Spruce is one of the most important tree species in Central Europe, which suffers from the increasing droughts. In a study conducted in Switzerland, long-term forest monitoring data of spruce trees at 82 different forest sites were analysed. It was found that long-term tree mortality has increased significantly as a result of the recent droughts. For example, observed mortality of this tree species in 2019, 2020 and 2022 was more than double compared to that observed after the 2003 drought . The study found that drought and nitrogen deposition are the main factors contributing to increased mortality, with high nitrogen deposition exacerbating the effects of drought.

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Tresch, S., Roth, T., Schindler, C., Hopf, S., Remund, J., Braun, S., 2023. The cumulative impacts of droughts and N deposition on Norway spruce (Picea abies) in Switzerland based on 37 years of forest monitoring. Science of The Total Environment, 16422.