Storms are the main abiotic disturbance in European forests, effects of which are expected to intensify in the future, hence the importance of forest stand stability is increasing. The predisposition of Norway spruce to wind damage appears to be enhanced by pathogens such as Heterobasidion spp., which reduce stability of individual trees. However, detailed information about the effects of the root rot on the stability of individual trees across diverse soil types is still lacking. The aim of the study was to assess the effect of root rot on the individual tree stability of Norway spruce growing on drained peat and mineral soils. In total, 77 Norway spruce trees (age 50–80 years) growing in four stands were tested under static loading. The presence of Heterobasidion spp. had a significant negative effect on the bending moment at primary and secondary failure of the tested trees irrespectively of soil type. This suggests increased legacy effects (e.g., susceptibility to pathogens and pests due to fractured roots and altered water uptake) of storms. Damaged trees act as weak spots increasing the susceptibility of stands to wind damage, thus forming a negative feedback loop and contributing to an ongoing decline in vitality of Norway spruce stands following storms in the study region in the future. Accordingly, the results support the importance of timely identification of the decayed trees, lowering stand density and/or shortening rotation period as the measures to counteract the increasing effects of storms on Norway spruce stands.

中文翻译：

---

根腐病的存在降低了挪威云杉（Picea abies）的稳定性：拉脱维亚的静态拉力试验结果

暴风雨是欧洲森林中主要的非生物干扰，预计其影响将在未来加剧，因此森林林分稳定的重要性正在增加。挪威云杉对风害的易感性似乎被诸如Heterobasidion spp。等病原体所增强，这些病原体降低了单个树木的稳定性。但是，仍然缺乏有关根腐病对不同土壤类型的单个树木稳定性影响的详细信息。这项研究的目的是评估根腐对挪威云杉在排水泥炭和矿物土壤上生长的单个树木稳定性的影响。总共对在四个林分中生长的77棵挪威云杉树（年龄在50-80年之间）进行了静态负载测试。Heterobasidion spp的存在。不论土壤类型如何，对试验树木的初次和二次破坏时的弯矩都有明显的负面影响。这表明风暴增加了遗留影响（例如，根部断裂和吸水率变化对病原体和害虫的敏感性）。受损的树木充当弱点，增加了林分对风害的敏感性，从而形成了负反馈回路，并导致挪威云杉林分在未来研究地区暴风雨后的生命力不断下降。因此，作为应对风暴对挪威云杉林分不断增加影响的措施，这些结果支持了及时识别腐烂树木，降低林分密度和/或缩短轮换周期的重要性。