Droughts have intensified in Central Europe and will likely become a major driver of forest ecosystem change in the future. Regional studies are needed to understand drought impacts on forests and to provide guidance for adaptive management. In this study, we have investigated the effects of an extraordinary drought period in 2018 – 2020 on tree growth in the State of Bavaria (Germany). We (i) assessed overall changes in tree growth compared to pre-drought conditions, (ii) mapped the spatial configuration of drought and its impact on growth across ecoregions, (iii) quantified the standardized drought effect for the most abundant tree species, and (iv) analyzed the inter- and intraspecific variability in growth responses to drought.

Covering a large environmental gradient, we compared 3,462 tree basal area growth records at 200 inventory plots with the pre-drought period of 2006 – 2017. We analyzed drought impacts on tree growth using nonparametric randomization tests and linear quantile mixed models (LQMMs).

Median annual tree growth declined by 41.3% during drought. Decreases in growth were statistically significant for 13 out of 20 species. Growth reductions were most distinct in northwestern ecoregions of Bavaria. After controlling for other covariates of tree growth, the most abundant conifers, Picea abies [Karst.] and Pinus sylvestris [L.], were overall more susceptible than the common broadleaves, Fagus sylvatica [L.], Quercus robur [L.], and Quercus petraea [Matt.]. Yet, all species exhibited a high intraspecific variation in drought response.

Altering tree species composition is a key strategy to adapt forest ecosystems. Our study reveals high potential to mitigate future drought impacts by admixing P. abies- and P. sylvestris-dominated forests with more drought-adapted broadleaved tree species. In addition, the high intraspecific variability in drought susceptibility indicates potential to promote provenances or individuals with low drought sensitivity to reduce the local loss of tree species.

干旱在中欧愈演愈烈，很可能成为未来森林生态系统变化的主要驱动力。需要进行区域研究以了解干旱对森林的影响并为适应性管理提供指导。在本研究中，我们调查了 2018 年至 2020 年的异常干旱期对巴伐利亚州（德国）树木生长的影响。我们 (i) 评估了与干旱前条件相比树木生长的总体变化，(ii) 绘制了干旱的空间结构及其对整个生态区生长的影响，(iii) 量化了最丰富树种的标准化干旱影响，以及(iv) 分析了生长对干旱反应的种间和种内变异性。

覆盖较大的环境梯度，我们将 200 个清查样地的 3,462 条树木断面积生长记录与 2006 年至 2017 年干旱前时期进行了比较。我们使用非参数随机化检验和线性分位数混合模型 (LQMM) 分析了干旱对树木生长的影响。

在干旱期间，年树木生长中位数下降了 41.3%。20 个物种中有 13 个的生长下降具有统计学意义。巴伐利亚西北部生态区的生长减少最为明显。在控制了树木生长的其他协变量后，数量最多的针叶树Picea abies [Karst.] 和Pinus sylvestris [L.] 总体上比常见的阔叶树Fagus sylvatica [L.]、Quercus robur [L.]更容易受到影响和Quercus petraea [Matt.]。然而，所有物种在干旱反应中都表现出高度的种内变异。

改变树种组成是适应森林生态系统的关键策略。我们的研究揭示了通过将冷杉和樟子松为主的森林与更适应干旱的阔叶树种混合来减轻未来干旱影响的巨大潜力。此外，干旱敏感性的高种内变异性表明有可能促进具有低干旱敏感性的种源或个体以减少当地树种的损失。