Climate sensitivity of disturbance regimes and implications for forest ecosystem management

Forest disturbance regimes have intensified distinctly across Europe in recent decades, and climate change is expected to further increase the frequency and severity of disturbance events. This intensification has distinct impacts on the sustainable provisioning of ecosystem services to society, with disturbances such as wind damage and bark beetle outbreaks increasingly challenging the continuous supply of renewable resources, protection against natural hazards and ecosystem carbon storage. While we are beginning to understand the responses of individual disturbance agents to changing environmental conditions, our knowledge and ability to predict realistic disturbance regimes (consisting of multiple agents interacting in space and time) is still limited. The development of adaptation strategies to climate-induced disturbance changes is further complicated by diverging appraisals of natural disturbances in the current literature: While disturbances pose a considerable risk for controlled forest management, they also foster the adaptive capacity and diversity of ecosystems, and are proposed as a blueprint for ecosystem-oriented management. In order to cope with the changing disturbance regimes of the future it is important to embrace both views on disturbance (risk vs. fundamental ecosystem process), yet such a comprehensive approach to disturbance management is currently still lacking. In this regard, the objectives of the proposed study are (i) to further understanding and prediction of climate-sensitive, multi-agent disturbance regimes, and (ii) assess impacts on ecosystem services as well as on biodiversity in order to (iii) deduce robust management strategies that minimize the risk for disturbance-related loss of ecosystem services while at the same time fostering ecosystem diversity and complexity. We will address the most detrimental disturbance regime in Europe, the wind–bark beetle complex, and exemplarily study the ecologically and socially diverse region of the northern Alps in Austria. Employing a combination of empirical and simulation approaches, we will investigate two contrasting forest landscapes, spanning a gradient from a conservation-oriented national park to a landscape managed for timber, protection against natural hazards and, increasingly, carbon. Drawing on 20 years of disturbance observations conducted by consortium members we will perform a detailed analysis of the spatio-temporal interactions between wind and bark beetle disturbances. These insights, in combination with previous efforts of the PI in disturbance modeling, will result in the development of a dynamic simulation model of disturbance interactions. We will subsequently use this model to study the climate sensitivity of the wind–bark beetle disturbance regime, and to investigate a variety of possible disturbance management strategies and their effects on ecosystem services as well as biodiversity. By addressing trade-offs among the latter explicitly, and accounting for dynamic interactions between disturbance agents, climate, and vegetation the project will improve the robustness of disturbance management and contribute to adapting sustainable forest management to changing climate and disturbance regimes.