Abstract：
In many regions of Europe, large wild herbivores alter forest community composition through their foraging preferences, hinder the forest\'s natural adaptive responses to climate change, and reduce ecosystem resilience. We investigated a widespread European forest type, a mixed forest dominated by Picea abies, which has recently experienced an unprecedented level of disturbance across the continent. Using the forest landscape model iLand, we investigated the combined effect of climate change and herbivory on forest structure, composition, and carbon and identified conditions leading to ecosystem transitions on a 300-year timescale. Eight climate change scenarios, driven by Representative Concentration Pathways 4.5 and 8.5, combined with three levels of regeneration browsing, were tested. We found that the persistence of the current level of browsing pressure impedes adaptive changes in community composition and sustains the presence of the vulnerable yet less palatable P. abies. These development trajectories were tortuous, characterized by a high disturbance intensity. On the contrary, reduced herbivory initiated a transformation towards the naturally dominant broadleaved species that was associated with an increased forest carbon and a considerably reduced disturbance. The conditions of RCP4.5 combined with high and moderate browsing levels preserved the forest within its reference range of variability, defining the actual boundaries of resilience. The remaining combinations of browsing and climate change led to ecosystem transitions. Under RCP4.5 with browsing effects excluded, the new equilibrium conditions were achieved within 120 years, whereas the stabilization was delayed by 50-100 years under RCP8.5 with higher browsing intensities. We conclude that forests dominated by P. abies are prone to transitions driven by climate change. However, reducing herbivory can set the forest on a stable and predictable trajectory, whereas sustaining the current browsing levels can lead to heightened disturbance activity, extended transition times, and high variability in the target conditions.
摘要：
在欧洲的许多地区,大型野生食草动物通过其觅食偏好改变森林群落组成，阻碍森林对气候变化的自然适应性反应，并降低生态系统的复原力。我们调查了一种广泛的欧洲森林类型，以云杉为主的混交林，最近在整个非洲大陆经历了前所未有的动荡。使用森林景观模型iLand，我们调查了气候变化和食草动物对森林结构的综合影响，composition,和碳，并确定了导致300年时间尺度上生态系统过渡的条件。八种气候变化情景，由代表性集中路径4.5和8.5驱动，结合三个级别的再生浏览，进行了测试。我们发现，当前浏览压力水平的持续存在会阻碍社区组成的适应性变化，并维持脆弱但不那么可口的冷杉的存在。这些发展轨迹是曲折的，其特点是干扰强度高。相反,食草动物的减少引发了向天然优势阔叶物种的转变，这与森林碳的增加和干扰的大大减少有关。RCP4.5的条件与高和中等浏览水平相结合，将森林保留在其参考变异性范围内，定义弹性的实际边界。浏览和气候变化的其余组合导致了生态系统的转变。在RCP4.5下，不包括浏览效果，新的均衡条件在120年内实现，而在RCP8.5下，随着更高的浏览强度，稳定被延迟了50-100年。我们得出的结论是，以冷杉为主的森林容易受到气候变化的驱动。然而,减少食草动物可以使森林处于稳定和可预测的轨道上，而维持当前的浏览水平会导致干扰活动加剧，延长的过渡时间，以及目标条件的高度可变性。
