Audley Jackson P, Fettig Christopher J, Mortenson Leif A, Hamud Shakeeb M
Pacific Southwest Research Station, USDA Forest Service, Vallejo, CA, USA.
Pacific Southwest Research Station, USDA Forest Service, Placerville, CA, USA.
Environ Entomol. 2025 Apr 17;54(2):274-286. doi: 10.1093/ee/nvaf014.
Disturbance plays a critical role in the ecology of forests including influencing the abundance and diversity of fauna. Although numerous studies have focused on forest responses to various disturbance events, less attention has been given to arthropod community responses. California experienced an extreme, multi-year drought from 2012 to 2015 which severely stressed trees and incited epidemics of several bark beetle species (Coleoptera: Curculionidae: Scolytinae). Water stress and bark beetles contributed to a significant mortality event of hundreds of millions of trees in the central and southern Sierra Nevada, causing significant structural and compositional changes in forests. Our study sought to characterize woodborer and wood-decay-related beetle responses to various levels of tree mortality and snag (dead standing tree) retention resulting from this tree mortality event. Of particular interest were responses to differences in the orientation of dead wood, standing snags versus fallen snags. Ethanol-baited panel flight intercept traps were deployed for multiple weeks in 2022 and 2023 on plots representative of 3 disturbance classes: (i) low tree mortality (<30%), (ii) high tree mortality (>50%) with low snag fall (≤50%), and (iii) high tree mortality (>50%) with high snag fall (>60%). Woodborers and wood-decay-related beetle assemblages were compared at the family and species level. Our analyses revealed several significant differences in community assemblages among disturbance classes. Despite these differences, our results failed to reveal clear, qualitatively distinctive assemblages among disturbance classes. Rather, we could only conclude general patterns from the observed dissimilarities in richness and abundance. In general, we observed a greater diversity of woodborers on high-mortality plots than on low-mortality plots. Similarly, the diversity of wood-decay-related beetles generally increased with greater amounts (basal area) of snag fall. The amount of tree mortality and snag fall were positively related to several woodborer and wood-decay-related beetles. Observed beetle assemblages, their corresponding life histories, and the influences of altered habitat availability are discussed.
干扰在森林生态中起着关键作用，包括影响动物的数量和多样性。尽管众多研究聚焦于森林对各种干扰事件的反应，但节肢动物群落的反应却较少受到关注。加利福尼亚在2012年至2015年经历了一场极端的多年干旱，这给树木带来了严重压力，并引发了几种树皮甲虫（鞘翅目：象甲科：小蠹亚科）的疫情。水分胁迫和树皮甲虫导致内华达山脉中部和南部数亿棵树木大量死亡，造成了森林显著的结构和组成变化。我们的研究旨在描述蛀木甲虫和与木材腐朽相关的甲虫对此次树木死亡事件导致的不同程度树木死亡率和倒木留存（枯立木）情况的反应。特别令人感兴趣的是对枯木方向差异的反应，即立木倒木与倒伏倒木。2022年和2023年，在代表3种干扰类型的样地中，用乙醇诱饵平板飞行拦截陷阱部署了数周：（i）低树木死亡率（<30%），（ii）高树木死亡率（>50%）且低倒木率（≤50%），以及（iii）高树木死亡率（>50%）且高倒木率（>60%）。在科和种的水平上比较了蛀木甲虫和与木材腐朽相关的甲虫组合。我们的分析揭示了不同干扰类型之间群落组合的几个显著差异。尽管存在这些差异，但我们的结果未能揭示不同干扰类型之间明显的、定性上独特的组合。相反，我们只能从观察到的丰富度和丰度差异中总结出一般模式。一般来说，我们观察到高死亡率样地上的蛀木甲虫多样性高于低死亡率样地。同样，与木材腐朽相关的甲虫多样性通常随着倒木量（断面积）的增加而增加。树木死亡率和倒木量与几种蛀木甲虫和与木材腐朽相关的甲虫呈正相关。讨论了观察到的甲虫组合、它们相应的生活史以及栖息地可用性改变的影响。
