Large-scale simulations of interactions between wind storms and bark beetle outbreaks.

Forests play a crucial role in maintaining biodiversity, regulating the climate, and providing essential ecosystem services. However, they are increasingly vulnerable to natural disturbances such as windstorms, insect outbreaks, fires, and droughts, which are exacerbated by climate change. These disturbances are often interconnected, with one event triggering or amplifying another, leading to complex consequences for forest ecosystems. Understanding and predicting these interactions is vital for assessing the resilience of forests and their future role in the global carbon cycle. This thesis focuses on modeling the interactions between two major disturbances: windstorms and bark beetle outbreaks. It provides an preliminary evaluation of these interactions and proposes practical improvements for more refined assessments over both the short and long term. Using the ORCHIDEE land surface model, the study simulates how these disturbances interact and affect forest dynamics on a large scale. By incorporating bark beetle outbreaks into the model, the study demonstrates its potential to provide new insights into how bark beetle populations respond to changing climatic conditions, such as temperature and drought, and how these outbreaks interact with wind-damaged trees. It shows that disturbances can alter forest carbon dynamics, particularly in areas prone to multiple stressors. However, modeling these processes remains challenging due to uncertainties in climate data, forest structure, and disturbance feedbacks. The findings highlight the importance of improving models to better predict the impacts of climate change on forest ecosystems. More accurate simulations of disturbance interactions will enhance our ability to forecast forest resilience and contribute to more effective forest management strategies in the face of escalating environmental changes.