Beschreibung:
Abstract. We present how variations in plant functional diversity affectclimate–vegetation interaction towards the end of the African Humid Period(AHP) in coupled land–atmosphere simulations using the Max Planck InstituteEarth system model (MPI-ESM). In experiments with AHP boundary conditions, theextent of the “green” Sahara varies considerably with changes in plantfunctional diversity. Differences in vegetation cover extent and plantfunctional type (PFT) composition translate into significantly different landsurface parameters, water cycling, and surface energy budgets. These changeshave not only regional consequences but considerably alter large-scaleatmospheric circulation patterns and the position of the tropical rain belt.Towards the end of the AHP, simulations with the standard PFT set in MPI-ESMdepict a gradual decrease of precipitation and vegetation cover over time,while simulations with modified PFT composition show either a sharp declineof both variables or an even slower retreat. Thus, not the quantitative butthe qualitative PFT composition determines climate–vegetation interactionand the climate–vegetation system response to external forcing. Thesensitivity of simulated system states to changes in PFT composition raisesthe question how realistically Earth system models can actually representclimate–vegetation interaction, considering the poor representation of plantdiversity in the current generation of land surface models.