A multi-component, multi-species model of vegetation–atmosphere CO2 and energy exchange for mountain grasslands

A model is presented which allows simulation of vegetation–atmosphere CO2 and energy exchange of multi-component, multi-species canopies, explicitly taking into account the structural and functional properties of the various components and species. The model is parameterised for a meadow and an abandoned area at the ECOMONT study area Monte Bondone (1500 m a.s.l., Trento/Italy). A series of sensitivity tests showed the model to be sensitive to vegetation optical and physiological properties, but not to soil optical properties, dwarf shrub bole respiration parameters and phytoelement inclination and width. Validation of canopy CO2 and energy exchange rates against the respective fluxes measured by the means of the Bowen-ratio-energy-balance method yields broadly satisfactory results. Though it proves difficult to validate canopy latent and sensible heat flux, due to the fact that the vegetation–atmosphere-transfer model does not include contributions by the soil, whereas measured fluxes do, indicating both the need for further model development as well as experimental studies. Finally, the model is used to test for the effects of simplifications in input data likely to occur when being applied at larger spatial and/or temporal scales.