Over the past century, climate warming, nitrogen deposition, acidic rain, widespread disturbance events, adaptive management, and natural stand maturation have substantially altered the composition and structure of forests. However, the absence of historical data on the environment makes it difficult to prove these long-term effects. Ecological indicator values based on plant species characteristics offer a promising approach to detect presumed changes at relevant spatial scales (i.e., site level). In this study, we discerned the shifts in taxa composition of principal Central European beech forests and their associated environmental drivers by integrating three data sources: (1) 254 historical (1937 – 1948) and resurveyed (2019 – 2022) vegetation relevés of beech-dominated forests sites in the Swiss Jura mountains, (2) derived ecological indicator values for vascular plants regarding temperature, soil moisture, micro-climatic conditions, soil nutrients, pH, humus layer, and light availability, and (3) related data on disturbance/management intensity in these forest sites over the past 75 years, categorized as ‘undisturbed’ and ‘disturbed’ sites. We found a significant decrease in alpha diversity (taxa richness per site) on ‘undisturbed’ sites (loss of 7.0 ± 1.48 taxa) but stability on ‘disturbed’ sites (gain of 2.1 ± 5.71 taxa). Both beta (Jaccard dissimilarity) and gamma diversity (overall taxa richness) increased over the study period. The average ecological indicator values per site (s) consistently indicated climate warming impacts on all sites ranging from 390 to 1480 m a.s.l., while effects of acidic rain on soil pH and nitrogen deposition on soil fertility were negligible, except in densely populated lowland forest areas. The s for light and micro-climatic conditions differed between ‘undisturbed’ and ‘disturbed’ sites, indicating darker and more oceanic, and more open and continental conditions, respectively. The decrease in alpha diversity on ‘undisturbed’ sites corresponded primarily with reduced light availability, suggesting that stand maturation is the main driver of taxa loss while climate warming and pollution mainly affected composition rather than taxa richness. In contrast, the rise in beta and gamma diversity likely stems from changes in forest management and disturbance regimes, which have increased structural diversity with various micro-climatic niches enriching the taxa pool. In conclusion, our study demonstrates the ability to differentiate the profound effects of climate warming and pollution agents on forest composition and underscores the critical role of adaptive management in mitigating these impacts. By fostering structural diversity and biodiversity, adaptive management enhances the resilience of forests, enabling them to better adapt to evolving environmental conditions.

中文翻译：

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气候变暖、污染和管理对中欧山毛榉林植被组成的影响

在过去的一个世纪里，气候变暖、氮沉降、酸雨、广泛的干扰事件、适应性管理和自然林分成熟已经极大地改变了森林的组成和结构。然而，由于缺乏环境历史数据，很难证明这些长期影响。基于植物物种特征的生态指标值提供了一种有前途的方法来检测相关空间尺度（即地点水平）的假定变化。在这项研究中，我们通过整合三个数据源来识别中欧主要山毛榉森林的分类群组成的变化及其相关的环境驱动因素：（1）254个历史（1937年至1948年）和重新调查（2019年至2022年）山毛榉植被相关数据瑞士汝拉山脉的主要森林地点，(2) 导出维管束植物的生态指标值，包括温度、土壤湿度、微气候条件、土壤养分、pH、腐殖质层和光可用性，以及 (3) 干扰的相关数据/过去 75 年这些森林地点的管理强度，分为“未受干扰”和“受干扰”地点。我们发现“未受干扰”位点的α多样性（每个位点的类群丰富度）显着下降（损失7.0±1.48个类群），但“受干扰”位点的α多样性（每个位点的类群丰富度增加2.1±5.71个类群）保持稳定。在研究期间，β（杰卡德相异性）和伽玛多样性（总体类群丰富度）均有所增加。每个地点的平均生态指标值一致表明，气候变暖对海拔390至1480米范围内的所有地点都有影响，而酸雨对土壤pH值的影响和氮沉降对土壤肥力的影响可以忽略不计，人口稠密的低地森林地区除外。 “未受干扰”和“受干扰”地点之间的光照和微气候条件的 s 有所不同，分别表明较暗且更具海洋性，以及更开放和大陆性条件。 “未受干扰”地点α多样性的减少主要与光可用性的减少相对应，这表明林分成熟是类群损失的主要驱动因素，而气候变暖和污染主要影响组成而不是类群丰富度。相比之下，β和γ多样性的增加可能源于森林管理和干扰制度的变化，这些变化增加了结构多样性，各种微气候生态位丰富了类群库。总之，我们的研究证明了区分气候变暖和污染因素对森林组成的深远影响的能力，并强调了适应性管理在减轻这些影响方面的关键作用。通过促进结构多样性和生物多样性，适应性管理增强了森林的恢复力，使其能够更好地适应不断变化的环境条件。