Sommerfeld Andreas, Rammer Werner, Heurich Marco, Hilmers Torben, Müller Jörg, Seidl Rupert
Institute of Silviculture University of Natural Resources and Life Sciences (BOKU) Vienna Austria.
Ecosystem Dynamics and Forest Management Group School of Life Sciences Technical University of Munich Freising Germany.
J Ecol. 2021 Feb;109(2):737-749. doi: 10.1111/1365-2745.13502. Epub 2020 Oct 12.
Bark beetle outbreaks have intensified in many forests around the globe in recent years. Yet, the legacy of these disturbances for future forest development remains unclear. Bark beetle disturbances are expected to increase further because of climate change. Consequently, feedbacks within the disturbance regime are of growing interest, for example, whether bark beetle outbreaks are amplifying future bark beetle activity (through the initiation of an even-aged cohort of trees) or dampening it (through increased structural and compositional diversity).We studied bark beetle-vegetation-climate interactions in the Bavarian Forest National Park (Germany), an area characterised by unprecedented bark beetle activity in the recent past. We simulated the effect of future bark beetle outbreaks on forest structure and composition and analysed how disturbance-mediated forest dynamics influence future bark beetle activity under different scenarios of climate change. We used process-based simulation modelling in combination with machine learning to disentangle the long-term interactions between vegetation, climate and bark beetles at the landscape scale.Disturbances by the European spruce bark beetle were strongly amplified by climate change, increasing between 59% and 221% compared to reference climate. Bark beetle outbreaks reduced the dominance of Norway spruce ( (L.) Karst.) on the landscape, increasing compositional diversity. Disturbances decreased structural diversity within stands ( diversity) and increased structural diversity between stands ( diversity). Overall, disturbance-mediated changes in forest structure and composition dampened future disturbance activity (a reduction of up to -67%), but were not able to fully compensate for the amplifying effect of climate change. . Our findings indicate that the recent disturbance episode at the Bavarian Forest National Park was caused by a convergence of highly susceptible forest structures with climatic conditions favourable for bark beetle outbreaks. While future climate is increasingly conducive to massive outbreaks, the emerging landscape structure is less and less likely to support them. This study improves our understanding of the long-term legacies of ongoing bark beetle disturbances in Central Europe. It indicates that increased diversity provides an important dampening feedback, and suggests that preventing disturbances or homogenizing post-disturbance forests could elevate the future susceptibility to large-scale bark beetle outbreaks.
近年来，全球许多森林中树皮甲虫的爆发日益加剧。然而，这些干扰对未来森林发展的影响仍不明确。由于气候变化，预计树皮甲虫造成的干扰将进一步增加。因此，干扰机制中的反馈受到越来越多的关注，例如，树皮甲虫的爆发是否会增强未来树皮甲虫的活动（通过引发同龄树木群落）或抑制其活动（通过增加结构和组成多样性）。我们研究了德国巴伐利亚森林国家公园中树皮甲虫 - 植被 - 气候的相互作用，该地区近期树皮甲虫活动空前活跃。我们模拟了未来树皮甲虫爆发对森林结构和组成的影响，并分析了干扰介导的森林动态如何在不同气候变化情景下影响未来树皮甲虫的活动。我们使用基于过程的模拟模型结合机器学习来解析景观尺度上植被、气候和树皮甲虫之间的长期相互作用。欧洲云杉树皮甲虫造成的干扰因气候变化而大幅增强，与参考气候相比增加了59%至221%。树皮甲虫的爆发降低了挪威云杉（(L.) Karst.）在景观中的优势地位，增加了组成多样性。干扰降低了林分内的结构多样性（多样性），增加了林分间的结构多样性（多样性）。总体而言，干扰介导的森林结构和组成变化抑制了未来的干扰活动（减少高达 -67%），但无法完全抵消气候变化的增强效应。我们的研究结果表明，巴伐利亚森林国家公园近期的干扰事件是由高度易感的森林结构与有利于树皮甲虫爆发的气候条件共同作用导致的。虽然未来气候越来越有利于大规模爆发，但新出现的景观结构支持大规模爆发的可能性越来越小。这项研究增进了我们对中欧当前树皮甲虫干扰长期影响的理解。它表明增加多样性提供了重要的抑制反馈，并表明防止干扰或使干扰后的森林同质化可能会增加未来对大规模树皮甲虫爆发的易感性。
