Wang Yixuan, Rammig Anja, Blickensdörfer Lukas, Wang Yuanyuan, Zhu Xiao Xiang, Buras Allan
Professorship for Land Surface-Atmosphere Interactions, Technical University of Munich, Hans-Carl-v.-Carlowitz-Platz 2, Freising 85354, Germany.
Professorship for Land Surface-Atmosphere Interactions, Technical University of Munich, Hans-Carl-v.-Carlowitz-Platz 2, Freising 85354, Germany.
Sci Total Environ. 2025 Jan 1;958:177938. doi: 10.1016/j.scitotenv.2024.177938. Epub 2024 Dec 16.
Germany experienced extreme drought periods in 2018 and 2022, which significantly affected forests. These drought periods were natural experiments, providing valuable insights into how different tree species respond to drought. The quantification of species-specific drought responses may help to identify the most climate-change-resilient tree species, thereby informing effective forest regeneration strategies. In this study, we used remotely sensed peak-season canopy greenness as a proxy for tree vitality to estimate the drought response of four widely abundant tree species in Germany (oak, beech, spruce, and pine). We focused on two questions: (1) How were the four tree species affected by these two droughts? (2) Which environmental parameters primarily determined canopy greenness? To address these questions, we combined a recently published tree species classification map with remotely sensed canopy greenness and environmental variables related to plant available water capacity (PAWC) and atmospheric vapor pressure deficit (VPD). Our results indicate that the more isohydric species featured a greater decline in canopy greenness under these droughts compared to the more anisohydric species despite similar soil moisture conditions. Based on spatial lag models, we found that the influence of PAWC on canopy greenness increases with increasing isohydricity while the influence of VPD decreases. Our statistical analysis indicates that oak was the only species with significantly higher canopy greenness in 2022 compared to 2018. Yet, all species are likely to be susceptible to accumulated drought effects, such as insufficient recovery time and increased vulnerability to biotic pathogens, in the coming years. Our study provides critical insights into the diverse responses of different tree species to changing environments over a large environmental gradient in Central Europe and sheds light on the complex interactions between soil moisture, climate variables, and canopy greenness. These findings contribute to understanding forests' climate-change resilience and may guide forest management and conservation strategies.
德国在2018年和2022年经历了极端干旱时期，这对森林产生了重大影响。这些干旱时期是自然实验，为了解不同树种如何应对干旱提供了宝贵的见解。对物种特异性干旱响应的量化可能有助于识别最具气候变化适应能力的树种，从而为有效的森林更新策略提供依据。在本研究中，我们使用遥感的生长季峰值冠层绿度作为树木活力的指标，来估计德国四种广泛分布的树种（橡树、山毛榉、云杉和松树）的干旱响应。我们关注两个问题：（1）这两种干旱对这四种树种有何影响？（2）哪些环境参数主要决定冠层绿度？为了解决这些问题，我们将最近发布的树种分类图与遥感冠层绿度以及与植物有效含水量（PAWC）和大气水汽压差（VPD）相关的环境变量相结合。我们的结果表明，尽管土壤湿度条件相似，但在这些干旱条件下，与更具变水特性的物种相比，更具恒水特性的物种冠层绿度下降幅度更大。基于空间滞后模型，我们发现PAWC对冠层绿度的影响随着恒水特性的增加而增加，而VPD的影响则减小。我们的统计分析表明，橡树是2022年冠层绿度显著高于2018年的唯一物种。然而，在未来几年，所有物种都可能易受累积干旱影响，如恢复时间不足和对生物病原体的易感性增加。我们的研究为中欧大环境梯度上不同树种对变化环境的多样响应提供了关键见解，并揭示了土壤湿度、气候变量和冠层绿度之间的复杂相互作用。这些发现有助于理解森林的气候变化适应能力，并可能指导森林管理和保护策略。
