乎其微，但在塑造爆发后的演替轨迹方面留下了持久的遗产。一个例外是历史上最严重的间伐处理（去除了 59-77% 的基础面积），为此，耐阴、不敏感的针叶树的树苗优势低于对照林分。六年后，间伐处理对树皮甲虫爆发的抵抗力影响微乎其微，但在塑造爆发后的演替轨迹方面留下了持久的遗产。一个例外是历史上最严重的间伐处理（去除了 59-77% 的基础面积），为此，耐阴、不敏感的针叶树的树苗优势低于对照林分。六年后，间伐处理对树皮甲虫爆发的抵抗力影响微乎其微，但在塑造爆发后的演替轨迹方面留下了持久的遗产。