The interacting effect of climate change and herbivory can trigger large‐scale transformations of European temperate forests

• Published in: Global change biology Vol. 30; no. 2; pp. e17194 - n/a
• Main Authors: Dobor, Laura, Baldo, Marco, Bílek, Lukáš, Barka, Ivan, Máliš, František, Štěpánek, Petr, Hlásny, Tomáš
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.02.2024
• Subjects: Browsing; Carbon; Climate change; Climate effects; Community composition; Composition; ecological resilience; ecosystem modelling; Ecosystem resilience; Ecosystems; Equilibrium conditions; European temperate forests; forest dynamics; Forests; Herbivores; Herbivory; large wildlife herbivores; Mixed forests; natural disturbances; Regeneration (biological); Resilience; Temperate forests; Variability; ecosystem modelling; European temperate forests; forest dynamics; natural disturbances; large wildlife herbivores; ecological resilience
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.17194

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. Large herbivores' browsing alters forest community composition. It also often compromises the forest's natural adaptive responses to climate change and management efforts. In Europe, pressure from herbivores coincides with a recent disturbance wave, which has particularly affected P. abies forests. We found that the persistence of the current browsing level impedes adaptive changes in these forests and sustains the vulnerable P. abies, which is not favored by game. Conversely, reduced herbivory initiates a transformation towards the naturally dominant broadleaved species, associated with considerably reduced future disturbance impacts. Therefore, game management is a crucial element in achieving ecosystem adaptation goals.