Modeling Carbon and Water Fluxes in European Terrestrial Ecosystems

Sammanfattning: The controlling mechanisms and feedbacks between climate, the carbon and water cycling and vegetation in European ecosystems have attracted much attention in recent years but they are still not sufficiently understood. A better understanding of them is necessary to predict how they will be affected by climate change. Process-based models of ecosystem structure and functioning provide a tool to study the role of the terrestrial biosphere in the global carbon cycle and to assess changes in and risks to biogeochemical cycles associated with a changing climate. This thesis describes the evaluation and application of LPJ-GUESS, a modeling framework that integrates representations of population dynamics processes, process-based representation of plant physiology and the fluxes of carbon and water between the terrestrial ecosystems and the atmosphere. The results from the model intercomparison and evaluation studies show that ecosystem models can be considered as useful tools for studies of climate change impacts on carbon and water cycling forests. However, the sources of variation among models and between models and observed data place some constraints on model results and to some extent reduce their reliability. The impact studies reported in this thesis provides a good representation of what would be the impacts of a potential climate change on natural systems on Europe and allow to quantify the associated uncertainties in projected impacts at local, regional and continental scale. They are also a step towards linking climate modeling community and the impact studies community.