The effects of rising temperatures and CO₂ on community structure and ecosystem functioning: A process-based modelling case study of the potential natural vegetation of Sweden

• We explore the potential effects of increasing atmospheric CO² concentrations and climate change on plant communities in Sweden focussing on the underlying physiological and vegetation dynamic processes; • We employ the LPJ-GUESS generalised ecosystem modelling framework to simulate potential vegetation dynamics, productivity and diversity using six of the common tree species and herbaceous vegetation of Sweden under present day climates and a future regional climate scenario derived from the SWECLIM project, concentrating on the effects of CO² and temperature change; • The environmental drivers in combination produced a complex of responses involving both direct effects and interactions. Productivity increases under the future scenario, with the most productive areas in central Sweden. Increasing CO² and temperature has the greatest effect in the south and increasing temperature alone in the mountains of the north. Future precipitation changes indicate a decline in productivity in the southeast, which is partially ameliorated by the effect of increasing CO² and water use efficiency. The effects on plant communities are varied; herbaceous mountain vegetation is replaced by tree species under a warmer climate though CO² has no direct effect on this process. In the south, increasing CO² seems to have a role with regard to increasing shade tolerance in light demanding species. thereby allowing them to remain in the succession longer and increasing diversity; • Understanding of the patterns of changes in community structure and their functional consequences with respect to changing climate and CO² can be useful in developing future adaptive strategies.