Forests provide essential ecosystem services that range from the production of timber to the mitigation of natural hazards. Rapid environmental changes, such as climate warming or the intensification of disturbance regimes, threaten forests and endanger forest ecosystem services. In light of these challenges, it is essential to understand forests' demographic processes of regeneration, growth, and mortality and their relationship with environmental conditions. Specifically, understanding the regeneration process in present‐day forests is crucial since it lays the foundation for the structure of future forests and their tree species composition. We used Swiss National Forest Inventory (NFI) data covering vast bio‐geographic gradients over four decades to achieve this understanding. Trees that reached a diameter at breast height of 12 cm between two consecutive NFI campaigns were used to determine regeneration and were referred to as ingrowth. Employing three independent statistical models, we investigated the number, species, and diameter of these ingrowth trees. The models were subsequently implemented into a forest simulator to project the development of Swiss forests until the mid‐21st century. The simulation results showed an ingrowth decrease and a shift in its species composition, marked by a significant reduction in Norway spruce Picea abies and concurrent increases in broadleaves. Nevertheless, the pace of this change towards climatically better adapted species composition is relatively slow and is likely to slow down even further as ingrowth declines in the future, in contrast to the fast‐changing climatic conditions. Hence, support through adaptive planting strategies should be tested in case ingrowth does not ensure the resilience of forests in the future. We conclude that since the regeneration of forests is becoming increasingly challenging, the current level at which ecosystem services are provided might not be ensured in the coming decades.

中文翻译：

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土壤和气候依赖性向内生长推断：阔叶树缓慢征服瑞士森林


森林提供从木材生产到减轻自然灾害等基本生态系统服务。气候变暖或扰动加剧等快速环境变化威胁着森林并危及森林生态系统服务。鉴于这些挑战，了解森林的再生、生长和死亡的人口统计过程及其与环境条件的关系至关重要。具体来说，了解当今森林的再生过程至关重要，因为它为未来森林的结构及其树种组成奠定了基础。我们使用瑞士国家森林清单（NFI）数据来实现这一理解，该数据涵盖了四十年来的巨大生物地理梯度。在连续两次 NFI 活动期间胸高直径达到 12 厘米的树木被用来确定再生，并被称为向内生长。我们采用三个独立的统计模型，调查了这些向内生长的树木的数量、种类和直径。这些模型随后被应用到森林模拟器中，以预测直到 21 世纪中叶瑞士森林的发展情况。模拟结果显示，向内生长的减少和物种组成的变化，其特点是挪威云杉、冷杉的显着减少和阔叶树的同时增加。然而，与快速变化的气候条件相比，这种向更适应气候的物种组成变化的步伐相对缓慢，并且随着未来向内生长的下降，可能会进一步放缓。因此，应测试通过适应性种植策略提供的支持，以防向内生长不能确保森林未来的恢复能力。 我们的结论是，由于森林的再生变得越来越具有挑战性，当前提供的生态系统服务水平在未来几十年可能无法得到保证。