A model of whole plant gas exchange for herbaceous species from mountain grassland sites differing in land use

A model is presented which aims at quantifying the CO2 and H2O gas exchange of whole plants in their natural microenvironment, the canopy. In an up-sc aling approach the model combines leaf (gas exchange, energy balance) and c anopy (radiative transfer, wind attenuation) scale simulations. Net photosy nthesis and stomatal conductance are modelled using a nitrogen sensitive mo del of leaf gas exchange. An analytical solution to the energy balance equa tion is adopted to calculate leaf temperatures. Radiative transfer, separat ely for the wavebands of photosynthetically active, near-infrared and long- wave radiation, is simulated by means of a model which accounts for multipl e scattering of radiation using detailed information on canopy structure as input data. partial pressures of CO2 and H2O, as well as air temperatures within the canopy are not modelled, but instead, measured values are used a s input data. Field studies were carried out at the ECOMONT pilot study are a Monte Bondone (Trentino, Italy, 1550 m a.s.l.). The model is parametrised for four forbs and one graminoid species occurring at three sites differin g in land use, i.e. an abandoned area, a meadow and a pasture. Independent measurements are used to validate each of the major submodels of the compre hensive whole plant gas exchange model. (C) 2000 Elsevier Science B.V. All rights reserved.