European beech (Fagus sylvatica L.) has strongly suffered from the exceptional 2018 drought and subsequent dry years that hit Central Europe. While many trees showed severe signs of crown dieback or died following the 2018 extreme drought, other co-occurring and neighboring trees showed no sign of dieback or only minor damage. The reasons why some trees were more severely impacted than others and which predisposing factors make some trees more vulnerable than others are still poorly understood. Here, we analyzed differences in long-term growth trends, neighborhood composition (competition and species diversity), early-warning signals, and growth responses to past severe droughts of co-occurring vital and severely declining beech trees at six sites in Switzerland. We aimed to connect tree vitality after 2018 with past long-term growth trajectories and investigated whether declining trees had already been more susceptible to drought than vital trees before dieback occurred.

Overall, trees that showed severe crown dieback had a stronger growth decline than vital trees in the last 50 years. Declining trees exhibited stagnating and then decreasing growth trajectories even before signs of crown dieback occurred. Interestingly, we did not find significant differences in growth response to past severe droughts between the vitality classes, with the exception that vital trees recovered faster from past more severe droughts. Further, we could neither detect any difference in the effect of competition and neighborhood species composition on growth response, nor predict crown dieback based on early-warning signals which try to predict regime shifts by sudden changes in the autoregressive coefficient with lag 1, standard deviation and skewness. Our results indicate that unlike vital trees, declining beech trees showed predisposing signs for crown dieback by having lower growth rates during the last 50 years.

欧洲山毛榉 ( Fagus sylvaticaL.) 遭受了 2018 年异常干旱和随后袭击中欧的干旱年份的严重影响。虽然许多树木在 2018 年极端干旱后表现出严重的树冠枯死迹象或死亡，但其他同时发生的树木和邻近的树木没有枯萎迹象或只有轻微损坏。一些树木比其他树木受到更严重影响的原因以及哪些诱发因素使一些树木比其他树木更脆弱的原因仍然知之甚少。在这里，我们分析了长期增长趋势、邻里构成（竞争和物种多样性）、预警信号以及对过去在瑞士六个地点同时发生的重要和严重衰退的山毛榉树的严重干旱的生长反应的差异。

总体而言，在过去 50 年中，树冠严重枯死的树木比重要树木的生长下降幅度更大。甚至在树冠枯死迹象出现之前，衰退的树木就表现出停滞然后下降的生长轨迹。有趣的是，我们没有发现活力类别之间对过去严重干旱的生长反应有显着差异，除了重要的树木从过去更严重的干旱中恢复得更快。此外，我们既不能检测到竞争和邻域物种组成对生长反应的影响的任何差异，也不能根据预警信号预测树冠枯死，这些信号试图通过滞后 1、标准偏差的自回归系数的突然变化来预测政权转变和偏度。我们的结果表明，与重要的树木不同，